The Bonnet Carré Spillway (BCS) opening in January of 2016, a large-scale Mississippi River (MR) discharge, impacted the dissolved organic matter (DOM) cycling in the Lake Pontchartrain Estuary (LPE). In recent years, these flood control BCS opening events are taking place both more frequently and earlier in the season. The 2016 MR discharge introduced DOM, particulate organic matter (POM), and nutrients that were different from those present in the LPE, as measured by dissolved organic carbon and nitrogen concentrations as well as ultraviolet-visible (UV-Vis), fluorescence, and parallel factor analysis (PARAFAC). During the diversion period and the subsequent week, the LPE water temperature remained low due to the infusion of cold river water, causing a suppression in the cycling of the introduced DOM, POM, and nutrients. Once temperature increased, the rates of abiotic and biological processing increased. The El Nino influence of 2016 resulted in multiple, abnormally high discharges into LPE from the northern tributaries (NTs), totaling ~ 50% of the BCS flood discharge. As a secondary source of DOM, the NTs discharge introduced DOM that was different from the MR and LPE sourced DOM. Both the MR and NTs discharges made large contributions to the DOM pool in LPE, with varying impacts at various sites along the transect over the course of the study. The dominant source of DOM at each site was determined using satellite images in conjunction with nutrient, UV-Vis, fluorescence, and PARFAC. Overall, these indicators allowed for a detailed mapping of carbon processing, providing a better understanding of the dynamics of carbon cycling within LPE under the influence of river flood pulse.

Investigation of carbon cycling in a subtropical estuary subjected to an early-season flood pulse, and secondary sources

255th National Meeting (2018)

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