Potential effect of variation in water temperature on development time of American lobster larvae
Studies typically assess the effects of temperature on development time, larval drift, and fisheries recruitment in American lobster at a range of constant temperatures. However, in nature, lobster larvae are exposed to varying temperatures, which might result in different development times than would be predicted from mean temperatures alone. To investigate this hypothesis, we conducted a modelling exercise in which we simulated larval development from hatch through stages I–IV under different combinations of mean and variance in temperature. Two thermal scenarios were modelled, the first based on estimated (i.e. interpolated by a model from empirical data) recent historical mean and variability of sea surface temperatures (SSTs) experienced by developing larvae in specific parts of the species' range, and the second based on a broad range of simulated combinations of mean and variability in temperature, including conditions that may be experienced by larvae in the future. The model calculated development times using daily SSTs and temperature-dependent development equations from previous studies of warm- and cold-water origin larvae. For warm-origin larvae, higher variability in temperature resulted in shorter development times at very cold and very warm mean temperatures, and longer development at intermediate mean temperatures, than lower (or no) variability. For cold-origin larvae, the effect of variable temperature was overall much smaller, and opposite to that for warm-origin larvae at very cold and very warm mean temperatures. These results show that lobster larvae experience meaningful variability of water temperature in nature, and that this variability can markedly impact larval development. Thermal variability therefore should be considered when estimating development and drift of lobster larvae, including under scenarios of climate change.