Interactive effects of ocean deoxygenation and acidification on a coastal fish Sillago japonica in early life stages

Abstract

Acidification and deoxygenation are major threats to ocean environments. Despite the possibilities of their co-occurrence, little is known about their interactive effects on marine organisms. The effects of low pH and low dissolved oxygen (DO) on the early life stages of the coastal fish Sillago japonica were investigated. Twenty-five experimental treatments fully crossed in five levels of pH 7.6-8.1 and DO 50-230 μmol/kg (20-100 % saturation degree) were tested, and hatching rate of the embryos and survivability of the larvae after 24 h at 25 °C were investigated. Low DO treatment significantly affected the embryos and larvae compared to low pH treatment. The 50 % lethal concentration of DO showed the highest value at pH 7.6 and the lowest value at pH 7.7 and 7.9 for embryos and larvae, respectively. Therefore, effects of deoxygenation on fishes were alleviated under acidified condition around pH 7.7-7.9.

Keywords: Dissolved oxygen; Embryos; Hypercapnia; Hypoxia; Japanese sillago; Larvae.