Science / Marine Biology Glossary

Niche Overlap: An overlap in resource requirements by two species

Nitrogen Fixation: The conversion of gaseous nitrogen to nitrate by specialized bacteria.

No-Take Reserves: Geographic areas where by law no one is allowed to fish or collect biological specimens. Rules could apply to one or all species.

Nonrenewable Resource: A resource that is in limited supply and can't be replenished by natural processes, at least not for thousands of years or more. Fossil fuels are nonrenewable resources. Compare renewable resource.

Nuisance Bloom: A rapid increase of one or only a few species of phytoplankton, resulting in densities high enough to cause discoloration of the surface water, possible increase of toxins, and degradation o . . . View Full Definition

Nutrient Cycling: The pattern of transfer of nutrients between the components of a food web

Nutrients: Those constituents required by organisms for maintenance and growth (we use this term in this book in application to plants)

Oceanic: Associated with sea-water environments seaward of the shelf-slope break

Oceanic Ridge: A sinuous ridge rising from the deep-sea floor

Oligotrophic: Refers to water bodies or habitats with low concentrations of nutrients

Omnivory: Being able to feed in more than one distinct way (e.g., an organism capable of carnivory and herbivory)

Optimal Foraging Theory: A theory designed to predict the foraging behavior that maximizes food intake per unit time

Organic: Part of or derived from living organisms. Or a chemical compound that contains carbon as an essential component. Compare inorganic.

Organic Nutrients: Nutrients in the form of molecules synthesized by or originating from other organisms

Osmoconformer: An organism whose body fluids change directly with a change in the concentrations of dissolved ions in the external medium

Osmoregulator: An organism that regulates the concentration of dissolved ions in its body fluids irrespective of changes in the external medium

Osmosis: The movement of pure water across a membrane from a compartment with relatively low dissolved ions to a compartment with higher concentrations of dissolved ions

Outwelling: The outflow of nutrients from an estuary or salt-marsh system to shelf waters

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