I More Than Most People Know—

Or Maybe Want To Know-

But Should Know  About The Uses Of Algae


Seaweeds are grouped by colors: reds, greens, and browns. Just to complicate matters, greens do not always look green, reds do not always look red, and browns, you guessed it, don’t always look brown


The nineteenth century produced just a whole hunch of wonderful things. In just that one period, the potato chip was invented and the purple eggplant was developed (they were originally white, you know). On the literary front, the word “frumious” was created by Lewis Carroll and the redoubtable Oscar Wilde penned "The Importance of Being Ernest" .Yes, altogether it was a marvelous century.

On the other hand, the twentieth century has produced only two things of any importance: Velcro and the Internet. Velcro is extremely useful because.,well, it’s Velcro. And the Internet is spiff because it allows you to waste huge amounts of time while actually seeming to be usefully engaged.

For instance, knowing that I would be writing an article about the ways humans use algae. Just a few minutes ago I searched the Web for the word “sushi” ( many types of sushi contain seaweed). I came up with literally hundreds of entries. My favorite was the Tokyo Food Page HTTP://www.twi’”rohbs/) a guide to Tokyo restaurants. And the best part of the Tokyo Food Page was the “sushi multimedia page” where you can actually hear the sound of dried seaweed being wrapped a round rice. I mean, heaven can wait.

Of course, humans use algae for many different purposes, not solely to entertain bored marine biologists.

Algae (singular alga) encompasses a wide variety of relatively primitive aquatic plants. Unlike land plants they have no roots, no stems, no leaves, no vessels to carry material up and down the plant, and nothing resembling a flower. Among the many thousands of species, you can find just about every size imaginable, from microscopic ones to 200—foot giants. We usually call any marine algae that is not microscopic “seaweed. ‘‘The word “kelp” is also often used for many types of algae, and the word comes from eighteenth cen­tury Scotland. Scottish potash makers originally derived potash (which they used in making fertilizer and black explosive powder) from wood ashes. Dwindling supplies of wood led them to use seaweed ashes, which were referred to as “kelp.” For a while, this was a real growth business, the time— share industry of the time. By about 1730, 60,000 persons in Scotland and environs were out torching seaweed.

Seaweeds come in a fashionable array of colors, and, in fact, that’s how they’re usually grouped. There are the greens (Chlorophvta, chloros = green. phyta = plant). reds (Rhodophyta. rhodon= rosy red, and browns (Phaeophyta, phae = tail, dusky). Just to complicate matters. greens do not always look green, reds do not always look red, and browns, you guessed it, don’t always look brown.

Humans have used seaweeds of various sorts for thou­sands of years. In Roman days, women reddened their cheeks with rouge extracted from Fucus, an algae whose name comes from the Latin word for rouge.  Peoples worldwide have eaten these plants, fed them to domestic animals, or used ‘them as fertilizers. One of the earliest records of human seaweed consumption occurs in a Chinese text dating from about 600 B.C. By about 1000 AD. the Chinese considered the red algae. Porphyra. such a delicacy that the peoples of southern China annual­ly presented the emperor with gifts of that plant. Today, over 450 species of algae are used for food or fertilizer, in medicine or in industry. Most of these are eaten directly, either fresh, dried, or as pickles or candy. The Japanese are the world’s biggest algae eaters; there, over twenty varieties of seaweeds are regularly eaten. Algae may make up perhaps 100 percent of Japanese food requirements.

Among the edible seaweeds,Porphyra is close to numero uno.. Extremely popular around much of the Pacific and also eaten in the North Atlantic, it is know as nori in Japan, zicai in China, and purple laver in Great Britain, This is really good stuff; it has the vitamin C con­tent of lemons, is loaded with B vitamins, and contains just gobs of iodine and other trace elements. Worth over one billion dollars to the Japanese seafood industry, it is one of the world’s most valuable seafood products. Much of it is cleaned, chopped, dried on mats, and sold in thin sheets. From there it’s added to sauces or soups or (as you have probably noted) wrapped around our rice to form sushi. While Porphyra is an extremely important edible algae, many other species are eaten fresh, fried, dried, or pickled. You can often find these in Asian markets, labeled as hijiki, wakame, ogo (Gracilaris) and kombu (Laminaria).

Okay, let’s leave the wonderful world of kelp pickles and journey into somewhat more rarified circles. You know the motto of that famous pork processors (whose name escapes me),that they use everything except the squeal? Many seaweed processors use everything except the slime. Agar is a gelling agent found in red seaweeds, including agarweed (Geidium robustum) and feather branch seaweed (Pterocladia).  It’s used as a culture substrate in growing bacteria in research and medicine. in canning fish, thickening ice cream, cream cheese, and making jams.

(Chondrus crispus) and Eucheuma. It, too, is used to thicken foods, particularly dairy products.  Here's a hot tip. Carrageenan is one of the only additives that can keep the chocolate in chocolate milk from settling out. It is often used in gelatin dishes in the tropics where refrigeration is unavailable because carrageenan gelatin holds together at relatively warm temperatures. It is also a major component of one fast— food operation’s “lean” hamburger. In fact, a good chunk of the Philippine seaweed industry goes to producing carrageenan for McSeaweeds.

Carrageenan has another property which makes it extremely useful to industry. Take a dab of toothpaste and smear it on the counter. Go on, there’s no one watching and besides if your roommates let you sing in the show­er, you can surely do this. Do you notice that the paste has a rather attractive sheen? Carrageenan is often used to produce that desirable quality.

Here in the good US of A, harvesting kelp, primarily giant kelp (Macorcystis) is a major industry. While some kelp had been harvested in California during the early 190Os, the industry w as very small until World War 1. During the late nineteenth and early twentieth centuries, the United States obtained nearly all its potash from German mines until it was recognized that the US had become dependent on Germany potash and a domestic supply was sought by the Government. Kelp was quickly found to be a good source, and from 1914 (when Germany cut off its potash supplies to the world) to 1919 there were many kelp harvesting companies in California. Undoubtedly the biggest of these was the Hercules Powder Company of Chula Vista, which extracted not only potash, but also ace­tone, both for explosives production.   Using these chemicals derived from kelp, Hercules produced huge amounts of explosives, including 23.000 tons of cordite for the British alone. ‘With the end of World War I, the market for these products collapsed, and it was not until the late 1920s that kelp harvesting again became a major industry.

From its rebirth until today, the kelp harvesting industry in California has primarily aimed at producing one product, alginic acid or algin. Algin has the curious ability to hold a large number of water molecules in suspension. This allows it to be used in a bewildering array of products. When added to water-based foods (such as bottled salad dressings or ice cream), it produces a thicker, creamier con­sistency. When placed in such bakery products as cake mixes, the baked goods tend to have an improved texture and retain moisture better. Among just a few industrial applications, algin products are used to coat paper, help print textiles, produce dental impressions, and aid in tablet dissolving. This is an extremely valuable commodity in California. The Kelco Company, today the largest of the kelp harvesters in California, estimates that its sales of algin alone exceed thirty-five million dollars per year.

I think beer commercials are what make America what it is, and without seaweed, those commercials would just not be the same. I love it when those really manly men, with teeth the size and color of the iceberg that sank the Titanic, stride into their favorite tavern and call for beer and lots of it.  Usually the manly men are celebrating winning some manly man contest, such as car eating, head butting, or trying to pull shoelaces through shoe holes after the little plas­tic sleeves have worn off.  And have you ever noticed that that manly men seem more excited about the foam than the brewski? Inevitably, the smiling bartender produces tankards of brew with sufficient foam to allow F-14's to make emergency landings. Really, I think that if the foam failed, the manly men would proceed to dismantle the tav­ern and, as an afterthought, the barman. Algin is sometimes used in brewing beer and, more importantly for the bartender, is added to many beers to stabilize all that foam.

Most kelp harvesting occurs between Monterey and San Diego, aboard harvesting vessels. These specially designed ships move slowly through the beds, pushing cutting racks ahead of them. The cut kelp is gathered on conveyors and loaded about the vessel. Kelp harvesters are limited by law to cutting only a limited amount of the plant including the surface canopy and the fronds, floats, and stipes which live

down to about forty feet below the surface. After harvest, the kelp is taken to a shore—based facility where it is chopped, washed, cooked, and clarified to remove various impurities. The algin is then dried, and finely ground.

While a lot of seaweed is harvested wild, aquaculture for these plants is a big, big business. This is particularly true in Asia, where most of it is produced and much of it is consumed. Worldwide, over five million tons, worth around five billion dollars, are grown in the spectacularly successful algae aciuaculture. China is the Big Kahuna in this business, with Japan and the Philippines a distant second and third.

What do you do for a headache? Oh, sure, you can take a couple of aspirin. meditate, or break out the old biofeed­back tape. I have a friend who lays her head over a package of frozen corn. But the word on the street is that many years ago the Native Americans of the Sitka, Alaska, region had a singular way of coping with a throbbing cranium. Apparently, when headache number twenty—three (lost a leg to a killer whale) hit, the sufferer would hobble (or in this case hop) down to the beach and search for a piece of bull kelp (Nereocystis). Bull kelp stipes are long, hollow tubes, with a flotation bulb at one end. The patient would insert one end of the stipe into an ear and put the bulb end on a hot stone. The heat would cause steam to form and that would travel up the tube into the ear, and I think you get the point.

Well, in a country where copper bracelets, magnets, and weird fungus soup are all viewed acceptable treatments for any number of ailments, it goes without saying that with just a little bit of the right kind of marketing, this could be very popular indeed.



II Mangroves of Northern Australia by James Duggan


Australian mangrove environments, like others around the world, are important nurseries for larval and juvenile fish and crustaceans, rich sources of nutrients, and havens for birds.

 The word mangrove can stand for an individual tree or a group of trees. A mangrove community is comprised of many different genera of plants which are not necessarily related to each other genetically.  All, however, have evolved similar physiological, reproductive, and morphological adaptations that enable them to thrive under adverse conditions where mortality rates are high and competition is intense.  Worldwide there are approximately 80 species, 59 of which are exclusive to mangrove ecosystems.  Mangrove communities occur where land and sea meet.

Air temperature, water salinity, wave protection, ocean currents, mud substrate, tidal ranges, and shallow shores all exert influence over mangrove community development and proliferation.   Extensive mangrove development occurs only when the air temperature of the coldest months is above 6S°F. and the water temperature of the warmest months exceeds 75°F. Year round water temperatures above 75°F.  limit the range of the mangrove.

 Mangroves seem to need al least some sodium chloride for optimal growth, and salt concentration in the water around mangroves is the single most important environmental characteristic.  Most  mangroves absorb some sodium and chloride ions. They must be able to control the intake of salt while maintaining the water balance necessary for survival. Some species absorb highly saline water and secrete the salt in a process called extrusion. Avicennia sp. and Aegialatis sp. excrete salt through glands in their leaves. In the genus Rhizophora, plants secrete salt through cork warts on their leaves. In Aegialatis sp. the salt flows from the vein of the leaf, via the palisade mesophyll layer, to the salt glands where it is somehow then pumped out of the leaf through a slit-like opening between the cuticle of the secretory gland and the leaf. In some species, salt glands are present

only if they are growing in saline conditions. Others have salt glands regardless of the salinity. Avicennia sp. is considered the most efficient salt secreting mangrove and tolerates high salinities.

  Other mangroves such as Rhizophora sp., Ceriops sp., Avicennia sp.  and Aegialatis sp. take up water while preventing the entry of salt in a process called extrusion. This mechanism is dependent the ultra-filtration properly in the roots.

  Still others like Excoecaria, Osbornia, Rhizophora, and Xylocarpus have developed a tolerance to high salt levels using a process called accumulation. Salt is stored in their bark, roots, and older leaves.   Leaf storage of salt is usually accompanied by water accumulation or succulence. In several species, sodium and chloride are deposited in senescent leaves that drop off, thus removing excess salt from the living tissue.  In deciduous species, the annual leaf fall may be a mechanism for the removal of excess salt prior to the new growing season.   Certain species of mangroves such as Rhizophora are able to use all three processes for salt regulation.  In any case the salt content of mangrove trees may affect their metabolic functioning and therefore other processes such as respiration, photosynthesis and protein synthesis.

Mangroves can grow only in areas protected from strong wave action such as bays lagoons, and estuarine areas.

Currents disperse mangrove seeds and seedlings and distribute them along the coast. In the Southern Hemisphere, all currents flow northward.  Few mangrove communities are found along the southern shores of Australia. In parts of Victoria and Western Australia, mangrove communities are considered remnants from a period when sea temperatures were much warmer than they are today. 

Some mangroves grow on sand, coral and other sediments.  The larger stands, however, are usually found growing in muddy areas such as deltas, lagoons, and along estuarine coastlines.  Decomposing mangrove leaves continually enrich the sediments in which the trees grow.

Local topography and tidal range are also influential. The greater the tidal range and more gradual the shoreline, the wider the mangrove zone will be.  There are some exceptions in Australia, such as off Cape York, where there are small tidal ranges but substantial mangrove communities.  Mangroves also tend to grow in relatively shallow water where new, small plants can become established. 

On the basis of fossil evidence, the center of origin for today's mangroves is likely to be southwestern Australia and the region from Northern Australia to Papua New Guinea.  In Australia the earliest fossilized pollens were from the Eocene period, about 54 million years ago.

In Australia and Papua-New Guinea about 30 species of trees and shrubs are considered to be part of the mangrove flora.  Three species appear to be purely Australian, including Aegialitis annulata, Bruguiera exaristata, and Osbornia octodenta.  The largest numbers of mangrove species occur on the northeastern coastlines of Australia. One explanation for this proliferation is that these areas are considered to have been the center of origin for mangroves and the area from which they were dispersed to Southeast Asia, where land connections existed.  Another is that the climate in Northern Australia is similar to when mangroves first evolved, and few or no species have been lost as of yet.  Also that part of the coast with its many estuaries and sheltered lagoons, provided ideal conditions for mangrove development.

Along the Queensland coast, the greatest number of species can be found where annual rainfall exceeds 50 inches and where elevations along the coast are greater than 2300 feet.  The cooler water and air temperatures in the south limit mangrove colonization to one species, Avicennia marina, which survives in isolated areas.

Another important factor in mangrove survival is the ability to conserve freshwater.  How is this accomplished?  In many cases mangroves are similar to desert plants in that they control water loss by reducing leaf size.  Also all mangroves leaves have a thick-walled epidermis and a thick, waxy cuticle covering the salt glands and the stomata, the minute pores which open and close to regulate the passage of gasses into and out of the leaf.  Most stomata are on the lower leaf epidermis.  Some species have stomata below the epidermis, helping reduce moisture loss.

To exist in such an aqueous environment, mangroves have had to specialize their root systems to overcome waterlogging, anaerobic conditions, and poor substrate support.   Most have longitudinal or lateral spreading cable root systems bearing fine nutritive roots.  Smaller, descending anchor roots support the plant.  These root systems are shallow, less than 6 feet deep, and have no taproots.  Mangroves also have above ground root systems--pneumatophores (roots arising from the cable root system which extends into the atmosphere) and knees (modified sections of the cable root which first grows upwards and then downward.)  Other root structures include stilt roots (branch roots rising from the trunk and growing into the substrate): buttress roots  (flattened and blade-like): and aerial roots (unbranched roots arising from the trunk on the lower branches and descending downward but usually not to the substrate).  Many species have one or more of these root systems which have also adapted to overcome waterlogging, oxygen deficiency, and salt intake.

Mangroves have also had to adapt to wind, waves, and in the southern areas, frost.  In northern Queensland tropical storms are frequent.  Farther south cold is a problem.

How do mangrove communities reproduce and survive under these rigorous conditions?  Most Australian species flower from spring to summer. Wind, insects, or birds pollinate these flowers. Bees pollinate the heavily scented flowers of the Avicennia species.  Birds pollinate the larger flowers of the Bruguiera species, and butterflies pollinate the smaller flowered species. Mainly moths pollinate some Ceriops species.

In the summer months most mangroves bear mature propagules, structures derived from the parent organisms that are capable of developing into new individuals.  Crabs and insects, wind and waves, unfavorable substances, premature sinking, and attachment by barnacles and tubeworms exact a high mortality rate on propagules.  In several genera, the seeds germinate while still attached to the parent trees and the embryos develop into seedlings without any dormant periods.  This is known as vivipary.  In some species like Avicennia, the embryo inside the fruit does not rupture the pericarp and thus has a resting stage before it germinates, a state known as cryptovivipary.  It is interesting to note that vivparous and cryptoviviparous seedlings can regulate salt intake while still attached to the parent tree.  However, when they fall off, the salt content increases rapidly until the ultrafiltration root systems are functional.

Mangrove seeds are buoyant and dispersed by water.  Some take up to one year to root themselves in the substrate and become established.  The adaptive significance of the mangroves reproductive strategies may include salt regulation, development of buoyancy, rapid rooting, and prolonged enrichment from the parent tree.  It is clear then that many factors are involved in the development of the mangrove ecosystem.  Modern day Homo sapiens may be the most significant factor of all.  In Australia as well as many other areas of the world, mangrove communities have been regarded as wastelands and were filled in for development.   Over 60% of Australia's commercial fisheries catch include species dependent on these mangrove areas for survival.  The future of these fish stocks and the survival of hundreds of species of marine organisms depend on these eerie yet beautiful and fragile ecosystems.



III SEAGRASS MEADOWS  by John Foster  U/N V16 No1 1986


 Seagrass meadows,.or grassbeds, have received much attention in the past few decades. As the major structural component of a biological community of great complexity, seagrasses have been studied from a variety of angles. We know much about the physiological activity, the conditions necessary for their survival, and even the process by which they decay and continue in the marine food web as detritus. A brief review of seagrass biology and an inventory of Atlantic coast species appeared in the spring, 1985, issue of this magazine.

 Seagrasses thrive from the tropics north to the Arctic Circle; however, the most luxurious stands and the most complex communities are found in the tropics and subtropics. One of the world's most extensive areas is found on the Atlantic coast of the United States, particularly in south Florida and in the eastern Gulf of Mexico. Caribbean and tropical Florida seagrass meadows are composed of the same dominant species found throughout the Gulf of Mexico and along the Atlantic coast to Cape Hatteras. These are turtle grass, Thalassia tesrudinum, manatee grass, Syringodium filiforme, and shoal grass, Halodule wrightii. Where turtle grass occurs, it is normally the dominant member of the grassbed, while shoal grass serves as a shallow water pioneer species. Manatee grass, although frequently occurring in pure stands, is often the transition species between shoal grass and turtle grass. This successional pattern does not always exist, but it provides a basis for considering the organisms which occupy the seagrass meadows. While there are variations in the zonation of seagrasses from place to place, some generalizations are possible. Shoal grass is more commonly encountered in the intertidal zone while turtle grass is normally found in deeper water and quite often in pure stands.

  Even though the seagrass meadows of the northeastern gulf contain the same species of seagrass as those of south Florida, there are differences in the organisms which make up the communities. A Florida seagrass meadow will contain certain groups of animals, whatever the region. There will be large numbers of polychaete worms, crustaceans (mostly small shrimps, amphipods and isopods), mollusks, echinoderms, and fishes. But, if you looked at a species list for a grassbed near Key Largo (in the upper keys) and compared it with one from St. Andrew Bay (in the northeastern gulf), you would find some glaring differences. Many animals do not occur in the northern area because of intolerance to the seasonal temperature changes found there. These two areas represent two separate zoogeographic provinces. The focus in this discussion is the zone referred to as Carolinian, found on the Atlantic coast from Cape Canaveral to Cape Hatteras and along the northern coast of the Gulf of Mexico. In some ways it serves as a transition between the warm Caribbean zone and the colder Virginian zone north of Cape Hatteras. A number of animals which occur in both zones are characterized by a wide tolerance to temperature change.

  St. Andrew Bay, Florida, is an estuary on the northern gulf coast with near seawater salinities due to limited freshwater inflow. The bay's main basin has two major arms extending from it, one of which is truncated by a dam in its uppermost section. Blocking the main body of the bay from the gulf is a long barrier peninsula. In 1934, a ship channel was cut through it, isolating the narrow end and creating Shell Island. The most conspicuous grassbeds are located in the quiet waters sheltered by the island, although grassbeds are present throughout the bay system.

  As the prime structural component of the community, seagrasses, by their presence on a generally level bottom, create a diversity of habitats  and substrates Not only do they provide habitat, they provide shelter for juvenile animals, food for some animals which graze on them directly, and food for multitudes of others which use them as detritus once they have decomposed.  After creating the habitat, they maintain it because the leaves slow water currents and hold the sediments in place. In addition, the roots and rhizomes form an underground matrix which stabilizes the sediments and provides more habitat.

  Since the grassbed is referred to as a community, it is proper to define that concept. It may be defined as a group of organisms occurring in a particular environment, presumably interacting with each other and the environment and separable from other groups which comprise adjacent communities. Seagrass communities are highly variable from place to place. Because of the subtle interaction of abiotic factors such as water temperature, salinity, tidal currents and sediments, a seagrass community can show great variability within the close confines of a bay system. Variations in abiotic factors lead to variations in the biotic component of the community.  A combination of abiotic factors, along with the amount of seagrass biomass present and the occurrence of seasonal fishes, combine to give the St. Andrew Bay grassbeds some spatial variability: This is true for most grassbeds, whatever their geography·

 What lives in the seagrass meadows of St. Andrew Bay? As in most marine environments, the organisms can be classified in general terms as permanent, seasonal, and transient residents with an additional group known as casual visitors.  Permanent residents are more likely to be invertebrates with limited mobility. An example of a permanent fish resident is the Code Goby, Gobiosoma robustum. This fish, a couple inches in length, is generally restricted to turtle grass bed where it may be found hiding within the vegetation all year. The predatory fishes which enter the grassbeds as juveniles, such as the pinfish and the speckled trout, make up the important seasonal residents. Transient fish species include migrating mullet or flounders, while casual visitors include small sharks and rays.

  The seagrass organisms can be further classified according to the location they occupy within the community.

  First is the biota on the seagrass leaves. This group consists of sessile animals such as the polychaete worm Spirorbis, whose coiled calcareous tubes dot the blades of turtle grass. Also, small algal species, known as epiphytes, cover the leaves with a felt-like growth. Hundreds of species have been identified and they provide rich browsing for amphipods, such as the tiny skeleton shrimp Caprella. Small caridean shrimps, known collectively as grass shrimps, make up a numerous group of animals which dwell upon the seagrass leaves. Small shrimps like Hippolyte zostericola and Tozeuma carolinese migrate up and down the leaves during the day and night. Tozeuma is known as the arrow shrimp because of its long serrated rostrum which terminates in a sharp point. It may be an inch or more in length and occurs in various colors, usually browns and greens. It hangs vertically in the seagrass as it feeds on small epifaunal animals and algae. In the stem area of the turtle grass, interwoven among several leaves, the terebellid polychaete Streblosoma hartmanae is found. This two to three inch worm forms a protective tube of sand grains from which it extends its feeding tentacles. It is a highly adapted deposit feeder -- it eats only organic detritus on the sand grains. Once the particles are collected on its sticky tentacles, they are transferred to the mouth by cilary action.

  Below the substrate, the rhizomes and roots create a complex maze. An inhabitant of this microhabitat is the long armed brittle star Ophiophragmus filograneus.

If a plug of the seagrass bottom were examined, one may be able to see the intertwining of the brialestar' s arms around the rhizomes. The central disk in this species is usually less than one half inch in diameter and so it is difficult to locate in the tangle. If separated and placed on the bare sand surface, it moves its arms in serpent-like fashion until it finally disappears into the substrate.

 Tube-building amphipods are also associated with these structured sediments. Ampelisca and Corophium use their tubes, made of mud and mucus, as places of refuge while they feed on detritus. They are often preyed upon by foraging fishes and larger invertebrates, but not to the extent of the free-living amphipods which are exposed as they crawl about the vegetation. Although normally unseen by observers in the grassbeds, the amphipods transform the abundant detritus, formed from decomposed seagrass, into energy for larger animals like the fishes. Another abundant crustacean is  the  tanaid  Hargeria  rapar.  This species, which is similar to an isopod, occurs all along the Atlantic coast and shows great sexual dimorphism, that is, structural differences between males and females. The males, only two or three millimeters in length, have extremely large, scissor-like chelae (pincers). They are fearsome when protruded from the end of the tube. In Apalachicola Bay, south of St. Andrew Bay, this is found to be the most abundant organism in beds of shoal grass -- over 18,000 individuals per square meter during the months of February and a yearly average of over 6000 per square meter. Hargeria is also a species which shows marked declines in population during the months when juvenile foraging fish are present.

 At times, crustaceans dominate the fauna of a grassbed, but polychaete worms are also found in tremendous numbers. Polychaetes are segmented worms of immense diversity in shape and size. Because of their great numbers, they are a major component in the community food web. In fact, benthic environments are examined for ecological well-being based on the numbers and species of polychaetes present. Outside the few species which live embedded within the grass leaves, most of this group occur as sediment infauna. Within this environment, they occupy several burrowing modes. The bloodworm Glycera,  known  as  a gallery  dweller, develops a network of chambers within the sediments with numerous openings to the surface. As a predator with an reversible pharynx armed with sharp teeth, Glycer uses the many openings of its burrow to ambush small invertebrates. With a rapid extension of the pharynx, the prey is seized by the teeth and drawn into the mouth. Bloodworms can grow to almost fifteen inches, so they are a predator to be reckoned with by seagrass dwellers .

  Other forms of polychaete tube-building occur in the seagrass habitat. A polychaete whose tube can be located by a swimmer in the grassbed is the plumed worm, Dioparra cuprea. This large carnivorous species constructs a vertical tube in the substrate composed of tough, parchment-like material. The buried end is rather thin and pale colored while the exposed end, extending a few inches above the bottom, is thicker and covered with debris. Dioparra is an active predator and feeds by extending its head from the tube and using a pair of strong jaws, captures  unwary animals. The worm itself is unmistakable, but seldom seen. It bears seven long antennae on its head, a number of brush-like gill filaments along the sides of the upper body, and has an iridescent color. The tubes are located among the roots of the seagrasses, but may also occur in mudflats or along bay beaches.

  What about the larger organisms that live on the substrate and can be seen by a snorkeler swimming in three feet of water? These are not nearly as numerous, nor trophically important, as the animals described, but they do provide greater interest because they are easily observed. The first underwater view a snorkeler will see in St. Andrew Bay in the Shell Island grassbeds will include many urchins. The group will consist, almost without exception, of the variegated urchin, Lytechinus variegatus. This species ranges from the Caribbean to North Carolina and is often quite abundant. As its name suggests, Lytechinus occurs in a variety of colors. The most common in St. Andrew Bay is reddish pink. It grows to a diameter of about three inches and has the unusual habitat of cloaking itself with bits of debris, like shell fragments or grass. The cloaking may be a response to light intensity.

  Not many animals in the grassbeds eat the seagrass directly; usually it is consumed in detrital form. Because this urchin can be so numerous, and because it is a direct herbivore on the seagrass, it can be a problem when the population explodes. Large areas of seagrass can be denuded in a short time period. Such occurrences are not common, but they are on record in Florida.

  Large decapod crustaceans are abundant in seagrass meadows. Often a trawl is necessary to obtain a good look at what is present because many decapods are too small or too cryptic to be seen while snorkeling. In addition, many species burrow in the substrate during the daylight hours. Such is the case with the penaeid shrimps of commercial value. Two very important species, the brown shrimp and pink shrimp, are present in the summer months. During months before the migration offshore to spawn, the adults may use the seagrass meadows as a refuge. In summer, newly hatched larvae, returning from offshore in the plankton, may use the grassbeds as a nursery. While present, they consume detritus and are preyed upon by small fishes.

The common Atlantic blue crab is also summer resident of the seagrass meadows. The blue crab's coloration makes it difficult to see in the grass, but a swimmer will have no difficulty spotting the brightly colored pincers which are raised in defense when the crab feels threatened. It will normally back away slowly at first, but if one presses, it will dart sideways to another dense area of seagrass. Blue crabs play havoc on the mollusks of the grassbeds, and much of the shell debris which litters the substrates can be traced to their crushing pincers or to those of the stone crab, Menippe mercenaria. A heap of blue and maroon fragments may mark the end of a mussel, but other bivalves, like the cross-barred venus and the thin shelled Lucines, fall prey to both species of crabs.

  Oysters do not comprise a major group of seagrass animals, but they do occur in the Shell Island grassbeds. They are present in small, tub-sized clumps, rather than in large reefs. Beneath many of the clumps, whether the oysters are living or not, is the burrow of a stone crab. Some of these crabs, which are commercially valuable for the sweet meat of their claws, may be three to four inches across the carapace. Along with the vicious jaws of the oysterfish, Opsanus beta, the crushing claws of the  stone crab discourage blind probing into cavities in the grassbed.

  The seagrass communities of northwest Florida host another commercially important mollusk, the bay scallop, Argopecten irradians concenrricus. In the spring, 1980 issue of the U.N., I reviewed the scallop's life cycle and its role in the grassbed. Because its life cycle includes an attachment and growth stage, the scallop tends to thrive in seagrass habitats. The grass blades provide an excellent stubstrate and refuge during the period prior to the free-living stage of the life cycle. Scallops are swimmers, yet they are capable of swimming only a few feet at a time, normally in avoidance of predators such as the banded tulip shell or various seastars. Beginning their free-living stage as small juveniles of one-half inch diameter, they grow throughout the winter season. By spring, they are one to two inches wide and they linger among the seagrass shoots, filter feeding on the rich particulate matter present in the water. By August, they may be three inches in diameter and covered with a variety of epifaunal organisms such as tube building polychaetes, amphipods, sponges, and tunicates. As the summer water temperatures peak and start a decline, usually by late September, the scallops discharge both eggs and sperm. They normally die soon after spawning, although some individuals may endure two seasons.

  The fishes of the seagrass community are mostly small, generalist feeders, utilizing the vegetation's epifauna. Clearly, the most abundant fish in Florida grassbeds, if only in spring and summer, is the pinfish, Lagodon rhomboides. It is a small fish, seldom over ten inches in length, and it feeds actively on amphipods and grass shrimp. The common behavior of grass shrimp of hiding among the seagrass blades is no doubt a response to predation by this species. In fact, substantial changes in the abundance of certain crustaceans can be directly  related  to the seasonal appearance and departure of the pinfish in the grassbeds. The pinfish, pigfish, spotted sea trout, and the silver perch are abundant in the grassbeds from May to September, at times comprising over 90 percent of the total fish population. These fishes spend the early part of their lives in  the  seagrass  meadows  and  later migrate into deeper water and to different habitats. Flounders are common summer residents of the grassbeds. They may be seen lying semi-buried in sandy patches in the grassbed or lying directly on the seagrass leaves, pressing them down several inches. Because flounders can change their color to match their surroundings, they may be quite difficult to see until they are disturbed, at which time they dart away abruptly. Perhaps the most bizarre and interesting fish in the seagrass community is the seahorse. Two species are found in St. Andrew Bay, Hippocampus erectus and H. zosterae. The latter species is smaller and found mostly in high salinity areas of the bay, but H. erectus is common throughout the bay, and especially in the grassbeds. The genus name comes from the Creek words hippos (horse) and kampos (sea monster). They are harmless, however, and many people seek them for marine aquariums. They will normally eat only live prey, such as grass shrimp, so are often difficult to maintain for long periods of time. In the natural environment, the prehensile tail allows the seahorse to grasp the seagrass blades and wait for small shrimp to come within striking distance. Then with a rapid movement of the head, they simply suck the prey animal into their mouth located at the end of the long snout. In an aquarium, this action produces a sound like the snapping of fingers.

 Only a fraction of the interesting animals in the seagrass community have been mentioned. To do justice to the subject, would require a book. Most of the animals are never seen, have no common names, and are obtainable only by trawling or by washing the substrate through a fine seive. All of the organisms, plant and animal, are part of a complex community which owes its existence to the structure provided by the seagrass. The animals are all tied, in some way, to the detrital food web which begins when the seagrasses die and decompose. The grassbeds of St. Andrew Bay, with those found everywhere else in the world, have these things in common.

IV Diatom Reading


The folloiwing was edited from a compilation of replies on internet  to the question below.  There were many authors of the answers and each are their own opinions/answers so its not textbook answers.  However, it makes for some interesting thought on why diatoms build their walls out of silica.

Why do diatoms build their walls from silica?  

   This is a compilation of replies to a question asked recently on the  mailing lists ALGAE-L and DIATOM_L.  The question was "why do diatoms  build their cell walls (tests) from silica?". Jan. Feb. 1996

 First, what aspects of diatom biology have  led them to become such a ubiqutous and successful group?  Second, how  much of this success can be attributed to the use of silica in their  frustules?  And finally what group of algae did the diatoms evolve from?

   I guess there are several perspectives from which to  answer, here are a couple:

 a) ecological: diatoms have found a resource that few other  groups exploit (but remeber things like the  silicoflagellates!) and have taken advantage.  Their  lifecycles often involve sedimentation when nutrients  deline and later resuspension, an so maybe nutrient  deficiency isn't such a barrier for them (see e.g. Victor  Smetachek's 1985 paper).

   b) chemical.  Things like CaCO3 will dissolve at depth  (remember carbonate compensation depth?), whereas silica is  more resistant.  Note the huge areas of the sea floor  covered in diatomaceous material.    c) biophysical.  Amorphous silica has interesting optical  properties, unlike CaCo3 which is largely opaque.  Why does  a photosynthetic organism like a coccolithophorid choose to  bury itself in opaque material?  Some belive silica  frustules can refract light to actally make it more  available for diatoms.  Maybe the complex frustule patterns  have functional significance.  

 According to Raven (JA Raven, Biol. Rev. 1983, 58, 179-207, silica deposition  is, on a unit weight basis, 3.7% as energeticaly costly to deposit as lignin,  and 6.7% as costly as cell-wall carbohydrate.  (See also E. Epstein,  Proc. Natl. Acad. Sci. USA, 1994, 91, 11-17.   

 Some considerations about the  question: 

  1. Silicon is the most spread earth element.

  2. Diatom ancestors, perhaps, came into the world when silicate was more  abundant.

 3. Fortunately, silicate can be limitant, otherwise...... (see algal  mucilage phenomen in   Adriatic s.). On the other hand, all the organisms  have an Achilles' heel. 

4. Without hard frustule most benthic diatoms should be unable to live where  they live;  in general, they are winning in competitions for substrate (e.g.  on the sand).   

 I hate diatoms growing in my macro-algal cultures. Usually they are too  exuberant. I'm gratefull to Lewin for germanium dioxide as French  revolutionaries were gratefull to M.eur Guillottin! 

    Whenever we ask "why" about something like silica in diatoms, we  start looking for ways that the feature adapts the organism to the  environment.  Possibly, silica does make diatoms more fit in some niches,  giving them the edge over competitors.  On the other hand, there may be  cases where they would be better off without silica, but they still  thrive.  The real "reason" they have silica may be evolutionary.  The ancestors of diatoms had silica scales and diatoms modified these  into frustules (I believe that is a current hypothesis).  Many protists  use silica.  It is possible that a different material could have been better  for diatoms, but a metabolism using silica was what they had to work  with.  Whether silica frustules were an adaptation that triggered  the radiation of diatoms, of if some other feature of these organisms was  more important for the success of this group, is very difficult to  determine.  Then again, it might just be chance. 

      Perhaps its useful to think of these features as a series of solutions to  challenges posed by an organisms' changing environment.     I like to think of the coccolithophorids as first having solved two  metabolic problems :

1)  high calcium in sea water and

2) high alkalinity of  the oceans.

 Calcification would have addressed both challenges.   Subcellular calcification is a neat solution because it takes advantage of  the secretory system to push crystals on 'rafts' away from the cell (I think  external encrustation as in corals and molluscs might pose additional  problems limiting growth/mobility).  The coccolith vesicle membranes are  conserved and the base plates are primarily carbohydrate which saves on  profligate expenditure of scarse nitorgen.  Coccoliths could have easily and  simply been secreted away from the organism to satisfy the hypothetical  problems mentioned above. If thats all that happened we would see naked,  subcellulary calcifying cells at present. Clearly, though, that's not all  that happened.  Coccospheres might have come later, as a subsequent  evolutionary stage.  Prabably in response to some other environmental  challenge where retention of the coccoliths  would confer added adaptive  value.  I suppose the fossil record can not be asked to provide evidence of  subcellular calcifiers with no coccospheres?  

   "Why do diatoms use silicate to form their tests?"    Simplest answer based on my belief that origin of features of organisms is  based in no small part on roles of the dice (MAINTENANCE of features may be  quite a different story):                                    

       Why not?    Silica is utilized by lots and lots of different animals and plants  (presumably due in some part to the fact that both carbon and silica have  four valence electrons).  Thus, the answer to your question is partly and  overly simply put as: They have silica  shells because their ancestors had silica shells.    Addressing the question of why has the silica shell been _maintained_ over  some 100 million plus years of evolution is a bit more complex.      Most simple answer:  Because diatoms can make silicate walls using about 30%  less energy (or so I have read, can't recall the citation, but it makes  sense) with minerals  such as silicate rather than CO2 and its various forms (which also become  limiting  in many regions, by the way) which they can better put into sugars and  making more little diatoms.  As long as silicate supply exceeds or equals  demand, diatoms win.    More complex, and partly assuming the first answer is reasonably accurate,  answer: 

  First, the North Atlantic isn’t the only place in the world.  Nitrate  apparently  "runs out" first in Yellowstone Lake and many other volcanic lakes,  phosphate in Lake  Superior, CO2 in other places.  Diatoms could have evolved someplace other than  the North Atlantic.  In fact, they had to.  When diatoms evolved (a common  mispractice of ecologists is to assume the world was always as it is and  that everything originally    adapted to modern conditions - there is a difference between adaptation and  ability to  function; i.e., a difference between proximate and ultimate causes - but  enough diatribe), the North Atlantic wasn't even there. 

  Third, remember, when diatoms  evolved, there may well have been no serious competitors for silica and  therefore  silica limitation was perhaps globally not a big deal early on!  Just as  humans litter  their own world, so diatoms may well have created silica limitation for  themselves.  I am, of course, ignoring radiolarians.  But they are animals.  Who cares? :)  Seriously,  they should be taken into account.  Is there any literature on competition  between rads  and diatoms for silica?  I think this might really be important for  radiation of marine  diatoms into freshwater where diatoms put a serious dent into silica  concentrations in many lakes and reservoirs (as the email from Fitzsimmons  noted) 

Fourth and most important to modern systems, Hutchinson's "paradox of the  plankton" articulated the fact that places isn’t even the same on a day to  day basis.  Diatoms just have to win some of the time to exploit certain  "niches", and phytoplankton niches are transient both in _TIME_ and space.  Thus, if using silicate does give a competitive advantage SOME of the time,  that is enough.  Something else will become limiting at some later time,  then mixing occurs and things start all over, there are gradients constantly  shifting (viz., resource competition theory), etc.  The author of the  original email  used the words "compete equally".  Of course, competing equally is almost  impossible.  The slightest differences will lead to one winner, given stable enough  conditions over  time and space.  Hutchinson's insight was to see that this doesn't happen in  nature; the race is always starting over.    A related question is why hasn't a "super" plankter evolved, one that  can shift its shell from silica to carbon based?  The hypothetical answer is  partly phylogenetically based.  Test making systems are presumably  homologous and have been  modified through time.  It would take some sort of gene duplication and/or       lateral  transference to provide the opportunity for evolution to produce two  different shell  making systems by providing two separate genetic blueprints for selection to  act on.  It could even be that most of the system stays the same, just that  some "homeobox" type  developmental controller system is affected.  But I am getting in way over  my head  here.  

      I would only add one more benefit to using silica: anti-grazer protection.  Some algae use sheaths, others spines; diatoms use silica that can break  into dangerous shards.  Some preliminary work suggests that long, fragile  species (like Nitzschia) break into many pieces, while Aulacoseira and  perhaps Stephanodiscus tend to stay intact.  These observations are based  on species frequencies (and fragmentation) inside fecal pellets versus  outside of pellets.      For further details, see Limnology & Oceanography 30:1010, (1985).

\ 1)  20 years ago  Peter Kilham, speculated (L&O 76, p.409-417)  that one of the major adaptive reasons for a Si frustule is to sink relative to  stream lines, thus overcoming diffusion limitation.  Motile cells can do this  as well, but diatoms cleverly use gravity to their benefit.  Of course, this  means that there has to be a certain amount of turbulence to pull this off  successfully- just another reason diatoms can do so well in large lakes and  oceans, or during mixing periods in smaller lakes. 

2.  Increase in surface area.  Laying your cell membrane out along a complex  structure can greatly increase your SA for absorption.  I remember ca 8 yrs ago  a paper (I think by Villareal) on a microtubule running the length of the  spines of Chaetoceros, suggesting this possibility even for the spines.

  3.  There was speculation about 20 years ago  that the frustule was acting as a light pipe, focusing  photons onto the chloroplasts.  I sort of remember there being a flurry of  tests of this idea-all negative.  On talking  to quite a lot of optical  physicists about this idea and they all said that theory breaks down at the  wavelengths of importance to diatoms, so they couldn't really help (their  suggestions included "scaling up" a diatom frustule and using microwaves to  check this out!!).  the speculation about optical properties of the siliceous  wall, proposed especially for centric diatoms with their archaic hexagonal  chambers (therefore compared to the ommatidia in the insect eye) was by  Johnathan R. Rider (the last adress I have is : Rider and associates 

 4.  About 25 years ago when  working on calcification, there were some  papers written which showed that Si was an essential element for the process of  calcification to occur, even though it was not incorporated into the CaCO3  structures.  Si as an essential Element for Calcification:  Carlisle E (1978) Essentiality and function of silicon. In: Bendz G &  Lindquist I (eds): Biochemistry of Silicon and related Problems.

: "Why do so many other  organisms not, if we consider that silicon is the second most element on  earth, and the plasmamembrane is essentially permeable to silicon?  Although  in modern diatoms the silicon for wall formation appears brought into the  cell by active pumps in addition (see refs. below by Werner, Volcani...etc)"  Well amorphous silica is rigid and inextensible, so growth of tissues would  be impossible, except when used as an endoskeleton like in sponges, or  sometimes in higher plants to stiffen leaf edges etc. Also for single cells  it has to consist of two pieces to allow cell growth and division. Or in the  most closed form, in statospore-cysts etc, you have to have at least a hole,  for the cytoplasm to crawl in and out.....

As to the low energy costs : Polycondensation of monosilicic acid into opaline silica is according to  these authors, just about 15% of that value needed for polycondensation of  sugars to form a cellulosic cell wall from the same size. So I would guess  that this is more important for a cell(species, clone) to survive, as being  fragile and kill, after its own death, their grazers with its broken corpse  as  I had interpreted the suggestion of somebody out there).  As Ed stated, this mechanism may have developed at a time, when everything  in the environments looked completely different to the present day  situation. So one should, I believe, then ask the question just for the  personal benefit of the cell and I am sure, that the grazer- and competition  problem comes much later.  There is an old theory, and it seems somehow not so weird in light of the  calculations and measurements presented by John Raven: The theory is from  Klaus Bonik, a Theoretical Biologist, who speculated just based on studies  of literature, that the development of the siliceous wall has started as a  waste product at a time, when warm, salty  ponds, puddles and oceans had  plenty of dissolved silicon in their nutrient broth. The plasmamembrane is  permeable for silicon (see also Raven 83), and may have been even more  permeable at that time, and they may not have possessed exclusion mechanism  for too much silicon, so they had to extrude it to the exterior under  ATP-consumtion. They finally learned, (through millions of years) that, if  they leave it at their cellular surface as an exoskeleton they would be able  to reduce their cytoskeleton for shape control and thus save energy (because  they need energy just for the formation of the exoskeleton, but not for its  maintenance as they would for cytoskeleton). Anybody who ever sectioned  diatoms, however, still finds a lot of cytoskeleton around. But nobody can  say, whether it would not be more without a rigid cell wall, which has  essentially the same function as any cell wall. And I predict, if we ever  will be able to clarify the funtions of a cell wall, we can best do it with  the diatom wall.

 Bonik,K (1978): Die Entstehung der Kieselalgen - ein stammesgeschichtliches  Modell. I. Die Enwicklung der Schale.  Natur & Museum, 108 (9) 267-273 

Bonik K (1979): Die Entstehung der Kieselalgen - ein stammesgeschichtliches  Modell II. Die Konsequenzen der Schalenbildung. Natur & Museum, 109 (1),1-9 

Pickett-Heaps, J, Schmid AM, Edgar L (1990) The cell biology of Diatom valve  formation. In: Round & Chapmann (eds) Progress in Phycological Research,  vol 7; 1-168. 

Schmid AM (1994) Aspects of morphogenesis and function of diatom cell walls  with implications for taxonomy. Protoplasma 181, 43-60   

\Then there are the excellent articles on Silicification by Joyce Lewin, M.  Darley, and Dietrich Werner :    Lewin J (1962) Silicification. In: Physiology and Biochemistry of Algae (R.  Lewin ed) Acad. Press NewYork  Darley M (1974) Silicification and Calcification In: Algal Physiology and  Biochemistry (WDP Stewart ed) Botanical Monographs vol 10;  Univ.-California press    pp 655-676

 Werner D (1977) Silicate Metabolism. in : The biology of diatoms (Werner D.ed)   Botanical Monographs 13, Blackwell Scientific publ.    

  Leadbeater, BSC & R.Riding (eds) 1986: Biomineralization in lower plants and  animals, The System. Associat. special Vol Nr 30., Clarendon Press Oxford    And finally: 

Gordon, R & Drum RW (1994) The chemical basis of diatom morphogenesis.  Internat.         Review on Cytology.          (This is an excellent article, although our theories diverge  somewhat on several topics) 






Corallines as carbon stores

Coralline algae take up carbon for use in the process of photosynthesis, as do most plants, but they have an additional mechanism of carbon uptake, the calcification process. Calcium is deposited in the cell walls of coralline algae in the form of calcium carbonate. One of the most exciting pieces of information which I have recently received came from a Brazilian marine biologist, E.C. de Oliveira, who has presented evidence that coralline algae may be one of the largest stores of carbon in the biosphere. If this is so, then they urgently need to be studied, since we know so little about even their basic ecology, particularly in the Indo-Pacific region.

Corallines in community ecology

Many corallines produce chemicals which promote the settlement of the larvae of certain herbivorous invertebrates, particularly abalone. This is adaptive for the corallines as the herbivores then remove epiphytes which might otherwise smother the crusts and pre-empt available light. This is also important for abalone aquaculture, as corallines appear to enhance larval metamorphosis and the survival of larvae through the critical settlement period. It also has significance at the community level, as the presence of herbivores associated with corallines can generate patchiness in the survival of young stages of dominant seaweeds. I have seen this in eastern Canada, and I suspect the same phenomenon occurs on Indo-Pacific coral reefs, yet nothing is known about the herbivore enhancement role of Indo-Pacific corallines, or whether this phenomenon is important in our coral reef communities.

Some corallines slough off a surface layer of epithallial cells, which in a few cases may be an anti-fouling mechanism which serves the same function as enhancing herbivore recruitment. This also affects the community, as many algae recruit on the surface of a sloughing coralline, and are then lost with the surface layer of cells. This can also generate patchiness within the community. The common Indo-Pacific corallines Neogoniolithon sp. and Sporolithon ptychoides slough epithallial cells in continuous sheets which often lie on the surface of the plants looking so much like wet tissue paper.

Not all sloughing serves an anti-fouling function. Epithallial shedding in most corallines is probably simply a means of getting rid of damaged cells whose metabolic function has become impaired.  My students and I have studied sloughing in the South African intertidal coralline algae, Spongites yendoi, a species which sloughs up to 50% of its thickness twice a year. This deep-layer sloughing, which is energetically costly, does not have any effect on seaweed recruitment when herbivores are removed. The surface of these plants is usually kept clean by herbivores, particularly the pear limpet, Patella cochlear. Sloughing in this case is probably a means of getting rid of old reproductive structures and grazer-damaged surface cells, and reducing the likelihood of surface penetration by burrowing  organisms.

Some coralline algae develop into thick crusts which provide microhabitat for many invertebrates. For example, off eastern Canada, I found that juvenile sea urchins, chitons, and limpets suffer nearly 100% mortality due to fish predation unless they are protected by knobby and under-cut coralline algae. This is probably an important factor affecting the distribution and grazing effects of herbivores within marine communities.  Nothing is known about the microhabitat role of Indo-Pacific corallines.  However, the most common species in the region, Hydrolithon onkodes, often forms an intimate relationship with the chiton Cryptoplax larvaeformis. The chiton lives in burrows that it makes in H. onkodes plants, and comes out at night to graze on the surface of the coralline. This combination of grazing and burrowing results in a peculiar growth form (called castles) in H. onkodes in which the coralline produces nearly vertical, irregularly curved lamellae.

Non-geniculate corallines are of particular significance in the ecology of coral reefs, where they provide calcareous material to the structure of the reef, help cement the reef together, and are  mportant sources of primary production. Coralline algae are especially important in reef construction, as they lay down calcium carbonate as calcite. Although they contribute considerable bulk to the calcium carbonate structure of coral reefs, their more important rôle in most areas of the reef, is in acting as the cement which binds the reef materials together into a solid and sturdy structure.

An area where corallines are particularly important in cobnstructing reef framework is in the algal ridge that characterizes surf-pounded reefs in both the Atlantic and Indo-Pacfic regions. Algal ridges are carbonate frameworks that are constructed mainly by nongeniculate coralline algae (after Adey 1978). They require high and persistent wave action to form, so are best developed on the windward reefs in areas where there is little or no seasonal change in wind direction. Algal ridges are one of the main reef structures that prevent oceanic waves from striking adjacent coastlines, and they thus help to prevent coastal erosion.

Economic importance

Despite their hard, calcified nature, coralline algae have a number of economic uses. One use dates back to the 18th century, and involves the collection of unattached corallines (maerl) for use as soil conditioners. This is particularly significant in Britain and France, where more 300 000 tonnes of Phymatolithon calcareum and Lithothamnion corallioides are dredged annually. Several thousand kilometres of maerl beds, composed of as-yet undetermined species belonging to the genera Lithothamnion and Lithophyllum,  exist off the coast of Brazil, and have been subjected to a low level of commercial exploitation. Maerl is also used as a food additive for cattle and pigs, as well as in the filtration of acidic drinking water.

Corallines are also used in medicine, where the earliest use involved the preparation of a vermifuge from ground geniculate corallines of the genera Corallina and Jania. This use stopped towards the end of the 18th century.  Modern medical science has found a more high-tech use for corallines in the preparation of dental bone implants. Apparently, the cell fusions provide an ideal matrix for the regeneration of bone tissue.


Since coralline algae contain calcium carbonate, they fossilize fairly well.  They are useful as stratigraphic markers of particular significance in petroleum geology. Coralline rock has also been used as building stones, with the best examples being in Vienna, Austria.



VI Red Tide Red Tide Update     

[1]. Local Conditions along the Southwest Florida Coast  Welcome to the Mote Marine Red Tide Update page.

Update as of: 1/9/03  In General: A patch of red tide has been detected 10 - 15 miles offshore of Sarasota. 

Sarasota Area:   A patch of red tide has been detected 10 - 15 miles offshore of Sarasota.  Levels were in the moderate range.  No dead fish or irritation has been reported .  

Update as of: 3/06/96 11:25  Sarasota Bay:  The concentration of red tide in New Pass continues to be in the moderate range today (see definition below). The samples collected in Sarasota Bay again show red tide to be in the low concentration range. DEP reports very low concentrations in Venice. Due to strong winds and patchy red tide conditions, respiratory irritation may still be a factor. We will continue to monitor concentrations daily.  Elsewhere:  The Department of Environmental Protection is continuing to report red tide from Clearwater to the Florida Keys. DEP reports medium levels of red tide at Clearwater, with some respiratory irritation in the area. They are also reporting discolored water and dead fish at St. Petersburg. Respiratory irritation has also been noted at Ft. Myers Beach, Naples Pier, and Marco Island. Many dead fish have been seen offshore and to the southwest of Sanibel Island. Please check back for more details.   


 * Very Low(1-10,000 cells/liter) = Little or no effect  

 * Low(10,000-100,000 cells/liter) = Shellfish harvesting ban  

 * Moderate(100,000-1 million cells/liter) = Some respiratory irritation and possible isolated fish kills   

*  High (1 million + cells/liter) = Respiratory irritation, fish kills and water discoloration  -

[2]. Florida Red Tide Changes its Name!   Recently, the Florida red tide Gymnodinium breve, or G. breve was reclassified in the taxonomy of dinoflagellates.  Its new name is Karenia brevis, or K. brevis.  Karenia was chosen in honor of Dr. Karen Steidinger, a prominent red tide scientist from the Florida Marine Research Institute in St. Petersburg, FL.  Our congratulations go to Dr. Steidinger for this honor.  We will be updating our web pages for the change to K. brevis.  Please forgive us if you occasionally still see a G. breve! 



  On a sultry fall morning of 1947, the community of Venice, Florida, awoke to thousands of dead fish along the beaches and a stinging, choking "gas" in the air. Some blamed nerve gas others a chemical spill, but scientists soon discovered, the cause : RED TIDE. Although this was the first scientific documentation of this catastrophic event along the Florida Gulf coast, reports of similar events are recorded as far back as the mid 1800's, and many more have been experienced since.  Red tides occur throughout the world, drastically affecting Scandinavian and Japanese fisheries, Caribbean and South Pacific reef fishes, and shellfishing along U.S. coasts. Most recently, it has been implicated in the deaths of hundreds of whales and dolphins along the U.S. Atlantic coast. These red tides are caused by several species of marine phytoplankton, microscopic plants that produce potent chemical toxins.  The Florida red tide is caused by blooms of a dinoflagellate that produce potent neurotoxin. These toxins cause extensive fish kills, contaminate shellfish and create severe respiratory irritation to humans along the shore.  Florida red tide blooms typically begin in the Gulf of Mexico 40-80 miles offshore and move slowly southeast with the prevailing ocean currents toward the Tampa Bay area. As the bloom progresses, the density of red tide organisms increase to several million cells in each liter of seawater, and the affected area expands to many square miles. The result is a mass of deadly toxin-containing water sweeping toward the southwest Florida coast, leaving a wake of dead and dying fish.  As the bloom approaches the shoreline, we begin to see and feel the obvious effects: dead fish, the characteristic burning sensation of the eyes and nose, and dry, choking cough. When the bloom is severe, fish die rapidly from the neurotoxic effects of the red tide which enter their bloodstream through the gills. Because the fish die so quickly, these toxins do not have time to build up in their tissue. Fish exposed to lower (sublethal) concentrations, however, may accumulate these toxins in their body. New evidence from current research suggests that such bioaccumulation in fish eaten by dolphins may have been a major factor in the deaths of more than 700 of these marine mammals in 1987.  Red tide populations well below the fish kill level pose a serious problem for public heath through shellfish contamination. Bivalve shellfish, especially oysters, clams and coquinas, accumulate so much toxin that they become toxic to humans. Public health concerns also emerge from studies of airborne toxins that show the presence of bacteria impacting our respiratory system along with the red tide toxins.  Because of the severe economic and public health effects of red tides, much consideration has been given to controlling the blooms. Control is feasible within confined areas, such as fish hatchery and aquaculture ponds, and research is underway to assess various control methods. Control in the broad expanses of the Gulf of Mexico, however, is neither feasible nor desirable at this time.  Although coastal pollution has enhanced red tide bloom in other areas, the Florida red tides represent a natural process, not caused by pollution. These blooms serve a purpose in the ecology of Florida Gulf coastal regions. Our responsibility is to understand the purpose and function of red tides, directing our efforts toward alleviating the adverse effects without causing further ecological damage.  The more we learn about red tide, the more intriguing this natural phenomenon appears. There is much more to this than is detected by our eyes and nose. The red tide organism plays a very important role in the conservation of solar energy to chemical energy (photosynthesis), a process that essential to the survival of most marine animals. Why this little menace also produces neurotoxin is still a mystery, but how toxins are produced and how they affect marine life as well as humans is the focus of much intensive research. 

[4]. THE FACTS   WHAT IS RED TIDE? Red tide is the result of massive multiplication (or "bloom") of tiny, single-celled algae called Gymnodinium breve (pronounced, "Jim-no-din-ee-um-bre-vay"), usually found in warm saltwater, but which can exist a lower temperatures. It is a natural phenomenon, apparently unrelated to manmade pollution. In high concentrations, G. breve may create a brownish-red sheen on the surface of the water; in other instances, it may look yellow-green, or may not be visible at all. Some red tides have covered up to several hundred square miles of water. No one can predict when or where red tides will appear, how long they will last and are affected by many variables such as weather and other factors.  WHERE DOES IT COME FROM? G. breve blooms are initiated miles offshore of the Florida Gulf Coast, moving onshore with winds and ocean currents. Scientists believe that G. breve algae may enter a dormant state at some point in their life cycle, forming cysts which settle miles off the west coast of Florida in ocean bottom sediments creating a "seed bed" effect. They think that strong flows of warm water from the Gulf Stream have carried the algae up the East Coast and inshore to the Carolinas.  HOW DOES IT AFFECT HUMANS? Irritations of the eyes, nose, throat, tingling lips and tongue are common symptoms that often occur during red tides. Waves, wind and boat propellers in high concentrations of red tides disperse toxin particles into the air causing these problems for people along the shoreline and on the gulf beaches. People suffering from severe or chronic respiratory conditions such as emphysema or asthma should try to avoid red tide areas. Symptoms usually disappear with 24 hours once the exposure is discontinued.  HOW DOES IT AFFECT MARINE LIFE? G. breve produces a poison, or toxin. Filter-feeding shellfish oysters, clams, mussels and other bivalve mollusks that consume G. breve concentrate the toxin in various organs. Red tide toxins are deadly to finfish. These toxins also are incorporated into the marine aerosol, which causes the respiratory irritation to people along the shore.                         

  What's Safe? What's Not?  Shrimp, Crab, Scallops and Lobsters in red tides are SAFE to harvest and eat, since these shellfish do not accumulate the red tide toxin in the meaty or hard muscle tissue which we normally consume. It is not a good idea to eat liver, organs, or other soft tissue of shellfish.  The muscle or "hard" meat of freshly caught finfish in red tides are SAFE to eat, provided the fish behave normally. Ther is no evidence of harmful effects in humans from contaminated fish have been reported. It is not a good idea to eat liver, organs or other soft tissues.  Oysters, Clams, Mussels, Mollusks, Whelks are Un-safe to harvest & eat since they may accumulate red tide toxins in their tissues. This remains effective until the Department of Environmental Protection determines that the waters are clear of red tide & shellfish are free of red tide toxins.  Swimming & Enjoying the Gulf Beaches are fine for most people however, some people have reported skin irritation after swimming. Use common sense -- if the red tide bothers you, you should avoid the area. However, respiratory irritation and fish kill are not always present. 

  Department of Environmental Protection: (813) 896-8626, St. Petersburg


 [5].          1.Name of Toxins: Various Shellfish-Associated  

 Shellfish poisoning is caused by a group of toxins elaborated by planktonic algae ( dinoflagellates, in most cases) upon which the shellfish feed. The toxins are accumulated and sometimes metabolized by the shellfish. The 20 toxins responsible for paralytic shellfish poisonings (PSP) are all derivatives of saxitoxin. Diarrheic shellfish poisoning (DSP) is presumably caused by a group of high molecular weight polyethers, including okadaic acid, the dinophysis toxins, the pectenotoxins, and yessotoxin. Neurotoxic shellfish poisoning (NSP) is the result of exposure to a group of polyethers called brevetoxins. Amnesic shellfish poisoning (ASP) is caused by the unusual amino acid, domoic acid, as the contaminant of shellfish.  

             2.Name of the Acute Diseases: Shellfish Poisoning:  

 Paralytic Shellfish Poisoning (PSP), Diarrheic Shellfish Poisoning (DSP), Neurotoxic Shellfish Poisoning (NSP), Amnesic Shellfish Poisoning (ASP).  

             3.Nature of the Diseases:  

 Ingestion of contaminated shellfish results in a wide variety of symptoms, depending upon the toxins(s) present, their concentrations in the shellfish and the amount of contaminated shellfish consumed. In the case of PSP, the effects are predominantly neurological and include tingling, burning, numbness, drowsiness, incoherent speech, and respiratory paralysis. Less well characterized are the symptoms associated with DSP, NSP, and ASP. DSP is primarily observed as a generally mild gastrointestinal disorder, i.e., nausea, vomiting, diarrhea, and abdominal pain accompanied by chills, headache, and fever. Both gastrointestinal and neurological symptoms characterize NSP, including tingling and numbness of lips, tongue, and throat, muscular aches, dizziness, reversal of the sensations of hot and cold, diarrhea, and vomiting. ASP is characterized by gastrointestinal disorders (vomiting, diarrhea, abdominal pain) and neurological problems (confusion, memory loss, disorientation, seizure, coma).  

            4.Normal Course of the Disease:  

 PSP: Symptoms of the disease develop fairly rapidly, within 0.5 to 2 hours after ingestion of the shellfish, depending on the amount of toxin consumed. In severe cases respiratory paralysis is common, and death may occur if respiratory support is not provided. When such support is applied within 12 hours of exposure, recovery usually is complete, with no lasting side effects. In unusual cases, because of the weak hypotensive action of the toxin, death may occur from cardiovascular collapse despite respiratory support.  

 NSP: Onset of this disease occurs within a few minutes to a few hours; duration is fairly short, from a few hours to several days. Recovery is complete with few after effects; no fatalities have been reported.  

 DSP: Onset of the disease, depending on the dose of toxin ingested, may be as little as 30 minutes to 2 to 3 hours, with symptoms of the illness lasting as long as 2 to 3 days. Recovery is complete with no after effects; the disease is generally not life threatening.  

 ASP: The toxicosis is characterized by the onset of gastrointestinal symptoms within 24 hours; neurological symptoms occur within 48 hours. The toxicosis is particularly serious in elderly patients, and includes symptoms reminiscent of Alzheimer's disease. All fatalities to date have involved elderly patients.  

              5.Diagnosis of Human Illnesses:  

 Diagnosis of shellfish poisoning is based entirely on observed symptomatology and recent dietary history.  

         6.Associated Foods:  

 All shellfish (filter-feeding molluscs) are potentially toxic. However, PSP is generally associated with mussels, clams, cockles, and scallops; NSP with shellfish harvested along the Florida coast and the Gulf of Mexico; DSP with mussels, oysters, and scallops, and ASP with mussels.  

        7.Relative Frequency of Disease:  

 Good statistical data on the occurrence and severity of shellfish poisoning are largely unavailable, which undoubtedly reflects the inability to measure the true incidence of the disease. Cases are frequently misdiagnosed and, in general, infrequently reported. Of these toxicoses, the most serious from a public health perspective appears to be PSP. The extreme potency of the PSP toxins has, in the past, resulted in an unusually high mortality rate.  

      8.Target Populations:  

 All humans are susceptible to shellfish poisoning. Elderly people are apparently predisposed to the severe neurological effects of the ASP toxin. A disproportionate number of PSP cases occur among tourists or others who are not native to the location where the toxic shellfish are harvested. This may be due to disregard for either official quarantines or traditions of safe consumption, both of which tend to protect the local population.  

       9.Analysis of Foods:  

 The mouse bioassay has historically been the most universally applied technique for examining shellfish (especially for PSP); other bioassay procedures have been developed but not generally applied. Unfortunately, the dose-survival times for the DSP toxins in the mouse assay fluctuate considerably and fatty acids interfere with the assay, giving false-positive results; consequently, a suckling mouse assay that has been developed and used for control of DSP measures fluid accumulation after injection of the shellfish extract. In recent years considerable effort has been applied to development of chemical assays to replace these bioassays. As a result a good high performance liquid chromatography (HPLC) procedure has been developed to identify individual PSP toxins (detection limit for saxitoxin = 20 fg/100 g of meats; 0.2 ppm), an excellent HPLC procedure (detection limit for okadaic acid = 400 ng/g; 0.4 ppm), a commercially available immunoassay (detection limit for okadaic acid = 1 fg/100 g of meats; 0.01 ppm) for DSP and a totally satisfactory HPLC procedure for ASP (detection limit for domoic acid = 750 ng/g; 0.75 ppm).     

       10.History of Recent Outbreaks:  

 PSP is associated with relatively few outbreaks, most likely because of the strong control programs in the United States that prevent human exposure to toxic shellfish. That PSP can be a serious public health problem, however, was demonstrated in Guatemala, where an outbreak of 187 cases with 26 deaths, recorded in 1987, resulted from ingestion of a clam soup. The outbreak led to the establishment of a control program over shellfish harvested in Guatemala.  

 ASP first came to the attention of public health authorities in 1987 when 156 cases of acute intoxication occurred as a result of ingestion of cultured blue mussels (Mytilus edulis) harvested off Prince Edward Island, in eastern Canada; 22 individuals were hospitalized and three elderly patients eventually died.  

 The occurrence of DSP in Europe is sporadic, continuous and presumably widespread (anecdotal). DSP poisoning has not been confirmed in U.S. seafood, but the organisms that produce DSP are present in U.S. waters. An outbreak of DSP was recently confirmed in Eastern Canada. Outbreaks of NSP are sporadic and continuous along the Gulf coast of Florida and were recently reported in North Carolina and Texas.

[6]. e-mail 5/4/97 Hi Again, 

 The red tide was getting pretty thick here in Encinitas, so I went to the beach near Stone Steps last night (May 3rd) to see if it was bioluminescent (knowing that  these types of blooms sometimes occur here).   I have never really studied or worked with dinoflagellates before and was completely unprepared for what I saw.  I'm sure that this is old news for anyone that has worked with or seen bioluminescent red tides. The cells emit bursts of light in a pulse and decay pattern when exposed to shock or pressure. Anyway, the entire coast was lit up with brightly glowing breakers in both directions.  When the waves break, they emit a flash like dim lightning and then glow brightly for several seconds after.  Light intensity seems to be dependent on cell density and "recharge time".  Walking on the beach leaves brightly glowing footprints behind you.  Swimming produces glowing trails etc.  I'm sure you've heard enough by now...  In summary, this tide is easily the most astounding natural phenomenon I have ever witnessed and I would encourage anyone in the area to make an attempt to see it. I will try to take some photographs tonight.


VII Bad Algae

Monday, December 3, 2001

Kaneohe targeted for fight against 5 alien, 2 local algae species.  The growth of algae threatens coral reefs and other nearshore marine ecosystems

By Diana Leone

You could call algae the feral pig of Hawaii's marine environment. Overgrowth of the seemingly benign plant threatens coral reefs, fish, other sea life and the natural beauty and tourism draw of nearshore waters. Come January, Kaneohe Bay will be the battleground against five alien algae and two overgrown local species. On the front line will be University of Hawaii doctoral students Jennifer Smith and Eric Conklin, working under the guidance of Waikiki Aquarium curator Cindy Hunter. "Hawaii has a really big problem with alien marine plants," said Smith, a botanist who has been studying the interaction between plants and corals for four years. The team will be wading, snorkeling and diving, trying different methods to banish the unwelcome guests. A $60,000 grant from the Hawaii Coral Reef Initiative will help the team figure out the best methods to get the bad algae out. They hope ultimately to pass on what they learn to volunteers, who then can help weed Hawaii's underwater garden.

Removal of alien species from coral reefs is a top priority for the Hawaii Coral Reef Initiative, said its director, Mike Hamnett. "Our biggest hope is to remove algae in ways that don't make the situation worse," Hamnett said. "It's going to be very carefully controlled and monitored." Most algae can regenerate from tiny broken pieces of plant. Unless the removal is done carefully, you could end up with a bigger problem than you started with. The yearlong research could have long-term effects for all the Hawaiian Islands, Hamnett said. "It's pretty significant because we've never done this." Kaneohe Bay was chosen as the proving ground because it hosts all of Hawaii's worst algae offenders in a variety of habitats, including both fringing and patch reefs, in varying depths and conditions of sea water. "We hope to get techniques in place before we get (volunteer) people out there. We don't know how much manpower it's going to take to clear even a small patch of reef in Kaneohe," Smith said. "We're doing this to make a difference," Smith said. "It's my hope that eradication of some species may be possible. ... I have a feeling we're never going to actually completely get rid of them. But by reducing their abundance, we can at least give the natural ecosystem a chance to come back." In the meantime, she said, "We need more state and federal help through public education, better land use management practices, more interaction between land and water resource management, and ... more regulation of the aquarium trade, aquaculture, ship ballast waters and boat hulls."

The 7 most harmful near-shore weeds

These are the algae cited as problems in Hawaii:

Acanthophora spicifera: This most common alien algae is yellowish to dark brown and has lots of short spikes coming off cylindrical branches. It's very abundant in Kaneohe Bay, and fish like it; probably too late for complete eradication.

Hypnea musciformis: This dark maroon algae has cylindrical branches, with large hooks on end of branches that it uses to wrap around other plants. This alien species is blamed for massive blooms in the Kihei area of Maui.

Avrainvillea amadelpha: This alien algae anchors on sandy or muddy bottoms, appearing as upright little paddles, olive green to almost dark brownish black. It is feltlike in texture, often has other things growing on top of it and is common at Kahala's shallow reef flats and in 30 or more feet of water at Portlock and Kahe Point. Believed to compete with native sea grass.

Gracilaria salicornia: Dense, three-dimensional mats of this dark brown to bright orange alien algae can be found covering the reef in front of the Waikiki Natatorium. It's "crispy" -- and is showing up in some poke mixes.

Kappaphycus spp.: This alien algae is only found in Kaneohe Bay. Its large branches can be more than a centimeter wide, with short little spines covering it; color ranges from light tan to purple. Very competitive and may be killing coral.

Dictyosphaeria cavernosa, or bubble algae: A local algae that has been a pest in Kaneohe Bay since the 1970s.

Cladophora sericea: This local algae has troubled West Maui with summertime blooms from Lahaina to Kahana in recent years. It has bright green, soft filaments and forms long green tufts.

Marine Plant Readings          NAME......................................................................................PD....

I. Uses of Algae

1. How do algae structurally differ from land plants?

2. What is "kelp" and discuss how whas it important in the 1700's?

3. What type of opinion can you form as to the validity of the names of seaweeds (ie red/green/brown?)

4. Where does the brown algae "Fucus" get its name from?

5. Today, there are over 450 species of useful algae.  What are some of the uses?

6. What data suggests the authors opinion that "Among the edible seaweeds, Porphyra is numero uno." Support your answer.

7. What is Carrageenan and what are its uses…how does it work??

8. What caused the kelp harvesting industry to take off?

9. Based on the last few paragraphs, is algae a worthwhile comodity?

10.  How was bull kelp used to get rid of headaches?




     BY JAMES DUGGAN    V21,N2,P8-12.




















           III SEA GRASS MEADOWS                  . UN/V16,N1






















IV  Diatom Reading                         NAME......................................................................................PD....

1. How is a resource diatoms have found that few others have found exploited?

2. How does silica help benthic diatoms in their environment?

3. What is the current hypothesis of diatom evolution?

4. What 2 problems did coccolithophores solve?

5. What energy benefit do diatoms derive by using silica over CO2 (carbonates)

6. What was used to determine how the species fragmented?

7. Why hasn’t a “super” plankter evolved?










VI Red Tide Update Reading.                                  

1.  On 3/6/96 what were red tide conditions for the west coast of Florida?

2.  For a MODERATE level of red tide, how many cells per liter are found?  What type of effects would this have?

3.  What organisms cause red tides?

4.  How does a red tide kill fish?

5. How would it effect you along the shoreline?

6.  Are red tides caused by pollution or is it a natural process?

7.  What role does the red tide organsim play in the environment?

8.  What is the name of the organism that causes red tides along Florida’s west coast?

9.  Where do these organisms come from?

10.  How does the red tide effect humans? marine life?

11.  What marine organisms are safe to eat after a red tide?  Why?

12.  Which organisms are UNsafe to eat after a red tide?  why?

13.  What are the 20 toxins derivitives of?

14.  What are the 4 diseases of shellfish poissioning?

15.  What are some symptom,s of these diseases and what is the time frame of each?

16.  What type of foods can be affected?

17.  Why is it hard to measure the true incidence of the disease?

18.  Why are there few outbreaks of PSP in the US?

19.  What type of outbreaks can occur in Florida?


VI B RED TIDES   other one        Questions:

1.  What is a red tide?

2.  What is the relation between red tides and poisonous shellfish?

3.  Is the absence of a red tide mean shellfish are safe to eat?  Explain.

4.  What protection does the public have against paralytic shellfish poisoning?

5.  What precautions should the public take in gathering shellfish?


VII  Bad Algae

1. What is being insinuated by the statement that Algae is the feral pig of Hawaii’s marine environment?

2. How do the alien marine plants get to the waters of Hawaii?

3. What are the plans to help the environment recover?

4. Which algae is competing with native seagrass?