Abstract
Benthic foraminifera are one of the most widely and abundantly distributed organisms in the fjords of Svalbard and Norway. Due to their short life span and quick reactivity to environmental changes they can be used as indicators of the “atlantification” process. Here, we compare the benthic foraminifera assemblages along the latitudinal gradient, from the fjords of northern Svalbard to southern Norway to assess whether the “atlantification” process may homogenise the foraminiferal assemblages in terms of their abundance and species composition. Furthermore, the previously published data on benthic foraminiferal faunas was updated to identify changes in distribution that have occurred over the last few decades. For this purpose, fjord mouths in western and northern Svalbard (Isfjorden, Wijdefjorden and Rijpfjorden) and northern and southern Norway (Balsfjorden, Raunefjorden and Hjeltefjorden) were resampled. The analysis revealed similarities between the Svalbard and Norwegian foraminiferal assemblages of up to 30%; however, there were essential differences in terms of abundance and biodiversity. These results suggest that Svalbard fjords will remain distinct in the future, even under conditions of further warming or “atlantification”. Svalbard fjords may be dominated by Atlantic Water- preferring species, whereas, in Norwegian fjords, pressure from human activity will probably be the main driver of environmental changes, leading to changes in the foraminiferal assemblages with the increasing dominance of opportunistic, hypoxia-tolerant species.
Highlights
Fjords are the most common coastal features in the European Arctic
The lowest foraminiferal abundance and species richness were recorded in Rijpfjorden, probably because of the cold Winter Cooled Water (WCW) at the fjord bottom and the prevalence of drifting sea ice at the surface (Cottier et al 2019)
The most abundant species in Rijpfjorden was A. glomeratum: this species thrives in cold, well-oxygenated waters (Williamson et al 1984; Alve 1991), which is in accordance with the presence of WCW at the bottom of the fjord
Summary
Fjords are the most common coastal features in the European Arctic. They are a unique transition zone between land and open sea, which provide valuable information on climatic and environmental changes (Syvitski and Shaw 1995; Cottier et al 2005). Our study updates the existing dataset to identify possible changes in benthic foraminifera species distribution that have occurred in the past three decades For this purpose, the mouths of the fjords in western and northern Svalbard (Isfjorden,Wijdefjorden and Rijpfjorden), as well as northern and southern Norway (Balsfjorden, Raunefjorden, Hjeltefjorden), are resampled. Rijpfjorden is a south–north-oriented fjord cutting into the northern coast of Nordaustlandet (Fig. 1A) It has the northernmost exposure of all of the studied fjords and is a true Arctic fjord that freezes every winter and is ice-covered for at least nine months a year (October – June; Ambrose et al 2006; Cottier et al 2019). Strong northern winds induce upwelling, causing denser waters to spill over the sills, resulting in salty, cold, oxygen-rich waters to fill the fjord, improving environmental conditions (Aksnes 2006) Neither of these fjords is influenced by glaciers. In the Norwegian fjords, sedimentation varies between 0.13 cm yr−1 and 0.28 cm yr−1 (Włodarska-Kowalczuk et al 2019)
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