Award: OCE-1737091

The goals of our project were to identify how mass mortality events of sea stars in the past decade have been influenced by genomic variation in the affected species; this may mean that some genotypes are more likely to survive than others, and we attempted both experimental and sequence-based efforts to determine these patterns. Overall, our team determined that genetic markers that appeared to have important phenotypic/survival effects at the beginning of this project were more complex and harder to interpret than we had hoped (Wares & Duffin, doi:10.1101/584235). Developing a high-quality genome for the sea star Pisaster ochraceus (Ruiz-Ramos et al, doi: 10.1111/mec.15386) enabled more thorough analysis of how variation in this species responded to the impacts of sea star wasting. This genome has been interpreted relative to RNA expression data comparing symptomatic and asymptomatic sea stars as well as those facing heat stress (Chandler & Wares, doi: 10.7717/peerj.3696; Ruiz-Ramos et al, doi: 10.1111/mec.15386). Full genome re-sequencing data for P. ochraceus have also enabled us to gain novel insights into the phenotypic and likely adaptive differences of populations in the Salish Sea relative to the outer Pacific coast (Duffin, Wares et al, in prep), the detailed understanding of where selection affected the Pisaster genome most strongly (Schiebelhut et al, in prep), and the expression pathways towards mortality (Duffin, Hewson, and Wares, in prep). This latter result built on the experimental outcomes of Aquino et al (doi: 10.3389/fmicb.2020.610009), which strongly suggests that the high mortality and deterioration of sea stars associated with sea star wasting is not pathogen driven but rather an environmental outcome of excess nutrient loading, warmer seas, and microbial feedback loops. As our work progressed, we organized an international consortium of experts on marine disease, echinoderm biology, and climate change to establish a new baseline of knowledge of sea star (asteroid) biology and how sea star wasting affects the integrity of these organisms. This consortium led to papers by Oulhen et al (doi: 10.1086/719928), Schiebelhut, Giakoumis et al (doi: 10.1086/722800 and doi: 10.1086/722284), Dawson et al (doi: 10.1086/727969) and Wares et al (doi: 10.1086/729512) which not only accomplished our goals of helping present a broader and updated perspective on sea star wasting through monitoring and genomic data, but also presented an outstanding networking opportunity that included many early career researchers taking on leadership roles in these publications. Three PhD students were guided by Wares and others on this project, with excellent career outcomes for all three as of this writing. The publications listed have already been cited over 115 times despite their recency. The net result of this project is not one that is easily built upon. We did not find an obvious pathogen as had been suggested in work that pre-dated our research, and all growing evidence suggests that an environmental disaster had instead been building with these diverse asteroids (sea stars) being one of the harbingers of climate and other environmental change. Much remains unknown about the impacts of sea star wasting on other coasts, because mortality can happen so quickly that only frequent monitoring offers hope of identifying and quantifying patterns of mortality (see Dawson et al, doi: 10.1086/727969). I am excited about the remaining in prep publications, however, as they will help identify the degree to which mortality is systemic rather than pathway-targeted in Pisaster, and will help us understand how patterns of phenotypic and life history variation may require updated study given that the Salish Sea populations of Pisaster ochraceus are substantially distinct from those on the outer coast (both papers in prep by Paige Duffin, PhD 2024, University of Georgia). Last Modified: 08/09/2024 Submitted by: JohnPWares