Pick an anthropological activity which alters the abiotic features of a freshwater ecosystem. Focus on lakes. Describe the effects this behavior has on the abiotic features for the zones of a lake. Describe which organisms may be affected. Describe how these abiotic features are tested by an ecologist.

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While the field of anthropology encompasses the study of non-human primates, it addresses human behavior and its impact on the environment. Two interrelated human activities crucial to food production have significant impact on lakes: agriculture and raising animals. The abiotic features of a lacustrine freshwater ecosystem include water and the soil within and around the lake.

The overall problem of Nonpoint Source Pollution (NPS) has effects on a lake’s abiotic features. According to the US Environmental Protection Agency (EPA), “runoff from farms is the leading source of impairments to surveyed rivers and lakes.” The most significant dimension is sedimentation, which results as soil particles wash off fields. This often decreases the amount of water that would naturally flow into streams and rivers. In addition, NPS is closely associated with chemicals used in agriculture. The use of petrochemical herbicides and pesticides leads to runoff. Following rainfall and snowmelt, the chemical residue moves from land into streams and rivers that feed into lakes.

Raising animals is also associated with NPS, especially through overgrazing; its effects include soil exposure, increased erosion, and the destruction of stream-banks and floodplains. Animal feeding also makes negative contributions, such as water contamination from manure entering water through runoff.

These kinds of pollution have notable impacts on abiotic features in all three lake zones. Salinization is one notable problem. Increased salt concentration may occur with the evaporation of irrigation water. Sedimentation-related runoff may make the water cloudy, reducing the amount of light available for photosynthesis, which in turn will reduce the amount of oxygen. These effects are significant in the littoral and limnetic or pelagic zones. Effects on the mineral content include increased phosphorus. Heavy metals also enter the water, causing long-term water pollution. Changes to lake-bottom soils, especially from sedimentation, affect the benthic zone.

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