Community structure and environmental drivers of coastal planktonic ciliates on the Fildes Peninsula, Antarctica

The Fildes Peninsula is one of the most frequently and intensively visited regions in Antarctica, and its near shore ecosystems are subject to multiple environmental pressures. However, the mechanisms underlying microbial community responses in this area remain insufficiently understood. This study investigates differences in the abundance, structure, and stability of planktonic ciliate communities in Ardley Cove and Great Wall Cove by comparing their responses to distinct environmental stressors. Using ciliate-specific primers combined with high-throughput sequencing, we achieved high taxonomic resolution of ciliate communities in the study area. The results show that Ardley Cove exhibited higher nutrient levels but lower planktonic ciliate species diversity. Its community was dominated by a few Oligotrichida ciliates, in contrast to the more diverse assemblages observed in Great Wall Cove. A co-occurrence network constructed from ciliate and bacterial communities revealed that Great Wall Cove possessed greater ecological stability and robustness. The relative abundance of Tintinnida displayed clear associations with key environmental gradients (e.g., chlorophyll-a and salinity), indicating its potential use as a candidate bioindicator for assessing ecological conditions in Antarctic coastal waters. Overall, this study provides an operational molecular ecological framework for evaluating the ecological health of polar environments.