Freshwater Ecosystems - Freshwater Ecology: Concepts and Environmental Applications - page 469

Wetlands

Deep groundwater Karst aquifers Lakes Streams

Wetlands, lakes

Shaded
streams
Groundwater

Low High

Open
streams

Seasonal variance

Homogeneous
aquifers

Wetlands

Large lakes Karst aquifers Streams

0 Light Full sun

Low High

Spatial variability of benthic substrata

Streams Karst aquifers

Wetlands

Small lakes

Large lakes,
aquifers

Large lakes

Karst aquifers

Deep groundwater Wetlands

Small lakes Streams

h d mo y centuries

Hydrological turnover time Low High

Spatial linkage

Large lakes Wetlands

Wetlands,
streams

Streams

Phytoplankton
Lakes

Deep groundwater Small lakes

Low High

Macrophytes,
periphyton

Allochthonous C input

0 m 100 m Oligotrophic lakes,

wetlands, streams

Depth Eutrophic lakes,

wetlands, streams Deep groundwater

Low High

Nutrient input

Large lakes Wetlands

Deep groundwater Karst aquifers Streams

Large lakes Karst aquifers

Deep groundwater Small lakes Streams

Wetlands

Low Hydrological variance High

Low Terrestrial influence High

FIGURE 22.14 Freshwater habitats aligned across abiotic gradients.

streams, and lake littoral zones) can contain diverse assemblages of or-
ganisms that process large detritus in addition to grazers and predators.
The vagaries of chance, dispersal, and time have acted in concert with these
abiotic gradients to allow evolution and community assembly to produce
the diversity of organisms associated with each of the habitats.
Many of the human-caused disturbances of freshwater habitats can be
characterized by shifts of systems on these axes of classification, particu-
larly those related to habitat modification. Description and understanding
of how these complex ecosystems are constrained are essential to describ-
ing and mitigating the effects that people have on freshwater, our most
valuable resource.

SUMMARY

1. Ecosystems can be represented by trophic levels and the fluxes of
carbon, energy, or nutrients between the trophic levels.
2. Biomass is an amount; production is a rate. The two should not be
confused.
3. Biodiversity may have an influence on ecosystem function,
particularly in low-diversity systems.