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Article

Severe Coastal Hypoxia Interchange with Ocean Acidification: An Experimental Perturbation Study on Carbon and Nutrient Biogeochemistry

1
Laboratory of Environmental Chemistry, Department of Chemistry, University of Athens, 15771 Athens, Greece
2
Department of Marine Sciences, University of the Aegean, University Hill, 81100 Mytilene, Greece
*
Author to whom correspondence should be addressed.
J. Mar. Sci. Eng. 2020, 8(6), 462; https://doi.org/10.3390/jmse8060462
Received: 25 May 2020 / Revised: 17 June 2020 / Accepted: 22 June 2020 / Published: 23 June 2020
Normally atmospheric CO2 is the major driver of ocean acidification (OA); however, local discharge/degradation of organic matter (OM) and redox reactions can exacerbate OA in coastal areas. In this work we study the response of nutrient and carbon systems to pH decrease in relation to hydrographically induced intermittent characteristics and examine scenarios for future ocean acidification in a coastal system. Laboratory microcosm experiments were conducted using seawater and surface sediment collected from the deepest part of Elefsis Bay; the pH was constantly being monitored while CO2 gas addition was adjusted automatically. In Elefsis Bay surface pCO2 is already higher than global present atmospheric values, while near the bottom pCO2 reaches 1538 μatm and carbonate saturation states were calculated to be around 1.5. During the experiment, in more acidified conditions, limited alkalinity increase was observed and was correlated with the addition of bicarbonates and OM. Ammonium oxidation was decelerated and a nitrification mechanism was noticed, despite oxygen deficiency, paralleled by reduction of Mn-oxides. Phosphate was found significantly elevated for the first time in lower pH values, without reprecipitating after reoxygenation; this was linked with Fe(II) oxidation and Fe(III) reprecipitation without phosphate adsorption affecting both available dissolved phosphate and (dissolved inorganic nitrogen) DIN:DIP (dissolved inorganic phosphate)ratio. View Full-Text
Keywords: CO2 addition; ocean acidification; pH decline; nitrification; microcosm experiment; anoxic sediment; hypoxic/anoxic boundary CO2 addition; ocean acidification; pH decline; nitrification; microcosm experiment; anoxic sediment; hypoxic/anoxic boundary
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MDPI and ACS Style

Kapetanaki, N.; Krasakopoulou, E.; Stathopoulou, E.; Dassenakis, M.; Scoullos, M. Severe Coastal Hypoxia Interchange with Ocean Acidification: An Experimental Perturbation Study on Carbon and Nutrient Biogeochemistry. J. Mar. Sci. Eng. 2020, 8, 462. https://doi.org/10.3390/jmse8060462

AMA Style

Kapetanaki N, Krasakopoulou E, Stathopoulou E, Dassenakis M, Scoullos M. Severe Coastal Hypoxia Interchange with Ocean Acidification: An Experimental Perturbation Study on Carbon and Nutrient Biogeochemistry. Journal of Marine Science and Engineering. 2020; 8(6):462. https://doi.org/10.3390/jmse8060462

Chicago/Turabian Style

Kapetanaki, Natalia, Evangelia Krasakopoulou, Eleni Stathopoulou, Manos Dassenakis, and Michael Scoullos. 2020. "Severe Coastal Hypoxia Interchange with Ocean Acidification: An Experimental Perturbation Study on Carbon and Nutrient Biogeochemistry" Journal of Marine Science and Engineering 8, no. 6: 462. https://doi.org/10.3390/jmse8060462

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