Download Introduction to Marine Ecology Lecture Notes

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 web-like 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.