Slice ‘n Dice
– MARCH 31, 2016
(From Spring 2016 Newsletter) Provided by Dr. Nancy Rabalais, CWC Director
The sediment core group from Coastal Waters Consortium-II held their first expedition into the marshes of Terrebonne Bay in December 2015 to collect pond and marsh sediment cores for examining the historical trends in phytoplankton composition and hydrocarbon remnants. The coring in the ponds was quite successful with six cores recovered, of which three were sliced ‘n diced into 1-cm increments for further study. Marsh coring was more difficult because of the dense root mats and smearing of the sediment structure as the core tube was inserted into the marsh. The environments did not particularly want to let go of their sediments, and extracting the cores was a monumental task.
The coring team, Mark Besonen, Gene Turner and Mike Parsons, was joined by Marci Savage, Wendy Morrison and Nancy Rabalais at the LUMCON Marine Center in Cocodrie for core processing. Each core was carefully split in half longitudinally, photographed in color to document the stratigraphy, and scanned for color/spectrophotometric and magnetic susceptibility measurements down core.
The core subsections were weighed and sorted into containers for analysis: hydrocarbon PAH determinations, dated with 210Pb and 137Cs to obtain the dates of the sections, high performance liquid chromatography (HPLC) pigments for phytoplankton biomass, diatom counts for community composition, and sedimentary characteristics of bulk density, water content, loss of carbon on ignition and sediment grain size. All the investigators have their 80+ 1-cm packets of mud from three cores to begin their analyses.
Additional cores will be taken in brackish and freshwater marshes in 2016.
What we hope to discover: through this work, we are hoping to discover a history of diatom assemblages coupled with chronic oil release, the dramatic 2010 Deepwater Horizon oil spill and eutrophication, and/or enhanced primary production of the overlying water.