Carly E. Karrick 🏳️‍🌈

In coral reef ecosystems, microbes play many important roles, ranging from enhancing immunity, to causing disease, to providing nutrition, and more. Given the importance of microorganisms in maintaining ecosystem- and organism-level stability, it is crucial to understand how microorganisms are distributed on a reef. Both abiotic (e.g., nutrient composition) and biotic (e.g., reef organisms) factors can influence microbial ecology (Shaver et al., 2017). Broadly, consumers have been proposed as vectors of beneficial and pathogenic microorganisms. For example, coral- and macroalgae-eating fishes have been shown to contain key coral symbionts and potentially pathogenic bacteria in their feces (Grupstra et al., 2021; Grupstra et al., 2022; Grupstra et al., 2023). However, reef detritivores like sea cucumbers may also play a role in the distribution of microorganisms on a reef as they “clean” sediment after aerating and consuming organic material in the substrate. Sea cucumbers are important culturally and commercially in French Polynesia (Mercier et al., 2025), and have been associated with altering microbial communities in the sediment (Pan et al., 2024; Maritan et al., 2025) and reduced coral disease (Clements et al, 2024). However, our understanding of the role of sea cucumbers in influencing microbial community composition in reef sediments is limited in species and ecological context. In French Polynesia, to what extent do distinct sea cucumber species and morphs influence sediment microbial communities, and does this change across nutrient gradients? To answer this question, I am using 16S amplicon sequencing to describe bacterial/archaeal communities and PMA-qPCR to quantify live vs. dead cell densities in sea cucumber feces and uneaten sediments.