Impaired hatching exacerbates the high CO2 sensitivity of embryonic sand lance Ammodytes dubius
Hannes Baumann, LF Jones, Christopher S. Murray, SA Siedlecki, Michael A. Alexander, E. C. Cross
Abstract
Rising oceanic partial pressure of CO 2 (pCO 2 ) could affect many traits in fish early life stages, but only few species to date have shown direct CO 2 -induced survival reductions. This might partly be because species from less CO 2 -variable, offshore environments in higher latitudes are currently underrepresented in the literature. We conducted new experimental work on northern sand lance Ammodytes dubius , a key forage fish on offshore Northwest Atlantic sand banks, which was recently suggested to be highly CO 2 -sensitive. In 2 complementary trials, we produced embryos from wild, Gulf of Maine spawners and reared them at several pCO 2 levels (~400-2000 µatm) in combination with static (6, 7, 10°C) and dynamic (10→5°C) temperature treatments. Again, we consistently observed large, CO 2 -induced reductions in hatching success (-23% at 1000 µatm, -61% at ~2000 µatm), and the effects were temperature-independent. To distinguish pCO 2 effects during development from potential impacts on hatching itself, some embryos were switched between high and control pCO 2 treatments just prior to hatch. This indeed altered hatching patterns, consistent with the CO 2 -impaired hatching hypothesis. High CO 2 also delayed the day of first hatch in one trial and peak hatch in the other, where later-hatched larvae were of similar size but with progressively less endogenous energy reserves. For context, we extracted seasonal pCO 2 projections for Stellwagen Bank (Gulf of Maine) from regional ensemble simulations, which indicated a CO 2 -induced reduction in sand lance hatching success to 71% of contemporary levels by 2100. The species’ unusual CO 2 sensitivity has large ecological and scientific ramifications that warrant future in-depth research.