Empirical evidence reveals seasonally dependent reduction in nitrification in coastal sediments subjected to near future ocean acidification

PLoS One. 2014 Oct 16;9(10):e108153. doi: 10.1371/journal.pone.0108153. eCollection 2014.

Abstract

Research so far has provided little evidence that benthic biogeochemical cycling is affected by ocean acidification under realistic climate change scenarios. We measured nutrient exchange and sediment community oxygen consumption (SCOC) rates to estimate nitrification in natural coastal permeable and fine sandy sediments under pre-phytoplankton bloom and bloom conditions. Ocean acidification, as mimicked in the laboratory by a realistic pH decrease of 0.3, significantly reduced SCOC on average by 60% and benthic nitrification rates on average by 94% in both sediment types in February (pre-bloom period), but not in April (bloom period). No changes in macrofauna functional community (density, structural and functional diversity) were observed between ambient and acidified conditions, suggesting that changes in benthic biogeochemical cycling were predominantly mediated by changes in the activity of the microbial community during the short-term incubations (14 days), rather than by changes in engineering effects of bioturbating and bio-irrigating macrofauna. As benthic nitrification makes up the gross of ocean nitrification, a slowdown of this nitrogen cycling pathway in both permeable and fine sediments in winter, could therefore have global impacts on coupled nitrification-denitrification and hence eventually on pelagic nutrient availability.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbonates / chemistry
  • Carbonates / metabolism
  • Climate Change
  • Geologic Sediments / chemistry*
  • Hydrogen-Ion Concentration
  • Nitrification*
  • Nitrogen Oxides / chemistry
  • Nitrogen Oxides / metabolism
  • Oxygen / chemistry
  • Oxygen / metabolism
  • Pigments, Biological / analysis
  • Seasons*
  • Seawater / chemistry*

Substances

  • Carbonates
  • Nitrogen Oxides
  • Pigments, Biological
  • Oxygen

Grants and funding

U.B. was financially supported by FWO project nr G.0033.11 and the Special Research Fund of Ghent University. C.V.C. and K.G. acknowledge a postdoctoral fellowship from the Flemish Fund for Scientific Research (FWO). K.G. also received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 265847. Additional funding was provided by the Special Research Fund of Ghent University (BOF-GOA 01GA1911W). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.