Estuaries and Coasts

, Volume 35, Issue 2, pp 603-621

First online:

Life Histories, Salinity Zones, and Sublethal Contributions of Contaminants to Pelagic Fish Declines Illustrated with a Case Study of San Francisco Estuary, California, USA

  • Marjorie L. BrooksAffiliated withDepartment of Zoology, Southern Illinois University Email author 
  • , Erica FleishmanAffiliated withBren School of Environmental Science and Management, University of CaliforniaJohn Muir Institute of the Environment, The Barn, University of California
  • , Larry R. BrownAffiliated withU.S. Geological Survey, California Water Science Center
  • , Peggy W. LehmanAffiliated withCalifornia Department of Water Resources, Division of Environmental Services
  • , Inge WernerAffiliated withAquatic Toxicology Laboratory, Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of CaliforniaSwiss Centre for Applied Ecotoxicology
  • , Nathaniel ScholzAffiliated withNOAA Fisheries, Northwest Fisheries Science Center, Environmental Conservation Division
  • , Carys MitchelmoreAffiliated withChesapeake Biological Laboratory, University of Maryland Center for Environmental Science
  • , James R. LovvornAffiliated withDepartment of Zoology, Southern Illinois University
  • , Michael L. JohnsonAffiliated withCenter for Watershed Sciences, University of California
    • , Daniel SchlenkAffiliated withDepartment of Environmental Sciences, University of California
    • , Suzanne van DrunickAffiliated withCooperative Institute for Research in Environmental Science (CIRES), University of Colorado at Boulder
    • , James I. DreverAffiliated withDepartment of Geology and Geophysics, Department 3006, University of Wyoming
    • , David M. StomsAffiliated withBren School of Environmental Science and Management, University of California
    • , Alex E. ParkerAffiliated withRomberg Tiburon Center for Environmental Studies, San Francisco State University
    • , Richard DugdaleAffiliated withRomberg Tiburon Center for Environmental Studies, San Francisco State University

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Human effects on estuaries are often associated with major decreases in abundance of aquatic species. However, remediation priorities are difficult to identify when declines result from multiple stressors with interacting sublethal effects. The San Francisco Estuary offers a useful case study of the potential role of contaminants in declines of organisms because the waters of its delta chronically violate legal water quality standards; however, direct effects of contaminants on fish species are rarely observed. Lack of direct lethality in the field has prevented consensus that contaminants may be one of the major drivers of coincident but unexplained declines of fishes with differing life histories and habitats (anadromous, brackish, and freshwater). Our review of available evidence indicates that examining the effects of contaminants and other stressors on specific life stages in different seasons and salinity zones of the estuary is critical to identifying how several interacting stressors could contribute to a general syndrome of declines. Moreover, warming water temperatures of the magnitude projected by climate models increase metabolic rates of ectotherms, and can hasten elimination of some contaminants. However, for other pollutants, concurrent increases in respiratory rate or food intake result in higher doses per unit time without changes in the contaminant concentrations in the water. Food limitation and energetic costs of osmoregulating under altered salinities further limit the amount of energy available to fish; this energy must be redirected from growth and reproduction toward pollutant avoidance, enzymatic detoxification, or elimination. Because all of these processes require energy, bioenergetics methods are promising for evaluating effects of sublethal contaminants in the presence of other stressors, and for informing remediation. Predictive models that evaluate the direct and indirect effects of contaminants will be possible when data become available on energetic costs of exposure to contaminants given simultaneous exposure to non-contaminant stressors.


Susceptibility to toxins Bioenergetic costs Impaired waterways Multiple stressors Pelagic organism decline Climate change Review