the Legacy continues…………………….
Gregory R. Mann, Ph.D. {ret.}

Marine Biological Sciences Glossary

This glossary defines words, terms & phrases you may have heard but don’t quite understand. This glossary graphics-bookworm-832650includes terminology used in coastal science, engineering, geology, marine biology, management, oceanography as well as the technologies that characterize, measure, describe or quantify the physical properties, processes and changes of coastal & ocean zones.


Abyssal Plain

The deep ocean floor, an expanse of low relief at depths of 4,000 to 6,000 meters

Abyssopelagic Zone

The 4,000 to 6,000 meter depth zone, seaward of the shelf-slope break


Given a change of a single parameter, a readjustment of the physiology of an organism reaching a new steady state 


Is the correctness of a measure when comparing to a known standard

Age Structure

The relative abundance of different age classes in a population

Aggregated Spatial Distribution

A case where individuals in a space occur in clusters too dense to be explained by chance


Non-reef-building (referring to scleractinian corals)


One of several variants that can occupy a locus on a chromosome 

Allopatric Specification

The differentiation of geographically isolated populations into distinct species


A variant of an enzyme type. These may be variants of a specific enzyme (e.g., cytochrome c) that are the products of a single genetic locus.


Negatively affecting one or several species

Amino Acids

Basic structural unit of proteins

Anadromous Fish

Fish that spends most of their life feeding in the open ocean but that migrates to spawn in freshwater 


Lacking oxygen

Arrow Worms

Members of the phylum Chaetognatha, a group of planktonic carnivores 

Asexual Reproduction

Reproduction of the individual without the production of gametes and zygotes

Assimilation Efficiency

The fraction of ingested food that is absorbed and used in metabolism

Assortative Mating

The mating of a given genotype mates with another genotype at a frequency disproportionate to that expected from random encounter


A horseshoe or circular array of islands, capping a coral reef system perched around an oceanic volcanic seamount


Diminution of light intensity; explained in the ocean, in terms of absorption and scattering

Autotrophic Algae

Algae capable of photosynthesis and growth using only dissolved inorganic nutrients

Auxotrophic Algae

Algae requiring a few organically derived substances, such as vitamins, along with dissolved inorganic nutrients for photosynthesis

Bathypelagic Zone

The 2,000 to 4,000 meter depth zone seaward of the shelf-slope break

Benthic-pelagic Coupling

The cycling of nutrients between the bottom sediments and overlying water column


Organisms that live associated with the sea bottom. Examples include burrowing clams, sea grasses, sea urchins, acorn barnacles


A broad area of low relief in the upper part of a beach

Between-Habitat Comparison

A contrast of diversity in two localities of differing habitat type (e.g., sand versus mud bottoms

Biogenically Reworked Zone

The depth zone within a sediment, that is actively burrowed by benthic organisms

Biogenic Graded Bedding

A regular change of sediment median grain size with depth below the sediment-water interface caused by the activities of burrowing organisms


Light emission often as flashes, by many marine organisms

Blood Pigment

A molecule used by an organism to transport oxygen efficiently, usually in a circulatory system (e.g., hemoglobin)

Bloom (Phytoplankton)

A population burst of phytoplankton that remains within a defined part of the water column

Bohr Effect

When blood pH decreases, the ability of hemoglobin to bind to oxygen decreases. An adaptation to release oxygen in the oxygen starved tissues in capillaries where respiratory carbon dioxide lowers blood pH


Pertaining to the Northern Hemisphere, north temperate zone


Capable of penetrating a solid substratum by scraping or chemical dissolution

Bottom-Up Control

Refers to food webs and a control of a population that comes from change lower in a food web (e.g., control of a population of mussels by abundance of phytoplankton food)

Boundary Layer

A layer of fluid near a surface, where flow is affected by viscous properties of the fluid

Brackish Sea

Semi-enclosed water body of large extent in which tidal stirring and seaward flow of freshwater do not exert enough of a mixing effect to prevent the body of water from having its own internal circulation pattern


Organisms that feed by scraping thin layers of living organisms from the surface of the substratum (eg., periwinkles feeding on rock-surface diatom films; sea urchins scraping a thin, filmy sponge colony from a rock)


Made of calcium carbonate

Carrying Capacity

The total number of individuals of a population that a given environment can sustain


An organism that captures & consumes animals

Catadromous Fish

Fish that spawns in saltwater but feed and spends most of its life in estuarine or freshwater

Character Displacement

A pattern in which 2 species with overlapping ecological requirements differ more when they co-occur than when they do not


Primary production of organic matter, using various substances instead of light as an energy source; confined to a few groups of microorganisms


Grams of chloride ions per 1,000 grams of seawater


In eukaryotic organisms, the cellular organelle in which photosynthesis takes place


A tree-like diagram showing evolutionary relationships

Coastal Reef

A coral reef occurring near and parallel to a coastline

Comb Jellies

Members of the phylum Ctenophora, a group of gelatinous forms feeding on smaller zooplankton


Having benefit for one member of a two-species association but neither positive nor negative effect on the other

Compensation Depth

The depth of the compensation light intensity

Compensation Light Intensity

That light intensity at which oxygen evolved from a photosynthesizing organism equals that consumed in its respiration


An interaction between or among two or more individuals or species in which exploitation of resources by one affects any others negatively

Complex Life Cycle

A life cycle that consists of several distinct stages (e.g., larva and adult)


An organism whose physiological state (e.g., body temperature) is identical to, and varies identically with, that of the external environment

Continental Drift

Horizontal movement of continents located in plates moving via sea-floor spreading

Continental Shelf

A broad expanse of ocean bottom sloping gently and seaward from the shoreline to the shelf-slope break at a depth of 100 to 200 meters


The contact at the sea surface between two water masses converging, one plunging below the other


Order of crustaceans found often in the plankton


Feeding on fecal material

Coral Reef

A wave-resistant structure resulting from cementation processes and the skeletal construction of hermatypic corals, calcareous algae and other calcium carbonate-secreting organisms


Tubular benthic sampling device that is plunged into the bottom in order to obtain a vertically oriented cylindrical sample

Coriolis Effect

The deflection of air or water bodies, relative to the solid earth beneath as a result of the earth’s eastward rotation

Counter-Current Exchange Mechanism

Mechanism by which two vessels are set side by side with fluid flowing in opposite directions, allowing efficient uptake and retention of heat, oxygen or gas depending upon the type of ex-changer


Condition of organisms in the water column that are dark-colored on top but light-colored on the bottom


Having bio-luminescent organs that are concentrated on the ventral surface so as to increase the effect of counter-shading

Critical Depth

That depth above which total integrated photosynthetic rate equals total integrated respiration of photo-synthesizers

Critical Salinity

A salinity of approximately 5% to 8% that marks a minimum of species richness in an estuarine system

Daily Estuary

An estuary in which tidal movements cause substantial changes in salinity at any one location on a daily basis

Deep Layer

The layer extending from the lowest part of the thermocline to the bottom

Deep-Scattering Layer

Well-defined horizon in the ocean that reflects sonar; indicates a layer usually consisting of fishes, squid or other larger zooplankton


Referring to numerical characteristics of a population (e.g., population size, age structure)


Grams of seawater per milliliter of fluid

Density-Dependent Factors

Factors, such as resource availability, that vary with population density

Deposit Feeder

An organism that derives its nutrition by consuming some fraction of a soft sediment


Particulate material that enters into a marine or aquatic system


Dominant planktonic algal form with siliceous test, occurring as a single cell or as a chain of cells


The net movement of units of a substance from areas of higher concentration to areas of lower concentration of that substance

Digestion Efficiency

The fraction of living food that does not survive passage through a predator’s gut


Dominant planktonic algal form, occurring as a single cell, often biflagellate

Directional Selection

Preferential change in a population, favoring the increase in frequency of one allele over another

Dissolved Organic Matter

Dissolved molecules derived from degradation of dead organisms or excretion of molecules synthesized by organisms


A rapid change in an environment that greatly alters a previously persistent biological community


A parameter describing in combination, the species richness and evenness of a collection of species

Diversity Gradient

A regular change in diversity correlated with a geographic space or gradient of some environmental factor

Ekman Circulation

Movement of surface water at an angle from the wind as a result of the Coriolis effect

El Niño-Southern Oscillation

Condition in which warm surface water moves into the eastern Pacific, collapsing up-welling and increasing surface-water temperatures and precipitation along the west coast of North & South America


The departure of individuals from a given area


Being symbiotic and living within the body of an individual of the associated species

Environmental Stress

Variously defined as (a) an environmental change to which an organism cannot acclimate and (b) an environmental change that increases the probability of death

Epibenthic (Epifaunal or Epifloral)

Living on the surface of the bottom

Epidemic Spawning

Simultaneous shedding of gametes by a large number of individuals

Epipelagic Zone

The 1 to 150 meter depth zone, seaward of the shelf-slope break


Microalgal organism living on a surface (e.g., on a seaweed frond)

Estuarine Flow

Seaward flow of low-salinity surface water over a deeper and higher-salinity layer

Estuarine Realms

Large coastal water regions that have geographic continuity,are bounded landward by a stretch of coastline with fresh-water input and are bounded seaward by a salinity front


A semi-enclosed body of water that has a free connection with the open sea and within which seawater is diluted measurably with freshwater that is derived from land drainage


Member of an order of holoplanktonic crustacea


Water bodies or habitats having high concentrations of nutrients


The component of diversity accounting for the degree to which all species are equal in abundance, as opposed to strong dominance by one or a few species

Fecal Coliform Bacteria

Technically, all the facultative anaerobic gram negative non-spore forming rod shaped bacteria that fermet lactose in EC medium with gas production within 24h at 44.5 degrees °C


The number of eggs produced per female per unit time (often: per spawning season)

Foliose Coral

A coral whose skeletal form approximates that of a broad, flattened plate

Food Chain

An abstraction describing the network of feeding relationships in a community as a series of links of trophic levels, such as primary producers, herbivores and primary carnivores

Food Chain Efficiency

Amount of energy of some other quantity extracted from a trophic level, divided by the amount of energy produced by the next-lower trophic level

Food Web

A network describing the feeding interactions of the species in an area


Protozoan group, individuals of which usually secrete a calcareous test; both planktonic and benthic representatives

Founder Principle

A small colonizing population is genetically unrepresentative of the source of population


An increase of water flow into an estuary during the late winter or spring, owing to increased precipitation and snow melt in the watershed


A major discontinuity separating ocean currents and water masses in any combination

Fugitive Species

A species adapted to colonize newly disturbed habitats


Haploid stage in the life cycle of a plant

Generation Time

The time period from birth to average age of reproduction

Genetic Drift

Changes in allele frequencies that can be ascribed to random effects

Genetic Locus

A location on a chromosome (possibly of a diploid organism with variants that segregate according to the rules of Mendelian heredity)

Genetic Polymorphism

Presence of several genetically controlled variants in a population


The genetic makeup of an organism with respect to a given genetic locus, the alleles it carries


The level of the taxonomic hierarchy above the species but below the family level

Geostrophic Flow

Movement of water in the oceans as a combined response to the Coriolis effect and gravitational forces created by an uneven sea surface


Moving in response to the earth’s gravitational field

Geographic Information System

A system that allows automatic location of information suitable for mapping and usually involves a software system that takes geographic position data and other data (e.g., type of bottom sediment) in order to create a map

Global Warming

Predicted increase in the earth’s oceanic and atmospheric temperature, owing to additions of carbon dioxide to the atmosphere, as a result of human activities

Global Positioning System

An electronic device that uses positioning signals from satellites in order to locate precisely latitude and longitude


Benthic sampling device with two or more curved metal plates designed to converge when the sampler hits bottom and grab a specified volume of bottom sediment


A predator that consumes organisms far smaller than itself (e.g., copepods graze on diatoms)

Greenhouse Effect

Carbon dioxide traps solar-derived heat in the atmosphere near the earth

Gregarious Settling

Settlement of larvae that have been attracted to members of their own species

Gross Primary Productivity

The total primary production, not counting the loss in respiration


A group of species, possibly unrelated taxonomically, that exploit overlapping resources


Major cyclonic surface current systems in the oceans


Depth zone within which salinity changes maximally

Hardy-Weinberg Law

Law that states that the frequencies of genotypes in a population at a locus are determined by random mating and allele frequency


An organism that consumes plants

Harmful Algal Bloom

A bloom of (usually) planktonic micro-algae belonging to a strain of a species that has a toxic harmful to marine organisms or humans consuming marine organisms

Heritable Character

A morphological character whose given state can be explained partially in terms of the genotype of the individual


An individual capable of producing both eggs and sperm during its lifetime



Heterotrophic Algae

Algae that take up organic molecules as a primary source of nutrition


With respect to a given genetic locus, a diploid individual carrying two different alleles

Highly Stratified Estuary

An estuary having a distinct surface layer of fresh or very-low-salinity water, capping a deeper layer of higher salinity, more oceanic water


A multiple-bar diagram representing the frequency distribution of a group as a function of some variable


Organisms spending all their life in the water column and not on or in the sea bed


An organism that regulates its body temperature despite changes in the external environmental temperature


With respect to a given genetic locus, a diploid individual carrying 2 identical alleles


Referring to the arrangement and movement of bodies of water, such as currents and water masses

Hydrothermal Vents

Sites in the deep ocean floor where hot, sulfur-rich water is released from geothermally heated rock


A refutable statement about one or a series of phenomena


Living within a soft sediment and being large enough to displace sedimentary grains

Inter-specific Competition

Condition in which one species’ exploitation of a limiting resource negatively affects another species


Living in the pore spaces among sedimentary grains in a soft sediment


Having the same overall concentration of dissolved substances as a given reference solution

Keystone Species

A predator at the top of a food web, or discrete sub-web, capable of consuming organisms of more than one trophic level beneath it

La Niña

Is the coupled ocean-atmosphere phenomenon that is the counterpart of El Niño as part of the broader El Niño–Southern Oscillation climate pattern

Laminar Flow

The movement of a fluid where movement of the entire fluid is regular and with parallel streamlines


A discrete stage in many species, beginning with zygote formation and ending with metamorphosis


A group of planktonic tunicates that secrete a gelatinous house, used to strain unsuitable particles (large particles are rejected) with an inner filter apparatus of the house, the so-called food trap or particle-collecting apparatus, is used to retain food particles


The value of a given experimental variable required to cause 50% mortality


The loss of soluble material from decaying organisms

Lecithotrophic Larva

A planktonic-dispersing larva that lives off yolk supplied via the egg


The side of an island opposite from the one facing a persistent wind

Life Table

A table summarizing statistics of a population, such as survival and reproduction, all broken down according to age classes


Accumulations of dead leaves in various states of fragmentation and decomposition

Logistic Population Growth

Population growth that is modulated by the population size relative to carrying capacity

Long-Shore Current

A current moving parallel to a shoreline


Benthic organisms (animals or plants) whose shortest dimension is greater than or equal to 0.5 millimeters


Animals whose shortest dimension is greater than or equal to 0.5 millimeters


An individual alga large enough to be seen easily with the unaided eye


Planktonic organisms that are 200-2,000 micrometers in size

Mainstream Flow

The flow in a part of the fluid (e.g., in a tidal creek) that is well above the bottom or well away from a surface and essentially not under the influence of the boundary layer

Mangrove Forest

A shoreline ecosystem dominated by mangrove trees, with associated mud flats

Marine Snow

Fragile organic aggregates, resulting from the collision of dissolved organic molecules or from the degradation of gelatinous substances such as larvacean houses

Marine Protected Area

A conservation geographic unit designed to protect crucial communities and to provide reproductive reserves for fisheries that hopefully will disperse over wider areas

Maximum Sustainable Yield

In fisheries biology, the maximum catch obtainable per unit time under the appropriate fishing rate


Benthic organisms (animals or plants) whose shortest dimension is less than 0.5 millimeters but greater than or equal to 0.1 millimeters


Animals whose shortest dimension is less than 0.5 millimeters but greater than or equal to 0.1 millimeters


Planktonic organisms that are greater than or equal to 2,000 micrometers in size


Organisms that spend part of their time in the plankton but also spend time in the benthos (e.g., planktonic larvae of benthic invertebrates)


The 150-2,000 meter depth zone, seaward of the shelf-slope break

Metabolic Rate

The overall rate of biochemical reactions in an organism which is often estimated by rate of oxygen consumption in aerobes


Major developmental change as the larva develops into an immature adult


A group of interconnected sub-populations, usually of sub-equal size and features individuals found in one sub-population which might have been determined by conditions affecting them when they were located in another sub-population


Benthic organisms (animals or plants) whose shortest dimension is less than 0.1 millimeters


Animals whose shortest dimension is less than 0.1 millimeters

Mixing Depth

The water depth to which wind energy evenly mixes the water column


Planktonic organisms that can be classified at several trophic levels and can be photosynthetic but also can ingest other plankton and are heterotrophic

Moderately Stratified Estuary

An estuary in which seaward flow of surface low-salinity water and moderate vertical mixing result in a modest vertical salinity gradient


Refers to a group of species that all have a single common ancestral species

Mucous-Bag Suspension Feeder

Suspension feeder employing a sheet or bag of mucus to trap particles non-selectively


An interaction between two species in which both derive some benefit


Conferring reciprocal benefit to individuals of two different associated species


Planktonic organisms that are 2-20 micrometers in size

Neap Tides

Tides occurring when the vertical range is minimal


Organisms with swimming abilities that permit them to move actively through the water column and to move against currents


Seawater environments landward of the shelf-slope break

Net Primary Productivity

Total primary production, minus the amount consumed in respiration


Planktonic organisms associated with the air-water interface


A general term referring to the range of environmental space occupied by a species

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

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 of water quality aspects such as dissolved oxygen

Nutrient Cycling

The pattern of transfer of nutrients between the components of a food web


Those constituents required by organisms for maintenance and growth


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

Oceanic Ridge

A sinuous ridge rising from the deep-sea floor


Refers to water bodies or habitats with low concentrations of nutrients


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


Deriving from living organisms

Organic Nutrients

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


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


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


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


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


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

The estimation of primary productivity by the measurement of the rate of oxygen increase

Parapatric Specification

The differentiation into distinct species of populations experiencing some gene flow


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 non-mineral constituents of living organisms


A condition in which organisms occur in aggregations


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


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


Chains of amino acids; often portions of a protein molecule

Phenotypic Plasticity

The capacity of an individual to produce different phenotypes under different conditions with 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


Enhanced respiration of plants in the light relative to dark respiration


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


Moving in response to light

Physiological Race

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


The photosynthesizing organisms residing in the plankton


Feeding on planktonic organisms


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


The planktonic larval form produced by scleractinian corals and coelenterates


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


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


Refers to species that have a float protruding above the sea surface such as the Portuguese Man-of-War


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


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


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

Population Density

Number of individuals per unit area or volume


The phylum comprising the sponges


A measure of the salt content of seawater in terms of kilograms of salt per kilograms of water in parts per thousand


Precision is the repeat-ability of a measurement


The consumption of one organism by another


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


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


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

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 seawater, which now happens to be a reference set of diluted seawater samples from the North Atlantic of known salt content


Group of holoplanktonic gastropods


Depth zone within which sea-water density changes maximally


Increase of metabolic rate with an increase of 10 ºC

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

Radiocarbon Technique

The estimation of primary productivity by the measurement of radiocarbon uptake


Protistan phylum, whose members are planktonic and secrete an often elaborate siliceous test


A belt of teeth, found in gastropods and chitons which are used for feeding

Random Spatial Distribution

Situation in which individuals are randomly distributed in a space; probability of an individual’s being located at any given point is the same irrespective of location in the space


The residue of those larvae that have: (1) dispersed; (2) settled at the adult site; (3) made some final movements toward the adult habitat; (4) metamorphosed successfully and (5) survived to be detected by the observer

Redox-Potential Discontinuity

That depth below the sediment-water interface marking the transition from chemically oxidative to reducing processes

Red Tide

A dense outburst of phytoplankton (usually dinoflagellates) often coloring water red brown


A device by which an individual can avoid predation


An organism that can maintain constant some aspect of its physiology (e.g., body temperature) constant despite different and changing properties of the external environment

Renewable Resource

A resource that can be regenerated (e.g., a growing diatom population that is being exploited by a copepod)

Reproductive Effort

The fraction of assimilated nutrients that are devoted to reproductive behavior and gamete production


The smallest amount of change that an instrument can discriminate


A commodity that is required by an organism and is potentially in short supply


Consumption of oxygen in the process of aerobic metabolism

Respiratory Pigment

A molecule, polymer or other complex adapted to bind and transport oxygen efficiently, usually in a circulatory system (e.g., hemoglobin)

Respiratory Quotient

The ratio of moles of carbon dioxide produced to oxygen consumed in respiration

Rete Mirabile

A counter-current exchange structure of capillaries that allows gas uptake in a fish swim bladder

Reverse Bohr Effect

Effect that occurs when lactate builds up in the blood of certain invertebrates and pH decreases, increasing the affinity of hemocyanin for oxygen

Reynolds Number

A number that represents the relative importance of viscous forces and inertial forces in a fluid

Rip Current

A concentrated rapid current moving offshore from a beach fronting a long-shore current


Bottom of low relief at the base of the continental slope


Abbreviation for remotely operated vehicle, usually a submersible tethered to a ship with facilities for video, remote sampling by grabbing arms and precise navigation


Number of kilograms of dissolved salts in one kilogram of seawater, measured in parts per thousand


A group of pelagic tunicates (phylum Urochordata), either colonial or solitary, with buccal and atrial siphons on opposite sides of the body

Salt Marsh

A coastal habitat consisting of salt-resistant plants residing in an organic-rich sediment accrediting toward sea level


An organism that feeds on dead or decomposing animals or macrophytes


Order of coelenterates, usually producing calcareous skeletons with hexameral symmetry

Scope for Growth

The surplus of energy available for growth beyond that required for maintenance


The true Sea Jelly, members of the phylum Cnidaria

Sea-Floor Spreading

The horizontal movement of oceanic crust

Seasonal Estuary

An estuary in which salinity at any one geographic point changes seasonally (e.g., decreases during the spring melt)


Side of an island that faces the direction of wave action generated either by winds or by currents generated by more indirect forces

Secondary Production

The production of living material per unit area (or volume) per unit time by herbivores which are usually expressed as grams carbon per meter square per year


A change in allele frequency over time in a population

Sequential Hermaphrodite

An individual that sequentially produces male and then female gametes or vice versa


Immobile because of an attachment to a substratum


Particulate matter suspended in seawater


Chitinous projections from copepod maxillipeds that trap food particles

Shelf-Slope Break

Line marking a change from the gently inclined continental shelf to the much steeper depth gradient of the continental slope

Sibling Species

Closely related species that are so similar that they are nearly indistinguishable morphologically


Parameter expressing the seawater density and equal to 1 minus the density of seawater, measured at a given temperature and at a pressure of 1 atmosphere


A group of specialized hydrozoan cnidarians, consisting of large planktonic polymorphic colonies


A benthic sampling device designed to slide along the sediment surface, digging into the bottom to a depth of at most a few centimeters


A steep-sloping bottom extending seaward from the edge of the continental shelf and downward toward the rise

Somatic Growth

Growth of the body, exclusive of gametes


The range of scatter of particle sizes about the median grain size of a sediment

Space Limited

Description of a situation in which space is a limiting resource

Spatial Auto-Correlation

A situation in which some parameter at any location (e.g., population density) can be predicted through a knowledge of the values of the parameter in other locations

Spatial Distribution

The arrangement of individuals in a space


The process of formation of new species


A population or group of populations that are in reproductive contact but are re-productively isolated from all other populations

Species-Area Effect

A regular logarithmic relationship between the number of species in a confined geographic area (e.g., an island) and the area in which the species occur

Species Richness

The number of species in an area or biological collection


Diploid stage in the life cycle of a plant

Spring Diatom Increase

The major rapid population increase of diatoms, occurring in the spring in temperate-boreal latitudes

Spring Tides

Fortnightly tides occurring when the vertical tidal range is maximum

Stability-Time Hypothesis

Hypothesis that states that higher diversity occurs in habitats that are ancient and stable environmentally

Standing Crop

The amount of living material per unit area or volume; may be expressed as grams of carbon and total dry weight

Stock Recruitment Models

Fishery models that predict the amount of juvenile recruitment as a function of the parent stock


In benthos, the presence of different infaunal species at distinct respective horizons below the sediment-water interface


Refers to the portion of the temperate zone closest to the equator


A predictable ordering of a dominance of a species or groups of species following the opening of an environment to biological colonization

Surface Layer

The layer of the ocean extending from the surface to a depth above which the ocean is homogeneous due to wind mixing

Survivor-Ship Curve

The curve describing changes of mortality rate as a function of age

Suspension Feeder

An organism that feeds by capturing particles suspended in the water column

Swash Rider

Invertebrate that can migrate up and down shore with the rising and falling tide, in order to maintain station at a level that is moist but not overly washed by the waves

Teleplanic Larva

Larva capable of dispersal over long distances, such as across oceans


Pertaining to the latitudinal belt between 23º 27′ and 66º 33′ north or south latitude

Tentacle-Tube-Foot Suspension Feeder

Suspension feeder that traps particles on distinct tentacles or tube feet (in echinoderms)

Terminal Anchor

In hydraulically burrowing organisms: any device used to anchor the leading portion of the burrower, permitting muscular contraction to drag the rest of the body into the sediment


Defense of a specified location against intruders

Tertiary Production

The production of living material per unit area (or volume) per unit time by organisms consuming the herbivores


Depth zone within which temperature changes maximally

Thermohaline Circulation

Movement of seawater that is controlled by density differences that are largely explained in terms of temperature and salinity

Tidal Current

A water current generated by regularly varying tidal forces


Periodic movement of water resulting from gravitational attraction between the earth, sun and moon

Top-Down Control

Refers to food webs where control of a population is mainly explained by consumption by a species or group of species at higher levels of the food chain (e.g., population change of population of Mussels controlled by Sea Star predation)

Trade Winds

Persistent winds at low latitudes in both the Northern & Southern hemispheres, blowing toward the west and the equator


Deep and sinuous depression in the ocean floor, usually seaward of a continental margin or an arcuate group of volcanic islands

Trophic Level

In a food chain, a level containing organisms of identical feeding habits with respect to the chain (e.g., herbivores)


Being within the latitudinal zone bounded by the two tropics (23º 27′ north and south latitude)


The weight of particulate matter per unit volume of seawater


Planktonic organisms that are less than 2 micrometers in size

Uniform Spatial Distribution

Situation in which individuals are more evenly spread in space than would be expected on the basis of chance alone


The movement of nutrient-rich water from a specified depth to the surface

Vertically Homogeneous Estuary

An estuary in which at any given location, wind or tidal mixing homogenizes salinity throughout the water column


Chemical substances required in trace concentrations acting as a co-factor with enzymes in catalyzing biochemical reactions


Refers to development of an organism through the juvenile stage within a parent

Wash Zone

The depth zone in which sediments are disturbed by wave action near the shoreline

Water Mass

A body of water that maintains its identity and can be characterized by such parameters as temperature and salinity


The land area that is drained by a river or estuary and its tributaries


Persistent eastward-equatorial winds in mid-latitudes in both the Northern and Southern Hemispheres


The side of an island that faces a persistent wind

Within-Habitat Comparison

A contrast of diversity between two localities of similar habitat type

Wrack Zone

A bank of accumulated litter at the strand-line

Year-Class Effect

The common domination of a species population by individuals recruited in one reproductive season


Occurrence of single species or groups of species in recognizable bands that might delineate a range of water depth or a range of height in the inter-tidal zone


Animal members of the plankton


A group of dinoflagellates living endosymbiotically in association with one of a variety of invertebrate groups (e.g., corals)

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