Study on the oxyhemocyanin, deoxyhemocyanin, oxygen affinity and acid-base balance of Marsupenaeus japonicus following exposure to combined elevated nitrite and nitrate

Marsupenaeus japonicus (11.47 +/- 0.71 g) exposed individually to six different nitrite and nitrate regimes {(0.002 (control), 0.359 and 1.456 mM nitrite combined with 0.005 (control) and 7.458 mM nitrate)} in salinity of 30 ppt (parts per thousand) were examined for hemocyanin oxygen affinity, the fractionation of oxyhemocyanin and deoxyhemocyanin, and the acid-base balance after 24 h. Ambient nitrite at concentration of 0.359 mM caused reduction of oxyhemocyanin and protein by 27 and 11%, respectively, whereas ambient nitrate as high as 7.458 mM caused reduction of oxyhemocyanin and protein by 10 and 7%. Ambient nitrite at concentration of 1.456 mM caused increases of P-50 (indicating reduced oxygen affinity) and pO(2,) but caused reduction in hemolymph pCO(2), pH, HCO3- and TCO2. Following exposure to combined solutions of 1.456 mM nitrite and 7.458 mM nitrate there were no further changes in oxyhemocyanin, protein, hemolymph P-50, pO(2), pCO(2), HCO3- and TCO2, but there was a significant reduction of pH. (C) 2002 Elsevier Science B.V. All rights reserved.