Food chain, organic

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). 

Kannan, N. Reusch, T.B.H. Schulz-Bull, D.E. Petrick, G. Duinker, J.C., Chlorohiphenyls Model compounds for metahoUsm in food chain organisms and their potential use as ecotoxi-cological stress indicators hy appUcation of the metahoUc slope concept Environ. Sci. Technol. 1995, 29, 1851-1859. 

Saiki MK. 1986b. Concentrations of selenium in aquatic food-chain organisms and fish exposed. In Howard AQ, ed. Selenium and Agricultural Drainage Implications for San Francisco Bay and the California Environment. Proc. Second Selenium Symp. Tiburon, CA The Bay Institute of San Francisco, 25-33. 

Resource managers and aquatic biologists need data on selenium concentrations in water, food-chain organisms, and fish and wildlife tissues in order to adequately assess the overall selenium status and health of aquatic ecosystems. Because selenium is depurated rapidly in aquatic birds, resource managers should... 

Khan MAQ, Coello W, Khan A A, Pinto H (1972b) Some characteristics of the microsomal mixed-function oxidase in the freshwater crayfish, Camarus. Life Sci 11 405-415 Khan MAQ, Kamal A, Wolin RJ, Runnels J (1972a) In vivo and in vitro epoxidation of aldrin by aquatic food chain organisms. Bull Environ Contam Toxicol 8 219-228 Khan MAQ, Stanton RH, Reddy G (1974) Detoxication of foreign chemicals by invertebrates. In Khan MAQ, Bederka JP (eds) Survival in toxic environments. Academic Press, New York, pp 177-201 Khan MAQ, Korte F, Payne JF (1977) Metabolism of pesticides by aquatic animals. In Khan MAQ (ed) Pesticides in the aquatic environment. Plenum Press, New York, pp 191-220 Kira S, Izumi T, Ogata M (1983) Detection of dibenzothiophene in mussel, Mytilus edulis, as a marker of pollution by organosulfur compounds in a marine environment. Bull Environ Contam Toxicol 31 518-525... 

Notwithstanding, the main obstacles to the agri-food chain organization refer to the agents opportunism and the lack of trust among them (Bankuti and Machado Filho, 1999 Pigatto et al, 1999 Bliska et al, 1998). In this case, the contractual break (Williamson, 1985) is frequent and, consequently, interruptions in the operation flow can happen (Zylberstajn, 2000). 

Heavy metal concentration, with the risk of passing into the food chain (organic sequestering agents)... 

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