Effects of an Adélie penguin colony on coastal meiofaunal assemblages of the Ross Sea (Antarctica)

Abstract Factors shaping biodiversity and functioning of coastal ecosystems in Antarctica are still largely unknown due to the overlap of multiple physical and bio-ecological forcings. Here, we investigated three coastal areas of the Ross Sea (Antarctica) across a coast-offshore transect (25–140 m depth), including an area located in front of the longest-dwelling penguin colony of the Adélie Cove Bay and other two areas, Camp Icarus Bay and Rod Bay, far from the penguin colony. The deposition of the penguin guano determined an extraordinary accumulation of organic matter in coastal sediments (6.9 ± 0.6 mgC g −1 ), among the highest values reported worldwide so far, which cause apparent detrimental effects on meiofaunal biodiversity, in terms of richness of taxa and nematode species. Meiofaunal abundance showed a wide spatial variability among bays and depths (range: 252 ± 103 to 5961 ± 659 ind. 10 cm −2 ) with lower abundance and biomass at shallow stations. Here, we found a limited food availability possibly associated with the occurrence of the ice-scouring along the coast. Overall, 17 meiofaunal higher taxa were identified and the richness of taxa reached the highest values at 140 m depth in all the three bays investigated. Nematodes were characterized by a high diversity with 100 species identified. A relevant number of exclusive nematode species was observed in each bay and only 16 species were common at all sampling areas. The huge variability of biodiversity among the investigated areas was apparently related to a combination of biological (food availability and trophic interactions) and physical (ice-scouring) factors generating a mosaic of different assemblages. The combination of these factors determined a high turnover (beta) diversity (up to 100% of turnover for meiofaunal rare taxa and 81% for nematode species), which is likely a key driver for the high regional biodiversity observed in the coastal Antarctic sediments.