Chemicals needed by plants and animals for growth, especially nitrogen and phosphorus.

Nitrogen (N) and phosphorus (P), which occur both as dissolved ionic forms and bound in dissolved or particulate organic molecules. The dissolved ionic forms are most biologically available and readily assimilated by stream plants. Nutrient concentrations are normally low in pristine waterways and higher in waterways that are impacted by human activities (for example fertilizer leachate/runoff, wastewater and effluent discharges).

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