Abstract:

Testing the effect of WAF (Water accommodated fraction) on TEP (transparent exopolymers) and marine snow formation. TEP was measured over time in the Control and WAF treatments and marine snow formation monitored.

Suggested Citation:

Uta Passow. 2017. Test of Coastal water with coastal microbial concentrate (TeCOAST): Production of TEP as a function of oil. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7VT1QDW

Purpose:

This first mesocosm experiment was a test of the general design and approach for following mesocosm experiments. It was also conducted to investigate the response of a natural plankton community to dispersed oil in comparison to conditions without oil. Specifically, the effect of oil addition to a coastal community for the production of transparent exopolymer particles (TEP) was tested.

Data Parameters and Units:

Sampling day (number) SSW = surrounding seawater, sample does not include marine snow; Avg = average (of three replicate mesocosms); Stdev = standard deviation; TEP = Transparent Exopolymer Particles (ug GX eq/L); GXeq = Gum Xanthan equivalent; Control = Control treatment containing seawater and plankton community; WAF = Water accommodated fraction treatment, containing WAF made from the seawater (see methods) and plankton community

Methods:

In order to create an environment for controlled testing of TEP formation two mesocosms consisting of 96 L glass tanks were used. The WAF (water accommodated fraction of oil) for this experiment was produced using 130 liter baffled recirculating tanks (BRT) and Macondo Surrogate oil. The seawater used was collected on July 30, 2015, 8 kilometers off-shore south of Galveston (TX) in the Gulf of Mexico. The seawater (34 ppt) was processed through a charcoal filter to remove large particulates and debris. The control tank was filled with 79 liters of this seawater. This seawater was also used to fill the 130 L baffled recirculating tank to generate WAF. The WAF was prepared by mixing a total of 24 ml (2 ml to start, 2 mL after 1 hr, then 5 ml at ~ 2, 3, 4 and 5 hrs) of Macondo Surrogate oil into 130 L of the seawater. Total mixing time from the start of oil addition to transfer to the mesocosms was 18 hrs. The WAF (79 L) was transferred to a tank and homogenized. Plankton (≥63 µm) samples were collected at the Galveston pier using a net and transferred into polycarbonate bottles. This concentrated plankton sample was introduced to each mesocosm and stirred (2 L to each tank for a final volume 81 L) immediately prior to starting the experiments. Banks of lights were placed behind each of the glass mesocosm tanks and a 12:12 light/dark cycle employed. Both mesocosms were sampled daily and TEP measured. Note: TEP could not be sampled in two other mesocosms, which contained Corexit, as Corexit interferes with the method. TEP concentrations were determined in triplicate using the colorimetric method and are expressed in Gum Xanthan equivalents (GXeq.) (Passow and Alldredge, 1995).

Error Analysis:

Coefficient of variation (standard deviation / average) were calculated from the triplicate TEP analysis.

Provenance and Historical References:

Passow, U., Alldredge, A.L., 1995. A dye-binding assay for the spectrophotometric measurement of transparent exopolymer particles (TEP). Limnology and Oceanography 40 (7), 1326-1335.

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