The larvae of congeneric gastropods showed differential responses to the combined effects of ocean acidification, temperature and salinity

•Larvae of subtidal Nassarius conoidalis and intertidal N. festivus were studied.•Mortality increased with pCO2 and temperature for both species.•N. conoidalis had higher mortality and respiration rate than N. festivus.•Higher pCO2 reduced larval swimming speed in N. conoidalis only.•Subtidal congeneric species is more sensitive to combined environmental stressors. The tolerance and physiological responses of the larvae of two congeneric gastropods, the intertidal Nassarius festivus and subtidal Nassarius conoidalis, to the combined effects of ocean acidification (pCO2 at 380, 950, 1250ppm), temperature (15, 30°C) and salinity (10, 30psu) were compared. Results of three-way ANOVA on cumulative mortality after 72-h exposure showed significant interactive effects in which mortality increased with pCO2 and temperature, but reduced at higher salinity for both species, with higher mortality being obtained for N. conoidalis. Similarly, respiration rate of the larvae increased with temperature and pCO2 level for both species, with a larger percentage increase for N. conoidalis. Larval swimming speed increased with temperature and salinity for both species whereas higher pCO2 reduced swimming speed in N. conoidalis but not N. festivus. The present findings indicated that subtidal congeneric species are more sensitive than their intertidal counterparts to the combined effects of these stressors.