Revisiting the footprints of climate change in Arctic marine food webs: An assessment of knowledge gained since 2010

Abstract

In 2011, a first comprehensive assessment of the footprints of climate change on Arctic marine ecosystems (such as altered distribution ranges, abundances, growth and body conditions, behaviours and phenologies, as well as community and regime shifts) was published. Here, we re-assess the climate-driven impacts reported since then, to elucidate to which extent and how observed ecological footprints have changed in the following decade (2011 to 2021). In total, 98 footprints have been described and analysed. Most of those impacts reported in the 2011 assessment are reconfirmed and can, hence, be assumed as continuing trends. In addition, novel footprints (behavioural changes, diet changes, altered competition and pathogen load) are described. As in 2011, most reported footprints are related to changes in distribution ranges, abundances, biomass and production. Range shifts have mostly been observed for fish species, while behavioural changes have mainly been reported for mammals. Primary production has been observed to further increase in Arctic seas. The footprints on pelagic herbivores, particularly the key species Calanus spp., are less clear. In comparison to 2011, more complex, cascading effects of climate change, such as increased bowhead whale body conditions due to increased primary production, have been reported. The observed footprints, and the trends that they indicate, strongly suggest that due to further northward range shifts of sub-Arctic and boreal species Arctic seas are likely to experience increasing species richness in the future. However, a tipping point may be reached, characterized by subsequent biodiversity decline, when Arctic-endemic species will go extinct as ocean warming and/or acidification will exceed their physiological adaptation capacity. Furthermore, as invading boreal species have a competitive advantage due to their wider physiological and trophic range, Arctic species abundances are predicted to decrease. Overall, the future Arctic Ocean will very likely experience increasing numbers and intensities of climate-change footprints.

Long-term annual trawl data show shifts in cephalopod community in the western Barents sea during 18 years

“…Our results are in line with a global trend that shows that cephalopods' biomass is increasing in tropical and temperate areas (Doubleday et al, 2016). Our results are also in line with the trends observed for other Arctic nekton, such as increasing abundance of boreal pelagic fishes (Frainer et al, 2017;Brandt et al, 2023).…”

“…megalops (Table 5). A gradual influx of Atlantic fauna in the Barents Sea is also well known for other invertebrates and fishes, providing a basis for ongoing Atlantification of the local ecosystems (Jørgensen et al, 2016;Frainer et al, 2017;Brandt et al, 2023). The records from our study show that the cephalopod community of the Barents Sea is subjected to the Atlantification since the 2005-2013 period.…”

“…Mean annual temperatures in the Arctic, both modelled and observed, continuously increase since the late 1990s/early 2000s (Swart et al, 2015;Rantanen et al, 2022). This warming, which results from climate change, is often hypothesized as a main cause of the Atlantification (e.g., Jørgensen et al, 2016;Frainer et al, 2017;Brandt et al, 2023).…”

“…The Arctic is heavily affected by climate change (Lind et al, 2018;Praetorius et al, 2018;Rantanen et al, 2022) with increase of temperature, decrease of sea-ice extent, weakening of ocean stratification, and changes in physical ocean dynamics and hydrochemistry (Brandt et al, 2023;Gerland et al, 2023). The Barents Sea is one of the fastest warming areas in the Arctic (Overland et al, 2014;Lind et al, 2018;Gerland et al, 2023).…”

“…Due to ocean warming, many warm-water species are entering the Arctic from the Atlantic, causing changes in biomass, distribution and ecology of local Arctic species and altering predator-prey interactions (Brandt et al, 2023;Gerland et al, 2023). The changes in the Arctic ecosystems, which make them more similar to the North Atlantic ecosystems over time, are known as the 'Atlantification' (Jørgensen et al, 2016).…”