Estuarine Influence On Biogeochemical Properites of the Alabama Shelf During the Fall Season

Authors

Brian Dzwonkowski, University of South AlabamaFollow
A.T. Greer, University of Southern MississippiFollow
C. Briseño-Avena, Oregon State University
J.W. Krause, Dauphin Island Sea Lab
I.M. Soto, University of Southern Mississippi
Frank J. Hernandez, University of Southern MississippiFollow
A.L. Deary, University of Southern MississippiFollow
Jeremy D. Wiggert, University of Southern MississippiFollow
D. Joung, University of Southern Mississippi
P.J. Fitzpatrick, Mississippi State University
Stephan J. O'Brien, University of Southern Mississippi
S.L. Dykstra, University of South Alabama
Y. Lau, Mississippi State University
Mustafa K. Cambazoglu, University of Southern MississippiFollow
G. Lockridge, Dauphin Island Sea Lab
Stephan D. Howden, University of Southern MississippiFollow
William M. Graham, University of Southern MississippiFollow

Document Type

Article

Publication Date

5-15-2017

Department

Marine Science

Abstract

Estuarine-shelf exchange can drive strong gradients in physical and biogeochemical properties in the coastal zone and exert a significant influence on biological processes and patterns. Physical, biogeochemical, and plankton data from an across-shelf transect extending south of Mobile Bay, Alabama, in conjunction with regional time series data, were used to determine the relative importance of estuarine-shelf interactions on the physical-biological structuring of the shelf environment during fall conditions (i.e., well-mixed, low discharge). This period was also characterized by a relatively unique weather event associated with the remnants of Hurricane Patricia, which drove a meteorological flushing of estuarine water onto the shelf. Survey data indicated generally low N:P ratios across the shelf, with slightly elevated dissolved inorganic nitrogen in the Region of Freshwater Influence (ROFI) that extended approximately 30 km offshore. The ROFI had higher values of chlorophyll-a, diatom-specific production, marine snow, and primary productivity, with notable contributions from the larger size cells (>5 µm). Furthermore, stratification provided a niche opportunity for Trichodesmium sp. aggregates, a typically oligotrophic cyanobacteria, at the offshore edge of the ROFI. The lens of estuarine water may have limited the vertical extent to which this population was mixed, providing enhanced light availability relative to the well-mixed offshore conditions. Following the biogeochemical trend, the highest zooplanktonabundances were also located within the estuarine outflow. While limited in spatial extent, the distinct geochemical and biological characteristics within the ROFI demonstrate the ecological impacts that estuarine-sourced waters can have during periods of generally low productivity in the Mississippi Bight.

Publication Title

Continental Shelf Research

Volume

140

First Page

96

Last Page

109

Recommended Citation

Dzwonkowski, B., Greer, A., Briseño-Avena, C., Krause, J., Soto, I., Hernandez, F. J., Deary, A., Wiggert, J. D., Joung, D., Fitzpatrick, P., O'Brien, S. J., Dykstra, S., Lau, Y., Cambazoglu, M. K., Lockridge, G., Howden, S. D., Graham, W. M. (2017). Estuarine Influence On Biogeochemical Properites of the Alabama Shelf During the Fall Season. Continental Shelf Research, 140, 96-109.
Available at: https://aquila.usm.edu/fac_pubs/15234