Abstract:
Enzymatic hydrolysis of six structurally-distinct polysaccharides were measured in two laboratory incubations with either surface or deep water microbial communities from the Gulf of Mexico (GC600). The treatments included unamended surface or deep-waters, and water amended with water accommodated fraction of oil (WAF), oil dispersant Corexit 9500, and chemically-enhanced WAF with Corexit (CEWAF). Polysaccharides used as substrates for hydrolysis experiments were arabinogalactan, chondroitin, fucoidan, laminarin, pullulan, and xylan. The dataset includes hydrolysis rates of each substrate measured in timecourse incubations. This dataset is a subset of R1.x132.135:0012.
Suggested Citation:
Kai Ziervogel. 2019. Polysaccharide hydrolysis rates in oil-contaminated surface and deep water incubations. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-0f7a-wj15
Data Parameters and Units:
Treatment (Initial whole water, Whole water, Corexit, WAF, CEWAF); Substrate (arabinogalactan, chondroitin, fucoidan, laminarin, pullulan and xylan); Timepoint (1-4); Hydrolysis rates (nmol monomer L-1 hr-1).
Treatment description:
Initial Whole Water - source water that was used to fill the roller bottles.
Whole water - initial whole water sampled at the end of the roller bottle incubations.
WAF - whole water amended with water accommodated fraction of crude oil sampled at the end of the roller bottle incubation.
Corexit - whole water amended with the chemical oil dispersant Corexit 9500
CEWAF - whole water amended with chemically-enhanced WAF
Timepoint description:
1 - immediately after the substrate addition (T0)
2 - after 3 days
3 - after 7 days
4 - after 14 days
Note: n.d. means not detectable.
Methods:
WAF was prepared with 0.85 L of sterile seawater amended with 0.15 L Louisiana sweet crude oil (Macondo surrogate oil from the Marlin Platform Dorado provided by BP). Dispersant-only solutions were comprised of 0.85 L of sterile seawater and 0.015 L of Corexit 9500. CEWAFs were prepared with 0.85 L of sterile seawater amended with 0.15 L Macondo surrogate oil and 0.015 L of Corexit 9500. Sterile seawater amended with oil and/or dispersant was mixed at 600 rpm (magnetic stirrer, Fisher Scientific Isotemp; Thermo Fisher Scientific Inc., Waltham, MA, USA) for 48 h at RT in the dark in clean 1 L glass bottles (furnace heat-treated; 500°C for 4 h) with teflon-lined caps (acid-rinsed, Milli-Q rinsed, and dried). The fluid mixture was allowed to settle for 1 h and the aqueous phase was sub-sampled into clean glass bottles (combusted at 500°C for 4 h), avoiding inclusion of the oil or dispersant phases. WAF, CEWAF and dispersant-only solution were prepared 3-5 days before initiation of the experiment, examined for potential cell contamination via DAPI staining, and stored at 4°C until usage. Nutrient treatments were amended with trace metals (1/1000 vol/vol of 1000× trace metal solution (16)) and nutrients (10 μM ammonium chloride, 10 μM potassium nitrate and 1 μM potassium phosphate, final concentrations, respectively). The effective dilution of the dispersant in seawater (dispersant to seawater ratio, v/v) was 1:60,000 in the dispersant only treatment, while the dispersant to seawater ratio was 1:30,000 v/v in the CEWAF (±nutrients) setups. There are 2 general experiment- using deep water incubation (April 16, 2013) and surface water incubation (Dec 12, 2014).
Setup and sampling of microcosms Establishment and sampling of microcosms was carried out at 8°C. First, the entire volume (160 L) of seawater was mixed carefully in a clean (soaked in 10% HCl for 24 h, Milli-Q rinsed, and dried) 200 L HDPE-tank and then dispensed into clean, combusted (500ºC for 4 h) 2 L glass bottles with teflon-lined caps (acid-rinsed, Milli-Q rinsed, and dried). Next, 0.4 L of sterile WAF, dispersant-only, or CEWAF (±nutrients) was added to 1.6 L seawater. To achieve comparable addition of dissolved organic carbon across treatments, the prepared solutions were diluted with an appropriate volume of sterile seawater (0.2 μm-filtered and pasteurized for 2 h at 65°C). Dispersant was much more soluble in water than oil; to generate 0.4 L of diluted solutions, only 1.56 ml of original dispersant-only solution or 3.26 ml of CEWAF (±nutrients) was added. For WAF, 0.4 L of undiluted WAF was added. The biotic control (no addition) and abiotic control (0.2 μm-filtered and pasteurized for 2 h at 65°C) were prepared contemporaneously and were comprised of 1.6 L seawater plus 0.4 L of sterile seawater (0.2 μm-filtered and pasteurized for 2 h at 65°C). Microcosms were established in triplicates and maintained at 8°C on a roller table in the dark at a rotation speed of 15 rpm.
A subset of the WAF, CEWAF, Corexit 9500, control, whole water and initial whole water in roller bottles were separately mixed with fluorescently-labeled substrates in incubation vials. Enzyme assays with fluorescently-labeled polysaccharides; hydrolysis detected by means of changes in molecular weights over the timecourse of the incubation, using a gel-permeation chromatography system with fluorescence detection.
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