Impacts of ocean acidification on sediment processes in shallow waters of the Arctic Ocean.
Despite the important roles of shallow-water sediments in global biogeochemical cycling, the effects of ocean acidification on sedimentary processes have received relatively little attention. As high-latitude cold waters can absorb more CO2 and usually have a lower buffering capacity than warmer waters, acidification rates in these areas are faster than those in sub-tropical regions. The present study investigates the effects of ocean acidification on sediment composition, processes and sediment-water fluxes in an Arctic coastal system. Undisturbed sediment cores, exempt of large dwelling organisms, were collected, incubated for a period of 14 days, and subject to a gradient of pCO2 covering the range of values projected for the end of the century. On five occasions during the experimental period, the sediment cores were isolated for flux measurements (oxygen, alkalinity, dissolved inorganic carbon, ammonium, nitrate, nitrite, phosphate and silicate). At the end of the experimental period, denitrification rates were measured and sediment samples were taken at several depth intervals for solid-phase analyses. Most of the parameters and processes (i.e. mineralization, denitrification) investigated showed no relationship with the overlying seawater pH, suggesting that ocean acidification will have limited impacts on the microbial activity and associated sediment-water fluxes on Arctic shelves, in the absence of active bio-irrigating organisms. Only following a pH decrease of 1 pH unit, not foreseen in the coming 300 years, significant enhancements of calcium carbonate dissolution and anammox rates were observed. Longer-term experiments on different sediment types are still required to confirm the limited impact of ocean acidification on shallow Arctic sediment processes as observed in this study.
Sorbonne Universités, Université Pierre et Marie Curie-Paris 06, Laboratoire d'Océanographie de Villefranche, Observatoire océanologique, Villefranche/mer, France; Centre National de la Recherche Scientifique-Institut National des Sciences de l'Univers, Laboratoire d'Océanographie de Villefranche, Observatoire océanologique, Villefranche/mer, France.
Frédéric
F
Gazeau
Department of Ecosystem Studies, Royal Netherlands Institute for Sea Research, Yerseke, The Netherlands.
Pieter
P
van Rijswijk
Department of Ecosystem Studies, Royal Netherlands Institute for Sea Research, Yerseke, The Netherlands.
Lara
L
Pozzato
Department of Ecosystem Studies, Royal Netherlands Institute for Sea Research, Yerseke, The Netherlands; Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands.
Jack J
JJ
Middelburg
D001110:Arctic Regions; D002254:Carbonates / Q000032:analysis; D003080:Cold Temperature; D058440:Denitrification; D019015:Geologic Sediments / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009566:Nitrates / Q000032:analysis; D009573:Nitrites / Q000032:analysis; D009792:Oceans and Seas; D010100:Oxygen / Q000032:analysis; D010710:Phosphates / Q000032:analysis; D025341:Principal Component Analysis; D012623:Seawater / Q000032:analysis*; D017640:Silicates / Q000032:analysis; D013538:Svalbard
D002254:Carbonates; D009566:Nitrates; D009573:Nitrites; D010710:Phosphates; D017640:Silicates; D010100:Oxygen