UC San Diego

The epidermal microbiome of sharks is hypothesized to be consistent across individuals of the same species, regardless of biogeographical influence, suggesting that there are mechanisms that are recruiting and maintain the microbial community. To explore this hypothesis, I conducted an extensive investigation into the epidermal microbiomes of the leopard shark (Triakis semifasciata) across environments and an acute temperature shift. I also tested phylosymbiotic trends between epidermal microbiomes and respective benthic shark hosts. Initially, my research involved the analysis of T. semifasciata's microbiomes in captive, semi-captive, and wild settings. The associated microbiomes demonstrated comparable taxonomic community structure and maintained biodiversity irrespective of the captivity status of the hosts, therefore suggesting the host maintains a consistent microbiome even when born into captivity, and when the host experiences a change in habitat. For my next research chapter, I explored the influence of their evolutionary lineage and physical traits on their skin microbiomes by investigating three benthic shark species, horn (Heterodontus francisci), leopard (Triakis semifasciata), and swell shark (Cephaloscyllium ventriosum). This phase underscored the strong correlation between the diversity of skin microbiomes and the host's phylogenetic lineage, while the relationship with inter-denticle distance was less robust, affecting individual species within the microbiome. Finally, I examined the impact of thermal shifts on T. semifasciata's epidermal microbiomes to investigate the ability of the microbiome to tolerate the effects of global warming. The microbiomes underwent significant alterations of community compositions and functional pathway profiles following temperature changes, suggesting complex adaptive responses. Despite these compositional shifts, the dispersion of these communities remained consistent across temperatures, suggesting degree of resilience or stability in these microbial ecosystems. My research holds significant implications, particularly in the context of anticipated global ocean warming trends and human-induced pressures on marine ecosystems. It not only enriches our understanding of benthic shark ecology, but also underscores the need for more research on marine organisms' microbial community responses to temperature change.