Seasonal rates of benthic primary production in a Greenland fjord measured by aquatic eddy correlation

Attard, Karl M., Glud, Ronnie N., McGinnis, Daniel and Rysgaard, Søren (2014) Seasonal rates of benthic primary production in a Greenland fjord measured by aquatic eddy correlation Limnology and Oceanography, 59 (5). pp. 1555-1569. DOI 10.4319/lo.2014.59.5.1555.

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We present the first year-round estimates of benthic primary production at four contrasting shallow (3–22 m depth) benthic habitats in a southwest Greenland fjord. In situ measurements were performed using the noninvasive aquatic eddy-correlation (EC) oxygen (O2) flux method. A series of high-quality multiple-day EC data sets document the presence of a year-round productive benthic phototrophic community. The shallow-water sites were on average autotrophic during the spring and summer months, up to 43.6 mmol O2 m22 d21, and
heterotrophic or close to metabolic balance during the autumn and winter. Substantial benthic gross primary
production (GPP) was measured year-round. The highest GPP rates were measured during the spring, up to
5.7 mmol O2 m22 h21 (136.8 mmol O2 m22 d21), and even at low light levels (, 80 mmol quanta m22 s21) during
late autumn and winter we measured rates of up to 1.8 mmol O2 m22 h21 (43.2 mmol O2 m22 d21) during peak
irradiance. The benthic phototrophic communities responded seasonally to ambient light levels and exhibited
year-round high photosynthetic efficiency. In situ downwelling irradiances as low as , 2 mmol quanta m22 s21
induced an autotrophic response and light saturation indices (Ik) were as low as 11 mmol quanta m22 s21 in the
winter. On an annual timescale, the average areal rate of benthic GPP was 11.5 mol O2 m22 yr21, which is , 1.4
times higher than the integrated gross pelagic primary production of the , 30–50 m deep photic zone of the fjord.
These results document the importance of benthic photosynthesis on an ecosystem level and indicate that the benthic phototrophic compartment should be accounted for when assessing carbon and nutrient budgets as well as responses of coastal Arctic ecosystems to climate change.

Document Type: Article
Additional Information: WOS:000345462100008
Keywords: Oxygen flux, respiration, turbulence, Arctic
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
Refereed: Yes
DOI etc.: 10.4319/lo.2014.59.5.1555
ISSN: 0024-3590
Date Deposited: 29 Jul 2014 09:08
Last Modified: 01 Sep 2017 23:38

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