Abstract:

Mesocosm experiments were performed with seawater collected from the Gulf of Mexico. Colored dissolved organic matter (CDOM) and chlorophylls “a” and “b” from three treatments: (1) control (seawater), (2) diluted chemically enhanced water-accommodated fraction of crude oil (DCEWAF), and Water-Accommodated Fraction (WAF) were measured. Replicate samples were collected for each treatment at 4 time points: Day 0, 4, 8, and 16. CDOM and Chlorophylls “a” and “b” from all treatments and replicates were analyzed.

Suggested Citation:

Gerardo Gold-Bouchot, Terry Wade. 2020. Colored dissolved organic matter (CDOM) and chlorophyll a and b data in seawater, water-accommodated fraction (WAF) and diluted chemically enhanced WAF (DCEWAF) of oil for the mesocosm LTMOSE, a Long Term Marine Oil Snow mesocosm Experiment. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/9A6N3FWC

Purpose:

To determine the changes in CDOM and chlorophyll concentrations during microbial oxidation of crude oil components.

Data Parameters and Units:

The dataset consists of several Excel files which are raw data, and a summary file in which the raw data is used to derive the following headers - Fmax1, Fmax2, Fmax3, and Fmax4 and Fluorescence (fluorescence intensity at 450 nm divided by the intensity at 500 nm, both at 370 nm excitation); Humification (ratio of the sum of the fluorescence between 435 and 480 nm and between 300 and 345 nm at a fixed excitation of 254 nm), and Biological (intensity at 380 nm divided by the intensity at 430 nm, both at an excitation of 310 nm) Indices were calculated. Headers also include Sample ID, Tank, Time (Days), Treatment, [Chl a], and [Cl b]. [Chl a], and [Chl b] refer to Chlorophyll a and to Chlorophyll b. Main Parameters: CDOM and chlorophyll a and b in WAF (water accommodated fraction), DCEWAF (diluted chemically enhanced water accommodated fraction) and control (seawater) treatments. Units: Fluorescence intensity in the original data file is in instrument units; Fluorescence intensities in the “Combined CDOM and Chlorophyll Addomex dataset 2017.xlsx" file are in Raman units, except the three indices, that are unitless because they are ratios of fluorescence intensities. Absorbance: Results are reported as Naperian absorption coefficients (in m-1) at 350 nm (a350). Chlorophyll a and b: mg/L.

Methods:

CDOM was measured by scanning emission-excitation matrices (EEMs), fluorescence, and absorbance of filtered samples from seawater sample from each treatment and replicates were analyzed using a Horiba Aqualog fluorometer. Absorbance was measured at the same time and under the same instrumental conditions. EEMs were analyzed by Parallel Factor Analysis (PARAFAC) using the ‘drEEM’ toolbox for Matlab. Four components were obtained, and the results for each are labeled Fmax1, Fmax2, Fmax3, and Fmax4. Fluorescence (fluorescence intensity at 450 nm divided by the intensity at 500 nm, both at 370 nm excitation); Humification (ratio of the sum of the fluorescence between 435 and 480 nm and between 300 and 345 nm at a fixed excitation of 254 nm), and Biological (intensity at 380 nm divided by the intensity at 430 nm, both at an excitation of 310 nm) Indices were calculated. Chlorophyll a and b were measured by fluorescence in dichloromethane extracts from unfiltered seawater from the mesocosms. Concentrations were calculated by using a calibration curve under the same instrumental conditions. For chlorophyll a conditions were: Exc = 434 nm and Em =670.6 nm. For chlorophyll b conditions were: Exc = 464 nm and Em = 655.6 nm.

Instruments:

Horiba Aqualog fluorometer.

Individual Files: