Potential fate of wetland soil carbon in a deltaic coastal wetland subjected to high relative sea level rise.

The fate of soil carbon in eroding coastal wetlands is of great concern, given the potential for a feedback loop from coastal wetland soil that would dramatically increase atmospheric CO2 concentrations. The biogeochemical transformations and overall fate of this soil carbon upon coastal erosion were investigated through geophysical and spectroscopic analysis of soil and associated dissolved organic matter. Bay water and core sections were collected across transects encompassing both intact and eroded, submerged, sections of a coastal marsh in Barataria Bay, Louisiana. We noted: i) a vertical increase in carbon content, humification of organic matter, and decrease in biotic degradation with depth at all sites; ii) an erosion and ultimate collapse of the top ~ 0-20 cm of the intact marsh's edge into the bay water due to the undercutting caused by tidal/wave forces; iii) the loss of the stored carbon from the submerged site's top 10 cm layer; and iv) leaching, dilution, abiotic, and biotic degradation of the marsh carbon due to the exposure to the bay water. This erosion and degradation of wetland soil carbon stores demonstrates the potential impact of rising sea levels on the future fate of coastal wetland carbon and atmospheric CO2 levels.

Investigation of an early season river flood pulse: Carbon cycling in a subtropical estuary.

The January 2016 Bonnet Carré Spillway (BCS) opening resulted in a large-scale Mississippi River (MR) flood discharge that qualitatively and quantitatively impacted the dissolved organic matter (DOM) cycling in the Lake Pontchartrain Estuary (LPE) located in Louisiana, USA. This early season flood event was a result of the delay of snow formation caused by warmer than normal watershed temperatures. During the diversion period and the subsequent weeks, the LPE water temperature remained lower than pre-flood water temperatures, suppressing carbon cycling. Following that period, the water temperature increased, leading to an increase in the rate of abiotic and biological carbon processing (i.e., mineralization, degradation, and consumption). There were multiple and abnormally high discharges into LPE from the northern tributaries, totaling 43% of the MR flood discharge. As a secondary DOM source, the northern tributaries discharge was qualitatively and quantitatively different from the discharge originating from the river or estuarine sources. The dominant DOM source was determined using satellite images in conjunction with UV-Vis, fluorescence EEMs, and PARAFAC indicators. Overall, the three sources (MR, northern tributaries, and LPE) characteristics were identified by UV-Vis, fluorescence EEMs, and PARAFAC parameters, namely: i) spectral slope (S275), serving as an indicator of lignin-like compounds' molecular weights, with a trend of MR > northern tributaries > LPE; ii) biological index (BIX), indicating freshness of DOM, with a trend of LPE > MR > northern tributaries; and iii) Fluorophore T intensity, serving as an indicator of the amount of terrestrial-like sourced DOM, with a trend of northern tributaries > LPE > MR. It was possible to identify DOM sources and monitor DOM transformation in the water column, increasing our understanding of DOM, carbon, and nitrogen ecological processing.

Influence of surfactants and humic acids on Artemia Franciscana's embryonic phospho-metabolite profile as measured by 31P NMR.

Surfactants, such as triton X-100 (Tx-100), cetylpyridinium chloride (CPC), and sodium dodecyl sulfate (SDS) are known to be toxic to Artemia Franciscana (Artemia) - an organism, frequently used to monitor the health of the aquatic environment. The phospho-metabolite profile of a living organism is often indicative of imbalances that may have been caused by environmental stressors, such as surfactants. This study utilizes in vivo31P NMR to monitor temporal changes in the phospho-metabolite profile of Artemia caused by Tx-100, CPC, and SDS and the ability of humic acid (HA) to mitigate the toxicity of these surfactants. It was found that, while Tx-100 does not have any effect on the phospho-metabolite profile, both CPC and SDS cause a complete retardation in growth of the phosphodiester (PDE) peak in the 31P NMR spectrum, which is indicative of the inhibited cell replication. This growth inhibition was independently verified by the decreased guanosine triphosphate (GTP) concentration in the CPC and SDS-exposed Artemia. In addition, upon introduction of HA to the CPC and SDS-exposed Artemia, an increase of PDE peak over time is indicative of HA mitigating toxicity.