Limnology is the study of inland waters - lakes (both freshwater and saline), reservoirs, rivers, streams, wetlands, and groundwater - as ecological systems interacting with their drainage basins and the atmosphere. The limnological discipline integrates the functional relationships of growth, adaptation, nutrient cycles, and biological productivity with species composition, and describes and evaluates how physical, chemical, and biological environments regulate these relationships.
The word limnology is derived from the Greek limne - marsh, pond and Latin limnaea - thing pertaining to a marsh. Stated simply, limnology is the study of the structural and functional interrelationships of organisms of inland waters as their dynamic physical, chemical, and biotic environments affect them.
Freshwater ecology is the study of the structure, function, and change of organisms in fresh waters as affected by their dynamic physical, chemical, and biotic environments. Saline waters (> 0.3% or 3 g per liter) are excluded from this definition.
Freshwater biology is the study of the biological characteristics and interactions of organisms of fresh waters. This study is largely restricted to the organisms themselves, such as their biology, life histories, populations, or communities.
Limnology encompasses an integration of physical, chemical, and biological components of inland aquatic ecosystems with the drainage basin, movements of water through the drainage basin, and biogeochemical changes that occur en route, and within standing (lentic) waters and exchanges with the atmosphere. The lake ecosystem is intimately coupled with its drainage area and atmosphere, and with its running (lotic) waters and ground waters that flow, and metabolize en route, components of the land being transported to the lake.
Understanding of the causal mechanisms operating in and controlling our natural world is a primary objective of limnology because of the premier importance of fresh water for the well being of humankind. The greater our understanding, the higher the probability to predict accurately patterns of events within aquatic ecosystems in response to human manipulations and disturbances. A combination of analytical techniques is used to acquire that understanding:
- Descriptive observations of patterns of biological processes and communities in relation to dynamic patterns of environmental properties. Such descriptive empirical analyses allow the generation of hypotheses, that is, conceptual predictive "models" of relationships among observed patterns.
- Experimental examination and evaluation of quantitative responses to selected disturbances imposed on the system. By imposing quantitatively known disturbances on specific parts of the community or ecosystem, much insight can be gained on controlling factors governing their operation. In some cases, entire lakes or streams are experimentally manipulated.
- Application of quantitative predictive models based on experimentally established, not random, governing variables. Models allow expansion of experimentally understood quantitative relationships, that is, hypothetical data can be inserted allowing a theoretical estimate of system responses to these variables.
Robert G. Wetzel
University of North Carolina