Pelagic



	PELAGIC, or open water, habitat is the most extensive of any of the coastal and marine habitats in the Bay. The vast majority of life in the Bay depends either directly or indirectly on phytoplankton found in the pelagic realm. Phytoplankton forms the base of the food web - they support grazing zooplankton, fish, and marine bacteria. In the Southern California Bight, the pelagic realm is home to 40% of the total fish species. In addition, the open Bay supports numerous species of seabirds, including the endangered California brown pelican and California least tern. Lastly, several species of marine mammals are frequently observed in the open Bay. Despite its extensive range, the pelagic realm of the Bay is not well monitored compared to other habitats; therefore, threats to this habitat are not well known. Nonetheless, scientists have noticed some potential threats. Two concerns have been raised regarding impacts to the pelagic habitat. The first is a rise in sea surface temperature. For almost two decades, from 1981 to 1998, sea surface temperatures have exceeded the previous 60-year mean in all but one year (Bedford, 2001). The rise in sea surface temperatures corresponded with a decline in zooplankton biomass (Scripps Institute of Oceanography 1995). Zooplankton are a vital link in the food chain, serving as the principal food for sardines, anchovies, hake, and mackerel - all commercially important species. In addition, another commercially and recreationally important group of species, rockfish depends on zooplankton in its juvenile stage. Some studies over the last two decades have shown declines in populations of species dependent on zooplankton such as anchovies and sooty shearwaters. The second concern regards the impact of storm water and dry weather runoff pollution on the pelagic habitat and, in particular, the sea surface microlayer. Contaminants concentrate in the sea surface microlayer, an important area for the early development of many fish and other marine species with planktonic life stages. Accumulation of pollutants, such as petroleum hydrocarbons, in this layer can be toxic or cause biological abnormalities in these species. Petroleum hydrocarbons, which do not dissolve in water and are buoyant, have been observed in the sea surface microlayer at concentrations 100 to 10,000 times greater than in other parts of the water column. Scientists also believe that there may be linkages between runoff and harmful algal blooms (HABs). While many HABs occur in relatively pristine waters and show no obvious connection to human activities, some of these phenomena may be related to agricultural and urban runoff. Both of these types of runoff provide nitrogen and phosphorus to the algal cells to make possible their rapid reproduction. HAB scientists generally accept that enrichment of coastal waters results in an enhancement of many algal species, some of which are harmful or toxic. Several efforts are underway to control sources of pollution that may impact the Bay's pelagic habitat. To reduce storm water and urban runoff pollution, the Los Angeles Regional Water Quality Control Board (RWQCB) issued the L.A. County Municipal Storm Water NPDES Permit to all 84 municipalities in L.A. County, L.A. County, and the L.A. County Flood Control District, as part of a comprehensive storm water pollution reduction program. The goal of the permit is to reduce pollutants in storm water discharges to the maximum extent possible in order to attain water quality objectives. The SMBRP has also directly funded many storm water pollution projects throughout the watershed. Another concern is the impact of the rapidly increasing fishery for California market squid. The coast of California supports large squid fisheries. Squid fishers work at night during the seasons when mating groups of squid school together, using bright lights to attract the squid to the surface, then scooping them up in large purse seine nets. This fishing strategy is risky because it relies on catching spawning aggregations, making it easy to over-fish. This over-fishing has the potential for severe impacts on the Bay's ecosystem. Squid are a vital link in the food chain as both predator and prey. They are an essential source of food for numerous fish, sea birds, and marine mammals. If you would like to read more about the Bay's pelagic habitat, visit our Habitats and Species page. References Bedford, Dennis. 2001. Giant kelp section: California's Living Marine Resources: A Status Report. California Department of Fish and Game (CDFG) & California Sea Grant Extension Program. Dailey, Murray D., Donald J. Reish, and Jack W. Anderson. 1993. Ecology of the Southern California Bight: A Synthesis and Interpretation. University of California Press, Berkeley, CA. Scripps Institute of Oceanography. 1995. Dramatic Drop in Zooplankton Reported off California Coast. Press Release, March 3, 1995.