Metal trends and effects in Potamocorbula amurensis in north San Francisco Bay
Metal trends and effects in Potamocorbula amurensis in north San Francisco Bay
复制标题
北旧金山湾山菘蓝的金属趋势和影响
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
S. Luoma
中科院分区：
文献类型：
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作者：
C. Brown;S. Luoma
Long-term, multi-disciplined field sampling was used to assess both the fate and effects of trace metals in northern San Francisco Bay. Bioaccumulation in the bivalve Potamocorbula amurensis was measured at near-monthly intervals between 1990 and 1997. Three accumulation patterns were detected. One pattern indicates that biological regulation of Cu and Zn is an important control on tissue concentrations. This was evident by the absence of persistent spatial or temporal trends in the tissue concentrations of Cu or Zn, and the correlation of Cu and Zn tissue concentrations with the weight of the clam. The pattern in Cr, Ni, and V tissue concentrations was related to the combined influences of riverine inputs and local industrial inputs. Seasonally, the highest tissue concentrations of Cr, Ni, and V coincided with high delta inflows. Cadmium and Ag tissue concentrations were not clearly related to any obvious source. However, they were linked inversely to condition index, glycogen content, reproductive status, and histopathology. The histopathological changes are biomarkers indicative specifically of contaminant stress. Trace metals can be an influential variable in ecosystem processes, affecting the well-being of organisms, populations and communities (Luoma, 1996). Metal bioaccumulation in macroinvertebrate tissues is an indicator of metal exposures that can either adversely affect the health of the organism, or be transferred up the food web to affect higher organisms. Bioaccumulation in the bivalve Potamocorbula amurensis has been used to assess both the fate and effects of trace metals in San Francisco Bay (Brown and Luoma, 1995). The present study began in 1990 and consists of monthly sampling at five sites in Northern San Francisco Bay (Figure 1). Four of these are deep water sites in the ship channel; near Chipps Island, near Roe Island, in Carquinez Strait near Martinez, and in San Pablo Bay northeast of Pinole Point. One site is in the shallow water of Honker Bay. Clams (60-100) are collected at each site and separated into replicate size composites (1mm shell length difference) of 12-15 clams each. Ag, Cd, Cr, Cu, Ni, V, and Zn are measured in the whole soft tissues of the clam. Condition index (mg dry weight for a standard shell length), glycogen content (% tissue dry weight), and reproductive status (Parchaso, USGS) are determined monthly to evaluate influences of metals and other environmental factors on the energetics and reproduction in P. amurensis as indicators of stress. Surface sediments are collected at the same time and analyzed for metals (Hornberger and Bouse, USGS). Collaborators from UC Davis (Drs. Hinton, Werner, Teh, Clark, Fan, Higashi, Kaufman) are simultaneously studying enzymatic, histopathologic, and biochemical biomarkers in these populations of P. amurensis to compare with the trends in contaminants. Figure 1. Map of sampling sites in Northern San Francisco Bay. Since the beginning of this study, we have observed metal trends over a wide variety of hydrographic regimes. These include three very low flow years (1991, 1992, and 1994) where annual mean delta outflow was less than 220 msec, and years of moderate to high delta outflow (1993, 1995, 1996, and 1997) where annual mean delta outflow was between 760 1710 msec (Oltmann, USGS data). Each of the metals showed slightly different accumulation patterns in P. amurensis and thus indicated the variety of factors that control bioaccumulation. Three basic patterns were detected. One pattern indicates that biological regulation of Cu and Zn is an important control on tissue concentrations. The pattern in Cr, Ni, and V tissue concentrations is related to the combined influences of riverine inputs and local industrial inputs. The third pattern in Cd and Ag tissue concentrations is not clearly related to any obvious source, but is linked to patterns in biomarker indicators of metal stress. Earlier studies (Luoma et al., 1990, Hornberger et al., 1999) showed that Cu contamination increases substantially in the industrialized regions of the Bay-Delta. However, there is no distinct spatial or temporal trend in the tissue concentrations of Cu (or Zn) in P. amurensis in the North Bay. Variability in Cu (and Zn) appears to be dominantly controlled by biological processes. Among all times at all sites, the amount of Cu in a 15mm shell length clam is strongly correlated (r = 0.53) with the weight of tissue. The same relationship occurs within each site. As animals add (or lose) tissue mass, they add (or lose) Cu. Changes in weight, which occur seasonally and site-tosite, control 53% of the Cu variability in P. amurensis. It is known that the bioaccumulation response to environmental Cu and Zn contamination differs among species (Phillips and Rainbow, 1993). P. amurensis appears to be a species that biologically regulates its tissue burden of Cu and Zn, and thus does not appear to be a useful indicator of Cu and Zn contamination patterns (Brown and Luoma, 1995). The second accumulation pattern shows that Cr, Ni, and V in the tissues of P. amurensis are related to both natural and anthropogenic inputs into the ecosystem. These metals are enriched in the ultramafic rocks that are common throughout the watershed and thus are naturally high in the sediments in the bay. Vertical cores of sediments indicate that the enrichment of Cr, Ni, and V extends back to before the Gold Rush and the acceleration of human activities in the area (Hornberger et al., 1999). These metals also have industrial sources in the North Bay. Chromium, Ni, and V concentrations in the tissues of the clams have a distinct temporal pattern that suggests the amount of freshwater flow into the bay from the delta affects their bioaccumulation. Vanadium has the strongest relationship with delta outflow. Vanadium concentrations increase during pulses of high inflows and are low in the tissues at all channel stations during low flow periods (Figure 2a). Tissue concentrations at the most landward site, near Chipps Island, are often as low as tissue concentrations at the most seaward site, San Pablo Bay, during low flows. However, when delta outflows increase, concentrations of V Martinez Honker Bay Chipps Is. Roe Island
