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Marine Ecology Progress Series

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MEPS 661:97-114 (2021)  -  DOI:

Resolving community metabolism of eelgrass Zostera marina meadows by benthic flume-chambers and eddy covariance in dynamic coastal environments

Nicola Camillini1,2,*, Karl M. Attard2,3, Bradley D. Eyre1, Ronnie N. Glud2,4

1Centre for Coastal Biogeochemistry, Faculty of Science and Engineering, Southern Cross University, 2480 Lismore, New South Wales, Australia
2Department of Biology, Hadal & Nordcee, University of Southern Denmark, 5230 Odense M, Denmark
3Tvärminne Zoological Station, University of Helsinki, J.A. Palménin tie 260, 10900 Hanko, Finland
4Department of Ocean and Environmental Sciences, Tokyo University of Marine Science and Technology, 26 108-8477 Tokyo, Japan
*Corresponding author:

ABSTRACT: Sediment resuspension is a common process in dynamic coastal settings, but its implications for remineralization and carbon turnover in seagrass meadows are poorly understood. Here, we assessed eelgrass Zostera marina metabolism in the Baltic Sea (SW Finland) using benthic flume-chambers and aquatic eddy covariance to critically evaluate the drivers of benthic O2 exchange during dynamic flow conditions. During quiescent weather conditions, the 2 methods resolved similar metabolic rates and net ecosystem autotrophy (±11% of each other). However, elevated flow speeds and sediment resuspension halfway through the study induced a 5-fold increase in the O2 uptake rates measured by eddy covariance, whereas chamber fluxes remained relatively unchanged. Following particle resettlement, instruments were redeployed and the benthic O2 uptake resolved by both techniques was just ~30% of the values measured before resuspension. Laboratory investigations revealed sediment resuspension could potentially increase benthic O2 uptake up to 6fold, mainly due to the reoxidation of reduced compounds (e.g. FeSx). This process was fully captured by the eddy O2 fluxes, but not by the chamber incubation. Consequently, the chamber and eddy net ecosystem metabolism amounted to -17 and -824 mmol C m-2, respectively, throughout the study period. The rapid reoxidation and long-term effects of resuspension on benthic O2 dynamics highlight the importance of fully capturing dynamic conditions when assessing the overall carbon turnover in coastal habitats. Future studies on the biogeochemical functioning of coastal environments should aim to capture the natural frequency and duration of resuspension events.

KEY WORDS: Benthic oxygen exchange · Seagrass · Oxygen storage · Wind waves · Sediment resuspension

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Cite this article as: Camillini N, Attard KM, Eyre BD, Glud RN (2021) Resolving community metabolism of eelgrass Zostera marina meadows by benthic flume-chambers and eddy covariance in dynamic coastal environments. Mar Ecol Prog Ser 661:97-114.

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