Ecosystems aquatic/marine

Atmospheric deposition of PBTs contributes significantly to the contamination of aquatic, marine, and terrestrial ecosystems and their food chains. Large water bodies, such as the Great Lakes, seas, and... 

Allelopathy any direct or indirect harmful or beneficial effects of one plant (including microorganisms) upon another through production of chemical compoimds that escape into environment. The field of allelopathy has broadened over the years and now addresses research in both terrestrial (natural and agricultural) and aquatic (marine and riverine) ecosystems. 

Environmental problems associated with PCBs are the result of a number of factors. Several open uses of PCBs have resulted in thein direct introduction into the environment, eg, organic diluents careless PCB disposal practices have resulted in significant releases into aquatic and marine ecosystems higher chlorinated PCBs are very stable in thein persistence in different environmental matrices and by a variety of processes (Fig. 1) PCBs are transported throughout the global ecosystem and preferentiaHy bioconcentrate in higher trophic levels of the food chain. 

EcoFate EcoFate is a software package for conducting ecosystem based environmental and ecological risk assessments of chemical emissions by point and non-point sources in freshwater and marine aquatic ecosystems, including lakes, rivers and marine inlets... 

Zinc ligands are soluble in neutral and acidic solutions, so that zinc is readily transported in most natural waters (USEPA 1980, 1987), but zinc oxide, the compound most commonly used in industry, has a low solubility in most solvents (Elinder 1986). Zinc mobility in aquatic ecosystems is a function of the composition of suspended and bed sediments, dissolved and particulate iron and manganese concentrations, pH, salinity, concentrations of complexing ligands, and the concentration of zinc (USEPA 1980). In freshwater, zinc is most soluble at low pH and low alkalinity 10 mg Zn/L of solution at pH 6 that declines to 6.5 at pH 7, 0.65 at pH 8, and 0.01 mg/L at pH 9 (Spear 1981). Dissolved zinc rarely exceeds 40 pg/L in Canadian rivers and lakes higher concentrations are usually associated with zinc-enriched ore deposits and anthropogenic activities. Marine... 

Zinc deficiency effects have been produced experimentally in freshwater sponges at <0.65 pg Zn/L (Francis and Harrison 1988), in rainbow trout fed diets containing <15 mg Zn/kg FW (Spry et al. 1988), in certain species of marine algae at <0.7 pg Zn/L (Vymazal 1986), and in certain species of marine invertebrates at <6.5 pg Zn/L (Clapper et al. 1985a, 1985b) or <34 mg Zn/kg DW whole organism (White and Rainbow 1985). Zinc deficiency in natural aquatic ecosystems has not yet been credibly documented. 

Stronkhorst J., Ciarelli, S., Schipper, C.A., Postma, J.R, Dubbeldam, M., Vangheluwe, M., Brils, J.M. and Hooftman, R. (2004). Inter-laboratory comparison of five marine bioassays for evaluating the toxicity of dredged material. Aquatic Ecosystem Health Management, 7, 147-159. 

Lakes, rivers, swamps, and marshes - common in temperate areas - contribute little to the diversity of natural products. Abundant dull-green grass and dull-colored fish and moUusks characterize lakes and rivers, in contrasts with the vivid colors of tropical fish and seaweeds. Haplosclerid sponges are occasionally abundant in freshwater, but their secondary metabolism is limited to demospongic acids (Dembisky 1994), in contrast with the variety of metabolites from marine sponges in the same order. Where not for cyanobacteria (which are as rich of unusual metabolites as the marine strains), tropical amphibians, and aquatic fimgi, freshwater ecosystems would have passed unnoticed in this book. 

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