Glacial melting and massive spring blooms caused by global warming have significantly altered the environmental conditions in the Svalbard fjords of the European Arctic. These changes included reduced salinity (the gradient of salinity from inner to outer fjords, ranging from 23 to 34 PSU), stratification of the water column, increased turbidity (>135 FTU), low nutrient conditions (0.06–1.13 μM PO4−, 1.19–3.54 μM NO3−, 1.19–3.54 μM NH4+, and −2.1 to 0.9 N*), reduced light penetration, and release of organic matter, resulting in changes in the structure and composition of the phytoplankton. Our study, conducted in Isfjorden, van Mijenfjorden/Bellsund, and Hornsund of Svalbard in early August 2019, observed the dominance of cryptophytes in the phytoplankton composition after the spring bloom. Our results show a different phenomenon from the previous diatom/dinoflagellate dominance in the late 1970s and the early 2020s. Changes in phytoplankton composition can be explained as follows. (1) The excessive consumption of nutrients during spring bloom and the reduction of nutrient mixing in the water column stratification due to glacier melting has formed nutrient-depleted conditions, providing favorable conditions for the small-sized phytoplankton that easily find nutrients. (2) A wide range of salinities has created beneficial conditions for cryptophytes, capable of controlling osmotic stress against various salinities, of surviving compared to diatoms and dinoflagellates. (3) Finally, the influx of organic matter into fjords due to glacier melting can increase turbidity and decrease light availability; therefore, cryptophytes with mixotrophic metabolisms could be more viable than diatoms with only autotrophic metabolisms. In summary, the dynamic environmental conditions after enhanced spring bloom and glacier melting will further alter phytoplankton compositions and, in turn, influence food webs at higher tropical levels in European Arctic fjord ecosystems.
Bibliographical noteFunding Information:
This work was primarily supported by the National Research Foundation of Korea (NRF) grants ( 2021M1A5A1075512 , PN22013 and 2019R1F1A1059106 ) funded by the Ministry of Science and ICT (MOIT) of the Korean Government. Partial support was supported by Korea Institute of Marine Science & Technology Promotion (KIMST) funded by the Ministry of Oceans and Fisheries ( 20220533 ), and by the National Marine Biodiversity Institute of Korea Research Program ( 2022M00300 ). Finally, we kindly acknowledge Dr. Matthias Forwick (UiT, Norway) for the help during the cruise in 2019 and the captains and crews of R.V. Helmer Hanssen, as well as the scientific parties on board.
© 2022 Elsevier Ltd
- Glacier melting
- Svalbard fjords
ASJC Scopus subject areas
- Aquatic Science