3 Homework-Answer this question and email it to  biovcc@Gmail.com

HW 3  There are marked differences in the type of organisms found at four different locations at the same tidal height along ta rocky shore.  What might account for this? Mention 3 possible explanations.



 Beaches and Rocky Shores


•The beach is a region between the high and low waterlines that is covered by sand or some other unconsolidated material.


•Turbulent waves along the shore usually remove mud from the beaches and hold it in suspension. 

•As the fine particles of mud are transported to deeper or less turbulent water, they settle on the bottom.


•A beach is described in terms of the average size of its sand particles, the range and distribution of these particles, the elevation and width of the berm,


•the slope of the foreshore and the slope of the inshore.


•Waves are primarily responsible for moving sand away from river mouths and along the coast.


•As a wave breaks, the sudden release of energy within a small area causes turbulence that dislodges sand particles.


•Waves approach the coast from almost any angle and if it comes in from the north say, then the water runs back to the sea in a southernly direction. 

•This forms what is known as the longshore current or littoral drift.  This current provides longshore transport that carries sand along the shore. Beach sand is always in transit from one place to another



•Size and power of waves affect the rates of longshore transport.

•On the east and west coast, LST runs in one direction usually, and that is south because most waves come from northern storms. 

•Sand is transported south at a rate of 150,000 to 1,600,000 m3/yr.


•Human activities have had both beneficial and harmful effects on the coastline. 

•Some activities include damming of rivers, land recovery programmers, dredging of inlets, development of dune areas and construction of erosion control structures.


•Erosion Control Structures

•Jetties built to prevent longshore currents from filling inlets or to bring about the deposition of sediments benefit the property immediately upcurrent but may cause the downcurrent shoreline to recede.


•Groins, small piles of rocks at right angles to the beach transform the longshore current into a zig zag current that destroys the linear form of the coast..



•When the first groin or jetty was constructed, it was observed to collect the sand on the upcurrent side of the jetty. 

•This became a way to enlarge an otherwise eroding beach!

•The removal of beach sediment is erosion and addition of material is deposition.



•Unfortunately, the jetty was interrupting the longshore current carrying the sand and while erosion was still occurring downcurrent, no more sand was being deposited so downcurrent to the jetty started to erode.

•“Solution?”—build another jetty..and that’s what they did…


•Tides produce short-term fluctuations along coastlines but sea level changes are long-term..and there lies the problem.


•To counter the erosion of the beaches and coastline due to sea-level rise, jetties were built along the coasts to “stabilize” the beaches. 



•From dumping loads of sand along the beach to pumping sand back in from the ocean, billion$ of dollar$ have and will be spent trying to rebuild our beaches.

•In Ocean City, NJ, attempts were made to pump sand in from the ocean.



•This time, beaches were rebuild taking size of sand grains, and replacing enough sand so it just wouldn’t drop offshore.


•1st Picture


•Looking south from the last picture..


•1st Picture

•1st Picture


•To try and stablize the beaches, fences were placed in the upper part of the beach to collect the sand from the beach when the wind blows.  Dune grass was planted to stabilize the sand…and in turn collects sand as it moves across the dune and keeps growing..


•Dunes are a mobile physical medium and ecological environment, frontal dunes are part of sediment exchange.

•They can migrate inland or seaward and should be allowed to move…and do…

•The next pictures are the “DUNES” built along the newly built beaches.

•Next….Sand Dunes…….


•Rocky Shores

•The rocky intertidal habitat has a very rich diversity of organisms especially in temperate climates.

•Attachment is critical and competition for space is a prime factor.

•The organisms are well adapted for withstanding tremendous SURF-EXPOSURE and…….

•Rocky Shores

•also tolerance to DESICCATION (low tides during the summer days),

•temperature changes, and

•salinity changes( rainfall during low tide).



•Rocky Shores

•When the tide goes out, the phenomenon of ZONATION is manifested - horizontal bands or zones of organisms.

•This is true for both plants and animals.

•Each zone has a particular color or texture from the organisms inhabiting that particular zone.

•Rocky Shores

•UNIVERSAL PATTERNS of zonation, occurring throughout the world, have been recognized, such that no matter where you might be observing the exposed intertidal, the middle littoral zone will often have a community of barnacles, mussels, and rockweeds




•Rocky Shores

•The nature of the rock between the tide marks may exert a certain selective influence on the organisms that attempt to colonize it, in the sense that some rocks are more susceptible to the activities of boring organisms and others are not and certain minor variations in zonation may also be attributed to it.


•Rocky Shores

•Rocks between the tidemarks include GRANITE, HARD QUARTZITIC SANDSTONES, SOFT SANDSTONES (calcareous or not), DOLERITE, CONGLOMERATES, LIMESTONES, SLATELIKE ROCKS, and various other materials.


•Rocky Shores

•You see, porous sandstone will hold water longer during low tide than granite and other non-porous rocks and therefore may exhibit a different type of zonation than other rocks nearby.



•Rocky Shores

•Rock texture/rough and smooth does not really seem to have much of an effect unless friability is considered where pieces of rock (bearing attached organisms) may break off.



•Rocky Shores

•            The proximity of sand also affects populations of adjacent rocky areas.

•             In some cases, sands shift a good deal, so that a low rocky reef may be buried under sand at one, and emerged at another time.

•            This does not always kill everything on the reef unless it lasts for a long time.


•Rocky Shores

•Desiccation / drying out plays a role in organisms to the degree which they can withstand exposure to the air between the tidemarks.

•It may affect organisms in two ways:

•it may be intense, but for short duration, or

•less severe, but of repeated occurrence.

•Rocky Shores

•It can be intensified by increased temperature and air movement (and light).

•Rocky Shores

•Factors controlling the distribution of organisms on the PACIFIC coast:

•Predation is #1; also competition, exposure to the waves, desiccation, and rain water.

•On the Washington coast the yearly water temperature change is only 5.5'C (10F).

•Rocky Shores

•East coast intertidal populations are affected dramatically by the relatively LARGE SEASONAL TEMPERATURE CHANGES:

•Predation is also important but less so than in the Pacific


•Rocky Shores

•The Upper intertidal zone: usually termed the LITTORINA ZONE, named after the small herbivorous gastropods (periwinkles) that occupy this zone that must survive long periods of exposure.



•Rocky Shores

•This zone extends higher than the highest tide where there is great exposure with spray from the various waves causing the organisms to extend higher into the littoral zone.

•There may be several species of these snails but each species occupy their specific niche..species 1 are the most tolerant and occupy the highest level  …



•Rocky Shores

•Species 2, less tolerant and occupy the next and so on. (one lower species mimics the air bladders of rockweed).

•There is even a higher zone than the periwinkles and it is occupied by LICHENS (Verrucaria) which occupy a dark zone above the periwinkles and/or blue-green algae (covered with mucilage to prevent total desiccation.



•Rocky Shores

•Middle intertidal zone: barnacles (upper part), rockweed (middle), & mussels (lower) occupy this zone and each will have one distinct advantage in regard to their area over the others.


•Rocky Shores

•            Barnacle life cycle

•             eggs hatch into napulus larva

•            molts 6 times and turns into cypris larva

•            cypris larva finds place to attach

•             secretes cement from cement glands on the 1st antennae to attach

•            develop into adult


•Rocky Shores

•Mussels and seaweeds can crowd out the barnacles but the barnacles can tolerate surf and desiccation better, giving them the upper position in the Mid-littoral.


•Rocky Shores

•The rockweeds in the middle of the mid-littoral zone provide a nice moist protective canopy when the tide is out, so many inverts. can survive underneath.

•The green crab hides under it during the day and comes out at night.


•Rocky Shores

•Below the rockweed are beds of mussels (Mytilis) using their byssal threads to attach.

•Their shape allows them to adapt well to the wave force and adductor muscles tightly hold them closed at low tide...protecting them from predators and desiccation.



•Rocky Shores

•Mussels will be preyed on by certain snails, seastars, crabs, shorebirds, lobsters etc. but while the mussels are uncovered for a while, the marine organisms can only get them while they are covered (and birds vice versa) Tough life!


•Rocky Shores

•FORAGING RUNS...the Predation above, which opens up the habitat for other species and thus increases species diversity.

•The greater the diversity, the more links in the food chain of that community.

•Rocky Shores


•There is less time of exposure to air as you get lower into the zone.

•These organisms while less tolerant of air are better adapted to wave exposure.



•Rocky Shores

•Dense strands of kelp can occur here and all this provides living and hiding spaces for a variety of inverts. (hydroids, bryozoans, nudibranches, worms, crabs, tunicates.

•Some are more conspicuous like the sea anemones, sea urchins, and sea stars.

•Rocky Shores

•Some inverts. can BURROW or BORE into hard substrates: rock, coral, wood by either mechanical abrasion or chemical dissolution.

•Some mussels, date mussels, secrete acid and dissolve limestone, gribbles are small wood-boring isopods that simply chew into wood. Teredo (shipworm) are also filter feeders as well as eat wood.

•Rocky Shores

•Tide pools are depressions of varying size in the intertidal such as when the tide is out, standing water is left behind like an oasis for algae and animals.

•They are subjected to great fluctuations in regard to temp. salinity, acidity, dissolved oxygen content...






•Rocky Shores

•The higher the pool is in the littoral zone, the longer the pool will be exposed, or isolated from the flush of the oceans waves.

•Depth in the pool is important, as is the overall size.

•Rocky Shores

•If then tide is out at night, the release of CO2 from the respiring animals and plants will increase (NO Ps) and increase the acidity of the pool.

•During the day, PS will cause the pH to increase

•Rocky Shores

•The larger pools in the mid zones allow the inverts, seastars etc. to live higher up on the rocks and therefore be able to feed in the upper areas longer.

•In California. some kelps get started in these pools but once a series of spring tides in June arrive (esp. sunny days), the species living beyond their limits will be killed off.

•Rocky Shores

•Biological succession: going from bare rock to a mature, or climax community, although nothing is permanent.

•Predation brings about open areas or physical abrasion by logs often destroy communities in the intertidal.

•Rocky Shores

•The term conditioning is used to refer to the process by which a bare rock surface must go through a sequence of first being settled by bacteria and algae and such slime-producing organisms before the larva of barnacles and zygotes of rockweeds will be able to attach themselves.

•Rocky Shores

•Then mussel larva will settle down and crowd out the barnacles and rockweeds restricting them to higher areas.

•Predators and mussels will next move into the picture.





•Rocky Shores

•Trophic structure on the rocky beach community: Primary production is the photosynthetic activity of the BENTHIC seaweeds and also a good part from the phytoplankton being washed over the area whenever the tide is in.


•Rocky Shores

•Also dissolved organic matter and detritus will be a source of nourishment for filter feeding/ suspension feeders/sponges, barnacles, mussels, while the grazers, chitons, periwinkles, limpets, sea urchins are scraping off the benthic flora.


•Rocky Shores

•Tidal fluctuations make for a good contribution coming from outside the narrow confines of the littoral zone and this results in a large biomass or carrying capacity and the numerous predators at various levels that enter this ecosystem and the rich diversity of species and high density of individuals inhabiting the intertidal zone of the rocky coastlines.

•Rocky Shores


•Few features of the shores are more obvious than zonation.

•All shores, no matter how large or small the tidal range (max. 17m Bay of Fundy) have at least some degree of zonation or vertical banding of the organisms living on them.

•Rocky Shores

•Just as plant communities occupy definite bands or zones on mountains corresponding to tolerances to decreasing temperature with increasing elevation, so intertidal communities occupy definite zones on the shore.

•Compared to the mountains though, the shorelines are much compressed vertically.








•Rocky Shores

•Generally where the range of tides is small or where the slope of the beach is steep, the zones are generally narrow. 

•Where the slope of the beach is flat and the range of tides is great, then the zones are wide.


•Rocky Shores

•Heavy wave action widens the zones, both above and below the calm water limits and the upper and lower borders of the zones are less distinct.

•An example of the coast of Vancouver Island where the algae, Porphyra is the highest level (above the highest barnacles)…….

•Rocky Shores

•and grows best in the winter because of the high storm surge and nighttime low tides and its burned off in the summer.

•The barnacle zone is the first clearly demarcated zone at the top of the shore and this zone occurs on almost every shore in the world.

•Rocky Shores

•This is followed by a zone of mixed barnacles and seaweeds, the mid tide region is marked by mussels and goose barnacles and beneath this zone is another of barnacles and algae and several whelks and limpets.


•Rocky Shores

•Below this zone and marking the beginning of the lower intertidal zone is the clearly marked zone of brown algae (kelp) interspersed with chitons,starfish, and surf grass.

•The zones are by no means constant in composition, number, width and these factors vary from season to season, year to year, shore to shore, and even rock to rock.

•Rocky Shores

•The "Universal" scheme of zonation

•After 30 years of studying intertidal zonation throughout the world, (tough job), husband and wife team T.A. and Anne Stephenson published their findings (1949) in which they presented their "universal" scheme of zonation. They attempted to formulate general zonation patterns for the whole world.

•Rocky Shores

•1. Supralittoral zone ..near sea but above the high tide mark with some marine influence (spray)

•2. Supralittoral fringe...upper limit of barnacles (in quantity) to nearest higher convenient landmark (upper limit of Littorina or lower limit of land lichens. Spring tides invade part of this zone.


•Rocky Shores

•3. Midlittoral zone: the entire intertidal areas, from the upper limit of barnacles to upper limits of large brown algae at the lower part of the shore. The barnacle demarcation is an important reference point in the universal scheme.


•Rocky Shores

•4. Infralittoral fringe: the lower fringe of the intertidal ..an area extending from the upper limit of whatever organism sets the lower limit of the midlittoral zone, to the ELWS (extreme low water spring) tide mark, or in areas of waves, to the lowest level visible between waves. Organisms living here cannot tolerate complete emersion but can live in an area of broken emergence through wave action.

•Rocky Shores

•Organisms living here cannot tolerate complete emersion but can live in an area of broken emergence through wave action.

•5. Infralittoral zone: the area between ELWS tidal level and corresponding more or less to the more commonly used "sublittoral" term.


•Rocky Shores

•This pattern pointed out by the Stephensons is sensitive to such factors as wave effects, slope of rocks, differing amounts of sun and shade. However, while shores may differ in relatively minor details as a result of such factors, most still adhere to the basic pattern.


Beach and Rocky Shores Review Answers

1.      it is regularly exposed to air

2. the substrate

3. a great deal of geologic activity

4.     attach themselves to the substrate

5.     higher

6.     living in moist areas at all times

7. a white, ridged shell

8.  filter feeders

9. become more parallel to the shore

10.            space

11.    vertical zonation

12.    physical factors

13.    upper intertidal

14. periwinkles

15. submerging and uncovering by the tides on a regular basis

16. intertidal zone


18.    climax community

19. red, green, and brown seaweeds

20. light

21.    seaweeds

22.   bays and lagoons (calm areas)

23.   is deficient in oxygen

24.   detritus

25    barnacles

26. beach

27. longshore current

28) the angle that waves hit the shoreline 

29 foreshore 

30 erosion /deposition 

31. drying out 

32. zonation

33help increase species diversity

34.   calcium carbonate

34. short term

36 steeper

37. energy//dislodges

38. longshore current or littoral drift

39. moist////capillary 

40 interstidual sand  //cacteria

41.  represent similar organisms present

42.  snails of species littorina live there