Habitat Protection Agricultural runoff and other sources of nonpoint source pollution can have significant impacts on aquatic species composition and numbers through the effects of soil sedimentation, changes in water column temperature and pH, reductions in dissolved oxygen, and impacts of dissolved nutrients and pesticides. Proposed and pending changes to clean water regulations will challenge agriculture and other nonpoint sources to provide the aquatic habitat protections necessary to meet water quality standards and protect a wide range of aquatic species. Undisturbed streams, lakes, wetlands and estuaries can contain a remarkable number of species. For example, a comprehensive inventory of stream biota in a small German stream, the Breitenbach, found more than 1,300 species in a 1.2 mile reach, including fish, invertebrates, microorganisms, aquatic plants and other species. While fish stocks often receive the greatest public attention when a manure spill or significant agricultural runoff event occurs, other aquatic biota are likely to be affected as well.
Fish are usually the largest vertebrates and predators in aquatic systems.
Their distribution in a given waterbody depends on the geographic location as well as intrinsic factors such as physical habitat, water quality, and competition. Aquatic plants usually consist of algae and mosses attached to permanent stream substrates. Rooted aquatic vegetation may occur where substrates are suitable and high currents do not scour the stream bottom. Luxuriant beds of vascular plants may grow in some areas where water clarity, substrates, nutrients, and slow water velocities exist. Stones that can't be moved easily by stream currents are often covered by mosses and algae and various forms of micro- and macroinvertebrates.