Abstract:

Sediment samples for microscopic analysis were collected on 2018-07-17 and 2019-06-18 from a twelve tank experimental mesocosm system located at Louisiana Universities Marine Consortium (LUMCON) in Cocodrie, Louisiana to document conditions prior to oil exposure treatments. Cell concentrations are presented, along with weights of sediments extracted for the counts.

Suggested Citation:

Rabalais, N.N.. 2020. Sediment microphytobenthos from an experimental mesocosm system prior to oiling: Cell concentration microscopy data from 2018-07-17 to 2019-06-18. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/JJ70ZC65

Purpose:

To collect pre-oiling baseline data prior to upcoming experiments that will examine the impacts of controlled oil dosed exposures on marsh ecosystems.

Data Parameters and Units:

Date: Date samples were collected from the mesocosm tanks (MM/DD/YYYY); Mesocosm Tank #: User-defined identifier assigned to each mesocosm tank; Sample Weight (g): Weight of the sample in grams; Concentrations of nine categories of phytoplankton enumberated from sediment samples (Pennates >90 µm, Pennates <90 µm, Stacked/ Sliding Pennates, Melosira, Skeletonema, Odontella, Coscinodiscus, Anabaena-type, Merismopedia). Units are microgram per gram dry sediment.

Methods:

Sediment samples were collected using 60 mL plastic syringes with the ends cut off. Syringes were pushed approximately 2-3 cm into the marsh and the sediment plugs extruded by placing the syringe plunger back in and creating a vacuum pressure. The top 0.5 to 1 cm from each syringe was placed into a 125 ml plastic sample bottle containing 1 ml of 50% glutaraldehyde. Filtered, ambient salinity water was added to the plastic sample bottles to make a diluted glutaraldehyde solution of 0.5 % and were refrigerated in the laboratory until processed, extracted following the method of Baustian et al., (2011), modified to extract only larger autotrophs (8-63 µm). One to three milliliters of suspended material were analyzed. Microscopic counts were made using an Olympus epifluorescence microscope (EFM) with blue and green excitation light and transmitted light. Filters were first examined at 200x until 100 cells or 100 fields were reached. The magnification was then changed to 100x and half of the same filter was scanned again for organisms not seen at the 200x count (this step allows for identification of large rare species). Diatoms were classified into seven categories (pennates <90 µm, pennates >90 µm, sliding/stacked pennates, Melosira, Skeletonema, Odontella, Coscinodiscus). Cyanobacteria were enumerated either as chain-forming Anabena-type or colonial Merismopedia. After cell extraction, sediment pellets were dried and weighed.

Provenance and Historical References:

Baustian, M., Rabalais, N., Morrison, W., & Turner, R. (2011). Seasonal microphytobenthos on the hypoxic ­northern Gulf of Mexico continental shelf. Marine Ecology Progress Series, 436, 51–66. doi:10.3354/meps09262

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