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The Amundsen Sea Embayment in West Antarctica is experiencing rapid ice mass loss, resulting in biogeochemical changes via altered nutrient and organic matter supply. However, organic carbon released from melting ice has not yet been accurately quantified. In this paper, we have integrated new dissolved organic carbon (DOC) data obtained close to the melting Dotson Ice Shelf (DIS) with published radiocarbon (Δ14C) data on sinking and suspended particulate organic carbon (POC), sedimentary OC, DOC and dissolved inorganic carbon to quantify the effect of ice melt to the carbon cycle. Elevated DOC concentrations in deep water near the DIS indicate the transport of carbon sources from the ice shelf to the water column at a rate of 4.6 ± 2.0 × 1010 g C yr−1. Furthermore, Δ14C‐DOC measurements suggest there is a possible dark chemoautotrophic production under the influence of meltwater input. The vertical profile of Δ14C in the sedimentary OC from the Sea Ice Zone and the edge of the DIS demonstrates the presence of aged organic carbon sources during warm episodes at ∼11.5 and 15.9 ka BP. Our study indicates that deep water is not only affected by OC discharge from meltwater but also by biological processes due to altered nutrient inputs. Limited data hampers a precise assessment of the influence of meltwater on the carbon cycle. Further sampling in front of the DIS will be beneficial to enhance our understanding of the role of Antarctic Ice Sheet melting in the downstream ecosystem. Plain Language Summary: The Amundsen Sea, in West Antarctica, is experiencing rapid ice melting because of a warming climate. As found in previous studies conducted in these seasonally ice‐free areas, nutrients released from melting ice sheets and upwelled by buoyant melt water stimulate surface primary production, which in return increases the surface uptake of CO2 in these regions. However, the direct release of organic carbon from melting ice has not been accurately quantified. To address this issue, we conducted radiocarbon analysis of dissolved organic carbon in water samples collected near the melting ice shelf in the Amundsen Sea. Available radiocarbon results from sedimentary organic carbon and sinking POC demonstrate that a warming climate may trigger the release of aged organic carbon from subglacial sediments. Our finding indicates the deep water in the regions is going through a biological process under the influence of meltwater input. Further sampling will be needed for the investigation of the role of meltwater in downstream ecosystems. Key Points: Elevated dissolved organic carbon (DOC) concentrations in front of the Dotson Ice Shelf (DIS) indicate an influence from the melting ice shelf and subglacial dischargeΔ14C‐DOC results demonstrate that meltwater has the potential to increase carbon uptake in the water column via chemoautotrophic productionExtra aged organic carbon sources for sedimentary OC in the Amundsen Sea Embayment during the warm episodes at ∼11.5 and 15.9 ka BP [ABSTRACT FROM AUTHOR]

ABSTRACT A key issue in the study of the carbon cycle is constraining the stocks and fluxes in and between C-reservoirs. Among these, the role and importance of fossil organic carbon (FOC) release by weathering of outcropping sedimentary rocks on continental surfaces is still debated and remains poorly constrained. Our work focuses on FOC fluxes due to chemical and mechanical weathering of marls in two experimental watersheds with typical badlands geomorphology (Draix watersheds, Laval and Moulin, Alpes de Haute Provence, France). Organic matter from bedrock, soil litter and riverine particles are characterized by Rock-Eval 6 pyrolysis. FOC fluxes due to mechanical weathering are then estimated by monitoring the annual particulate solid exports at the outlets of the watersheds (1985-2005 period). FOC fluxes from chemical weathering were calculated using Ca2+ concentrations in dissolved loads (year 2002) to assess the amount of FOC released by the dissolution of the carbonate matrix. Results show that FOC delivery is mainly driven by mechanical weathering, with a yield ranging from 30 to 59 t km-2 yr-1 in the Moulin (0.08 km2) and Laval (0.86 km2) catchments, respectively, (1985-2005 average). The release of FOC attributed to chemical weathering was 2.2 to 4.2 t km-2 for the year 2002. These high FOC fluxes from badlands are similar to those observed in tectonically active mountain catchments. At a regional scale, badland outcropping within the Durance watershed does not exceed 0.25% in area of the Rhône catchment, but could annually deliver 12 000 t yr-1 of FOC. This flux could correspond to 27% of the total particulate organic carbon (POC) load exported by the Rhône River to the Mediterranean Sea. At a global scale, our findings suggest that erosion of badlands may contribute significantly to the transfer of FOC from continental surfaces to depositional environments. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A mesocosm experiment was conducted for 32 days in an eutrophic pond to study the effects of the bioturbation of the freshwater snail, Bellamya aeruginosa, on the benthic environment and to further understand cycling of organic carbon in water containing algal blooms. Chlorophyll-a (chl-a), phaeopigment, and organic matter contents of sediment, sediment oxygen consumption (SOC), and dissolved organic carbon (DOC) fluxes were determined on day 1, 16, and 32, respectively. The SOC decreased on day 16 and increased on day 32 significantly with the increase in snail density. DOC fluxes showed a net sediment uptake in all enclosures throughout the experiment. DOC fluxes in the high and mid density treatments were lower than those of the control. The concentrations of chl-a and phaeopigment in the sediment increased significantly with snail density, indicating that the presence of snails reduced the biomass of phytoplankton. The results suggest that freshwater snails, B. aeruginosa, could influence the algal biomass (chl-a) of small water bodies by their bioturbation effects on sediment characteristics and the fluxes of organic carbon. A mesocosm experiment was conducted for 32 days in an eutrophic pond to study the effects of the bioturbation of the freshwater snail, Bellamya aeruginosa, on the benthic environment and to further understand cycling of organic carbon in water containing algal blooms. Chlorophyll-a (chl-a), phaeopigment, and organic matter contents of sediment, sediment oxygen consumption (SOC), and dissolved organic carbon (DOC) fluxes were determined on day 1, 16, and 32, respectively. The SOC decreased on day 16 and increased on day 32 significantly with the increase in snail density. DOC fluxes showed a net sediment uptake in all enclosures throughout the experiment. DOC fluxes in the high and mid density treatments were lower than those of the control. The concentrations of chl-a and phaeopigment in the sediment increased significantly with snail density, indicating that the presence of snails reduced the biomass of phytoplankton. The results suggest that freshwater snails, B. aeruginosa, could influence the algal biomass (chl-a) of small water bodies by their bioturbation effects on sediment characteristics and the fluxes of organic carbon. [ABSTRACT FROM AUTHOR]