Combined effects of temperature and food on ribbed mussel larvae (Geukensia demissa)

Ribbed mussels are a key species in North American Atlantic salt marshes. Like many marine bivalves, they have planktotrophic larvae that facilitate dispersal, exposing early life stages to many thermal and nutritional environments across their latitudinal range. However, climate change is reshaping thermal and nutritional seascapes, potentially altering population dynamics through early life stage performance. To test whether changing environmental conditions, like temperature and food availability, influence early life stages, we tested their combined effects on larval survival, growth, and development in ribbed mussels. Survivorship was lowest at 15 °C, peaked at 20 °C and 25 °C, and declined at 30 °C. Growth and development rates increased with temperature, with larvae growing and metamorphosing faster and at larger sizes. Reduced food availability decreased survivorship and growth, particularly at higher temperatures, but had no effect on the rate of development, suggesting that food and temperature interact in non-additive ways. Our findings highlight the need to assess the effects of climate change on larval stages across their biogeographic range. Incorporating thermal and nutritional sensitivities of larvae in predictive models will be essential for understanding climate impacts on ribbed mussels and informing restoration and conservation in salt marsh ecosystems.