Figure 2. Anticipated level of marine ice loss and related stressors in polar marine ecoregions by the end of this century (high-red, medium-yellow, low-green). Layers source: United States National Ice Center, Esri Data and Maps, National Snow and Ice Data Center, GLIMS Randolph Glacier Inventory, Natural Earth, Maps.com.
Environmental stressors from marine ice loss
Marine habitat expansion due to glaciers and ice shelves retreat
In the Arctic and Southern Ocean, all ecosystem components and services are expected to benefit from marine habitat expansion after ice shelf and glacier loss, with the former exposing much more area (Fig. 3). Planktic organisms can respond rapidly due to short lifespan, high growth rate, and less restricted lateral exchange in the pelagic system (Clarke et al. 2007, Bertolin and Schloss 2009, Cape et al. 2014). Fast colonisation by benthic diatoms, macroalgae and pioneer zoobenthic species has also been observed in the newly formed ice-free areas, while fish were rare (Quartino et al. 2013, Ahn et al. 2016, Campana et al. 2018, Braeckman et al. 2019). Massive blooming of benthic diatoms can either inhibit further colonisation by macroalgal and zoobenthic species or precondition the substratum for the establishment of pseudoperennial and annual macroalgae (Fricke et al. 2008). Benthic grazers play a key role in controlling their abundance during successional processes and reduce the competition for space (Campana et al. 2018). The dietary flexibility of benthic species is a potential ecological driver and central to its success in the colonisation of newly ice-free coastal habitats (Seefeldt et al. 2017). Glacier retreat was also shown to enlarge the foraging grounds for planktivorous seabirds and littoral habitats accessible to benthophages (Stempniewicz et al. 2017). Similarly, ice shelf and glacier retreat enables the formation of sea ice in the newly formed glacial bays, increasing the surface area available for sympagic algae and ice-obligate species. Although rapid shifts towards local primary production have been reported due to ice shelf collapse (Ingels et al. 2018), little is known about how this may affect benthic sub-ice shelf life that has recently been discovered (Griffiths et al. 2021, Owsianowski and Richter 2021). On the one hand, the emergence of highly productive coastal zones can lead to more efficient sinks of anthropogenic carbon and nutrient cycling as well as support higher biodiversity and benefit fish stocks. On the other hand, the environmental conditions of the least-disturbed habitat on the planet, the sub-ice shelf habitats, risk extinction as Earth’s ice imbalance continues.