Late spring bloom development of pelagic diatoms in Baffin Bay

• Published in: Elementa: Science of the Anthropocene
• Main Authors: Augustin Lafond, Karine Leblanc, Bernard Quéguiner, Brivaela Moriceau, Aude Leynaert, Véronique Cornet, Justine Legras, Joséphine Ras, Marie Parenteau, Nicole Garcia, Marcel Babin, Jean-Eric Tremblay
• Format: Article in Journal/Newspaper
• Language: English
• Published: BioOne 2019
• Subjects: diatoms; spring bloom; sea ice; community composition; baffin bay; arctic; Environmental sciences; GE1-350; Arctic; Arctic Ocean; Baffin Bay; Greenland; Pacific; Baffin; Climate change; ice pack; Phytoplankton; Sea ice
• Online Access: https://doi.org/10.1525/elementa.382; https://doaj.org/article/ae7f2a54214948fdb8d5884169737d23

The Arctic Ocean is particularly affected by climate change, with changes in sea ice cover expected to impact phytoplankton primary production. During the Green Edge expedition, the development of the late spring–early summer diatom bloom was studied in relation with the sea ice retreat by multiple transects across the marginal ice zone. Biogenic silica concentrations and uptake rates were measured. In addition, diatom assemblage structures and their associated carbon biomass were determined, along with taxon-specific contributions to total biogenic silica production using the fluorescent dye PDMPO. Results indicate that a diatom bloom developed in open waters close to the ice edge, following the alleviation of light limitation, and extended 20–30 km underneath the ice pack. This actively growing diatom bloom (up to 0.19 μmol Si L–1 d–1) was associated with high biogenic silica concentrations (up to 2.15 μmol L–1), and was dominated by colonial fast-growing centric ('Chaetoceros' spp. and 'Thalassiosira' spp.) and ribbon-forming pennate species ('Fragilariopsis' spp./'Fossula arctica'). The bloom remained concentrated over the shallow Greenland shelf and slope, in Atlantic-influenced waters, and weakened as it moved westwards toward ice-free Pacific-influenced waters. The development resulted in a near depletion of all nutrients eastwards of the bay, which probably induced the formation of resting spores of 'Melosira arctica'. In contrast, under the ice pack, nutrients had not yet been consumed. Biogenic silica and uptake rates were still low (respectively <0.5 μmol L–1 and <0.05 μmol L–1 d–1), although elevated specific Si uptake rates (up to 0.23 d–1) probably reflected early stages of the bloom. These diatoms were dominated by pennate species ('Pseudo-nitzschia' spp., 'Ceratoneis closterium', and 'Fragilariopsis' spp./'Fossula' arctica). This study can contribute to predictions of the future response of Arctic diatoms in the context of climate change.