Glossary of Marine Biology



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r . The intrinsic rate of increase of a population


Radiocarbon technique (primary productivity). The estimation of primary productivity by the measurement of radiocarbon uptake


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


Radula. A belt of teeth, found in gastropods and chitons. 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


Recruitment. 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


Refuge. A device by which an individual can avoid predation


Regulator. 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


Resolution. The smallest amount of change that an instrument can discriminate. See Accuracy and Precision.


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


Respiration. 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 countercurrent 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. As Re increases, inertial forces become more important. In sea water, Re increaseswith increasing water velocity and with the size of the object in the water


Rip current. A concentrated rapid current moving offshore from a beach fronting a longshore current


Rise. Bottom of low relief at the base of the continental slope


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


Salinity. Number of kg of dissolved salts in one kg g of seawater, measured in parts per thousand. Actually this definition stands alongside another definition based upon water standards whose electrical conductivities are measured. See PPT and PSU.


Salps. 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 accreting toward sea level


Scavenger. An organism that feeds on dead or decomposing animals or macrophytes


Scleractinia. 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


Scyphozoa. the true jellyfish, 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)


Seaward. 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. Usually expressed as grams carbon per meter square per year


Selection. 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


Sessile. Immobile because of an attachment to a substratum


Seston. Particulate matter suspended in seawater


Setules. 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


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


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


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


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


Snow. See marine snow


Somatic growth. Growth of the body, exclusive of gametes


Sorting (of a sediment). 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 autocorrelation. 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


Speciation. The process of formation of new species


Species. A population or group of populations that are in reproductive contact but are reproductively 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


Sporophyte. 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 maximal


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, total dry weight, and so on


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


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


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


Succession. 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


Survivorship 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