Runoff from agricultural fields, urban areas, and construction sites can carry away soil, producing cloudy or muddy water. Soil in the water, called suspended sediment, blocks out the sunlight that bottom-dwelling plants in lakes and rivers need to survive. If these plants, called submerged aquatic vegetation (SAV), are deprived of sunlight for extended periods, they will die.
SAV is an important component of the ecosystem because it provides a habitat for aquatic organisms, produces oxygen, and traps sediment. If hypoxic conditions occur — a state where the level of oxygen in the water is very low — the aquatic organisms living there must either move or die. Often, suspended sediments and excessive nutrients are both present, creating a harmful combination of eutrophic conditions — when there is an overproduction of organic matter — and cloudy water. Suspended sediments can also clog the gills of fish and other aquatic organisms.