Abstract:

Transparent exopolymer particles (TEP) from a long term mesocosm experiment (16 days) to investigate the aging of oil in marine snow in association with exopolymeric substances (EPS).

Suggested Citation:

Uta Passow. 2017. Long Term Marine Oil Snow Experiment (LTMOSE): TEP as a function of time. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N75D8Q8D

Purpose:

Starting conditions and setup of this mesocosm experiment resembled that of COAST, coastal water with coastal microbial concentrate (4 days) as far as possible, but was sampled over a longer timespan (16 days) to investigate the aging of oil in marine snow and in association with EPS.

Data Parameters and Units:

Sampling day SSW = surrounding seawater, sample does not include marine snow; Slurry = Marine snow with some undefined fraction of SSW inadvertently included; Avg = average (of three replicate mesocosms); Stdev = standard deviation; TEP = Transparent Exopolymer Particles (mg GXeq/mesocosm); 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 twelve glass tanks, about 110 liter capacity each, were used as mesocosms. Six replicate tanks were considered controls and six oil treatments, produced with a water accommodated fraction of oil (WAF; WAF-treatments). The WAF was produced using 130 liter baffled recirculating tanks (BRT) and Macondo Surrogate oil. Seawater was collected 8 km offshore south of Galveston (TX) and pre-treated with a charcoal filter to remove large particles and debris. The salinity was 25 PSU. Additionally, natural concentrated plankton was collected using a net (≥63 µm) and prefiltered (115 µm) to remove zooplankton, jellyfish and debris. The six Control tanks were filled directly with seawater from the storage tank. WAF was prepared by mixing 25 mL (5 ml ~ 5 min over 25 min) of Macondo surrogate oil into six baffled recirculating tanks (Wade et al., submitted) containing ~130 L of seawater and mixing vigorously for 4 hrs to create a “high energy” WAF (Knap et al. 1983). The WAF was then introduced into the WAF mesocosm tanks. The concentrated natural plankton was introduced to each of the tanks (1.5 L each for a total volume of 106 L per tank) immediately prior to starting the experiments. Banks of lights were placed behind each of the glass tanks and a 12:12 light dark cycle used (7pm to 7 am). The first three control and WAF mesocosms were sampled day 1 and sacrificed day 4 for a quantitative marine snow collection. The second set of triplicate Control and WAF mesocosms were sampled day 8 and sacrificed day 16 for a quantitative marine snow collection. Days 1 and 8 only surrounding seawater samples were collected through a 5 cm diameter Teflon faucet, positioned 10 cm from the bottom of each mesocosm. Days 4 and 16 the whole tank was sacrificed after collection of surrounding seawater, to quantitatively sample all sunken marine snow. 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 to identify problems. Averages and standard deviations were calculated from the three replicate mesocosms of each treatment.

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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