Award: OCE-1947639

Climate change is driving shifts in the distribution of marine organisms around the world and as such, establishing the temperatures that organisms can tolerate provides a foundation for understanding how species will respond to ocean warming. Many organisms that live on the seafloor have larvae (babies) that swim or drift on the ocean currents for a period of time before settling on the bottom to grow into adults.The range of temperatures that the larvae can tolerate influences the depth where the larvae reside, where they choose to settle on the bottom, and ultimately a species range.While much is known about the thermal tolerance of adults, far less is known about the acceptable temperature range for the earliest life stages.Moreover, very few studies actually link thermal tolerance determined in laboratory studies with the performance and distribution of larvae in the ocean.We use the American lobster (Homarus americanus) as a model species to explore the limits of temperature tolerance in larvae and how tolerance changes as the larvae develop and eventually settle on the seafloor.Successful larval settlement supports the adult populations that underpin one of the most valuable fisheries inNorth America. Our research broadens our understanding of larval response to temperature stress and helps inform our understanding of how this valuable natural resource will respond to climate change.Our project provided training for a graduate student, six NSF-REU summer undergraduate interns, and other undergraduate students.Two of the collaborating institutions, Hood College and University of New England, are predominantly undergraduate institutions and this project provides course content and equipment to support student research. The overarching goal of our project is to define the upper and lower limits of temperature tolerance in the larval stages of lobsters and mechanistically link their thermal tolerance to settlement patterns in the ocean.Our work is unique in that we work with both laboratory reared and wild caught larvae.The specific objectives of our project are: 1) define lower and upper thermal limits of the four larval stages (I-IV) and stage V juveniles via laboratory experiments, and identify developmental shifts in sensitivity using assays of growth, mortality, oxygen consumption, and molecular methods in the laboratory; 2) identify physiological markers of thermal stress to further define the thermal tolerance of larvae; 3) compare thermal tolerance of laboratory reared stage IV larvae with their wild counterparts; 4) Assess thermal stress in stage IV larvae in the field by deploying caged larvae at different depths (and thus temperatures); and 5) measure the patterns of larval lobster settlement and juvenile abundance in nature as a function of depth, temperature, and abundance of larvae in the water. Last Modified: 07/18/2024 Submitted by: DouglasBRasher