Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Summary of parameters measured in experimental and control microcosms as part of the Dauphin Island Cubitainer Experiment (DICE).

Experimental design, methods, and results are further described in Howard et al. (2010) and Rinta-Kanto et al. (2011).

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.

BCO-DMO made the following changes:
- Modified parameter names to conform with BCO-DMO naming conventions.
- Replaced blanks with 'nd' to indicate 'no data'.
- Added the site coordinates provided in the publications above.

The recent discovery of key genes that mediate competing pathways at a critical juncture in the marine sulfur cycle has allowed biogeochemists to make rapid advances in understanding where and when sulfur transformations occur in the ocean, and most importantly, what factors regulate them. This project describes an environmental functional genomics project that will rapidly increase our knowledge of the role that bacterioplankton play in dimethylsulfoniopropionate (DMSP) cycling in ocean surface waters, focusing particularly on biological controls of volatile sulfur exchange across the ocean/atmosphere boundary.

The investigators have asked three critical hypotheses to explain the regulation of bacterial DMSP degradation: that involve investigations on the energy constraints of DMSP cycling, the role that DMSP concentration in the oceans plays, and the sulfur requirements for bacterial growth. These research areas serve as the focus for hypothesis-driven laboratory and field studies using functional genomics approaches that will track patterns in gene expression in relation to sulfur metabolism. The hypotheses will be tested with:
1) chemostat systems with a model marine bacterium Silicibacter pomeroyi;
2) microcosm experiments with Gulf of Mexico seawater; and
3) field studies at various sites in the Gulf of Mexico. Marine bacterioplankton play a key role in regulating the flux of DMSP-derived sulfur to the atmosphere, a process of great importance for global climate regulation and marine productivity.

The investigators will also be involved in graduate and undergraduate student education, and two post-doctoral associates will be trained to address multidisciplinary challenges in environmental microbiology. High school biology students in Athens, GA will participate in marine microbial biology research that includes bacterial diversity and discovery studies in coastal Georgia, follow-up training in molecular tools and bioinformatics in their own classroom, and summer internships at the University of Georgia and Dauphin Island Sea Laboratory.

(The description above is from the NSF Award Abstract).