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