Porewater exchange as a driver of carbon dynamics across a terrestrial-marine transect: Insights from coupled 222Rn and pCO2 observations in the German Wadden Sea

Santos, Isaac R.; Beck, Mélanie; Brumsack, Hans‐Jürgen; Maher, Damien T.; Dittmar, Thorsten; Waska, Hannelore; Schnetger, Bernhard

doi:10.1016/j.marchem.2015.02.005

Cited by 68 publications

(40 citation statements)

References 80 publications

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“…We therefore suggest that some of the atmospheric CO 2 fixed into organic matter by mangroves is mineralized in situ via anaerobic degradation and exported as alkalinity to the coastal ocean via tidal pumping. High alkalinity exports driven by pore water exchange have now been reported for a number of other coastal systems [ Faber et al ., ; Santos et al ., ; Stewart et al ., ; Burt et al ., ].…”

Section: Discussionmentioning

confidence: 97%

Are mangroves drivers or buffers of coastal acidification? Insights from alkalinity and dissolved inorganic carbon export estimates across a latitudinal transect

Sippo

Maher

Tait

et al. 2016

Global Biogeochemical Cycles

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Mangrove forests are hot spots in the global carbon cycle, yet the fate for a majority of mangrove net primary production remains unaccounted for. The relative proportions of alkalinity and dissolved CO 2 [CO 2 *] within the dissolved inorganic carbon (DIC) exported from mangroves is unknown, and therefore, the effect of mangrove DIC exports on coastal acidification remains unconstrained. Here we measured dissolved inorganic carbon parameters over complete tidal and diel cycles in six pristine mangrove tidal creeks covering a 26°latitudinal gradient in Australia and calculated the exchange of DIC, alkalinity, and [CO 2 *] between mangroves and the coastal ocean. We found a mean DIC export of 59 mmol m À2 d À1 across the six systems, ranging from import of 97 mmol m À2 d À1 to an export of 85 mmol m À2 d À1 . If the Australian transect is representative of global mangroves, upscaling our estimates would result in global DIC exports of 3.6 ± 1.1 Tmol C yr À1 , which accounts for approximately one third of the previously unaccounted for mangrove carbon sink. Alkalinity exchange ranged between an import of 1.2 mmol m À2 d À1 and an export of 117 mmol m À2 d À1 with an estimated global export of 4.2 ± 1.3 Tmol yr À1 . A net import of free CO 2 was estimated (À11.4 ± 14.8 mmol m À2 d À1 ) and was equivalent to approximately one third of the air-water CO 2 flux (33.1 ± 6.3 mmol m À2 d À1 ). Overall, the effect of DIC and alkalinity exports created a measurable localized increase in coastal ocean pH. Therefore, mangroves may partially counteract coastal acidification in adjacent tropical waters.

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Section: Discussionmentioning

confidence: 97%

Are mangroves drivers or buffers of coastal acidification? Insights from alkalinity and dissolved inorganic carbon export estimates across a latitudinal transect

Sippo

Maher

Tait

et al. 2016

Global Biogeochemical Cycles

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179

163

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“…The latter were shown to be of great importance for carbon, nutrient, and trace metal cycles in the large tidal flat area called Wadden Sea stretching from the Netherlands to Denmark, and the frequent water exchange between tidal flat areas and the North Sea transport carbon, nutrient, and trace metals to coastal waters of the North Sea (e.g. Beck et al, 2008;Billerbeck et al, 2006;Grunwald et al, 2010;Marchant et al, 2014;Moore et al, 2011;Riedel et al, 2011;Røy et al, 2008;Santos et al, 2015). Pore water discharge rates calculated for nearby sandy Wadden Sea sediments vary depending on the method applied and the sediment depth considered Moore et al, 2011;Riedel et al, 2010), among which the method most comparable to the model approach applied in our study resulted in lower flux rates (0.97 m −3 per tide and meter of shoreline, which equals~2 m −3 per day and meter of shoreline; Riedel et al, 2010) compared to our study.…”

Section: Pore Water Discharge Influences Phytobenthos and Nearshore Wmentioning

confidence: 99%

The drivers of biogeochemistry in beach ecosystems: A cross-shore transect from the dunes to the low-water line

et al. 2017

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This study addresses key processes in high-energy beach systems using an interdisciplinary approach. We assess spatial variations in subsurface pore water residence times, salinity, organic matter (OM) availability, and redox conditions and their effects on nutrient cycles as well as on microbial community patterns and microphytobenthos growth. At the study site on Spiekeroog Island, southern North Sea, beach hydrology is characterized by the classical zonation with an upper saline plume (USP), a saltwater wedge, and a freshwater discharge tube in between. Sediment and pore water samples were taken along a cross-shore transect from the dunes to the low-water line reaching sediment depths down to 5 m below sediment surface. Spatial variations in pore water residence time, salinity, and organic matter availability lead to steep redox and nutrient gradients. Vertical and horizontal differences in the microbial community indicate the influence of these gradients and salinity on the community structure. shoreline. We propose that this nutrient efflux triggers growth of microphytobenthos on sediment surfaces of the discharge zone. A first comparison of nutrient discharge rates of the beach site with a nearby sandy backbarrier tidal flat margin indicates that the beach system might be of less importance in supplying recycled nutrients to nearshore waters than the backbarrier tidal flat area.

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“…Only the terrestrial source of SGD represents new nutrient loads to surface waters. However, the recirculated saline component may contain high concentrations of nutrients because of biological and chemical reaction between saline groundwater and sediments (Moore et al, 2006;Santos et al, 2015). Saline SGD can buffer the seasonality of new nutrient inputs, and maintain productivity in coastal waters (Billerbeck et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Fresh meteoric versus recirculated saline groundwater nutrient inputs into a subtropical estuary

Sadat‐Noori

Santos

Tait

et al. 2016

Science of The Total Environment

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Porewater exchange as a driver of carbon dynamics across a terrestrial-marine transect: Insights from coupled 222Rn and pCO2 observations in the German Wadden Sea

Cited by 68 publications

References 80 publications

Are mangroves drivers or buffers of coastal acidification? Insights from alkalinity and dissolved inorganic carbon export estimates across a latitudinal transect

Are mangroves drivers or buffers of coastal acidification? Insights from alkalinity and dissolved inorganic carbon export estimates across a latitudinal transect

The drivers of biogeochemistry in beach ecosystems: A cross-shore transect from the dunes to the low-water line

Fresh meteoric versus recirculated saline groundwater nutrient inputs into a subtropical estuary

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