The Princeton Guide to Ecology

Healthy freshwater ecosystems play crucial roles in the global environment by controlling fluxes of minerals, nutrients, and energy, and, by providing goods and services critical to humans including water for drinking or irrigation and fish for consumption. Freshwater ecosystems also provide regulating services such as carbon sequestration, flood control, and cultural services such as recreational fishing, swimming, or aesthetic enjoyment of the open water. These goods and services are all supported by underlying ecological processes (also called ecosystem functions) such as primary production, decomposition, and nutrient processing. The well-known and dramatic decline in freshwater biodiversity that has occurred in the last several decades has been accompanied by local and regional losses of freshwater ecosystem services. These losses are being driven largely by human activities. Ecosystem services cannot be restored once lost without a focus on the underlying ecological processes that support them, and, thus, a great deal of research is ongoing to understand and quantify the linkage between services and the rates of key ecological processes.

anaerobic. Absence of oxygen, also called anoxic (e.g., anaerobic sediments).

chemotroph. An organism that makes its own food but, instead of using energy from the sun as photosynthetic organisms do, uses inorganic chemicals as an energy source; includes wetland bacteria called methanogens that produce methane (a greenhouse gas) by decomposing organic matter in anaerobic environments.

denitrification. The microbial process that converts nitrate ((

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geomorphology. The study of the formation, alteration, and configuration of landforms and their relationship with underlying structures.

hydrology. The study of the properties, distribution, and effects of water on the earth’s surface.

hyporheic zone. The subsurface region under and lateral to a stream in which groundwater and surface water mix; considered metabolically important in streams and rivers.

organic matter, particulate and dissolved. Derived from the degradation of dead organisms, plant or animal; particulate organic matter would include leaf pieces, wood, animal body parts, etc.; dissolved organic matter refers to organic molecules that are typically less than 0.7 mm; also called dissolved organic carbon.

point- / non-point-source pollution. Point-source pollution comes from clearly identifiable local sources, includes outlet pipes from wastewater treatment plants or other industrial sources. Non-point-source pollution comes from many diffuse sources and is carried by rainfall or snowmelt as it moves over or through the ground to fresh water. These pollutants include excess fertilizers, herbicides from agricultural or residential areas, oils or other toxic chemicals from urban runoff, salt from roads or irrigation practices, bacteria or nutrients from livestock, pet waste, or pollutants from atmospheric deposition.

primary and secondary production. The production of new living material through photosynthesis by

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