A toxic "rust tide", a type of harmful algae bloom, has emerged on Long Island's East End as a result of nitrogen pollution from wastewater and fertilizer. The algae, whose scientific name is Cochlodinium, has been appearing on Long Island since 2004 and can kill finfish and shellfish when densities exceed 500 cells per milliliter. In Sag Harbor, densities were found to exceed 30,000 cells per milliliter. The rust tide presented itself earlier than expected, usually appearing in the western Peconic Estuary mid August, and is present in densities that scientists have not seen on Long Island in years. Though non-toxic to humans, Long Islanders should exercise caution when heading to the East End beaches.