Document Type


Publication Date




Publication Title

Continental Shelf Research




104114 (19 pp.)


Large freshwater pulses to coastal ecosystems change local hydrologic regimes and alter biogeochemical processes. The Mississippi Bight coastal ecosystem, located in the northern Gulf of Mexico shelf, is influenced by extensive freshwater inputs: the Mississippi River (MSR) and several smaller rivers to the east. Under river flood conditions, MSR waters flow through the Bonnet Carré Spillway (BCS) to relieve pressure on levees in New Orleans, Louisiana. In 2015, mild wintertime temperatures and heavy rainfall throughout the MSR watershed led to extreme flooding and prompted an unusually early BCS opening on January 10, 2016 for 23 days. This study examines the effects of such intermittent freshwater diversions on local shelf circulation, planktonic distributions, and potential contaminant transport pathways. Physical, chemical, and remote sensing data collected one month after the BCS opening suggested the region was comprised of three water masses: shelf saltwater, MSR waters, and local river waters. Observations and circulation model results showed the BCS waters remained within the estuarine lakes and sounds, where winter wind patterns mixed the waters and prevented BCS waters from flowing onto the shelf. Freshwater within the Mississippi Bight was primarily from concurrent flooding of local rivers. Two distinct clusters of microplankton (offshore versus nearshore stations) and zooplankton (Chandeleur Sound versus other stations) community compositions were detected. No algal blooms were observed during this BCS opening. The 2016 wintertime BCS opening resulted in muted effects on the sounds and shelf because of its short duration and uncharacteristically early release.


© 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (

Data Availability

Article states: "All data are publicly available through the Gulf of Mexico Research Initiative Information & Data Cooperative (GRIIDC) at Doi numbers for the presented data are as follows: 10.7266/N79C6VGW for ADCP, 10.5067/AQUA/MODIS/L3M/CHL/2014 for remote sensing, 10.7266/N7416V4D for VIIRS backscattering, 10.5067/GPM/IMERG/3B-MONTH/05 for accumulated precipitation from NASA’s Integrated Multi-satellite Retrievals for Global Precipitation Measurement, 10.7266/n7-w5y1-bc57 for microplankton, 10.7266/N73B5XKG for CTD casts, 10.7266/N70000H4 for bio-optics and flow-through, 10.7266/N7P55M4G for CONCORDE Synthesis Model output, 10.7266/N72F7KHX for CMA atmospheric forcing, 10.7266/N7542KZP for NCOM model output, 10.7266/N75T3J3B for biogeochemistry and trace metals, 10.7266/n7-sps7-rq23 for river discharges, and 10.7266/n7-5faw-an77 for zooplankton."

Original Publication Citation

Parra, S. M., Sanial, V., Boyette, A. D., Cambazoglu, M. K., Soto, I. M., Greer, A. T., ... & Dinniman, M. S. (2020). Bonnet Carré Spillway freshwater transport and corresponding biochemical properties in the Mississippi Bight. Continental Shelf Research, 199, 104114. doi: 10.1016/j.csr.2020.104114


0000-0001-7519-9278 (Dinniman)

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Oceanography Commons


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