Understanding drivers and predictors of thermal tolerance in marine fishes

Abstract

Understanding how species and ecosystems will respond to thermal stress under future warming scenarios is critical for conservation, management, and ecology of aquatic organisms. Most aquatic species are ectotherms, and are particularly vulnerable to warming, as their metabolism, locomotion, and behavior are all directly linked to environmental temperatures. Warming is expected to directly influence the survival and distribution of many of the world’s ectotherms, yet responses will not be uniform across taxa. As such, several questions being studied across disciplines include (1) “Which species and ecosystems will be mostly affected by warming?”, (2) “How are species from different habitats responding to thermal stress?”, and (3) “What forces may be driving differences in maximum thermal tolerance across species?”. Fish present great opportunities to evaluate these broad questions. In this dissertation, these questions were addressed by looking specifically at an ecologically relevant group of marine species, cryptobenthic fishes. The first chapter evaluated variations in maximum thermal tolerance within and between communities in the Western Atlantic. In the second chapter, I integrate molecular approaches, specifically gene expression and single nucleotide polymorphisms, to understand how species from distinct environmental regimes respond to acute thermal events. Lastly, the third chapter is a meta-analysis comprised of the findings from over 200 studies to identify the factors shaping variation in thermal tolerance across freshwater and marine fishes and evaluate how species may fare under future warming scenarios. Collectively, this work links organismal, molecular, and macroecological perspectives, advancing our understanding of thermal tolerance in aquatic ectotherms providing insight into the resilience of natural communities under climate change.