Blooms and subsurface phytoplankton layers on the Scotian Shelf: Insights from profiling gliders

作者：Ross Tetjana^*; Craig Susanne E; Comeau Adam; Davis Richard; Dever Mathieu; Beck Matthew

来源：Journal of Marine Systems, 2017, 172: 118-127.

DOI：10.1016/j.jmarsys.2017.03.007

Understanding how phytoplankton respond to their physical environment is key to predicting how bloom dynamics might change under future climate change scenarios. Phytoplankton are at the base of most marine food webs and play an important role in drawing CO2 out of the atmosphere. Using nearly 5 years of simultaneous CM, irradiance, chlorophyll a fluorescence and optical backscattering observations obtained from Slocum glider missions, we observed the subsurface phytoplankton populations across the Scotian Shelf, near Halifax (Nova Scotia, Canada) along with their physical environment. Bloom conditions were observed in each of the 5 springs, with the average chlorophyll in the upper 60 m of water generally exceeding 3 mg m(-3). These blooms occurred when the upper water column stratification was at its lowest, in apparent contradiction of the critical depth hypothesis. A subsurface chlorophyll layer was observed each summer at about 30 m depth, which was below the base of the mixed layer. This subsurface layer lasted 3-4 months and contained, on average, 1/4 of the integrated water column chlorophyll found during the spring bloom. This suggests that a significant portion of the primary productivity over the Scotian Shelf occurs at depths that cannot be observed by satellites highlighting the importance of including subsurface observations in the monitoring of future changes to primary productivity in the ocean.

• 出版日期2017-8