Invertebrates, aquatic, consumption

System 20. aquatic plants—bentos, plankton, coastal aquatic plants (XII) aquatic animals including bottom sediment invertebrates, fishes, amphibians, mammals, vertebrates, their biological reactions and endemic diseases (VIII) aerosols, atmospheric air (31, 32)—foodstuffs, forages (XV). Human poisoning through consumption of fish and other aquatic foodstuffs with excessive bioaccumulation of pollutants is the most typical example of biogeochemical migration and its consequences. 

Significant concentrations of cyanotoxins have been found to accumulate in the tissues of macroinvertebrates such as mollusks and crustaceans, presenting an indirect route of exposure for invertebrates, fish, and aquatic mammals at higher trophic levels (Negri and Jones 1995). In natural systems, mortality among benthic invertebrate herbivores is probably low because most bloom-forming bacteria are planktonic and only periodically come into contact with the benthos. Nevertheless, Kotak et al. (1996) determined that enhanced mortality of snails at the end of a bloom cycle in Canadian lakes was due to consumption of Microcystis cells that had formed a scum on the surface of macrophytes. Oberemm et al. (1999) found that aqueous microcystins, saxitoxins, and anatoxin-a all resulted in developmental delays in fish and salamander embryos. Interestingly, more severe malformations and enhanced mortality were observed when larvae were exposed to crude cyanobacterial extracts than to pure toxins applied at natural concentrations (Oberemm et al. 1999). 

Potable water containing chlorine or copper is generally considered toxic to many invertebrates. Yet, the lack of minerals, etc., in distilled water makes it osmotically unacceptable to many aquatic organisms. The fact that the water is fit for human consumption does not mean the water is acceptable to aquatic organisms. 

Toxic episodes associated with the consumption of aquatic species, whether they be bottom-dwelling invertebrates such as clams and mussels, or species higher up the food chain such as crabs or fish, have been present throughout our history. Almost all cultures that have inhabited coastal areas note warnings about the consumption of certain species at certain times of the year or during particular climactic conditions. These stories are found in both the oral and written histories of peoples worldwide, whether they be the ancient Egyptians, the aboriginal peoples of Australasia, or the Beothuk and Mi Kmaq tribes of eastern Canada. 

I conservatively estimate that, in terms of total carbofuran in water, damage is possible to aquatic invertebrates at >2.5 xg/L and to teleosts at >15.0 xg/L. These levels could be attained during a heavy rainfall shortly after carbofuran treatment of adjacent fields. Among sensitive species of warmblooded animals, dietary concentrations as low as 10.0 xg/kg ration have demonstrable effects, which were measurable only after extended periods postingestion for comparison, this level is about one-fifth of that allowed in meat by-products for human consumption. Current maximum permissible aerosol levels of 0.05 xg/L (50.0 ixg/m ) appear sufficient to protect wildlife with the proviso that concentrations do not exceed 2.0 xg/L at any time. 

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