短期酸化对魁蚶摄食、呼吸代谢及能量收支的影响

Effects of Short-Term Acidification on Feeding,Respiratory Metabolism,and Energy Budget of Scapharca broughtonii

采用实验生态学方法,研究了魁蚶(Scapharca broughtonii)摄食、呼吸代谢及能量收支对短期酸化(pH分别为8.2、7.9、7.6)的响应。结果显示,魁蚶的摄食率(IR)和排粪率(FER)均受pH影响显著(P<0.05),都随pH的降低而减少;魁蚶的耗氧率(OR)受pH影响显著(P<0.05),随pH降低呈明显的下降趋势,表明低pH在一定程度上抑制魁蚶的呼吸;排氨率(NR)受pH影响不显著,随pH的降低呈先下降再上升的趋势;O:N值随pH的降低而减小。不同pH条件下的能量收支结果显示,魁蚶的摄食能、呼吸能、排粪能和生长余力(SFG)均随pH的降低而减少。通过建立能量收支方程发现,pH显著影响魁蚶的能量分配(P<0.05),随pH的降低,魁蚶的呼吸能和排泄能占摄食能的比例增加,而排粪能和生长能占比减少,说明低pH条件下,魁蚶会做出适当生理调整降低IR,增加代谢率,导致能量减少,继而造成SFG减少。研究表明,短期酸化条件下,魁蚶的摄食和新陈代谢显著降低,可能是细胞能量需求的增加和氮损失的协同作用。

Ocean acidification is one of the major changes in marine ecosystem in this century.This has a negative effect on the fertilization,development,growth,and survival of marine mollusks.Presently,physiological effects of ocean acidification on some economic shellfish are not clear.To study the effects of ocean acidification on the physiological ecology of economic shellfish is of great significance for environmental science,ecology,and aquaculture.The feeding,respiratory metabolism,and energy budget of Scapharca broughtonii at different pH levels(pH 8.2~7.6)were studied in the laboratory.The results showed that the feeding and defecation rates of S.broughtonii were significantly(P<0.05)affected by pH,and there was a declining trend on the feeding and defecation rates with a decrease in pH value.The oxygen consumption rate was also significantly(P<0.05)affected by pH,showing an obvious downward trend with decreasing pH value.There was an initial decrease in ammonia excretion rate,which then increased with a decrease in pH value.O:N ratio at low pH value was lower than that of normal seawater,indicating that low pH value could inhibit the respiratory metabolism of S.broughtonii to some extent.The energy budget at different pH values indicated that energy ingestion,respiratory consumption,fecal energy loss,and energy absorbed in the growth process all decreased with a decrease in pH value.Interestingly,energy loss during excretion decreased first and then increased.According to energy budget equation,we found that pH had a significant effect on energy distribution of S.broughtonii(P<0.05).As the pH value decreases,the proportion of energy consumed during respiration and excretion increases,while the proportion involved in excrement and growth decreases.Under low pH conditions,S.broughtonii will make appropriate physiological adjustments to reduce the feeding rate and increase the metabolic rate,resulting in a decrease in energy,which leads to a decrease in energy deposition in the growth process.This study suggested that the feeding and metabolism of S.broughtonii decreased significantly under short-term acidification,which may be a synergistic effect of increased cell energy demand and nitrogen loss.