Seasonal metabolism and carbon export potential of a key coastal habitat : The perennial canopy-forming macroalga Fucus vesiculosus

• The important role of macroalgal canopies in the oceanic carbon (C) cycle is increasingly being recognized, but direct assessments of community productivity remain scarce. We conducted a seasonal study on a sublittoral Baltic Sea canopy of the brown alga Fucus vesiculosus, a prominent species in temperate and Arctic waters. We investigated community production on hourly, daily, and seasonal timescales. Aquatic eddy covariance (AEC) oxygen flux measurements integrated similar to 40 m(2) of the seabed surface area and documented considerable oxygen production by the canopy year-round. High net oxygen production rates of up to 35 +/- 9 mmol m(-2) h(-1) were measured under peak irradiance of similar to 1200 mu mol photosynthetically active radiation (PAR) m(-2) s(-1) in summer. However, high rates > 15 mmol m(-2) h(-1) were also measured in late winter (March) under low light intensities < 250 mu mol PAR m(-2) s(-1) and water temperatures of similar to 1 degrees C. In some cases, hourly AEC fluxes documented an apparent release of oxygen by the canopy under dark conditions, which may be due to gas storage dynamics within internal air spaces of F. vesiculosus. Daily net ecosystem metabolism (NEM) was positive (net autotrophic) in all but one of the five measurement campaigns (December). A simple regression model predicted a net autotrophic canopy for two-thirds of the year, and annual canopy NEM amounted to 25 mol O-2 m(-2) yr(-1), approximately six-fold higher than net phytoplankton production. Canopy C export was similar to 0.3 kg C m(-2) yr(-1), comparable to canopy standing biomass in summer. Macroalgal canopies thus represent regions of intensified C assimilation and export in coastal waters.

Ämnesord

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

NATURVETENSKAP  -- Geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences (hsv//eng)

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