Laboratory-simulated marine heatwave accelerates early embryonic development in the sea urchin Arbacia punctulata at its cold range edge

Marine heatwaves are discrete periods of anomalously warm sea temperatures that are globally increasing in frequency and intensity. Marine heatwaves that occur in spring and summer may coincide with the developmental timing of sensitive early life-history stages of benthic marine invertebrates. The successful development of these early life stages, along with other physical and biological factors, will determine the abundance of benthic populations. Here, we examine the effects of a laboratory-simulated marine heatwave on early development (fertilization and embryonic cleavage) in the sea urchin Arbacia punctulata taken from its cold (northern) range edge in the Northwest Atlantic. We predicted that a marine heatwave would yield accelerated development given that ambient temperatures at this cold range edge are likely suboptimal for development of A. punctulata. Consistent with this hypothesis, we observed faster fertilization and cleavage rates in a marine heatwave treatment (27.5°C) as compared to an ambient temperature treatment (21.8°C) within the first 3 hours of development. The results contribute to our understanding of how marine heatwaves can affect the earliest life stage of A. punctulata.