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Title: Dynamics of benthic metabolism, O 2 , and pCO 2 in a temperate seagrass meadow
Abstract

Seagrass meadows play an important role in “blue carbon” sequestration and storage, but their dynamic metabolism is not fully understood. In a denseZostera marinameadow, we measured benthic O2fluxes by aquatic eddy covariance, water column concentrations of O2, and partial pressures of CO2(pCO2) over 21 full days during peak growing season in April and June. Seagrass metabolism, derived from the O2flux, varied markedly between the 2 months as biomass accumulated and water temperature increased from 16°C to 28°C, triggering a twofold increase in respiration and a trophic shift of the seagrass meadow from being a carbon sink to a carbon source. Seagrass metabolism was the major driver of diurnal fluctuations in water column O2concentration and pCO2, ranging from 173 to 377 μmol L−1and 193 to 859 ppmv, respectively. This 4.5‐fold variation in pCO2was observed despite buffering by the carbonate system. Hysteresis in diurnal water column pCO2vs. O2concentration was attributed to storage of O2and CO2in seagrass tissue, air–water exchange of O2and CO2, and CO2storage in surface sediment. There was a ~ 1:1 mol‐to‐mol stoichiometric relationship between diurnal fluctuations in concentrations of O2and dissolved inorganic carbon. Our measurements showed no stimulation of photosynthesis at high CO2and low O2concentrations, even though CO2reached levels used in IPCC ocean acidification scenarios. This field study does not support the notion that seagrass meadows may be “winners” in future oceans with elevated CO2concentrations and more frequent temperature extremes.

 
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Award ID(s):
1832221 1851424 1824144
NSF-PAR ID:
10459195
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Limnology and Oceanography
Volume:
64
Issue:
6
ISSN:
0024-3590
Page Range / eLocation ID:
p. 2586-2604
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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