Glossary - Freshwater Ecology: Concepts and Environmental Applications - page 498

Rhithron, brook environment
Rice paddies, wetlands that allow for rice
culture
Riffle, a rapidly flowing portion of a river or
stream where the influence of the bottom
can be seen at the surface
Riparian, related to or located on the bank of
a stream or river
Rising limb, the portion of the hydrograph that
is increasing during or immediately after
a storm
River continuum concept, an ecosystem-based
view of streams and rivers as a continuum
from small forested headwater streams to
large rivers
Run, a portion of a river or stream where flow
is rapid, but the surface is smooth
Runoff coefficient, the proportion of precipita-
tion falling on a catchment that enters the
river or stream without entering the soil
Salinity, amount of inorganic salts dissolved in
water, stated as %, ‰, g kg 1 , ppm, mg
liter 1 , mg dm 3 ; in seawater, closely con-
nected to Cl concentration and conduc-
tance; salinity of seawater is approximately
3.5% (35,000 ppm)
Saltern, saline water with a similar composi-
tion to seawater
Sapropel, reduced, nondescript sediment of pol-
luted or hypereutrophic lakes; black with
FeS, often odorous with H 2 S
Saprophytes, heterotrophs that decompose or-
ganic carbon
Saturating concentration, equilibrium concen-
tration when pure water is left in full con-
tact with the atmosphere or in full contact
with an undissolved substance
Scalar collector, a spherical light collector
Scale, to arrange in a graduated series
Scintillation counter, an instrument used to
quantify radioactive isotopes
Scraper (grazer), an organism that obtains its
food by scraping off biofilms
Scum, a layer of floating algae or organic ma-
terial
Seasonality index, ratio of runoff in wet season
to runoff in dry season

Secchi disk, a circular disk with black and white
quadrants that is lowered into the water to
estimate water clarity
Secondary consumer, eats primary consumers
Secondary production, production of primary
consumers
Sediment, the particulate matter that settles to
the bottom of a liquid
Sensitivity analysis, to systematically test the
sensitivity of a model to the assumptions
used to construct it
Seiche, rocking of a lake or a layer of a lake
Seine, a long net used to trap fish
Sessile, attached to bottom
Seston, suspended organic particles
Shannon-Weaver diversity, an index of diver-
sity that includes both species richness and
evenness (also called Shannon-Weiner)
Sheet flow, a shallower layer of water flowing
across the surface of soil
Shoreline development, the circumference of a
lake divided by the circumference of a cir-
cle with the same area; used as an indicator
of trophic state
Shredder, an organism that makes its living
shredding organic material for food
Significance, an estimate of the statistical
certainty
Silica, SiO 2
Silicic acid, H 4 SiO 4
Simulation modeling, nonexperimental method
used to explore possible hypotheses
Sinkhole, surface depression formed in karst
area when a subsurface cavity collapses
Sinter, sediments from mineral springs, includ-
ing the siliceous geyserite and the calcare-
ous tufa or travertine
Sinuosity, the degree of meandering
Size class, discrete size range of an organism
Size fractionate, separate into size classes
Slough, swamp, shallow lake, or slowly flow-
ing marsh
Solubility, the ability to dissolve in a liquid
Solvents, can dissolve both gasses and ions
Species richness, number of species in an area