Nutrient flux and physical stability drive phytoplankton biomass variability along the Alabama shelf

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In the northern Gulf of Mexico (nGoM), river-dominated estuaries like Mobile Bay (Alabama, USA) are generally nutrient-rich and turbid, but light limitation reduces water-column productivity. Qualitative analyses have shown that discharge plumes deliver nutrients from Mobile Bay offshore, fueling shelf primary production. The current conceptual model is that during transit through Mobile Bay, nutrients may be consumed abiotically (mixing) or heterotrophically, with phytoplankton consumption stimulated as light transmittance in the water column increases. Using physical and biogeochemical data from a long-term transect (September 2009 to June 2012) that extended from Mobile Bay out to the 35m isobaths of the nGoM (~50 km offshore), aspects of nutrient delivery and biological response were quantitatively examined in this river-dominated coastal region. There were linear relationships between dissolved silicic acid and salinity, which demonstrated clear linkages between nutrient flux and river discharge. Additionally, there was a linear relationship between physical stability (i.e. stratification) and phytoplankton biomass accumulation on the shelf but no relationship was observed in the turbid estuarine waters. These quantitative relationships enforce intuitive cause-effect thoughts regarding processes within this system.


CTD and Niskin bottle data were merged to facilitate broader analysis. Niskin bottles were routinely collected from just below the surface and just above the benthos, hereafter referred to as surface and bottom, respectively. CTD data were continuously collected during a drop sample at the occupied station.

DOI: 10.57778/mcg4-f330

Suggested Citation

Sutton, J., Dzwonkowski, B., Krause, J., Hernandez, F., & Graham, W. (2023). Nutrient flux and physical stability drive phytoplankton biomass variability along the Alabama shelf [Data set]. Dauphin Island Sea Lab.

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Additional Info

Field Value
Author Jenny R. Sutton
Last Updated March 8, 2023, 19:20 (UTC)
Created February 10, 2023, 16:26 (UTC) Brian Dzwonkowski <> Jeffrey Krause <> Frank Hernandez <> William Graham <>
Place Keywords Alabama, Gulf of Mexico
Temporal Begin 2009-09
Temporal End 2012-06
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