Abstract
In the northern Gulf of Mexico, shelf hypoxia poses serious risks to fisheries, coastal economies, and ecosystem health. Although nutrient loading is a primary driver of dissolved oxygen dynamics, physical forcing (wind conditions, stratification, etc.) and its interannual variability also play essential roles in coastal shelf regions. This project aims to assess hypoxia and related physical stressors on the Alabama shelf, where little monitoring has occurred despite growing evidence of substantial hypoxic conditions. This research project will involve collecting water samples from two offshore and two inshore stations along the Alabama shelf during the 2023-2025 period. These water samples were analyzed for parameters indicative of nutrient loading, turbidity, and chlorophyll concentration to identify the biogeochemical conditions responsible for hypoxia. The results of this study are expected to facilitate the development of more effective mitigation and adaptation strategies to address the impacts of physical and biogeochemical processes on hypoxia in coastal oceans.
Purpose
Four sampling stations were established across the Alabama shelf pertaining to nutrient, turbidity, and chlorophyll a gradients. Two of these sampling stations were nearshore, receiving fluvial inputs from Mobile Bay, while the remaining two were offshore, indicative of conditions experienced across the continental shelf. Samples from two depths (surface and bottom) were collected at each station. The surface sample was collected with an over the gunnel water grab, and the bottom sample was collected using a Niskin bottle. The Niskin bottle sample was collected by use a hydroweight at the base of a line with the Niskin bottle affixed to the line ~1 m above the hydroweight. The hydro weight and Niskin bottle were lowered till the hydro weight made contact with the bottom. At this point the hydroweight was raised just off the bottom, and a message was sent down the line after a short pause (~20 sec). The water samples are stored in a dark ice chest till processing at the end of the day. The processing methodologies for each individual parameter can be found at
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DOI: 10.57778/9v89-x221
Suggested Citation
Lehrter, J., Dzwonkowski, B., Puzhankara, A., Mohan Rao, D. R., Alyssa, B., Allison, F., & Nicholas, L. B. (2026). Summer water sample surveys in coastal Alabama from 2023-06-01 to 2025-08-31 [Dataset]. Dauphin Island Sea Lab. https://doi.org/10.57778/9V89-X221
Related Publication Citation
Attribution
This project was paid for [in part] with federal funding for the Alabama Center of Excellence from the Department of the Treasury under the Resources and Ecosystems Sustainability, Tourist Opportunities, and Revived Economies of the Gulf Coast States Act of 2012 (RESTORE Act) in cooperation with the State of Alabama Department of Conservation and Natural Resources under the Alabama Center of Excellence Program at the MESC/Dauphin Island Sea Lab.
