The Chesapeake Bay has been adversely affected by excessive nutrient loading from tributaries that drain the watershed. Excessive nutrient loading has resulted in eutrophication of the Bay and in related ecological shifts that have adversely affected water quality and important aquatic species. Specific adverse impacts have included depression of dissolved oxygen levels, which affect benthic organisms, and loss of submerged aquatic vegetation, which provides fish habitat. Excessive nutrient loading results from human activities in the watershed, and efforts are currently underway to identify these activities and mitigate their effects