The geographic range of the American lobster, Homarus americanus, spans a steep thermal gradient along the coastal Northwest Atlantic. As CO2 emissions increase globally, this range is rapidly warming and acidifying. Larval H. americanus hatch with a finite amount of maternally sourced lipid stores in their yolk sac, which provide an energetic buffer during the intermediate period between hatch and first feed. This study examines the response of newly-hatched, unfed H. americanus larvae to the combined effects of elevated pCO2 and temperature. Using a space-for-time approach, we compared larvae of two distinct sub-populations from thermally contrasting regions: Rhode Island, at the warmer, southern limit of the species range, and Midcoast, Maine, a cooler northern region. Average larval initial post-hatch weight was similar across regions and variability therein could be explained by maternal effects. Under 6 days of starvation, larvae from the two regions lost ∼14% of their initial dry weight and 25% of their Carbon weight. Still, end-century elevated temperature or acidification did not substantially alter those rates for larvae from either region. However, under an identical range of conditions over the 6-day experiment, larvae from the warmer regime maintained relatively stable oxygen consumption rates, while those from the cooler regime started 50% higher, then dropped by 80% within 2 days. If depressed metabolic functioning translates to reduced feeding efficiency for cool regime larvae, our findings suggest that subpopulations in the southern edge of the species range have a relative advantage in food-scarce environments under these conditions, adding to previous evidence for countergradient variation in this species. Further analysis of total fatty acid losses conducted on Midcoast larvae suggested starved larvae exposed to elevated temperature (19°C) experienced considerably greater losses of key lipid groups than larvae under ambient conditions (16°C, 400 ppm), particularly within the first 2 days of exposure. Our results highlight the short time frames over which ocean warming can accelerate the depletion of energy stores and make larvae more vulnerable to starvation.
Niemisto M., Contreras A., Wahle R. A. & Fields D. M., 2025. Increased temperature and acidification elevate the risk of starvation in American lobster larvae. ICES Journal of Marine Science 82(6): fsaf088. doi: 10.1093/icesjms/fsaf088. Article.
