Physiological responses of two sublittoral nassariid gastropods to hypoxia

Anthropogenic hypoxia of coastal bottom waters now affects hundreds of thousands of km² worldwide. The present study investigated the physiological responses of 2 sublittoral nassariid gastropods, Nassarius conoidalis and N. siquijorensis, to hypoxia using endpoints, including scope for growth (SfG) and the related energy budget items (i.e. rate of energy intake from food, rate of energy lost to respiration and rate of energy lost to excretion) over a 31-d laboratory experiment. Our results showed that after exposure for ≥8 d, the stronger hypoxia treatment of 1.5 mg O₂ l^–1 significantly reduced the rate of energy intake for ­Nassarius siquijorensis, while N. conoidalis stopped feeding in the same treatment. SfG was sig­nificantly reduced in N. siquijorensis after exposure to 1.5 mg O₂ l^–1 during the mid and late exposure period. Exposure to ≤3 mg O₂ l^–1 also resulted in a negative SfG for N. conoidalis, except for the weaker hypoxia treatment during the late exposure period. Nassariid gastropods occur in great abundance in Hong Kong waters; therefore, any adverse effect on these gastropods may lead to major ecological consequences, including altered trophodynamics and disrupted nutrient recycling processes in coastal ecosystems.