Adaptation Actions for a Changing Arctic: Perspectives from the Barents Area

132

Adaptation Actions for a Changing Arctic: Perspectives from the Barents Area

Box 6.1 Observed changes in Barents Sea fish and benthic species The Barents Sea is home to roughly 100 species of fish that are regularly recorded during surveys (Bogstad et al., 2008;Wienerroither et al., 2011). Of these, just over half are considered boreal species while about one third are Arctic species (Andriyashev and Chernova, 1995; Bogstad et al., 2008, 2014). The species are distributed in patterns of fish communities that shift in composition and distribution with changing climatic conditions (Fossheim et al., 2006; Johannesen et al., 2012; Aschan et al., 2013). The general increase in overall abundance and expansion of boreal species that has accompanied the warming of the past few decades, referred to as ‘borealization’ (Figure 6.2), is likely to continue under the projected warming over the next 50 years (Fossheim et al., 2015). A decrease in total benthic biomass between surveys in 1924– 1935 and 1968–1970 through almost the entire Barents Sea (Figure 6.3) has been attributed to climate change by many researchers. However, this situation changed in the period 1991-1994 with biomass shifting and showing a considerable increase in the central region.The mechanisms underlying the changes in biomass are not clear. Some studies have suggested that this was due to a change in faunal distribution during the cold period between the 1960s and 1980s (Bochkov and Kudlo, 1973; Bryazgin, 1973; Antipova, 1975), while others have invoked declining biomass of resident boreal-Arctic species during the warm period from the 1930s to the 1960s (Galkin,1987; Kiyko and Pogrebov,1997,1998).The dominant boreal-Arctic species have an optimum temperature range that is positioned within the long-term mean temperature measured for the region. According to the latter theory, any deviations from the long-term mean have negative impacts on the reproduction,abundance,and biomass of boreal-Arctic species (Anisimova et al., 2011 and references therein). Monitoring of benthos at the Kola transect, which was started in 1994 by the Murmansk Marine Biological Institute, revealed an increase in the relative number of boreal species following the historical maximum

temperature anomaly recorded in 2006. Benthic biomass increased through the entire 17-year monitoring period and peaked in 2010.This is believed to have been caused by the long period of warming and abnormally high bottom temperatures between 2006 and 2012 (Olga Ljubina, Murmansk Marine Biological Institute, pers. comm.).

2004

Fish communities Atlantic Central Arctic

2012

Figure 6.2 Comparison of the abundance of fish communities in the Barents Sea between 2004 and 2012 (Fossheim et al., 2015).

1924-1935

1968-1970

1991-1994

Total biomass, g/m

>500

<10

10-25 25-50 50-100 100-300 300-500

Figure 6.3 Distribution of benthic biomass in the Barents Sea for three survey periods (after Brotskaya and Zenkevich, 1939; Antipova, 1975; Kiyko and Pogrebov, 1997) (Institute of Marine Research).