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Ammonia sensitivity of the glass eel ( Anguilla anguilla L.): Salinity dependence and the role of branchial sodium/potassium adenosine triphosphatase
Author(s) -
da Silva Joana Moreira,
Coimbra Joao,
Wilson Jonathan M.
Publication year - 2009
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1897/08-104.1
Subject(s) - salinity , seawater , ammonia , sodium , potassium , chemistry , adenosine triphosphatase , zoology , environmental chemistry , fishery , atpase , biology , ecology , biochemistry , enzyme , organic chemistry
Eel aquaculture is capture based and thus dependent on the fishery for juvenile glass eels. This fishery typically takes place in estuaries where salinity varies and ammonia levels can be elevated. Also, during capture and transport glass eels are kept at high densities and ammonia from endogenous production can increase to toxic levels. Ammonia is known to have detrimental effects on fish growth and survival. In the present study, the salinity dependence of ammonia sensitivity in glass eels acclimated to either seawater or freshwater was determined, and the possible role of branchial sodium/potassium adenosine triphosphatase (Na + /K + ‐ATPase) was investigated. Freshwater‐acclimated glass eels were found to be more sensitive to ammonia with a lethal concentration to 50% of the test organisms (LC50) value for 96 h of 3.30 mM for total ammonia nitrogen (TAN) and 117 μM for un‐ionized ammonia (UIA), versus values of 4.95 mM and 138 μM, respectively, for seawater‐acclimated animals. Freshwater glass eels also had significantly lower body TAN levels than seawater‐acclimated glass eels, although body accumulation profiles during exposure were similar. The higher branchial Na + /K + ‐ATPase activities in seawater glass eels might explain this difference in sensitivity; however, activities decreased significantly with increasing ammonia levels. There was also no salinity dependence of net ammonia flux rates (0.388 μmol of TAN/g/h). Holding glass eels at high densities characteristic of transport conditions resulted in elevated ammonia concentrations to approximately 3 mM, which coincidently approaches to the freshwater LC50 value and may therefore contribute to mortality.