Sea surface phytoplankton community response to nutrient and light changes
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ORIGINAL PAPER
Sea surface phytoplankton community response to nutrient and light changes Nur Ili Hamizah Mustaffa1 · Liisa Kallajoki1 · Helmut Hillebrand1,2,3 · Oliver Wurl1,4 · Maren Striebel1 Received: 19 December 2019 / Accepted: 6 July 2020 © The Author(s) 2020
Abstract The sea surface microlayer (SML) is the boundary layer between the ocean and the atmosphere and plays a unique role in marine biogeochemistry. Phytoplankton communities in this uppermost surface layer are exposed to extreme ultraviolet (UV) radiation and potentially high nutrient supplies. In order to understand the response of SML communities to such contrasting conditions, we conducted experiments at three different sites, the North Sea (open ocean) and two sites, outer and middle fjord, in the Sognefjord, Norway, with differing physical and chemical parameters. We manipulated light, nitrogen (N) and phosphorus (P) supply to natural communities collected from the SML and compared their response to that of the underlying water (ULW) communities at 1-m depth. Phytoplankton communities in both SML and ULW responded significantly to N addition, suggesting the upper 1-m surface phytoplankton communities were N-limited. While phytoplankton growth rates were higher with high N and high light supply, biomass yield was higher under low light conditions and with a combined N and P supply. Furthermore, biomass yield was generally higher in the ULW communities compared to SML communities. Nutrient and light effects on phytoplankton growth rates, particulate organic carbon (POC) and stoichiometry varied with geographical location. Phytoplankton growth rates in both SML and ULW at the open ocean station, the site with highest salinity, did not respond to light changes, whereas the communities in the middle fjord, characterized by high turbidity and low salinity, did experience light limitation. This work on the upper surface phytoplankton communities provides new insights into possible effects of coastal darkening and increases understanding of oceanic biogeochemical cycling.
Responsible Editor: U. Sommer. Reviewed by A. Deininger and an undisclosed expert. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00227-020-03738-2) contains supplementary material, which is available to authorized users. * Nur Ili Hamizah Mustaffa [email protected] 1
Institute for Chemistry and Biology of the Marine Environment, Carl Von Ossietzky Universität Oldenburg, Schleusenstrasse 1, 26382 Wilhelmshaven, Germany
2
Helmholtz-Institute for Functional Marine Biodiversity at the University of Oldenburg (HIFMB), Ammerländer Heerstrasse 231, 26129 Oldenburg, Germany
3
Alfred Wegener Institute, Helmholtz-Centre for Polar and Marine Research (AWI), Am Handelshafen 12, 27570 Bremerhaven, Germany
4
Center for Marine Sensors, Institute for Chemistry and Biology of the Marine Environment, Carl Von Ossietzky Universität Oldenburg, Schleusenstrasse 1, 26382 Wilhelmshaven, Germany
Introduction The sea-surface mic
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