Semester of Graduation

Fall 2021

Degree

Master of Science (MS)

Department

Oceanography and Coastal Sciences

Document Type

Thesis

Abstract

Estuaries in the northern Gulf of Mexico (GoM) are undergoing profound alterations due to changes in climate and implementation of coastal restoration activities and these may lead to the increasing frequency of harmful algal blooms (HABs). The introduction of large volumes of nutrient-rich, fresh Mississippi River water into nutrient-poor Lake Pontchartrain Estuary is known to substantially change the chemistry and ecology of the estuary, and warm temperatures paired with the persistent nutrient loading into the estuary supports the proliferation of potentially toxic cyanobacteria blooms (CyanoHABs). Throughout 2019, a long-term opening of the Bonnet Carré Spillway (BCS), initially from February to April then reopening from May to July, introduced excess nutrients available for biological uptake in the estuary. To understand the implications of timing and duration of BCS openings on CyanoHABs prevalence and toxicity in Lake Pontchartrain Estuary, this study aimed to characterize key physical, chemical, and biological conditions in the estuary as well as the diversity of potentially toxic pelagic cyanobacteria and their toxin production in selected stations. Monthly samples were collected and processed for water characterization, nutrients, pigments, microscopy, and “microcystin” toxin analyses. Results indicate that the two historical successive openings of the BCS in 2019 had a major influence on the spatiotemporal dynamics of the 2019 CyanoHAB prevalence. Particulate toxin concentration corresponded to the cyanobacteria biomass, but not equally. The understanding and prediction of CyanoHABs in Lake Pontchartrain Estuary will greatly attribute to the overall future health and understanding of not just Lake Pontchartrain Estuary but the connected estuaries and lakes as well. Additionally, since the fate of CyanoHABs is reliant on this nutrient loading and physical dynamics, the future effects of sources like the BCS and connecting tributaries have on water systems’ quality and ecosystem can be further evaluated.

Committee Chair

Bargu, Sibel

DOI

10.31390/gradschool_theses.5467

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