Affiliation:
1. Alfred‐Wegener‐Institut Helmholtz‐Zentrum für Polar‐ und Meeresforschung (AWI) 27570 Bremerhaven Germany
2. Institute of Biological Sciences, Applied Ecology and Phycology University of Rostock 18059 Rostock Germany
3. Takuvik International Research Laboratory Université Laval and CNRS G1V0A6 Québec Canada
4. Alfred Wegener Institute Helmholtz‐Centre for Polar and Marine Research 27570 Bremerhaven Germany
Abstract
AbstractCoastal kelp forests produce substantial marine carbon due to high annual net primary production (NPP) rates, but upscaling of NPP estimates over time and space remains difficult. We investigated the impact of variable underwater photosynthetically active radiation (PAR) and photosynthetic parameters on photosynthetic oxygen production of Laminaria hyperborea, the dominant NE‐Atlantic kelp species, throughout summer 2014. Collection depth of kelp had no effect on chlorophyll a content, pointing to a high photoacclimation potential of L. hyperborea towards incident light. However, chlorophyll a and photosynthesis versus irradiance parameters differed significantly along the blade gradient when normalized to fresh mass, potentially introducing large uncertainties in NPP upscaling to whole thalli. Therefore, we recommend a normalization to kelp tissue area, which is stable over the blade gradient. Continuous PAR measurements revealed a highly variable underwater light climate at our study site (Helgoland, North Sea) in summer 2014, reflected by PAR attenuation coefficients (Kd) between 0.28 and 0.87 m−1. Our data highlight the importance of continuous underwater light measurements or representative average values using a weighted Kd to account for large PAR variability in NPP calculations. Strong winds in August increased turbidity, resulting in a negative carbon balance at depths >3–4 m over several weeks, considerably impacting kelp productivity. Estimated daily summer NPP over all four depths was 1.48 ± 0.97 g C · m−2 seafloor · d−1 for the Helgolandic kelp forest, which is in the range of other kelp forests along European coastlines.
Funder
Deutsche Forschungsgemeinschaft
Subject
Plant Science,Aquatic Science
Cited by
1 articles.
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