Glossary of Marine Biology

 

O P Q

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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. Deriving from living organisms

 

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

 

Overdominance. Selection favoring heterozygotes

 

Oxygen dissociation curve. A curve showing the percent saturation of a blood pigment, such as hemoglobin, as a function of oxygen concentration of the fluid

 

Oxygen minimum layer. A depth zone, usually below the thermocline, in which dissolved oxygen is minimal

 

Oxygen technique (primary productivity). The estimation of primary productivity by the measurement of the rate of oxygen increase

 

Parapatric speciation. The differentiation into distinct species of populations experiencing some gene flow

 

Parasite. An organism living on or in, and negatively affecting, another organism

 

Particulate organic matter. Particulate material in the sea derived from the decomposition of the nonmineral constituents of living organisms

 

Patchiness. A condition in which organisms occur in aggregations

 

Pelagic. Living in the water column seaward of the shelf-slope break

 

Pellets. Compacted aggregations of particles resulting either from egestion (fecal pellets) or from burrow-constructing activities of marine organisms

 

Penetration anchor. In hydraulically burrowing organisms, any device used to penetrate and gain an initial purchase on the sediment so that the body can be thrust in farther

 

Peptides. Chains of amino acids; often portions of a protein molecule

 

pH. Measure of he acidity or basicity of water (-log10 of the activity of hydrogen ions in water)

 

Phenotypic plasticity. The capacity of an individual to produce different phenotypes under different conditions. Non-genetic potential variability within the range of a single individual.

 

Phi scale. Scale used for measuring the grain size of sediments. = -log2 (grain diameter)

 

Photic zone. The depth zone in the ocean extending from the surface to that depth permitting photosynthesis

 

Photorespiration. Enhanced respiration of plants in the light relative to dark respiration

 

Photosynthate. A substance synthesized in the process of photosynthesis

 

Photosynthetic quotient. In photosynthesis, the moles of oxygen produced, divided by the moles of carbon dioxide assimilated

 

Photosynthetic rate. The rate of conversion of dissolved carbon dioxide and bicarbonate ion to photosynthetic product

 

Phototactic. Moving in response to light

 

Physiological race. A geographically defined population of a species that is physiologically distinct from other populations

 

Phytoplankton. The photosynthesizing organisms residing in the plankton

 

Planktivorous. Feeding on planktonic organisms

 

Plankton. Organisms living suspended in the water column and incapable of moving against water currents

 

Planktotrophic larva. Planktonic-dispersing larva that derives its nourishment by feeding in the plankton

 

Planula. The planktonic larval form produced by scleractinian corals and coelenterates

 

Plate. Major section of the earth's crust, bounded by such features as mid-ocean ridges

 

Pleistocene. Period of time, going back to approximately 2 million years before the present, in which alternating periods of glaciation and deglaciation have dominated the earth's climate

 

Pleuston. Refers to plankton that have a float protruding above the sea surface, such as the Portugese man-of-war.

 

Poikilotherm. An organism whose body temperature is identical to that of the external environment

 

Polyp. An individual of a solitary coelenterate or one member of a coelenterate colony

 

Polyphyletic. Refers to a group of species that do not have one common ancestor species

 

Population density. Number of individuals per unit area or volume

 

Porifera. The phylum comprising the sponges.

PPT. A measure of the salt content of sea water in terms of kg salt per kg of water, reckoned in parts per thousand. A conductivity version of this measure is the PSU, which differs from PPT by very little, on the order of 0.02 PSU or less.

Practical Salinity. See PSU

Precision. Precision is the repeatability of a measurement. A measurement can be precise, but not accurate. See Accuracy and Resolution.

 

Predation. The consumption of one organism by another

Predator. An organism that consumes another living organism (carnivores and herbivores are both predators by this definition)

 

Primary producer. An organism capable of using the energy derived from light or a chemical substance in order to manufacture energy-rich organic compounds

 

Primary production. The production of living matter by photosynthesizing organisms or by chemosynthesizing organisms. Usually expressed as grams of carbon per square meter per year

 

Province. A geographically defined area with a characteristic set of species or characteristic percentage representation by given species

 

Protein polymorphism. Presence of several variants of a protein of a given type (e.g., a certain enzyme, such as carboxylase) in a population

 

Pseudofeces. Material rejected by suspension feeders or deposit feeders as potential food before entering the gut

 

PSU. Practical Salinity Units. A measure of the salt content of seawater (practical salinity), based upon electrical conductivity of a sample relative to a reference standard of sea water, which now happens to be a reference set of diluted sea water samples from the North Atlantic of known salt content. See PPT.

 

Pteropods. Group of holoplanktonic gastropods

 

Pycnocline. Depth zone within which sea-water density changes maximally

 

Q10 Increase of metabolic rate with an increase of 10ºC

 

Quantitative genetics. The study of the genetic basis of traits, usually explained in terms of the interaction of a group of genes with the environment