Seasonal changes in foraminiferal assemblages along environmental gradients in Adventfjorden (West Spitsbergen)

Abstract

Foraminifera are numerically abundant components of the benthic fauna; thus, they are very important compounds in glaciomarine environments. However, ongoing oceanographic changes may influence their distribution, abundances and diversity differently at different times of the year. In the present study, we aimed to assess seasonal environmental changes in an Arctic fjord (Adventfjorden, W Spitsbergen) and the structure and distribution of benthic foraminiferal assemblages during four seasons (January, May, August, November). The study revealed that the benthic foraminiferal assemblages in Adventfjorden are susceptible to environmental changes related to enhanced inflow of shelf-transformed water (STW). We distinguished three zones in the fjord: (1) the deeper outer part influenced by STW, with living specimens staying in the few uppermost layers of sediment, (2) the shallower interior influenced by freshwater outflows and high sediment load, resulting in the dominance of opportunistic glaciomarine taxa constantly buried in the sediment, and (3) the central part, where the seasonal variation in the foraminifera assemblage reflects the interplay between the influence of riverine inputs and STW. Our study also revealed that the presence of STW in Adventfjorden favours an early spring appearance of juvenile foraminifera; however, the majority of the specimens are later withered and do not contribute to the summer pool of mature individuals. On the other hand, the majority of the mature specimens can survive during the winter because of sufficient organic matter stocks and year-long ice-free conditions.

Could Norwegian fjords serve as an analogue for the future of the Svalbard fjords? State and fate of high latitude fjords in the face of progressive “atlantification”

“…A. glomeratum, which has been positively correlated with the presence of TAW entering the inner bays of Isfjorden, i.e. Adventfjorden (Szymańska et al 2017;Kucharska et al 2019). As Isfjorden is widely open to the main flow of the WSC, it has been constantly influenced by AW since at least the early 1990s.…”

Foraminifera‐derived carbon contribution to sedimentary inorganic carbon pool: A case study from three Norwegian fjords

“…The length of the corer was 30 cm, but the upper 10 cm was used in our analysis. Such length is advised to represent multi-seasonal foraminiferal assemblages and to analyse deep-dwelling species (Jorissen, 1999;Kucharska et al, 2019;Szymańska et al, 2017). Water depth during sampling varied from 180 to 300 m (Table 1).…”