Marine Ecology

vEcology is the study of the inter-relationships between the physical and biological aspects of the environment. It is the study of how organisms adapt to their environment and in turn alter it.

Marine Ecology

vMarine ecology is the branch of ecology dealing with the interdependence of all organisms living in the ocean, in shallow coastal waters, and on the seashore.

Classification of Organisms
by Environment

v   horizontal: neritic  |  oceanic

v   vertical:

–  epipelagic (top) / euphotic (good)

–  mesopelagic (middle) / disphotic (low)

–  bathypelagic (deep) / aphotic (without)

–  abyssopelagic (“bottomless”)

Divisions of the Marine Environment

Marine Ecology

vThe marine environment for all organisms consists of non-living, abiotic factors and living, biotic factors


Marine Ecology

vAbiotic The abiotic factors include all the physical, chemical and geological variables that have a bearing on the type of life that can exist in an area. Included are:   water

v Light                          dissolved gases

vpressure              temperature

vtides                                 pH

vcurrents                    salinity

vWaves                 substratum

vexposure to air.      nutrient supply

Basic Ecology

v   factors regulating the distribution and abundance of organisms in the ocean.

v   influence of physical and chemical parameters on organisms in the various ecosystems that constitute the ocean.

v   An ecosystem includes both the living (biotic) and non-living (abiotic) portions of the environment.

–  e.g., coral reefs, the North Pacific Gyre.

Hydrostatic Pressure

v   Hydrostatic pressure is the pressure caused by the height of water.

v   It is a function of the density of water and the total height of the water column.

v   Pressure generally increases at a rate of 1 atm per 10 m of water.

Hydrostatic Pressure

v   enormous in the deep sea yet animals live there. 

v   Animals do not contain gases. 

v   However, mesopelagic fish have gas-filled swim bladders to help maintain neutral buoyancy

–   unable to move rapidly between depths

–   pressure change could cause bladder explode.


v    The distribution of species closely follows the shape of isotherms.

Figure 9-10

v   controls rates of chemical reactions and thus metabolic rates, growth rates, feeding rates, etc.


v   Temperature tolerance varies tremendously among marine organisms. 

v   Young stages are generally less tolerant of large changes.

v   e.g., eggs and young of the California sardine cannot survive below 13 oC.

Figure 9-11

v    Temperature  may indirectly effect a species due to a direct effect on its predator.

–    This is exemplified by the interrela-tionship of clams, crabs, and temperature in Casco Bay, ME.


v   Many of the elements used for growth.

v   Salinity tolerance is also important in limiting distribution.



v   Salinity fluctuates most in coastal waters due to shifts in river flow.

–  Organisms that are mobile can migrate offshore if they cannot tolerate a certain salinity, but attached organisms must cope with the changes or die.

–  clams, oysters, and barnacles manage to survive by closing their shells.


molecules move from high to low concentrations


v   internal fluids of marine organisms also contain salts

v   chemical gradient - salts inside the body relative to the surrounding seawater

v   salts will diffuse from an area of high concentration to low concentration.

–  nutrient uptake and the elimination of waste products.


v   Diffusion is also the mechanism by which water molecules pass through cell membranes.  This is called osmosis.


Marine Ecology


vBiotic The biotic factors are the interactions among living organisms.

Marine Ecology


vZonation Two major divisions in the marine world.

vPelagic zone...waters of the world and

v Benthic zone..the ocean bottom.


Marine Ecology


vThe pelagic zone include the productive coastal waters..neritic zone

vand deep waters of the open ocean..oceanic zone.

vAnother division in the pelagic zone is related to light penetration..the photic and aphotic zones..


Marine Ecology


vThe benthic zone extends from the seashore to the deepest parts of the sea.

vThe material that makes up the bottom is the substratum and the organisms living there are the benthos.

Distribution of
Marine Lifestyles

v   16.7% of Earth’s animals are marine

v   2% inhabit pelagic environment (most of the oceans are cold and dark)

v   98% are benthic!

Marine Ecology

vTides uncover parts of this zone and the area uncovered is the intertidal zone, above is the supratidal zone, affected by salt spray but not covered by sea water.

v Below the intertidal zone is the subtidal zone..submerged and extending seaward.

vThe elevation and slope determines the length of time its exposed.

Marine Ecology

vThis affects organisms living there because some are restricted to zones according to their adaptations to this type of zone (intertidal etc.).

Classification of Organisms
by Lifestyle

v   biota based on lifestyle.

–  plankton (floaters)

–  nekton (swimmers)

–  benthos (bottom dwellers)


v   Plankton are weak swimmers, and are known as drifters, unable to counteract currents. 

–  Phytoplankton (plants)

–  Zooplankton (animals)


v   Nekton are active swimmers capable of counteracting currents

–  Fish

–  Squids

–  Reptiles

–  Birds

–  Mammals

Marine Ecology


Pelagic world include the

drifting organisms...plankton and

the swimmers...nekton.

Marine Ecology

Plankton comprise the large and small organisms that drift or float while tides and currents move them through the water.

Most plankton do have a limited ability to move and can migrate vertically through the water from day to night.

Some drifters can photosynthesize while others are consumers..


Marine Ecology

Plankton is very important as it occupies the first two or three links in the marine food chains.

Nekton use fins, jets of water, strong flippers, flukes and flippers to swim through the water.

Marine Ecology

vOrganisms living in pelagic waters also put up with changes in salinity, temperature etc. and inhabit the coastal areas etc. which fit their adaptations.

v(can withstand large changes (eury-- prefix) and narrow tolerance (steno))


v    Epiflora or epifauna live on the sea bottom.

v   Infauna live in the sea bottom.

v   Benthic plants are restricted to shallow waters - why?

v   Benthic animals occur everywhere from shallow depths to the deep sea.

Marine Ecology

vOther zones include the surface waters of the coastal areas called the neritic zone and the waters of the ocean called the epipelagic zone.

vThe open ocean is less productive than the neritic zone which contains plant plankton, fish larva, invertebrate larva that will eventually end up near the coast.

Marine Ecology

vThe open ocean is divided into zones depending on the amount of light it receives...from the epipelagic layer to the mesopelagic zone 200-1000m in which daytime inhabitants migrate upwards during the night, bringing back nutrients and some exhibit bioluminescence (light producing organs called photophores).

The ocean can also be divided into zones based upon depth of light penetration.

v   The photic zone is the depth where light is sufficient for photosynthesis.

v   The dysphotic zone is where illumination is too weak for photosynthesis.

v   The aphotic zone receives no light from the surface because it is all absorbed by the water above.


Marine Ecology

vThe deep sea layers bathypelagic 1000-4000m and the abyssopelagic zone (below 4000m) have limited food supplies although bacteria have been found that can make their own food.




Marine Ecosystems

v   Ecosystems


v           Ecosystems (or ecological systems) are systems of communities in a large geographical area.


v   In order for an ecosystem to be successful, four things are required:

Marine Ecosystems

•   .An energy source

•  Organisms capable of capturing this energy in the form of organic molecules

•  .Organic material must be available to all other organisms

•   Cycling of nutrients must occur between the abiotic and biotic portions of the system


Marine Ecology


vEnergy transfer is accomplished in a series of steps by groups of organisms known as autotrophs, heterotrophs, and decomposers.

vEach level on the pyramid represents a trophic level.






Marine Ecology

vAutotrophs absorb sunlight energy and transfer inorganic mineral nutrients into organic molecules.

vThe autotrophs of the marine environment include algae and flowering plants and in the deep sea are chemosynthetic bacteria that harness inorganic chemical energy to build organic matter

Marine Ecology

vAUTOTROPHIC food molecules to organisms that can't absorb sunlight.

vHETEROTROPHS Consumers that must rely on primary producers as a source of energy...heterotrophic nutrition.

Marine Ecology

vThe energy stored in the organic molecules is passed to consumers in a series of steps of eating and being eaten and is known as a food chain.

vEach step represents a trophic level and the complex food chains within a community interconnect and is known as a food web.


Marine Ecology

vDECOMPOSERS-- The final trophic level that connects consumer to producer is that of the decomposers.

vThey live on dead plant and animal material and the waste products excreted by living things.

v The nutritional activity of these replenish nutrients that are essential ingredients for primary production.

Marine Ecology

vThe dead and partially decayed plant and animal tissue and organic wastes from the food chain are DETRITUS.

vThis contains an enormous amount of energy and nutrients.

v Many filter/deposit feeding animals use detritus as food.

vSaprophytes decompose detritus completing the cycle.

Marine Ecology


v Primary producers usually outnumber consumers and at each succeeding step of the food chain the numbers decrease.

vThe numerical relationship is called the pyramid of numbers. (base as opposed to each step.)



Marine Ecology

•The energy pyramid is the energy distribution at each trophic level as it passes from producers through the consumers.

• Some energy is lost as it passes to the next level because …………..


Marine Ecology

(a) consumers don't usually consume the entire organism

(b) energy is used to capture food

(c) organisms used energy during their metabolism

v(d) energy is lost as heat.


Marine Ecology

vGenerally only 10% will pass on to the next level. (The shorter the better..)

Marine Ecology

Scavengers..feed on dead plants and animals that they have NOT killed...crabs ripping chunks of flesh from fish on the beach are scavengers.

Most scavengers consume detritus rather than flesh and deep sea animals can feed on both.



Marine Ecology

•Each chain or part of the web serves to link phytoplankton to larger pelagic animals through the zooplankton.

•Herbivorus zooplankton eat phytoplankton while carnivorus zooplankton occupy the third level as secondary consumers.

Marine Ecology

Benthic If the organism resides primarily in or on the substrate and doesn't swim or drift for extended periods as an adult it is considered benthic.

They either burrow , crawl, walk, (motile) or are sessile..permanently affixed to the substrate or each other.

Living on the bottom are epifauna and living within are infauna. The substrate could be a source of food.

Marine Ecology

•Demersal organisms, such as flounder alternate between swimming and resting on the bottom.


Marine Ecology


• Phytoplankton, plant plankton,are the important primary food producers in the pelagic environment.

• The animal members of the plankton are the zooplankton which range from bacteria size to 15m jellyfish.

•Phytoplankton are the trees of the sea which float near the surface to make the most of the sunlight for photosynthesis

Marine Ecology

•Two forms of phytoplankton, dinoflagellates and diatoms are particularly important as founders in the planktonic food webs because most of the animal life in the oceans depend on these.

• The dinoflagellates are usually found in warmer waters, and the diatoms are usually more abundant in cooler waters.

Marine Ecology

•Other plankton, coccolithophores and silicoflagellates are also abundant as well as blue-green algae (in certain locations it can become the dominant) and green algae but usually in the coastal water (some are in the open ocean as findings of chlorophyll b indicate.

Marine Ecology

•Phytoplankton have adaptations which deal with methods of keeping them in the upper zones to stay in the sunlight..

• Size...small sizes retards sinking, structure...

•Shape/structure of the diatoms effects sinking rate and

•Density...decrease by storing droplets of oil in the cytoplasm

Marine Ecology

•Blooms Although unknown, the availability of nutrients, amount of vertical mixing, salinity, density, temperature, and depth of water affect phytoplankton growth rates.

•Blooms called red tides have occurred in almost all oceans.

Marine Ecology

•Red tides usually refer to the discoloration of the waters as a result of the absorption of light by pigmentation in planktonic organisms.

•The red water usually results from actions of non-toxic organisms and the term red tide is inadequate when used with reference to PSP (paralytic shellfish poisoning) and toxic dinoflagellates will not always discolor the water (too few) but may be numerous enough to toxify shellfish.


Marine Ecology

•But evidence that PSP may be increasing in intensity and spreading to new areas is surfacing.

•About 60 species of dinoflagellates may color offshore waters however only 6 have been shown to produce toxic substances.

•Some toxins, saxitoxin, is 50x more poisonous than curare (used by SA Indians)


Marine Ecology

•Repeated cell divisions as result of long period of dry weather following a violent storm which stirs up bottom sediments, reach concentrations of 25,000 dinoflagellates /ml of water.

Marine Ecology

•Bioluminescent phytoplankton bloom in the ocean and produce a bluish-green light.

• Phosphorescent Bay in Puerto Rico contains high concentrations of bioluminescent phytoplankton throughout the year.

• One type, Noctiluca sp., by  disturbing water, passing of boat, wave breaking, initiates bioluminescence.

Marine Ecology

•Zooplankton..500,000 per gal and range in size from single cell to jellyfish.

•Almost any animal phylum can be found wandering through the sea but the most common are Copepods (95%).

• Two types of zooplankton....Holoplankton or permanent members of the community and temporary residents called Meroplankton.




Marine Ecology

•Holoplankton have evolved efficient means of remaining adrift...special appendages, droplets of oil and wax, tread water, jelly-like layer, gas-filled float.

Marine Ecology

•. A majority of inverts and many vertebrates have planktonic stages (meroplankton).

• Drifting eggs and larva of fish, crabs, barnacles, worms, clams, snails, sponges, lobsters, etc.

•They use the water mass to feed and disperse their planktonic young to new habitats.

Marine Ecology

•The reproductive cycles often coincide with maximum concentrations of food and favorable currents.

•EX. polar oceans, spring phytoplankton bloom triggers increases in zooplankton coinciding with migration patterns of whales, seals and penguins.

Marine Ecology

•Vertical migrations refers to Copepods and other zooplankton moving up toward the surface to feed in the evening responding to the changing light reducing predation during the day because they are in deeper layers.

• This varies among species but light, shadows and pigments of phytoplankton (color) helps zooplankton locate food.


Marine Ecology

•Thus buoyancy, mobility, vertical migration, and chemical sensing enables Copepods to search open water for concentrations of food.

•Trophic levels in zooplankton communities-- Energy incorporated in organic molecules by marine plants flows to the zooplankton community in a complex series of interconnected food chains.

Marine Ecology

•Nekton Free swimming organisms equipped to direct their movements through the sea including cephalopods, fishes, marine mammals, sea turtles and marine birds.

•Many are at the top of the trophic levels either as carnivores or herbivores without natural predators..except man.

•Swimming allows escape or movement toward food and methods of locomotion are very diverse, from jets of water, flippers, large tail fins and flukes.

Marine Ecology

•Planktivorous nekton are animals that feed directly on plankton such as baleen whales and some fish.

•Herbivorous Nekton are ones that feed on large seaweeds and sea grasses (turtles and manatees)

•Carnivorous Nekton are the dominant carnivorous animals of the pelagic environment and generally these animals migrate great distances in search of food. 

Marine Ecology


• Food production occurs mainly through Photosynthesis.

• It is measured and called Primary food production which will occur in the photic zone as phytoplankton manufacture organic matter during photosynthesis.

• The primary productivity varies seasonally and geographically.

• It is measured as g of Carbon/m2/year. (Long Island Sound 500g, Antarctica. 2-400g etc.)


Marine Ecology

•It seems that the more vertical mixing that occurs in an area, the higher the primary production is because in the tropics where there is little vertical mixing, their Primary Productivity is low because of the depletion of nutrients in the surface waters.

Marine Ecology

•Primary productivity decreases as depth increases as there is less light and less photosynthesis.

•Accessory pigments in algae enable them to make the most of the little light that does get to them.

•The boundary where the food production (photosynthesis) is balanced out by the rate of respiration (the use of the food) is called the compensation depth.


Marine Ecology

•Copepods metabolize droplets of diatom oil to liquid waxes and fats which can be used as long-term energy reserves. (waxes; long/fats short).

•It is these waxes and oils that get used for blubber when the Copepods/krill are fed on by marine birds and mammals.

Marine Ecology

•Detritus food chains are also secondary when decaying material enter the detritus chain as decaying materials, wastes, pieces of animal tissue.

•The swarms of Copepods feeding on diatoms excrete packets of partially digested matter called fecal pellets.

Marine Ecology

•These pellets usually aren't eaten by other pelagic organisms and provide food for bacteria when they settle as well as a host of detritus feeders on the bottom (transfer of energy from the top to the bottom)

Marine Ecology

•While there is a loss of energy to the grazers, many consumers are adapted to feed on detritus thereby returning energy to the food chains.

•Chitonolytic bacteria can break down chitin which represents an enormous source of organic carbon.

•TK 9/16/2002

Marine Ecology

•These bacteria play a big role in making sure the billions of tons of chitin produced in the marine environment each year get broken down and their nutrients are returned to the primary food makers.

Marine Ecology

Symbiotic...refers to close nutritional relationship between two different species...

commensalism- one benefits

mutualism both benefit and parasitism

one benefits at hosts expense.

Marine Ecology

Population Cycles ..density or numbers of individuals depends on

1. natality or rate of production of new organisms and

2. mortality..rate of death in a population.

Marine Ecology

Now to be stable the two must be in equilibrium but under favorable conditions, populations can increase numbers (can be seasonal and geographical) but this also increases mortality because of decreased food supply and living space and increased predation.

If mortality is greater, then the population decreases.

Marine Ecology

These favorable conditions depend on

1. high concentration of nutrient rich water,

2. rapid cycling of materials by decomposers,

3. high numbers or rapid turnover of producer organisms

4. Light

5. nutrients including nitrate, phosphate, silicon, potassium, magnesium, copper, iron.

Marine Ecology

Silicon dioxide needed for outer glass covering of diatoms and forms internal structural parts of sponges, K and NO4 and PO4 needed in plant proteins, lipids and carbohydrates during photosynthesis.

The nutrients can be considered a limiting factor as well as pH temp. light , depth salinity nesting sites and predation.