Freshwater Ecosystems - Freshwater Ecology: Concepts and Environmental Applications - page 448

22 Freshwater
Ecosystems
General Approaches to Ecosystems
Groundwater Ecosystems
Streams
Lakes and Reservoirs
Wetlands
Comparison of Freshwater Ecosystems
Summary
Questions for Thought
The ecosystem viewpoint of ecology was initiated during the first half
of the 20th century. In an extremely influential paper published posthu-
mously, Raymond Lindeman (1942) described how flux of energy could be
used to characterize ecosystems. Explicitly accounting for energy flux arose
from the new ecological idea that an ecosystem is the sum of the biotic and
abiotic (chemical and physical) parts of an environment. A more compre-
hensive, contemporary definition is provided by Covich (2001):
Ecosystems are thermodynamically open, hierarchically organized commu-
nities of producers, consumers, and decomposers together with the abiotic
factors that influence species growth, reproduction, and dispersal. These
abiotic factors include the flow of energy and the circulation of materials
together with the geological, hydrological, and atmospheric forces that in-
fluence habitat quality, species distributions, and species abundances. En-
ergy flows through many species, and the way in which this flow affects
the persistence of ecosystems is influenced by land-use changes, precipita-
tion, soil erosion, and other physical constraints such as geomorphology.
This holistic view of ecology is powerful because it allows for analysis
of entire systems rather than abstract parts of systems. However, ecosystems
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