Effects of high pCO2 on snow crab embryos: Ocean acidification does not affect embryo development or larval hatching

Abstract

Ocean acidification, a decrease in ocean pH due to absorption of anthropogenic CO2, has variable effects on different species. To examine the effects of decreased pH on snow crab (Chionoecetes opilio), a commercial species in Alaska, we reared ovigerous females in one of three treatments: ambient pH (~8.1), pH 7.8, and pH 7.5, through two annual reproductive cycles. Morphometric changes during development and hatching success were measured for embryos both years and calcification was measured for the adult females at the end of the 2-year experiment. Embryos and larvae analyzed in year one were from oocytes developed, fertilized, and extruded in situ, whereas embryos and larvae in year two were from oocytes developed, fertilized, and extruded under acidified conditions in the laboratory. Embryo morphology during development was unaffected by pH during both years. The number of successfully hatched live larvae was unaffected by pH treatment in both years. Embryo mortality was very low, hatching success high, and neither differed with treatment in either year. Percent calcium in adult females' carapaces did not differ among treatments at the end of the experiment. The results from this two-year study suggest that snow crabs are well adapted to projected ocean pH levels within the next 2 centuries, although other life-history stages still need to be examined for sensitivity.

Effects of high pCO2on snow crab larvae: Carryover effects from embryogenesis and oogenesis reduce direct effects on larval survival

“…Transgenerational and selective breeding experiments suggest that many species have the capacity to evolutionarily adapt to ocean acidification via natural selection [26, 53–56]. In the case of snow crabs, the mortality over the course of the experiment did not vary much between the treatments which makes this a less likely, though still possible, mechanism [57]. Alternatively, a stress response in the females could induce greater maternal investment in oocytes.…”

“…In this study, we demonstrate that, at least for the parameters measured, snow crab larvae are resistant to low pH conditions and have the physiological plasticity to adapt to projected future carbonate chemistry conditions, especially since the embryos are similarly resistant [57]. However, more work needs to be done before it can be concluded the species as a whole will not be effected.…”