Methemoglobinemia in Recirculating Aquaculture Systems

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Humans have been performing aquaculture since Egyptian times. Aquaculture, by definition, is the process of growing aquatic organisms for consumption by human populations. Traditionally, aquaculture has been carried out in flow through systems, or pens in open water. These methods greatly increase the biogeochemical loading, as the fish excrete ammonia (~90%) and urea (~10%) (Timmons and Ebeling, 2013). The biogeochemical nitrogen cycle is driven by microorganisms, that perform nitrification, anaerobic ammonia oxidation. Nitrification leads to the production of nitrite and nitrate from the oxidation of ammonia. Ammonia and nitrite are inherently toxic to fish; however, the sensitivity to these nitrogenous compounds varies by species. It was suggested that in Cyprinus carpio, or common catfish, ammonia is regulated at the gill interface by Na+/K+-ATPase. With nitrite, fish are most sensitive in the early stages of growth; this is most often observed as poor gill structure and inflammation of muscle tissue (Kroupova et al., 2010). In a separate review, Dolomatov, et al., 2011, concluded that the most critical times for nitrite regulation are during the incubation of eggs; larvae rearing; and wintering fish.

In recent years, recirculating aquaculture systems (RAS) have been employed to minimize water usage and environmental nutrient loading due to intensive fish farming. The recirculating of water throughout an RAS relies upon nitrifying microorganisms to transform ammonia and nitrite into nitrate. Nitrate is generally non-toxic to the fish species being raised. Additionally, as recirculating aquaculture systems have evolved, stocking densities have been pushed to their limit. As these RAS are pushed to their limits, problems with...

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Timmons, Michael B.; Ebeling, J. M. (2013). Recirculating Aquaculture (3rd ed.). Ithaca: Ithaca Publishing Company, LLC.

Titov, V. Y., & Petrenko, Y. M. (2005). Proposed mechanism of nitrite-induced methemoglobinemia. Biochemistry. Biokhimii͡a, 70(4), 473–83. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/15892615

Tomasso, J. R., & Grosell, M. (2005). Physiological basis for large differences in resistance to nitrite among freshwater and freshwater-acclimated euryhaline fishes. Environmental Science & Technology, 39(1), 98–102. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/15667081

Wahidulla, S., & Rajamanickam, Y. R. (2010). Detection of DNA damage in fish Oreochromis mossambicus induced by co-exposure to phenanthrene and nitrite by ESI-MS/MS. Environmental Science and Pollution Research International, 17(2), 441–52. doi:10.1007/s11356-009-0198-1

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