Contrasting interannual changes in phytoplankton productivity and community structure in the coastal Canadian Arctic Ocean

Abstract

The rapid physical changes affecting the Arctic Ocean alter the growth conditions of primary producers. In this context, a crucial question is whether these changes will affect the composition of phytoplankton communities, augment their productivity, and eventually enhance food webs. We combined satellite and model products with in situ datasets collected during fall and provide new insights into the response of phytoplankton biomass and production in the Canadian Arctic by comparing an interior shelf (Beaufort Sea) and an outflow shelf (Baffin Bay). Correlation analysis was used to distinguish between seasonal and interannual variability and revealed that most biological variables are responding to the interannual pressures of climate change. In southeast Beaufort Sea, a change in phytoplankton community composition occurred, with a significant increase in diatoms from 2% (2002) to 37% (2010-2011) of the total protist abundance. In 2011, photosynthetic picoeukaryotes were twice as abundant as in 2002. For these two phytoplankton groups, abundance was correlated with the duration of the open-water period, which also increased and affected vertical stratification and sea-surface temperature. In contrast, there was a sharp decline in centric diatom abundance as well as in phytoplankton biomass and production in northern Baffin Bay over the years considered. These decreases were linked to changes in seasonal progression and sea-ice dynamics through their impacts on vertical stratification and freshwater input. Overall, our results highlight the importance of stratification and the duration of the open-water period in shaping phytoplankton regimes-either oligotrophic or eutrophic-in marine waters of the Canadian Arctic.

Resistance of Arctic phytoplankton to ocean acidification and enhanced irradiance

“…In all treatments, the assemblages were dominated by C. socialis (or C. gelidus according to recent taxonomic description; Chamnansinp et al 2013;Blais et al 2017). C. socialis/gelidus was also dominating the [5 lm fraction of the initial and final assemblages of another experiment initiated with waters from within the DCM at the same time as our experiment (Hussherr et al 2017).…”

“…All final assemblages were solely dominated by C. socialis. Please note that this species, previously identified as C. socialis in many studies (e.g., Booth et al 2002;Tremblay and Gagnon 2009;Martin et al 2010), has recently been described as a new species, i.e., C. gelidus, being mainly found in polar waters (Chamnansinp et al 2013, Blais et al 2017). …”

Role for Atlantic inflows and sea ice loss on shifting phytoplankton blooms in the Barents Sea

“…However, these ongoing poleward shifts observed in the inflow shelves cannot be translated to “interior” (i.e., Beaufort and Russian seas) and “outflow shelves” (i.e., Baffin Bay, Canadian Archipelago, East Greenland shelf…), due to their entirely different functional type [ Carmack and Wassmann ; Michel et al ]. In the less sea‐ice‐covered interior shelves, stronger atmosphere‐ocean interactions promote the existence of coastal hotspots of high phytoplankton productivity crucial for supporting marine ecosystems [ Tremblay et al ., ; Ardyna et al ., ; Blais et al ., ]. On the contrary, outflow shelves (e.g., Baffin Bay) seem to experience drastic decrease in phytoplankton biomass and productivity [ Bergeron and Tremblay , ; Blais et al ., ], and in the bloom magnitude [ Marchese et al ., ].…”

Summer and fall distribution of phytoplankton in relation to environmental variables in Labrador fjords, with special emphasis on Phaeocystis pouchetii

“…All of these processes are critically dependent on phytoplankton taxonomic composition, and any change at the base of the marine food web can have repercussions on the entire ecosystem (Winder & Sommer 2012). Many studies have highlighted alterations in phytoplankton size structure and taxonomic composition due to increasing environmental changes (Moran et al 2010, Hilligsoe et al 2011, Marañón et al 2012, Blais et al 2017. Understanding the composition of the phytoplankton community and the variables influen cing its dynamics are essential for a better prediction of the impacts of global warming on aquatic eco systems.…”

“…and Chaetoceros spp., as well as the prymnesiophyte Phaeocystis pouchetii (Hariot) Lagerheim, usually dominate these blooms (Gradinger & Baumann 1991, von Quillfeldt 2000, Lovejoy et al 2002. During summer, when surface nutrients are depleted, the maximum production is usually observed at the subsurface, close to the nutracline (Martin et al 2010) where the phytoplankton community is generally dominated by diatoms (Ardyna et al 2011, Ferland et al 2011, Simo-Matchim et al 2016) and/or autotrophic nanoflagellates (Ardyna et al 2017). In late summer and early fall, the decrease in water column stratification by surface cooling and wind mixing favours the supply of nutrients to surface waters.…”