Marine Ecology
The oceans are populated by uncounted millions of species, most of which have not yet been identified.
Marine ecology is the study of relationships between species and their environments.
The marine environment consists of nonliving abiotic factors such as water, light, temperature, pH, salinity,
substratum, nutrient supply, dissolved gases (DO), pressures, tides and currents and living biotic
factors.
A species is an organism that possess similar inherited characteristics and have the ability to interbreed and
produce fertile offspring.
A population consists of a group of individuals of one species living in a particular area.
A community is several interacting populations in a particular area.
An ecosystem encompasses the interacting populations (community) in an area along with the abiotic or physical
factors of the area.
Ecosystems require a source of energy. The sun is the source of energy for most ecosystems.
Ecosystems must cycle nutrients between the abiotic and biotic environments.
Habitats
The place where a population lives is called its habitat.
The area that is covered and uncovered during the cycles of the tide is known as the intertidal zone.
Ecologists recognize two major divisions of the marine world, the pelagic zone (open water) and
the benthic zone (ocean bottom).
The pelagic zone can be divided vertically into the photic or light zone (down to 200 m) and the aphotic zone
which is in darkness down to the abyssal zone (the bottom).
The pelagic or photic zone can be divided horizontally into the neritic zone (over the continental shelf) and the
oceanic zone (open ocean).
The neritic zone is the most productive (ability to produce biomass or living matter) in the ocean due to the
upwelling of nutrients and availability of light.
Feeding
The niche of an organism is its role in the community; how it interacts or uses resources in the community.
Trophic levels are energy or feeding levels of organisms.
Producers are photosynthetic organisms that produce food (sugar). Producers are known as autotrophs
because they produce their own food. Producers are at the base of the biomass or energy pyramids
and are at the bottom of food chains or food webs (interconnected food chains). The producers of the
marine environment are primarily algae, phytoplankton, and larger plants like kelp.
Primary consumers or herbivores are organisms that eat only autotrophs (plant matter).
Secondary consumers or carnivores are organisms that eat primary consumers (animal matter).
Tertiary consumers are the top carnivore eating secondary consumers (animal matter).
Organisms that obtain their nutrients from consuming other organisms are known as heterotrophs.
Omnivores are organisms that consume both plant and animal matter.
Nekton refers to free swimming marine organisms, most of which are consumers.
A predator is an organism that kills and eats another organism (plant or animal), the prey.
Scavengers feed on dead plants and animals that they have not killed.
Decomposers are organisms (bacteria, fungi, protist) that break down organic material into inorganic nutrients
(nitrates NO3 and phosphates PO4)
Only about ten percent of the energy is transferred from one trophic level to the next (producer  primary
consumer  secondary consumer  decomposer) within the energy pyramid.
A few marine species absorb dissolved organic matter through diffusion as their principal source of sustenance.
Since most plant material and detritus (dead material) consists of small particles dispersed in the water, many
marine species are suspension feeders. Many suspension feeders are filter feeders that have a weblike or mat-like structure to capture food particles. Crustaceans such as copepods, mollusks such as
slugs and snails, and many cnidarians such as jellyfish and anemones are suspension or filter feeders.
Larger jellyfish and anemones are primarily carnivorous hunters eating fish and invertebrates.
Sea urchins and nudibranchs (sea slugs) are surface grazers that scrap off algae or detritus as they move.
Symbiotic Relationships
Symbiosis refers to a close nutritional association between two different species.
Mutualism refers to a symbiotic relationship where both organisms benefit.
Commensalism refers to a symbiotic relationship where one organism benefits and the other is unaffected.
Parasitism refers to a symbiotic relationship where one organism benefits to the detriment (harm) of the other.