Antarctic shallow water benthos in an area of recent rapid glacier retreat

Abstract

The West Antarctic Peninsula is one of the fastest warming regions on Earth. Faster glacier retreat and related calving events lead to more frequent iceberg scouring, fresh water input and higher sediment loads, which in turn affect shallow water benthic marine assemblages in coastal regions. In addition, ice retreat creates new benthic substrates for colonization. We investigated three size classes of benthic biota (microbenthos, meiofauna and macrofauna) at three sites in Potter Cove (King George Island, West Antarctic Peninsula) situated at similar water depths but experiencing different disturbance regimes related to glacier retreat. Our results revealed the presence of a patchy distribution of highly divergent benthic assemblages within a relatively small area (about 1 km 2 ). In areas with frequent ice scouring and higher sediment accumulation rates, an assemblage mainly dominated by macrobenthic scavengers (such as the polychaete Barrukia cristata), vagile organisms and younger individuals of sessile species (such as the bivalve Yoldia eightsi) was found. Macrofauna were low in abundance and very patchily distributed in recently ice-free areas close to the glacier, whereas the pioneer nematode genus Microlaimus reached a higher relative abundance in these newly exposed sites. The most diverse and abundant macrofaunal assemblage was found in areas most remote from recent glacier influence. By contrast, the meiofauna showed relatively low densities in these areas. The three benthic size classes appeared to respond in different ways to disturbances likely related to ice retreat, suggesting that the capacity to adapt and colonize habitats is dependent on both body size and specific life traits. We predict that, under continued deglaciation, more diverse, but less patchy, benthic assemblages will become established in areas out of reach of glacier-related disturbance.

Climate change, glacier retreat and a new ice‐free island offer new insights on Antarctic benthic responses

“…The walls of the island are of hard rocky substrate with steep slopes, even with vertical cliffs, and reach a maximum depth of 30 m. The island topography is irregular, with occasional step‐like terraces, numerous overhangs, small caves and crevices, and it is surrounded by soft bottoms. Sediment accumulation rates at this location are relatively high (Pasotti et al ).…”

“…The 25 de Mayo/King George Island, one of the South Shetland Islands where Potter Cove is located, is not an exception: ice caps registered a loss of about 20.5 km 2 in area between 2000 and 2008 (Rückamp et al 2011). The Fourcade Glacier surrounding Potter Cove shows an accelerated retreat, affecting the hydrographical characteristics of the cove and driving significant changes in established benthic communities (Monien et al 2011, Rückamp et al 2011, Schloss et al 2012, Bers et al 2013, Quartino et al 2013, Deregibus et al 2015, Pasotti et al 2015, Sahade et al 2015. This glacier retreat is also opening new ice-free areas, providing an excellent opportunity to study colonisation and succession processes in Antarctic ecosystems.…”

The reproductive ecology of the Antarctic bivalve Aequiyoldia eightsii (Protobranchia: Sareptidae) follows neither Antarctic nor taxonomic patterns

“…Previous records show densities of A. eightsii of up to 1540 m −2 at Signy Island (Peck and Bullough 1993) and biomass contributions equivalent to 56.6% of the total macrofaunal biomass at Faro station in Potter Cove (Pasotti et al 2015a). The geographical distribution of A. eightsii is patchy around the Antarctic continent (Dell 1990), but is extended to sub-Antarctic regions including King George Island (62 o 10′S) and the Magellan Strait (53 o 28′S) (González-Wevar et al 2012).…”

Is the meiofauna a good indicator for climate change and anthropogenic impacts?

“…In recently ice-free areas close to a glacier in the West Antarctic Peninsula, meiofauna showed relatively low densities. However, the pioneer nematode genus Microlaimus reached high abundance in these newly exposed sites (Pasotti et al 2014).…”