Antarctic ecosystem responses following ice‐shelf collapse and iceberg calving: Science review and future research

Abstract

The calving of A‐68, the 5,800‐km2, 1‐trillion‐ton iceberg shed from the Larsen C Ice Shelf in July 2017, is one of over 10 significant ice‐shelf loss events in the past few decades resulting from rapid warming around the Antarctic Peninsula. The rapid thinning, retreat, and collapse of ice shelves along the Antarctic Peninsula are harbingers of warming effects around the entire continent. Ice shelves cover more than 1.5 million km2 and fringe 75% of Antarctica's coastline, delineating the primary connections between the Antarctic continent, the continental ice, and the Southern Ocean. Changes in Antarctic ice shelves bring dramatic and large‐scale modifications to Southern Ocean ecosystems and continental ice movements, with global‐scale implications. The thinning and rate of future ice‐shelf demise is notoriously unpredictable, but models suggest increased shelf‐melt and calving will become more common. To date, little is known about sub‐ice‐shelf ecosystems, and our understanding of ecosystem change following collapse and calving is predominantly based on responsive science once collapses have occurred. In this review, we outline what is known about (a) ice‐shelf melt, volume loss, retreat, and calving, (b) ice‐shelf‐associated ecosystems through sub‐ice, sediment‐core, and pre‐collapse and post‐collapse studies, and (c) ecological responses in pelagic, sympagic, and benthic ecosystems. We then discuss major knowledge gaps and how science might address these gaps. This article is categorized under: Climate, Ecology, and Conservation > Modeling Species and Community Interactions

Seasonal Food Web Dynamics in the Antarctic Benthos of Tethys Bay (Ross Sea): Implications for Biodiversity Persistence Under Different Seasonal Sea-Ice Coverage

“…Predation and necrophagy, which are common in these communities, are considered successful strategies above all when basal resource inputs are limiting and in the presence of disturbance caused by ice-scouring (McClintock, 1994;Smale et al, 2007;Dunlop et al, 2014). The latter reduces the diversity and abundance of benthic animals and algae (McClintock, 1994;Smale et al, 2007;Dunlop et al, 2014;Ingels et al, 2020), with a substantial impact on the local availability of food sources. The incidence of ice-scouring is generally known to be higher in shallow than in medium-depth waters (Gutt and Piepenburg, 2003), although the availability of sympagic algae is greater, and can explain the lower number of taxa found after than before the sea-ice break-up.…”

“…The effects of seasonality are expected to increase with latitude, with tremendous changes observed in polar areas (Clark et al, 2013;Chown et al, 2015;Ingels et al, 2020), where light and sea-ice dynamics drive the structure and functioning of aquatic food webs (Poloczanska et al, 2016;Wing et al, 2018). Seaice influences key ecological processes in polar ecosystems, such as phytoplankton blooms, physical disturbance of the seabed due to iceberg scouring (Gutt and Piepenburg, 2003;Arrigo, 2014), reproductive cycles, recruitment, and trophic interactions among a wide range of species (Constable et al, 2014).…”

“…For this purpose, we measured variations in the food web structure of the shallow-water Antarctic benthic community under two different sets of sea-ice coverage conditions. Since the number of species in shallow-water Antarctic benthic communities is subject to natural seasonal variation (Gutt and Piepenburg, 2003;Thrush and Cummings, 2011;Clark et al, 2013;Ingels et al, 2020), to avoid any bias arising from species number in the interpretation of niche and food web metrics, we also considered taxa common to both study periods.…”

Responses of Southern Ocean Seafloor Habitats and Communities to Global and Local Drivers of Change

“…Whilst suspension feeding ophiuroids halved in abundance, local populations of deposit feeding species increased (Gutt et al, 2013). A detailed discussion of ecological responses to ice shelf loss is presented in Ingels et al (2020), including shifting food regimes associated with modified phytodetrital inputs. The retreat of glacier tongues, long and narrow sheets of ice that project out from the coastline, may also have similar benthic effects to ice-shelf disintegration.…”

Breaking All the Rules: The First Recorded Hard Substrate Sessile Benthic Community Far Beneath an Antarctic Ice Shelf

“…Frontiers in Marine Science | www.frontiersin.org This contrasts sharply with the areas beneath the floating ice shelves, which are hidden from daylight and often far from areas of primary productivity (Ingels et al, 2021). Ice shelves cover roughly a third of the Antarctic's 5 million km 2 of continental shelf (Ingels et al, 2018).…”