Phytoplankton seasonal dynamics in Kongsfjorden, Svalbard and the adjacent shelf

• Main Authors: Hegseth, Else N, Assmy, Philipp, Wiktor, Józef M, Wiktor, Józef, Kristiansen, Svein, Leu, Eva, Tverberg, Vigdis, Gabrielsen, Tove M, Skogseth, Ragnheid, Cottier, Finlo
• Format: Book Part
• Language: English
• Published: Springer 2019
• Subjects: Arctic; Kongsfjorden; Phytoplankton; Svalbard; Time-series; Arctic Ocean; Climate change; glacier; Kongsfjord*; Sea ice; Spitsbergen
• Online Access: https://pure.uhi.ac.uk/en/publications/96a56b65-ddbd-4c43-b8d8-2cd8e2576d08; https://doi.org/10.1007/978-3-319-46425-1_6

Phytoplankton phenology is a key driver of biological and chemical processes in marine ecosystems because it directly affects cycling of nutrients, the strength of the biological carbon pump, and energy transfer to higher tropic levels. However, phytoplankton time-series from the Arctic are scant, thus limiting our ability to link phytoplankton phenology to environmental variability. Kongsfjorden on the west coast of Spitsbergen is an established coastal monitoring site at the entrance to the Arctic Ocean. In this review we have compiled previously published phytoplankton investigations, chlorophyll fluorescence time-series data and unpublished phytoplankton data covering the years 2002–2014 from Kongsfjorden and the shelf outside the fjord to elaborate the most pertinent environmental factors responsible for the seasonal and inter-annual variability in phytoplankton bloom dynamics, biomass and species composition. In general, phytoplankton dynamics in Kongsfjorden follow the classic spring-bloom paradigm, with the main biomass peak in April–May dominated by spore-forming diatom species and the colony-forming haptophyte Phaeocystis pouchetii, followed by a diverse, but low biomass community characterised by dinoflagellates and small flagellates and their protozoan grazers during summer. Despite this general trend, phytoplankton phenology is subject to large inter-annual variability with no clear long-term trend. This variability can be mainly attributed to variability in the magnitude and depth of Atlantic Water (AW) inflow, sea ice cover and glacier melt-water discharge. We have shown the impact of environmental variability on phytoplankton phenology, but high-resolution monitoring of annual cycles over many years is required to resolve the ephemeral variations of phytoplankton populations in space and time against the backdrop of climate change.