The evolution of light and vertical mixing across a phytoplankton ice-edge bloom

Type Article
Date 2019-05
Language English
Author(s) Randelhoff Achim1, 2, 3, 4, Ozierm Laurent1, 2, 3, 4, 5, Massicotte Philippe1, 2, 3, 4, Becu Guislain1, 2, 3, 4, Gali Marti1, 2, 3, 4, Lacour Leo1, 2, 3, 4, Dumont Dany6, Vladoiu Anda7, Marec Claudie1, 2, 3, 4, 8, Bruyant Flavienne1, 2, 3, 4, Houssais Marie-Noelle7, Tremblay Jean-Eric1, 2, 3, 4, Deslongchamps Gabriele1, 2, 3, 4, Babin Marcel1, 2, 3, 4
Affiliation(s) 1 : Laval Univ, Takuvik Joint Int Lab, Quebec City, PQ, Canada.
2 : CNRS, Paris, France.
3 : Univ Laval, Dept Biol, Quebec City, PQ, Canada.
4 : Univ Laval, Quebec Ocean, Quebec City, PQ, Canada.
5 : Fisheries & Oceans Canada, Remote Sensing Unit, Bedford Inst Oceanog, Dartmouth, NS, Canada.
6 : Univ Quebec Rimouski, Inst Sci Mer Rimouski, Rimouski, PQ, Canada.
7 : Sorbonne Univ UPMC Paris 6 CNRS UPMC IRD MNHN, Lab Oceanog & Climat LOCEAN, Inst Pierre Simon Laplace, Paris, France.
8 : CNRS IFREMER IRD UBO, LOPS, Plouzane, France.
Source Elementa-science Of The Anthropocene (2325-1026) (Univ California Press), 2019-05 , Vol. 7 , N. 20 , P. 19p.
DOI 10.1525/elementa.357
WOS© Times Cited 34
Keyword(s) Arctic, Phytoplankton, Ice edge, Spring bloom, Light, Turbulence

During summer, phytoplankton can bloom in the Arctic Ocean, both in open water and under ice, often strongly linked to the retreating ice edge. There, the surface ocean responds to steep lateral gradients in ice melt, mixing, and light input, shaping the Arctic ecosystem in unique ways not found in other regions of the world ocean. In 2016, we sampled a high-resolution grid of 135 hydrographic stations in Baffin Bay as part of the Green Edge project to study the ice-edge bloom, including turbulent vertical mixing, the under-ice light field, concentrations of inorganic nutrients, and phytoplankton biomass. We found pronounced differences between an Atlantic sector dominated by the warm West Greenland Current and an Arctic sector with surface waters originating from the Canadian archipelago. Winter overturning and thus nutrient replenishment was hampered by strong haline stratification in the Arctic domain, whereas close to the West Greenland shelf, weak stratification permitted winter mixing with high-nitrate Atlantic-derived waters. Using a space-for-time approach, we linked upper ocean dynamics to the phytoplankton bloom trailing the retreating ice edge. In a band of 60 km (or 15 days) around the ice edge, the upper ocean was especially affected by a freshened surface layer. Light climate, as evidenced by deep 0.415 mol m(-2) d(-1) isolumes, and vertical mixing, as quantified by shallow mixing layer depths, should have permitted significant net phytoplankton growth more than 100 km into the pack ice at ice concentrations close to 100%. Yet, under-ice biomass was relatively low at 20 mg chlorophyll-a m(-2) and depth-integrated total chlorophyll-a (0-80 m) peaked at an average value of 75 mg chlorophyll-a m(-2) only around 10 days after ice retreat. This phenological peak may hence have been the delayed result of much earlier bloom initiation and demonstrates the importance of temporal dynamics for constraints of Arctic marine primary production.

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Randelhoff Achim, Ozierm Laurent, Massicotte Philippe, Becu Guislain, Gali Marti, Lacour Leo, Dumont Dany, Vladoiu Anda, Marec Claudie, Bruyant Flavienne, Houssais Marie-Noelle, Tremblay Jean-Eric, Deslongchamps Gabriele, Babin Marcel (2019). The evolution of light and vertical mixing across a phytoplankton ice-edge bloom. Elementa-science Of The Anthropocene, 7(20), 19p. Publisher's official version : , Open Access version :