TA4 Integrating Sublethal Responses and Ecologically Relevant Endpoints
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() Interplay of tidal marsh plant biogeochemical and landscape ecology with nutrient and contaminant loads.

Higashi, R1, Ustin, S2, Williams, S3, Fan, T4, 1 Univ. of California, Center for Heath and Environment, Davis, CA, USA2 Univ. of California, Dept. of Land, Air and Water Resources, Davis, CA, USA3 Bodega Marine Laboratory, Univ. of California, Bodega Bay, CA, USA4 Univ. of Louisville, Dept. of Chemistry, Louisville, KY, USA

ABSTRACT- Pollutants integrate into the natural biogeochemistry through components such as plants and microbes. Our emphasis is on rooted plants because they are often the entry point of pollutants into the foodchain, are integrators of the soil, and are major drivers of the biogeochemistry of marshes. We have begun to uncover markers that may be indicators of bioavailability, transport, and/or biotransformation of metals. At Stege marsh (Richmond, CA), we found that many toxic metals were exuded as water-soluble salts by Spartina leaves. This represents a direct exposure route for water-column organisms, not mediated by herbivores, and no model currently accounts for such a metals conduit. On the basis of their ecophysiology, we hypothesize that leaf metal exudation will depend on salinity regimes and nitrogen status, as well as several other factors, thus tying into freshwater release policies and nutrient runoff management. This indicator is amenable to large-scale sampling to relate to landscape-scale metrics, because collection and analysis is high-throughput. Thus, we are relating salt metals, plant biomass and photosynthetic rate, animal toxicity, and other measures to remote-sensing indicators. Newer airborne and spaceborne instruments measure a detailed reflectance spectrum (400-2500nm), providing a basis that can extract more information about plant canopies than is derived from traditional visible-NIR techniques. Spatial variability in biomass and species composition can be determined from these data, allowing development of a spatial model to estimate the metals transported by Spartina into the aquatic system. The authors would like to acknowledge the many other researchers in the Pacific Estuarine Ecosystems Indicator Research consortium for sharing their data for this presentation, and the USEPA for funding support.

Key words: salt marsh, Spartina sp., landscape ecology, biogeochemistry

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