Marine Ecology Progress Series
MEPS is a leading hybrid research journal on all aspects of marine, coastal and estuarine ecology. Priority is given to outstanding research that advances our ecological understanding.
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DOI: https://doi.org/10.3354/meps08795
copiedBenthic O2 exchange across hard-bottom substrates quantified by eddy correlation in a sub-Arctic fjord
Oxygen exchange across the seabed is a key measure for quantifying benthic carbon turnover. However, technical limitations have restricted such measurements to sedimentary areas. Few assessments on hard-bottom substrates exist although such biotopes are frequent along many coastlines. In spring 2009, we used the non-invasive eddy correlation technique to quantify the in situ O2 exchange rate across 3 typical substrates in West Greenland: (1) in soft sediments, the O2 exchange in darkness averaged 2.0 mmol m–2 h–1. The rate exceeded the O2 exchange quantified from microprofile measurements by 80%, but was not significantly different from parallel core incubations. (2) Measurements across consolidated sand and stones revealed a high activity with average O2 exchange similar to that of sedimentary areas. Despite being net heterotrophic, the benthic primary production on average amounted to 27 mmol O2 m–2 d–1, which per unit area is similar to the pelagic gross production of the central fjord. Carbon fixed by benthic diatoms and coralline red algae was efficiently recycled by microbes or grazed by the abundant epifauna. (3) A vertical cliff covered with sea cucumbers also revealed high O2 consumption rates (1.2 mmol m–2 h–1). The O2 exchange derived from the eddy correlation approach exhibited pronounced short-term variability reflecting the interplay of several dynamic controls, most importantly short-term variations in local hydrodynamics. All together, measurements across hard-bottom substrates revealed active benthic communities that mediate high carbon turnover rates.
KEYWORDS
Aquatic eddy correlation measurements show that hard-bottom communities recycle large quantities of organic material and play an important role in coastal carbon cycling. Photo: G. Ehlme
Hard-bottom substrates dominate many coastal environments, but studies on benthic primary production and carbon mineralisation have been focused on soft sediments. Aquatic eddy correlation measurements now allow for non-invasive in situ studies of oxygen exchange across complex benthic habitats such as cliffs, reefs, and maerl and gravel beds. Glud and co-workers used this novel approach to show that the productivity of biofilms and coralline algae covering consolidated sand and stone is similar to that of soft bottom sediments, and that microbial biomass is efficiently recycled by the epifauna. At non-photic water depths, filter-feeders covering cliff walls efficiently graze on the pelagic microbial community. Hard-bottom communities thus play an important but little studied role in coastal carbon turnover.
Ronnie N. Glud (Co-author)
- Scottish Association for Marine Science, Dunstaffnage Marine Laboratory, PA37 1QA, Dunbeg, UK
- Greenland Climate Research Centre (c/o Greenland Institute of Natural Resources), Kivioq 2, PO Box 570, 3900 Nuuk, Greenland
- Southern Danish University, Institute of Biology and Nordic Center for Earth Evolution (NordCee), 5230 Odense M, Denmark
Peter Berg (Co-author)
- Department of Environmental Science, University of Virginia, 291 McCormick Road, Charlottesville, Virginia 22904, USA
Andrew Hume (Co-author)
- Scottish Association for Marine Science, Dunstaffnage Marine Laboratory, PA37 1QA, Dunbeg, UK
- Department of Environmental Science, University of Virginia, 291 McCormick Road, Charlottesville, Virginia 22904, USA
Paul Batty (Co-author)
- Greenland Climate Research Centre (c/o Greenland Institute of Natural Resources), Kivioq 2, PO Box 570, 3900 Nuuk, Greenland
Martin E. Blicher (Co-author)
- Greenland Climate Research Centre (c/o Greenland Institute of Natural Resources), Kivioq 2, PO Box 570, 3900 Nuuk, Greenland
Kunuk Lennert (Co-author)
- Greenland Climate Research Centre (c/o Greenland Institute of Natural Resources), Kivioq 2, PO Box 570, 3900 Nuuk, Greenland
Søren Rysgaard (Co-author)
- Greenland Climate Research Centre (c/o Greenland Institute of Natural Resources), Kivioq 2, PO Box 570, 3900 Nuuk, Greenland
