Are Sponges Good Natural Sentinels for Monitoring Fish Diversity in Antarctic Coastal Waters?

Monitoring biodiversity in Antarctic ecosystems poses significant challenges, particularly due to the harsh environment. Traditional methods, such as beach seines, are time-consuming, resource-intensive, and difficult to carry out in Antarctica. To address these limitations, eDNA-based techniques have emerged as a valuable alternative. We employed eDNA metabarcoding from water samples and sponges to assess coastal fish communities along the Western Antarctic Peninsula, aiming to explore species diversity across a latitudinal gradient. Our analysis identified 14 Antarctic fish species and one marine mammal. Although previous research has validated the use of sponge-derived DNA for fish biodiversity studies, our results showed that seawater samples provided a very similar or, in many cases, an even more comprehensive view of the fish community. Interestingly, while sponge species exhibited variability in their performance, no significant differences were observed among them. Both water and sponge samples revealed similar beta diversity patterns, successfully capturing community composition at each location. The coastal fish fauna in the studied areas is highly dominated by notothenioids, with the genera Notothenia, Lindbergichthys, and Trematomus being the most abundant. All the species detected in both water and sponge samples were endemic to Antarctica, widely distributed, and previously known to inhabit the region. These findings are especially important given the increasing human activities, including commercial fishing and krill harvesting, that are impacting the Antarctic marine ecosystem.