Kelp Beds



	KELP BEDS extend low relief, hard bottom habitat from the seafloor to the surface, creating a vertically structured habitat. In California, kelp beds provide protection and habitat for more than 800 species of fishes and invertebrates, many of which are uniquely adapted for life in kelp forests. Because most established kelp beds occur over hard bottom substrate, giant kelp beds in Santa Monica Bay are limited to two areas, the Palos Verdes Shelf and the area from Malibu west to Point Dume. (Map of kelp beds) Santa Monica Bay's kelp beds have faced a variety of threats, past and present. From the late 1930s to 1974, the principal threat to the beds off the Palos Verdes Peninsula was the discharge of wastewater from the White Point outfall on the Palos Verdes Shelf. The high volume of outfall contained a large quantity of suspended solids that most likely buried the hard bottom habitat. Other reasons for the decline may have included increased turbidity and reduced light penetration due to the discharge of total suspended solids, which may have prevented the growth of young kelp plants. Suspended solids may have also supported abnormally high densities of sea urchins, which are major kelp predators. From the mid-'70s to 1997, however, improved wastewater treatment processes resulted in an 80% reduction in the discharge of total suspended solids from the White Point outfall. That, along with kelp replanting efforts in the 1970s, resulted in a remarkable increase in the kelp canopy from a low of 5 acres in 1974 to a peak of more than 1,100 acres in 1989. More recently, erosion and sedimentation have threatened the kelp beds off the Palos Verdes Peninsula. Since 1980, an active landslide at Portuguese Bend on the Palos Verdes Peninsula has supplied more than seven times the suspended solids as the Whites Point outfall (LACSD 1997). On the Malibu coast, increased erosion and sediment load have resulted from hillside development. When that sediment is carried into the Bay via storm runoff it may contribute to the decline of kelp beds in the area. The SMBRP has sponsored two research projects to determine both the current and historical extent of rocky substrate and key factors that impact the health of kelp beds. The results of these research projects should provide more insight into the causes of kelp decline and guidance for future kelp restoration activities. The earliest efforts to re-establish kelp beds in the Bay began in 1967 on the Palos Verdes Shelf. Initial efforts met with little success; however, efforts were re-initiated by the California Department of Fish and Game in 1970 and continued through 1977. In 1974, the kelp beds off the Palos Verdes Peninsula began to show signs of recovery. During the 1980s, the kelp canopy dramatically increased, peaking in 1989 at 1,125 acres. Once the beds were re-established, the CDFG discontinued active restoration efforts. In 1996, the environmental group, Santa Monica BayKeeper, embarked on an SMBRP-sponsored kelp restoration project, again focused on the Palos Verdes Shelf. Through this project, BayKeeper has successfully cultivated giant kelp in the lab and transferred the microscopic plants to suitable substrate in the Bay. At the pilot restoration site, north of Rocky Point, Baykeeper biologists and volunteers successfully removed sea urchins and re-established kelp that continues to thrive. Baykeeper is currently attempting to restore kelp habitat near Escondido beach and Paradise Cove, along the Malibu coastline in northern Santa Monica Bay. Another potential threat to kelp beds in the Bay is increased grazing by sea urchins. In some cases, episodic grazing by sea urchins on live kelp plants is natural; however, "the intensive fishing for sea urchin predators such as California sheephead and spiny lobster, and for sea urchin competitors such as abalone, has tremendously altered the sea urchin population dynamics within the kelp forest. As a result, sea urchin populations increased exponentially in some areas and overgrazed the kelp, creating areas referred to as urchin barrens" (Bedford, 2001). This may be balanced, however, by the commercial harvesting of sea urchins, which also increased in the 1990s (CDFG, unpubl. data). Finally, at least three major events affected kelp beds throughout southern California during the 1980s and 1990s: 1) the 1982-1984 El Niño and a devastating 200 year storm; 2) the 1992-1994 El Niсo and subsequent storms; and 3) the 1997-1998 El Niсo, which was the warmest of the three. The warm water and storms associated with the El Niсo destroyed plants, inhibited kelp growth, and resulted in minimal canopy development throughout the region. For an 18-year period from 1981 to 1998, sea surface temperatures exceeded the previous 60-year mean in all but a single year, 1988 (Bedford, 2001). While it is unlikely that warmer water temperature will destroy kelp beds, it may inhibit growth and result in smaller kelp beds over the long run. It is unclear, however, whether the warmer water temperature is attributable to a natural cyclical event that will reverse itself, or the result of global warming. Several agencies monitor the health of kelp beds. Two of these programs focus on the Palos Verdes kelp beds. The California Department of Fish and Game conducts biannual aerial surveys of the kelp canopy and the L.A. County Sanitation District, as part of its required monitoring under the NPDES Program, conducts quarterly diver surveys. These surveys collect data on the abundance of macroalgae, invertebrates, and fishes at each station. Monitoring of the Malibu kelp beds is more limited, however BayKeeper conducts occasional aerial and diver surveys. Kelco, a kelp harvesting and processing company, conducts aerial surveys of kelp beds throughout the Southern California Bight in order to estimate kelp biomass and the harvest potential based on the size and condition of kelp beds. If you would like to read more about kelp habitat in the Bay, visit our Habitats and Species page. References Bedford, Dennis. 2001. "Giant kelp" California's Living Marine Resources: A Status Report. California Department of Fish and Game (CDFG) & California Sea Grant Extention Program. California Department of Fish and Game. 1997. Unpublished data (on commercial fishery landings). Los Angeles County Sanitation Districts (LACSD). 1997. Palos Verdes Ocean Monitoring: Annual Report 1996.