Glossary - Freshwater Ecology: Concepts and Environmental Applications - page 491

Flow boundary layer, the zone in which turbu-
lent flow is rare and laminar flow domi-
nates; near solid surfaces
Fluvial, produced by action of a stream or river
Fluxes, movements of materials between pools
or compartments in a cycle (e.g., of water
through the global hydrologic cycle)
Food chain, the most simplistic view of food
webs in which only trophic levels are
considered
Food web, a network of predator-prey in-
teractions that occur in an ecological
community
FPOM, fine particulate organic material
free groundwater, groundwater not trapped or
confined
Freshwater, water with less than 1000 ppm dis-
solved salts
Froude number, a dimensionless measure relat-
ing inertia forces to gravitation effects; im-
portant when gravity is dominant (i.e., flow
in open channels)
Fulvic acids, the humic fraction that does not
precipitate when a solution is acidified
Functional feeding group, a subset of organ-
isms from a community that feed using sim-
ilar strategies (e.g., filterers, scrapers, and
shredders)
Functional redundance, the degree to which
different species provide the same ecosys-
tem function
Functional response, the number of prey eaten
per unit prey density
Fungi, a kingdom of parasitic and saprophytic
organisms
Gape limited, size of prey consumed is limited
by mouth size
Gas vesicles, intracellular protein structures
that lend buoyancy to cyanobacteria
GIS (Geographic Information System), a com-
puter-based mapping system that can be
used for complex spatial and temporal geo-
graphic analysis
Glacial, relating to or produced by glaciers
Glacier, a large body of flowing ice
Global water budget, estimated water move-
ment (fluxes) between compartments
throughout the world

Graben, a depression between two faults when
one block slips down relative to two others
and creates a basin (see also horst ); lakes
can form in the depression
Gravitational water, water in rocks and soils
above groundwater
Gravitoidal particles, particles that will settle
Grazer, primary consumer; eats algae or plants
Greyfish, Australian fish living in backwater,
shoreline vegetation, lake edges, or stagnant
channels in dry seasons
Gross photosynthesis, the total amount of pho-
tosynthesis; in bottle experiments, the O 2
production in the light bottle minus that in
the dark bottle
Groundwater, water in or below the water table
Groundwater recharge, replenishment of

groundwater
Gyttja, partially reduced, minute-grained, or-
ganic, profundal sediments of eutrophic
lakes; copropel, mainly of autochthonous
origin
[ 3 H ] tritium, a radioactive isotope of hydrogen
used as a tracer
Habitat diversity,

diversity, between-habitat

diversity, within-habitat diversity
Halophilic, salt loving; requires saline water
for growth or reproduction
Hardness, a characteristic of water that does
not allow soap to dissolve; primarily caused
by Ca 2 and Mg 2
Head, the potential energy of water from
gravity
Heat budget, an account of heat incorporated
and lost by a water body during a specified
time period
Heat capacity, amount of energy required to
increase the temperature of a material
Heat of fusion, the number of calories required
to melt 1 g of solid substance to liquid form
Herbivore,

diversity;

organism that eats primary

producers
Hermaphrodite, an organism with both male
and female sexual reproductive organs
Heterocyst, specialized cyanobacterial cell in
which nitrogen fixation occurs at high rates
Heterogeneous, consisting of dissimilar ingre-
dients or constituents