Free-Drifting Icebergs: Hot Spots of Chemical and Biological Enrichment in the Weddell Sea

Abstract

The proliferation of icebergs from Antarctica over the past decade has raised questions about their potential impact on the surrounding pelagic ecosystem. Two free-drifting icebergs, 0.1 and 30.8 square kilometers in aerial surface area, and the surrounding waters were sampled in the northwest Weddell Sea during austral spring 2005. There was substantial enrichment of terrigenous material, and there were high concentrations of chlorophyll, krill, and seabirds surrounding each iceberg, extending out to a radial distance of approximately 3.7 kilometers. Extrapolating these results to all icebergs in the same size range, with the use of iceberg population estimates from satellite surveys, indicates that they similarly affect 39% of the surface ocean in this region. These results suggest that free-drifting icebergs can substantially affect the pelagic ecosystem of the Southern Ocean and can serve as areas of enhanced production and sequestration of organic carbon to the deep sea.

Major impacts of climate change on deep-sea benthic ecosystems

“…These predictions of temperature change are in alignment with evidence that the deep Greenland Sea has warmed by 0.7°C since the 1950s (~ 0.01°C yr -1 ; Somavilla et al, 2013). Bathyal waters off Antarctica are also warming by 0.005-0.01°C yr -1 (Smith et al, 2007;Purkey and Johnson, 2010).…”

“…In the longer term, iceberg scouring and dropstone deposition will tend to elevate diversity on regional scales through (re)colonization processes, although the immediate effect of scouring will be local elimination of many species (Gutt et al, 1996;Gutt and Piepenburg, 2003). In addition, recent evidence suggests that iceberg production followed by melting might significantly elevate local nutrient levels, driving greater primary production and POC flux to the seafloor in deeper waters (Smith et al, 2007), though this will probably decline after initial increases under continued warming. Thus, the immediate direct impacts on seafloor communities will be relatively short-lived, but the wider effects may be longer lasting.…”

“…For example, in the Arctic, the commercially important snow crab has extended its range to the north (Alvsvåg et al, 2009;Bluhm et al, 2009), and warming appears to have led to the appearance of highly predacious, temperature-sensitive king crabs (Lithodidae) in waters of the WAP . These invasive top predators can threaten the diversity of epi-and infaunal communities, as well as physically disturb large areas of soft sediment (Smith et al, 2007). On the other hand, warming-induced extensions of the ranges of temperate-subpolar benthic species into polar oceans (Bluhm et al, 2011) may increase benthic diversity, both in the short-term (Węsławski et al, 2011) and the long-term (Rasmussen et al, 2003;, although these invasive species are likely to displace less competitive, endemic species unable to cope with increased temperatures (Figure 4A).…”

“…Despite emerging evidence that climate-driven changes in deep-sea environmental conditions may perturb the functioning of oceanfloor ecosystems (Danovaro et al, 2001;Smith et al, 2007Dunlop et al, 2016;, our understanding of the extent to which projected physical and chemical changes will lead to deleterious ecological consequences is still very poor (Philippart et al, 2011). Given that deep-sea ecosystems are vitally important to the Earth system (Danovaro et al, 2014) and are at considerable risk from ongoing climate change (Mora et al, 2013;Jones et al, 2014;Levin and Le Bris, 2015), our goal in this paper is to understand and predict the nature and consequences of climate change at the deep seafloor until 2100.…”

Advection in polar and sub-polar environments: Impacts on high latitude marine ecosystems

“…In southern areas of the continental shelf that are associated with sea ice for most of the year, such as the southern Antarctic Peninsula and the Ross Sea, the Antarctic silverfish (Pleuragramma antarcticum) is an important species in food webs (Ducklow et al, 2007;K.L. Smith et al, 2007;Nicol et al, 2008aNicol et al, , 2008bHeerah et al, 2013).…”