Tidewater glacier retreat in Antarctica: The table is set for fast-growing opportunistic species, is it?

Abstract

The rapid warming of the West Antarctic Peninsula (WAP) is causing an important expansion of marine coastal areas due to glacier retreat. These new ice-free areas offer additional habitats for the colonization of benthic species in areas formerly occupied by ice. The establishment of benthic species can represent important negative feedback to the warming process due to the new carbon fixed and stored. Opportunistic, fast-growing, and high turnover species are expected to colonize these new emerging areas. At Potter Cove, the glacier retreat has opened wide areas of soft bottoms, which provides an excellent study area to assess the colonization process and the success of opportunistic species. Here, we examined the population response of the opportunistic soft coral Malacobelemnon daytoni species in the soft bottom area of Potter Cove with different exposure times due to glacier retreat. Our results show a significant variation of M. daytoni population among the sampled areas in terms of presence, abundances, and distribution. In the long-term ice-free areas, opened for more than 60 years, we observed a ~20-fold increase of M. daytoni densities within just 15 years. However, this extraordinary population outburst was not observed in the newer ice-free areas (≤15 years). We registered very low densities in areas of 15 years and no colonies in areas with 10 years of open sea conditions. These were unexpected results based on colonization capabilities showed by the species and habitat suitability of the new areas. Indeed, using Species Distribution Models (SDMs) we also obtained contrasting outputs. SDMs based on long-term areas presence data predicted high habitat suitability and the potential presence of the species in the newer areas. However, when based on newer and older areas data, SDMs showed low habitat suitability and potential absence of the species in the newer areas. This work suggests that species that can be considered as fast and efficient colonizers, could not perform in that way under certain conditions. This deepens the current knowledge on species natural history and environmental relationships, especially to improve our prediction capabilities under changing environmental conditions.