Experimental results: summary of microcosm data from Dauphin Island Cubitainer Experiment (DICE) from samples collected by R/V E.O. Wilson in the Gulf of Mexico, Alabama (En-Gen DMSP Cycling project) from 2006-10-01 to 2006-10-31 (NCEI Accession 0291389)

Acquisition Description:
See Howard et al. 2011 and Rinta-Kanto et al. 2011 for detailed methods, summarized below:

"In October 2006, seawater was collected from surface waters (<1 m deep) in the Gulf of Mexico off the coast of Dauphin Island, AL (lat: 30 03.041N; lon: 87 59.708W). Water was filtered through a 200-um mesh into six 20-liter polyethylene Cubitainers with minimal headspace.

Three microcosms were amended with 10 um sodium nitrate (NaNO3) and 0.6 um potassium phosphate (K2HPO4) to serve as the experimental microcosms. Three microcosms were left untreated to serve as the control. The Cubitainers were maintained at 27 degrees C on a 12-hour light/dark cycle for the duration of the experiment.

Chemical and activity measurements were collected from the microcosms at the beginning of the experiment (Day 0) and every day for the duration of the experiment at the same time. Chlorophyll-a samples were collected by filtration on Whatman GF/F fiters. The filters were extracted in 90% acetone for 24 hours at -20 degrees C. The extracts were quantified by fluorometry on a Turner Designs TD-700.

Samples for dissolved dimethylsulfoniopropionate (DMSPd) were collected by filtration through GF/F filters. Total dimethylsulfoniopropionate (DMSP), dissolved + particulate, was measured by acidifying whole seawater with 5 ul per ml of 50% H2SO4. Dissolved and total DMSP were quantified as dimethylsulfide (DMS) after alkaline hydrolysis. Bacterial production was measured by [3H]leucine incorporation.

Rates of DMSPd consumption were determined by multiplying the DMSPd concentrations by their respective DMSPd loss rate constant from parallel samples. DMSPd consumption rate constants were determined by measuring the loss of tracer levels of [35S]-DMSP from the dissolved (< 0.2 um) pool over time. DMS production and DMS yield (ratio of DMS production to DMSPd consumption) were measured as described in Vila-Costa et al. (2008)"

References:
Vila-Costa, M., Kiene, R.P., and Simó, R. (2008) Seasonal variability of the dynamics of dimethylated sulfur compounds in a coastal northwest mediterranean site. Limnol Oceanogr 53: 198–211.