Yet, nonpoint sources are difficult to identify or control. In Hawaii, a Sea Grant project to trace the flux of heavy metals in nearshore waters sparked additional research by the U.S. Geological Survey to evaluate the effect of land use on water quality. In Louisiana, Sea Grant is working with state officials to remove heavy metals from runoff that now pours directly into estuaries from highway bridges and an extensive causeway system. In a comprehensive study of nonpoint source pollution in Southern California's Santa Monica Bay, Sea Grant researchers mapped the stormwater plume, identifying the toxic elements posing threats to human and marine life. Local officials and stormwater managers in the City and County of Los Angeles are using this information to reduce the effects of nonpoint runoff on public beaches and marine ecosystems.
Immediate needs are varied.
Urban watersheds should be mapped to define sources of biological and chemical contaminants. The role of wetlands and other natural means to reduce runoff effects on streams, bays and nearshore waters must be explored. Sea Grant researchers also can develop models that assess the impact of proposed mitigation efforts. Ports and harbors are often dredged to deepen channels, improve navigation and increase capacity, but expansions may threaten adjacent fragile wetlands or compete with fishing, development and community needs. While clean sediments may be beneficial for beach nourishment and coastal development, a greater challenge is disposal of sediments containing metals, PCBs, DDT, and petroleum-derived hydrocarbons.