Effect of sulfide on the physiological energetics of Mercenaria mercenaria

Abstract

Marine sulfide is mainly produced by the reduction of sulfate. Eutrophication and anoxic conditions caused by tidal fluctuations have accelerated the production of sulfide and widened its distribution. Sulfide has toxic effects on aquatic animals, and it has important effects on physiological activities such as feeding and respiration in buried bivalves. The aim of this study was to estimate the impact of sulfide on the energy budget of the intertidal bivalve Mercenaria mercenaria. Acute toxicity experiments were first conducted on small (SS), medium (MS), and large (LS) size clams, and then clearance rate (CR), absorption efficiency (AE), respiration rate (RR), and ammonia excretion rate (ER) were measured at 24, 48, 72, and 96 h using 0 (control group), safe concentration (low sulfide group), and 96 h half-lethal concentration (high sulfide group) as sulfide concentration gradients, and scope for growth (SFG) was calculated. The results indicated that sulfide reduced the CR, AE, RR, and ER of M. mercenaria, and these indicators were lower in the high sulfide group than in the low sulfide group. The sulfide concentration and exposure time had significant effects on CR, AE, RR, and SFG. The CR of the SS low sulfide group reached its maximum value at 48 h, and the CR of the LS low sulfide and high sulfide groups reached their maximum values at 96 h and 48 h, respectively. SFG experienced a significant decrease with the extension of time, and for both MS and LS, the SFG of sulfide-treated groups was negative at all times, with the exception of 24 h. These results suggest that M. mercenaria exhibits metabolic inhibition and metabolic compensation in response to sulfide exposure. This study provides important insights for comprehending the physiological response of buried bivalves in sulfide environments and provides a scientific fundation for implementing corresponding culture measures.