species diversity of fish and shellfish decrease as seagrasses are eliminated from nutrient-enriched coastal waters.
Some phytoplankton species excrete large quantities of mucilage during blooms that is whipped into foam by wind mixing and washes ashore, making beaches undesirable for holiday visitors. Other phytoplankton species produce toxic chemicals that can impair respiratory, nervous, digestive and reproductive system function, and even cause death of fish, shellfish, seabirds, mammals, and humans. The economic impacts of harmful algal blooms can be severe as tourism is lost and shellfish harvest and fishing are closed across increasingly widespread marine regions. Marine scientists are trying to determine if and how nutrient enrichment selectively promotes the growth of harmful algal species, and if the frequency of harmful algal blooms has increased globally in response to nutrient enrichment.