Marine Ecology

Ecology 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.

There are two major marine provinces: the benthonic (bottom) and the pelagic (water column).

• The benthonic environment is divided by depth into the: Intertidal zone, Sublittoral zone, Bathyal zone, Abyssal zone, and the Hadal zone

• The pelagic environment is divided into the Neritic Zone and the Oceanic Zone

9-1 Ocean Habitats

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

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

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

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

9-1 Ocean Habitats

In 1735 Linnaeus developed the taxonomic classification used in zoology.

• The categories are from largest to smallest: Kingdom, Phylum, Class, Order, Family, Genus and Species.

• The name of a species consists of the genus name combined with a trivial name.

• The genus name begins with a capital.

9-2 Classification of Organisms

The five major kingdoms in the ocean are: Monera, Protista, Fungi, Metaphyta and Metazoa.

• Monera are the bacteria and blue-green algae.

• Protista are single-celled organisms with a nucleus.

• Fungi are abundant in the intertidal zone and are important in decomposition.

• Metaphyta are the plants that grow attached to the sea floor.

• Metazoa include all multicellular animals in the ocean.

9-2 Classification of Organisms

Marine organisms can also be classified by lifestyle.• Plankton are the organisms which float in

the water and have no ability to propel themselves against a current.

• They can be divided into phytoplankton (plants) and zooplankton (animals).

• Nekton are active swimmers and include marine fish, reptiles, mammals, birds and others.

• Benthos are the organisms which live on the bottom (epifauna) or within the bottom sediments (infauna).

• Some organisms cross from one lifestyle to another during their life, being pelagic early in life and benthonic later.

9-3 Classification of Lifestyle

Environmental factors in the marine environment include: temperature, salinity, pressure, nutrients, dissolved gases, currents, light, suspended sediments, substrate (bottom material), river inflow, tides and waves.• Ecosystem is the total environment including

the biota (all living organisms) and non-living physical and chemical aspects.

• Temperature can control distribution, degree of activity and reproduction of an organism.

• Salinity can control the distribution of organisms and force them to migrate in response to changes in salinity.

9-4 Basic Ecology

• Hydrostatic pressure is the pressures exerted by a column of water surrounding an organism.

9-4 Basic Ecology

More than 90% of marine plants are algae and most are unicellular and microscopic.

• To photosynthesize (produce organic material from inorganic matter and sunlight) plants must remain within the photic zone.

• Diatoms are single cells enclosed in a siliceous frustrule (shell) that is shaped as a pillbox.

• Dinoflagellates are single cells with two whip-like tails (flagella).

9-5 Selective Adaptive Strategies

Zooplankton include the copepods and foraminifera.

• Copepods are small herbivores (plant-eating organisms) that filter diatoms from the water.

• Foraminifera are single-celled, microscopic organisms which build shells of calcium carbonate.

9-5 Selective Adaptive Strategies

The morphology of fish has evolved to allow them to move through the water easily.• The fish’s body must overcome three types of

drag (resistance): Surface drag, Form drag, and Turbulent drag.

• Speed is dependent upon body length, beat frequency, and the aspect ratio of the caudal fin.

• Aspect ratio is the ratio of the square of the caudal fin height to caudal fin area: AR = (Caudal Fin Height)2/Caudal Fin Area

• There are three basic body forms, each adapted to a different life style.

• There is a strong correlation between predation success and body form.

9-5 Selective Adaptive Strategies

Intertidal benthonic communities generally display vertical zonation that parallels sea level.

• Zonation reflects the amount of time the area is submerged and the ability of the organism to survive the stress of exposure.

• Benthonic communities also vary in response to substrate (bottom material).

9-5 Selective Adaptive Strategies