Benthic colonization in newly ice-free soft-bottom areas in an Antarctic fjord

November Benthic colonization in newly ice-free soft- bottom areas in an Antarctic fjord Cristian Lagger 0 1 Natalia Servetto 0 1 Luciana Torre 0 1 Ricardo Sahade 0 1 0 Universidad Nacional de CoÂrdoba, Facultad de Ciencias Exactas, FÂõsicas y Naturales, Laboratorio de EcologÂõa Marina, CoÂrdoba, Argentina, 2 Consejo Nacional de Investigaciones CientÂõficas y TeÂcnicas (CONICET), Instituto de Diversidad y EcologÂõa Animal (IDEA) , CoÂrdoba , Argentina 1 Editor: Andrea Belgrano , Sveriges lantbruksuniversitet , SWEDEN Extended glacier retreat is among the main consequences of the rapid warming of the West Antarctic Peninsula. Particularly, in the inner part of Potter Cove (South Shetland Islands, Antarctica) large areas are now exposed to open sea conditions owing to the retreat of Fourcade glacier. During the 2010 austral summer, underwater photographic surveys were undertaken by SCUBA diving up to 30 m in these new ice-free areas 80 m from the glacier front. Our main aim was to investigate colonization and early succession of the benthic assemblages on soft-bottom areas. Here, we reported a total of 1,146 animals belonging to 13 taxa. Filter-feeders comprised the largest trophic group and sessile fauna showed much higher coverages and densities than mobile fauna at all depths. The most abundant groups were ascidians and bryozoans, which together comprised ~90% of all taxa documented. In a region where most of marine-terminating glaciers are in retreat, these results are an important contribution to improve our knowledge on colonization in the newly ice-free areas. - Funding: Logistic and financial support was provided by Instituto AntaÂrtico Argentino, Alfred Wegener Institute, CONICET, FONCyT, EU (European Union) via grants PICTO-DNA NÊ 119, and IMCONet [FP7 IRSES (International Research Staff Exchange Scheme), Action No. 319718]. The funders had no role in study design, data collection Introduction Southern Ocean benthic fauna, including those found beneath the extent of existing ice shelves or inhabit the former extent of the ice shelf, is much more diverse and complex than expected [1±5]. These marine ecosystems are currently threatened by the changing environmental conditions; especially along the Western Antarctic Peninsula (WAP), which is one of the regions where warming is proceeding more rapidly on Earth [6±9]. Massive ice losses, represented by ice-shelf collapses and sea-ice reduction are among the main impacts of this rapid regional warming [10±12]. Furthermore, estimations of ice mass change suggest that glaciers in this region are particularly sensitive [ 13 ], and an accelerated mass loss has occurred during the last 60 years [ 14,15 ]. A recent Antarctic Peninsula glacier basin inventory indicates that 90% of the studied marine-terminating glaciers have been reduced in area since the 1940s [16]. The loss of ice coverage drives hydrological modifications on coastal regimes that may neg atively affect pelagic and benthic communities [17±19]. This loss of ice also opens up new areas for biological productivity and benthic colonization [20±22].Then, this in turn could drive to positive or negative feedbacks on climate change [ 20,23 ], depending on the prevalence of either one or the other process. and analysis, decision to publish, or preparation of the manuscript. The slow growth rates and population turnover registered in natural and artificial substrates [24±29], together with the relative constancy of environmental variables prevailing in Antarctic ecosystems, has led to an image of a certain stability in structural patterns and a low speed in ecological processes in the Antarctic benthos [ 6,30,31 ]. However, in the last years there have been also reports of rapid responses, fast colonization and growth rates of some species [3,21,32±35]. In addition, we also documented in a rocky island, recently uncovered by glacier retreat at Potter Cove, a benthic assemblage characterized by high species richness, diversity and structural complexity [ 22 ]. These finding challenge the extended idea of slow colonization processes in Antarctica. Antarctic benthic colonization studies in newly ice-free areas due to glacier retreat are extremely limited as well as glacier retreat effects (e.g. ice scouring, high sedimentation rates, large salinity shifts, etc.) on benthic systems. Then, the progressive retreat of Fourcade glacier in Potter Cove (up to 1 km since the 1950s, [ 36 ]) is not only a good example of the observed situation in the majority glaciers on the WAP but also provides an opportunity to examine these newly ice-free areas and the ongoing ecological processes. Considering that the estimated area affected by changes in the extension of tidewater glaciers is around 2.97 × 106 km2 [ 37 ], information on these processes is necessary. Our main aim was to investigate the colonization and early succession of the benthic assemblages in new ice-free soft bottom (...truncated)