Levels of metals from salt marsh plants from Southern California, USA

Salt marshes in Southern California are surrounded by urban development and therefore subjected to various levels of anthropogenic disturbances. In the San Diego area urban development increases in density from north to south, which would imply an impact on individual marshes. The objective of the field component of this study was to investigate the level of metal contamination in plants and associated with sediment surrounding plant roots in four salt marshes. Generally, metals associated with sediment showed a decreasing concentration gradient from northern to southern marsh. In contrast, plant metal concentration showed a reverse trend with an increasing gradient from northern to southern marsh. Increasing organic matter and decreasing grain size of sediment, which affect bioavailability of metals, appeared to be the main factors controlling such trend rather than the density of urbanization. Samples were collected in the summers of 2007-08, and winter of 2008. Winter season showed a 4.5x increase in metal content in plants compared to summer; however, metals associated with sediment increased 2.5x in winter. These results suggest that metal accumulation occurred mainly from dissolved metals in seawater in the winter. The laboratory objective was to test the rate of metal uptake by plants by a dose response of copper bioaccumulation experiment in aquaria using one of three local marsh plants. Metals were taken up by plant roots then subsequentially transported throughout the plant tissues. The linkage to marsh ecosystems for development of effective management strategies in biomonitoring programs for environmental quality assessment will be discusse