Aquatic ecosystem metals

METAL SPECIES IN THE AQUATIC ECOSYSTEMS AND THEIR EFFECT ON THE WATER QUALITY... 

Water birds have not been shown to be directly affected by acidification. However, the prey of waterbirds may be of concern as these lower food-chain organisms may have elevated levels of toxic metals related to acidification of their habitat. Moreover, most water birds rely on some component of the aquatic food-chain for their high protein diet. Invertebrates that normally supply caJcium to egg-laying birds or their growing chicks are among the first to disappear as lakes acidify. As these food sources are reduced or eliminated due to acidification, bird habitat is reduced and reproductive rate of the birds is affected. The Common Loon is able to raise fewer chicks, or none at all, on acidic lakes where fish populations are reduced 37 and 5S). However, in some isolated cases, food supplies can be increased when competitive species are eliminated (e.g.. Common Goldeneye ducks can better exploit insects as food when competition from fish is eliminated). The collective influences of acidification are difficult to quantify on a specific area basis but for species that rely on a healthy aquatic ecosystem to breed, acidification remains a continuing threat in thousands of lakes across eastern North America 14). 

Overall the results reported in this review indicate that water scarcity might increase metal exposure (due to low dilution), metal uptake (due to higher retention under low flow), and metal toxicity and/or accumulation (depending on the dose and time of exposure), but also might cause opposite effects depending on the source of pollution. In addition, water scarcity will influence nutrient loads and will also modulate the fate and effects of metals. Thus, future studies addressing the role of environmental stress on the effects of toxicants at community scale are key to predict the impact of toxicants in the aquatic ecosystems. 

Jackson TA. 1998. Mercury in aquatic ecosystems. In Langston WJ, Bebiarmo MJ, editors. Metal metabolism in aquatic environments. London, UK Chapman Hall, p. 77-158. 

Rai, P.K., Heavy metal pollution in aquatic ecosystems and its phytoremediation using wetland plants An ecosustainable approach, International Journal of Phytoremediation, 10, 133-160, 2008a. 

Mishra, V.K., Upadhyaya, A.R., Pandey, S.K., and Tripathi, B.D., Heavy metal pollution induced due to coal mining effluent on surrounding aquatic ecosystem and its management through naturally occurring aquatic macrophytes, Bioresource Technology, 99 (5), 930-936, 2008. 

Zhou QF, Zhang JB, Fu JJ, Shi JB, Jiang GB (2008) Biomonitoring an appealing tool for assessment of metal pollution in the aquatic ecosystem. Anal Chim Acta 606 135-150... 

Cyanide compounds are useful to society in terms of their key role in synthetic and industrial processes, for certain fumigation and agricultural uses, and for some therapeutic applications (Ballantyne and Marrs 1987). Cyanides are present in effluents from iron and steel processing plants, petroleum refineries, and metal-plating plants, and constitute a hazard to aquatic ecosystems in certain waste-receiving waters (Smith et al. 1979) and to livestock (USEPA 1980 Towill et al. 1978). Cyanide serves no useful purpose in the human body, yet it is present in our food, air, and water (Becker 1985). 

Patrick, R. 1978. Effects of trace metals in the aquatic ecosystem. Amer. Sci. 66 185-191. 

The following flowchart is useful for calculation of critical loads of heavy metals for both terrestrial and aquatic ecosystems (Figure 4). 

Calculation Methods for Critical Loads of Heavy Metals The selection of a computation method or model is the third step in the flowchart for calculating critical loads of heavy metals (Figure 4). There are different models that can be used to calculate critical loads for terrestrial and aquatic ecosystems, based on receptor properties and on certain critical limits. Relevant aspects in relation to the selection of a calculation method are... 

Emission factors have been estimated for the release of trace metals to water from various source categories and these have been used to estimate inputs of these metals into the aquatic ecosystem. The global anthropogenic input of nickel into the aquatic ecosystem for 1983 is estimated to be between 33 and 194 million kg/year with a median value of 113 million kg/year (Nriagu and Pacyna 1988). 

Leonova G.A. (2004). Biogeochemical Indicators of Aquatic Ecosystem Pollution by Heavy Metals. Water Resources, 31(2), 195 -202. 

Besser, J.M., Kubitz, J.A., Ingersoll, C.G., Braselton, W.E. and Giesy, J.P. (1995) Influences on copper bioaccumulation, growth, and survival of the midge, Chironomus tentans, in metal contaminated sediments, Journal of Aquatic Ecosystem Health 4 (3), 157-168. 

Dave, G. and Dennegard, B. (1994) Sediment toxicity and heavy metals in the Kattegat and Skaggerak, Journal of Aquatic Ecosystem Health 3 (3), 207-219. 

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