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Karstic submarine g...
Karstic submarine groundwater discharge into the Mediterranean: Radon-based nutrient fluxes in an anchialine cave and a basin-wide upscaling
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Chen, X. G. (author)
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Cukrov, N. (author)
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- Santos, Isaac R. (author)
- Gothenburg University,Göteborgs universitet,Institutionen för marina vetenskaper,Department of marine sciences
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Rodellas, V. (author)
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Cukrov, N. (author)
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Du, J. Z. (author)
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(creator_code:org_t)
- Elsevier BV, 2020
- 2020
- English.
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In: Geochimica Et Cosmochimica Acta. - : Elsevier BV. - 0016-7037. ; 268, s. 467-484
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Abstract
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- Anchialine caves are common in Mediterranean karstic shorelines and elsewhere, delivering point-source fresh groundwater and nutrients to the coastal ocean. Here, we first quantified submarine groundwater discharge (SGD) in a typical karstic system (Zaton Bay, Croatia) receiving groundwater from anchialine caves using a radon (Rn-222) mass balance model. We then combine our new observations with the literature to provide a Mediterranean-scale estimate of karstic fresh SGD nutrient fluxes. We found that SGD and related nutrient fluxes in the upper brackish layer were much higher than those in the underlying layer in Zaton Bay. In the upper brackish layer, both SGD (m d(-1)) and associated nutrient fluxes (mmol M(-2)d(-1)) in the wet season (SGD: 0.29-0.40; DIN: 52; DIP: 0.27) were significantly higher than those in the dry season (SGD: 0.15; DIN: 22; DIP: 0.08). Red tides were observed in the wet season but not in the dry season. Nutrient budgets imply that SGD accounted for >98% of the total dissolved inorganic nitrogen (DIN) and phosphorous (DIP) sources into Zaton Bay. These large SGD nutrient fluxes with high N/P ratios (190-320) likely trigger and sustain red tide outbreaks. Combining our results with 30 previous studies in the region revealed that point-source DIN and DIP fluxes via karstic fresh SGD may account for 8-31% and 1-4%, respectively, of riverine inputs in the Mediterranean Sea. Overall, we demonstrate the importance of karstic SGD as a source of new nutrients with high N/P ratios to the Mediterranean Sea and emphasize how SGD lagging precipitation can drive red tide outbreaks. (C) 2019 Elsevier Ltd. All rights reserved.
Subject headings
- NATURVETENSKAP -- Geovetenskap och miljövetenskap -- Geofysik (hsv//swe)
- NATURAL SCIENCES -- Earth and Related Environmental Sciences -- Geophysics (hsv//eng)
- NATURVETENSKAP -- Geovetenskap och miljövetenskap -- Geokemi (hsv//swe)
- NATURAL SCIENCES -- Earth and Related Environmental Sciences -- Geochemistry (hsv//eng)
Keyword
- Subterranean estuary
- Permeable sediments
- Adriatic Sea
- Algal bloom
- Coastal carbon
- Carbonate
- pore-water exchange
- dissolved organic-matter
- eastern hainan island
- krka river estuary
- subterranean estuary
- fresh groundwater
- borne
- nutrients
- north pacific
- surface-water
- mass-balance
- Geochemistry & Geophysics
Publication and Content Type
- ref (subject category)
- art (subject category)
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