Seasonal and annual trends in forage fish mercury concentrations, San Francisco Bay.
نویسندگان
چکیده
San Francisco Bay is contaminated by mercury (Hg) due to historic and ongoing sources, and has elevated Hg concentrations throughout the aquatic food web. We monitored Hg in forage fish to indicate seasonal and interannual variations and trends. Interannual variation and long-term trends were determined by monitoring Hg bioaccumulation during September-November, for topsmelt (Atherinops affinis) and Mississippi silverside (Menidia audens) at six sites, over six years (2005 to 2010). Seasonal variation was characterized for arrow goby (Clevelandia ios) at one site, topsmelt at six sites, and Mississippi silverside at nine sites. Arrow goby exhibited a consistent seasonal pattern from 2008 to 2010, with lowest concentrations observed in late spring, and highest concentrations in late summer or early fall. In contrast, topsmelt concentrations tended to peak in late winter or early spring and silverside seasonal fluctuations varied among sites. The seasonal patterns may relate to seasonal shifts in net MeHg production in the contrasting habitats of the species. Topsmelt exhibited an increase in Alviso Slough from 2005 to 2010, possibly related to recent hypoxia in that site. Otherwise, directional trends for Hg in forage fish were not observed. For topsmelt and silverside, the variability explained by year was relatively low compared to sampling station, suggesting that interannual variation is not a strong influence on Hg concentrations. Although fish Hg has shown long-term declines in some ecosystems around the world, San Francisco Bay forage fish did not decline over the six-year monitoring period examined.
منابع مشابه
Mercury in San Francisco Bay forage fish 1 2 3
23 In the San Francisco Estuary, management actions including tidal marsh restoration could 24 change fish mercury (Hg) concentrations. From 2005 to 2007, small forage fish were 25 collected and analyzed to identify spatial and interannual variation in biotic 26 methylmercury (MeHg) exposure. The average whole body total Hg concentration was 27 0.052 µg g-1 (wet weight) for 457 composite sample...
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ورودعنوان ژورنال:
- The Science of the total environment
دوره 444 شماره
صفحات -
تاریخ انتشار 2013