Effects of dissolved and complexed copper on heterotrophic bacterial production in San Diego bay.

Bacterial abundance and production, free (uncomplexed) copper ion concentration, total dissolved copper concentration, dissolved organic carbon (DOC), total suspended solids (TSS), and chlorophyll a were measured over the course of 1 year in a series of 27 sample "Boxes" established within San Diego Bay. Water was collected through a trace metal-clean system so that each Box's sample was a composite of all the surface water in that Box. Bacterial production, chlorophyll a, TSS, DOC, and dissolved copper all generally increased from Box 1 at the mouth of the Bay to Box 27 in the South or back Bay. Free copper ion concentration generally decreased from Box 1 to Box 27 presumably due to increasing complexation capacity within natural waters. Based on correlations between TSS, chlorophyll a, bacterial production or DOC and the ratio of dissolved to free Cu ion, both DOC and particulate (bacteria and algae) fractions were potentially responsible for copper complexation, each at different times of the year. CuCl2 was added to bacterial production assays from 0 to 10 microg L(-1) to assess acute copper toxicity to the natural microbial assemblage. Interestingly, copper toxicity appeared to increase with decreases in free copper from the mouth of the Bay to the back Bay. This contrasts the free-ion activity model in which higher complexation capacity should afford greater copper protection. When cell-specific growth rates were calculated, faster growing bacteria (i.e. toward the back Bay) appeared to be more susceptible to free copper toxicity. The protecting effect of natural dissolved organic material (DOM) concentrated by tangential flow ultrafiltration (>1 kDa), illite and kaolinite minerals, and glutathione (a metal chelator excreted by algae under copper stress) was assessed in bacterial production assays. Only DOM concentrate offered any significant protection to bacterial production under increased copper concentrations. Although the potential copper protecting agents were allowed to interact with added copper before natural bacteria were added to production assays, there may be a temporal dose-response relationship that accounts for higher toxicity in short production assays. Regardless, it appears that effective natural complexation of copper in the back portions of San Diego Bay limits exposure of native bacterial assemblages to free copper ion, resulting in higher bacterial production.

Trifluoroacetate in ocean waters.

Trifluoroacetate (TFA) is a ubiquitous xenochemical presently increasing in concentration in some environmental compartments, especially in the plant biomass of industrialized countries. Direct anthropogenic emissions of TFA are probably low, and the major anthropogenic sources are most likely various TFA precursors. As TFA has been found in ocean waters from remote locations, the question arose whether it is also a naturally occurring environmental chemical. Determination of the depth dependence of TFA in the ocean water column should shed some light on this question. However, in environmental analytical studies, the risk of systematic errors can be high and may lead to wrong conclusions. Therefore, special attention has been paid to the fact that TFA is a common atmospheric pollutant in the urban environment and that contributions from sampling, storage, and transport potentially lead to artificially high TFA values. The results of the ocean water sampling campaigns indicate that TFA is a naturally occurring chemical, homogeneously distributed in ocean waters of all ages with a concentration of about 200 ng/L.