Unveiling the meiobenthic community structure of Prydz Bay, Antarctica during austral summer

Abstract

Meiobenthos are bottom-dwelling aquatic invertebrates having a size range of 63–500 μm. They play a pivotal role in ecosystem functioning, biogeochemical and trophic nutrient cycling. Due to the presence of Antarctic Circumpolar Current and steep gradient in nutrients and temperature, many taxa of the Southern Ocean (SO) show diverse biodiversity patterns in comparison to other deep sea areas of the world. Over the years, several Indian SO Expeditions have been carried out in the Indian sector of SO (ISSO), but this is a pioneer attempt to unveil the meiobenthic community structure and their functional diversity pattern from Prydz Bay (Indian sector of Southern Ocean), Antarctica. Meiobenthic community structures were investigated in eight different sampling sites along with their vertical profiling from the Prydz Bay during the austral summer 2020. Total meiofaunal abundance ranged from 24 to 521 indv. 10 cm-2, with the highest abundance recorded at station 23 and the lowest at station 9. A total of 9 meiobenthic taxa were found from this eco-region, with the highest percentage being the free-living marine nematodes as metazoan taxa. A total of 86 free-living nematode species were identified, where Sabatieria was the most common genus and represented by eleven species. Several univariate and multivariate analyses deciphered a distinct spatial variation in the meiobenthic community structure. Sediment texture and depth were the most significant environmental variables in shaping nematode assemblages. Biological Trait Analysis was performed using a total of 24 traits in 5 categories to unravel the functional diversity of free-living marine nematodes. The most dominant morphotypes were slender body shape, conical tail shape, dotted cuticle pattern, and non-selective deposit feeders with colonizing abilities of 2 (c–p score 2, in a scale from 1 to 5). Maturity Index (MI) and Index of Trophic Diversity (ITD) were highest in stations 15 and 32, respectively. RLQ approach with fourth-corner analysis was used to decipher the relationship between traits and environmental parameters. The RLQ analysis revealed the positive association of non-selective deposit feeder and slender body-shaped nematodes with higher water depth. The characterization of meiobenthic (especially nematode) communities in the context of taxonomic and functional attributes could help to evaluate the ecological status of ISSO. Further long term monitoring is also needed to get a comprehensive idea about their role in benthic ecosystem functioning in the milieu of global climate change.