Consequences of food limitation on the performance of early stage American lobster larvae

In the Gulf of Maine, larval settlement of the American lobster (Homarus americanus) to coastal nurseries has been on the decline despite record high levels of broodstock. Recent evidence suggests larvae may be subject to food limitation due to climate-linked changes in the abundance and distribution of important zooplankton prey. However, little is known about the diets of lobster larvae and their ability to survive starvation in the earliest larval stages. In this study two distinct experiments were conducted to better understand diet and metabolic demands of early stage larvae. The firstexperiment was designed to evaluate the effect of an herbivorous or carnivorous diet on the development rate of Stage I larvae. In the laboratory we subjected day-old lobster larvae to four different diet treatments over 9 days: a starved control, brine shrimp-only (Artemia sp.), phytoplankton-only (Tetraselmissp.), and both foods combined. We found the lowest survival in starved and algae-fed larvae, the greatest survival in those fed brine shrimp only, and intermediate survival in those fed a mixed diet. Only larvae with brine shrimp in their diet molted to stage II and remained active for the duration of the trial. These data suggest diets consisting of higher levels of lipid and protein are necessary for early survival and development. In our second experiment we compared the consequences of starvation on stage I larvae from thermally contrasting northern (Maine) and southern (Rhode Island) populations. Over 6 days, larvae lost a significant amount of carbon weight, ¼ of their weight for Maine populations and ⅓ for Rhode Island populations. Oxygen consumption rates (OCR) also decreased over 6 days for both populations. These findings suggest early feeding on a zooplankton diet is essential for larval survival and development. Warming waters could magnify metabolic demands and exacerbate the effects of food limitation, potentially narrowing the bottleneck between broodstock and recruits.