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, HCO(3)(-) and TCO(2). 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), HCO(3)(-) and TCO(2), but there was a significant reduction of pH.