Abstract:

The dataset contains diatom abundances (valves per gram, wet weight sediment) extending down to a depth of greater than 20 cm in sediment cores collected in coastal marshes in Terrebonne and Barataria Bays, Louisiana, in May 2016. Sample collection information is also reported as well as photographs of representative individuals for each diatom taxa.

Suggested Citation:

Zingre, Jeffrey A., Parsons, Michael L.. 2019. Sediment-preserved diatom assemblage data from coastal marsh sediment cores collected in Terrebonne and Barataria Bays, Louisiana from 2016-05-07 to 2016-05-08. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-z6c0-v463

Purpose:

The diatom data were collected to compare against measured oil concentrations at various horizons in the sediment cores to determine if (and to what extent) diatom assemblages (as preserved in the sediments) changed in the presence of oil residues. The primary focus was on Macondo oil residue buried in the sediments, although residues from other oiling events were likely present.

Data Parameters and Units:

File Core_Diatom_Abundance_sub2.xlsx: Worksheet Sample Key: Core: User-defined identifier assigned to each core; Date: Date of core collection (MM/DD/YY); LAT (dec degrees): Latitude of the sample collection site; LONG (dec degrees): Longitude of the sample collection site; Site Description: Description of the area of core collection; Collection Type: Mechanism of core collection Worksheet Absolute Abundance: Absolute abundance data (the number of diatom valves per gram wet weight) is presented with CoreID_Depth Interval values as column headers and Diatom taxon in the first column. CoreID_Depth Interval: User-defined identifier assigned to each core, containing collection location (GI=Grand Isle-cores 1, 2, 5; T=Terrebonne Bay-cores 2, 4, 6) and depth intervals designations (range of numbers in centimeters indicating the top and bottom depths of the core slice). Diatom taxon: Phytoplankton categories identified in each core slice. Category names are made up of Genus and a user-defined ID#. Worksheet Diatom Picture Key: List of filenames for photographs taken of each diatom taxa reported on the Absolute Abundance tab. File names include the Genus and ID# of the diatom taxa as well as the cell length and/or cell length range. Photos are located in the Windows folder Diatom_Images. File Diatom_Images: Windows folder containing photographs of representative diatom taxa for which abundances are reported in File Core_Diatom_Abundance-sub2.xlsx.

Methods:

Subsamples were digested in boiling nitric acid, permanently mounted on slides using Naphrax mounting media and counted on an Olympus BX51 microscope fitted with DIC components at a power of 600x. Encountered diatoms were identified to sub-genus level, in which actual species names or sub-genus designations were assigned (e.g., Achnanthes sp. 1 vs sp. 2). Valves were quantified by comparing valve counts to a known quantity of glass microspheres added to the sample. Some taxa will need further analysis to identify to species level or are undescribed species (TBD). Photographs of representative diatom taxa were collected using an Olympus DP72 and with Olympus DP2-BSW camera software.

Individual Files: