Saturday, March 15, 2003
Dr. Chris Hasegawa, Professor, Institute for Earth Systems Science and Policy, California State University Monterey Bay
Board Representative, Association of Monterey Bay Area Governments
William J. Douros, Superintendent, Monterey Bay National Marine Sanctuary
Kevin Raskoff, Research Fellow, Monterey Bay Aquarium Research Institute
Jellyfish and other gelatinous members of the open-ocean community are some of the most spectacularly strange and poorly understood organisms in the sea. Their delicate bodies are difficult to sample with conventional oceanographic techniques and their habits and behaviors are largely unknown. Many local species can appear in huge numbers, seemingly out of nowhere. This is partially explained by the unusual life-cycle of most jellyfish, with bottom-dwelling polyps which give rise to free-swimming medusae, allowing for very rapid reproduction and growth in a short period of time, allowing jellies to take swift advantage of favorable conditions. These large blooms of medusae have a profound affect on the ecosystem, as they are voracious predators, capable of capturing a tremendous number and wide assortment of prey.
While many species of jellyfish in the Monterey Bay are thriving, there are some very rare species which have been only found a handful of times. So little is understood of the distributions and life histories of these species that is it unknown whether they are indeed threatened, or are merely exceedingly rare. Not until we better understand the distributions and ecology of these jellies can we hope to answer questions about appropriate management strategies for these extraordinary and beautiful creatures.
Scott Benson, Fishery Biologist, Sea Turtle Research Program, Southwest Fisheries Science Center, National Marine Fisheries Service
Melissa Miller, Veterinary Pathologist, Marine Wildlife Veterinary Care & Research Center, California Department of Fish and Game and U.C. Davis School of Veterinary Medicine
California's southern sea otter (Enhydra lutris nereis) is a federally-listed threatened species. Southern sea otter populations have increased more slowly than their Alaskan counterparts, and recently appear to have declined to just over 2,000 individuals. High otter mortality appears to be a significant factor in this decline, and, based on examination of freshly dead otters, nearly 40% of southern sea otter mortality is the result of infectious disease. Infectious causes of mortality include a wide range of bacteria and parasites, some of which are also associated with significant disease in terrestrial animals and humans. One major infectious cause of sea otter mortality are brain infections caused by single-celled protozoan parasites, including the human pathogen Toxoplasma gondii. Interestingly, the only animals known to shed the environmentally-resistant "egg" stage of Toxoplasma in their feces are cats. Cats are commonly infected by consuming infected mice and birds that can carry the parasite in their muscles and nervous tissue. However, sea otters rarely, if ever consume these terrestrial intermediate hosts, and marine hosts for Toxoplasma have not been recognized. Because of the apparent terrestrial origin of Toxoplasma, we expected to find that infections of wild sea otters, a marine mammal, would be uncommon. However, using cell culture and immunohistochemistry techniques, we detected active T. gondii brain infections in 36% of freshly dead California sea otters examined between 1997 and 2001.
We hypothesized that the most plausible explanation for the high number of wild California sea otters infected by Toxoplasma was exposure to infective parasite eggs shed in cat feces that reach the ocean through streams, urban runoff and/or sewage effluent. A recent epidemiological study allowed us to begin the process of tracing potential environmental sources for Toxoplasma infection for sea otters, from the land, to the sea. We learned that 42% of live and 62% of necropsied California otters had serum antibodies to Toxoplasma. Interestingly, otters sampled in the ocean near areas of high freshwater runoff (major streams and rivers) were 3 times more likely to be seropositive for Toxoplasma than otters sampled near areas of low freshwater outflow. In addition, two high-risk sites for Toxplasma exposure were identified along the coast, and at one of these sites, otters were 9 times more likely to have serum antibodies to Toxoplasma than otters sampled at all other sites. In a related study, cats fed Toxoplasma parasites isolated from sea otters were shown to pass Toxoplasma eggs in their feces. After reaching the sea, these eggs could be picked up by filter-feeding marine bivalves that could serve as an efficient source of Toxoplasma infection for sea otters. Because of their high metabolic rate, sea otters consume 25% of their body weight in shellfish and other invertebrates each day. Thus, contamination of marine shellfish by terrestrial-origin wastewater containing Toxoplasma eggs is a logical hypothesis to explain the high prevalence of Toxoplasma infection in California sea otters.
This study provides specific evidence of contamination of the coastal marine ecosystem with the zoonotic terrestrial pathogen, Toxoplasma gondii, and reveals extensive infection of threatened southern sea otters along the California coast. It also supplies statistical evidence implicating land-based surface runoff as a source of Toxoplasma infection for sea otters, and provides a convincing illustration of biological pollution of the marine ecosystem. Related studies suggest that sea otters may also be exposed to other terrestrial-origin biological pollutants, such as bacteria and other parasites. Sea otters and humans compete for some of the same invertebrate prey species. Thus if otters are ultimately found to be exposed to Toxoplasma and other pathogens through consumption of filter-feeding prey, this study has potent implications for human health.
Kriss Neuman, Biologist, Wetlands Program, Point Reyes Bird Observatory
The snowy plover (Charadrius alexandrinus) is a small, federally threatened shorebird that nests and winters on the sandy beaches of Monterey Bay. During spring and summer, snowy plovers nest and raise chicks from Sunset State Beach south to Marina, at the Moss Landing Wildlife Area, and at pocket beaches in northern Santa Cruz County. In 2002, snowy plovers nesting locally fledged more than 210 chicks--the second greatest number ever documented in the Monterey Bay region. The number of chicks fledged per breeding male was 1.4, well over the estimated 1.0 chicks per male necessary to stabilize the population. Despite these increases, the range of the plover in Monterey Bay has contracted and nesting success at historic sites on the fringes of the bay has declined. What are the causes of range constriction and reduced nesting success? Recreational use of beaches continues to increase, causing an increase in human-related disturbance to nesting plovers. Habitat fragmentation and urbanization have enhanced the accessibility of beach habitat to nonnative predators, such as the red fox (Vulpes vulpes regalis), and invasive predators such as the common raven (Corvus corax) and American crow (Corvus brachyrhynchos). As plovers become more concentrated into smaller habitat areas, the need for management of these habitats increases.
Baldo Marinovic, Assistant Research Biologist, Center for Ocean Health, University of California, Santa Cruz
Krill are a centrally important prey species in pelagic ecosystems throughout the world. Most species, including humans, are only one or two trophic levels away from krill; in other words they are either prey of krill, predators of krill, or predators of krill predators. Within the Central California pelagic ecosystem, krill are the primary prey item for seven of the ten most commercially valuable fishery species including market squid and king salmon. They are also the exclusive diet of blue whales which typically forage within the Sanctuary's waters from July to October each year. There is increasing evidence to suggest that while krill abundance within the Sanctuary's waters may fluctuate interannually in association with variable oceanographic processes, the long term trend appears to be stable. Similar results are suggested for krill abundance in Southern Californian waters where longer term data sets exist. This may be due to the short life span (< 2 years) for local species of krill as well as their ability to rapidly reproduce in response to periods of high phytoplankton productivity. Caution must be taken, however, in applying these results towards the effective management of pelagic ecosystems owing to the relative short time scale of the dataset within Central California. Additionally, krill predators may be particularly vulnerable during years of low krill abundance associated with acute interannual oceanographic events such as the recent 1997/98 El Niño.
William J. Douros, Superintendent, Monterey Bay National Marine Sanctuary
The Monterey Bay, Cordell Bank and Gulf of the Farallones National Marine Sanctuaries are conducting a joint management plan review, which includes evaluating regulations, boundaries, strategies and programs for the effective management and protection of these sanctuaries. Required by law, a periodic review of each sanctuaryís management plan ensures that the sanctuaries continue to best conserve, protect, and enhance their nationally significant living and cultural resources. Recent scientific discoveries, advancements in managing marine resources, and new resource management issues are all incorporated into this review process. The review also involves extensive public participation and provides an opportunity for the public to shape the future direction and management of each sanctuary.
Through a public scoping process held last fall, a variety of issues were identified, and with further public input, priority issues for further action have been selected. During the remainder of the joint management plan review, action plans to address these priority issues will be developed and woven into a revised management plan. At the Sanctuary Currents Symposium these priority issues will be discussed, as well as what they mean regarding the future of our sanctuaries.