Interannual variability in the structure of macrobenthic assemblages in the maritime Antarctic intertidal zone

The incessantly disturbed Antarctic intertidal zone is currently facing additional challenges associated with climate change, such as warming and increased meltwater runoff. However, long-term biological data that would enable quantification of how these environmental changes affect the intertidal zone and its ecosystem functioning are still lacking. Therefore, the main goal of this study was to evaluate the interannual variability in the structure of an intertidal macrobenthos assemblage in maritime Antarctica (Admiralty Bay, King George Island 62° S). Sampling was carried out in 2011, 2017 and 2019, in early January, at three intertidal levels: low, mid and high. The results clearly show that the intertidal zone remained relatively rich and abundant over the investigated period. The interannual pattern of diversity and species richness was as follows: 2019 > 2017 > 2011. Each studied year was dominated, to varying degrees, by the bivalve Altenaeum charcoti , the gastropods Laevilacunaria antarctica , Laevilitorina caliginosa and Onoba sp., along with the amphipod Paramoera edouardi . The primary driver of interannual variability seems to be random physical disturbances, such as temperature anomalies, ice activity, and wind force. In addition, year-to-year temperature changes may further affect the state and development of intertidal assemblages in a given year. The interannual variation documented here provides a stronger basis for assessing how Antarctic intertidal assemblages may respond to the rapid environmental changes projected for this region. • Species richness and diversity were highest in 2019 and lowest in 2011. • Species recruitment was high, mainly for taxa adapted to harsh conditions. • Five widespread species dominated at all tide levels each year. • Interannual variability of macrofauna seems to reflect random physical disturbances. • Year-to-year temperature changes may influence intertidal assemblage structure.