In:
Biogeosciences, Copernicus GmbH, Vol. 19, No. 2 ( 2022-01-24), p. 347-358
Abstract:
Abstract. Submarine sinkholes are found on carbonate platforms around the world. They are thought to form and grow when groundwater interactions generate
conditions corrosive to carbonate minerals. Because their morphology can restrict mixing and water exchange, the effects of biogeochemical processes
can accumulate such that the sinkhole water properties considerably diverge from the surrounding ocean. Studies of sinkhole waters can therefore
reveal new insights into marine biogeochemical cycles; thus sinkholes can be considered “natural laboratories” where the response of marine
ecosystems to environmental variations can be investigated. We conducted the first measurements in recently discovered sinkholes on Luymes Bank,
part of Saba Bank in the Caribbean Netherlands. Our measurements revealed a plume of gas bubbles rising from the seafloor in one of the sinkholes,
which contained a constrained body of dense, low-oxygen ([O2] = 60.2 ± 2.6 µmol kg−1), acidic
(pHT = 6.24 ± 0.01) seawater that we term the “acid lake”. Here, we investigate the physical and biogeochemical processes that
gave rise to and sustain the acid lake, the chemistry of which is dominated by the bubble plume. We determine the provenance and fate of the acid
lake's waters, which we deduce must be continuously flowing through. We show that the acid lake is actively dissolving the carbonate platform, so
the bubble plume may provide a novel mechanism for submarine sinkhole formation and growth. It is likely that the bubble plume is ephemeral and that
other currently non-acidic sinkholes on Luymes Bank have previously experienced acid lake phases. Conditions within the acid lake were too
extreme to represent future marine environmental responses to anthropogenic CO2 emissions on human timescales but may reflect the impact
of proposed schemes to mitigate climate change by the deliberate addition of CO2 and/or alkalinity to seawater. Other Luymes Bank
sinkholes did host conditions analogous to projections for the end of the 21st century and could provide a venue for studies on the impacts of
anthropogenic CO2 uptake by the ocean.
Type of Medium:
Online Resource
ISSN:
1726-4189
DOI:
10.5194/bg-19-347-2022
DOI:
10.5194/bg-19-347-2022-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2022
detail.hit.zdb_id:
2158181-2
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