The effects of CO2 level and temperature on embryos and free embryos of the Patagonian pejerrey Odontesthes hatcheri (Actinopterygii, Atherinopsidae)

Abstract

Climate Change includes an increase of both the concentration of atmospheric CO2 and of global temperature. Embryos (= eggs) of Odontesthes hatcheri were collected in spring–summer from the littoral of Lake Morenito (Andes of Argentina). Embryos and free embryos were exposed to different temperatures (within a currently natural thermal range) and CO2 levels (obtained by bubbling lake water with gaseous CO2). High temperature and high CO2 led to low embryonic survival. Embryonic abnormalities were observed. Incidence of colorless blood cells and delayed dorsal pigmentation increased significantly at high CO2 level. Free embryo survival decreased with time, being particularly low at high CO2 level. Free embryo body shape also signaled the effects of high CO2. The combined effect of temperature and CO2 was additive. As temperature and atmospheric pCO2 increasing continues, the best survival at hatching observed in our experiments (50–60%, pH 7.5, 14 °C) will deteriorate (< 20% at 18 °C and pH 7.0). These Climate Change-related results and the fact that the species is already threatened by translocated species suggest a fragile situation. Spatial variation of temperature and pCO2 led us to reconsider the suitability of shallow littoral vegetated areas of the lakes as anti-predatory refuges for fish early life periods.