Table of Contents

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

Phytoplankton diversity along with carbon and nitrogen uptake rates from cruise RR1604 along the GO-SHIP IO9 repeat hydrography section of the Indian Ocean.

All nutrient and cell count methodology is described in the published work coming out of this data set (see below). 

Samples were initially collected with a CTD/Niskin rosette, as supplied by the ship.

Urea and total dissolved phosphorus (for calculation of dissolved organic phosphorus) were determined on a Thermo Scientific Genesys 10UV spectrophotometer. See Lomas et al. (2010) for a description of the latter. 

Cell counts for heterotrophic bacteria and nanoplankton (<20 um) cells were performed on a BD FACSJazz flow cytometer, using standard methods and 0.53 um bead stocks for reference material. Visualization of heterotrophic bacteria was performed with SYBR Green stain.

Biomass calculations were derived from flow cytometry data output, as per Casey et al. (2013). 

Larger (>20 um) autotrophs were enumerated on a FlowCam (Fluid Imagining Technologies). 

Biomass and isotopic enrichment, used to calculate specific and absolute uptake rates, were assessed on a Thermo Finnegan Delta V mass spectrometer, as operated by the Bigelow Analytical Services team.

Sample accuracy was assessed by using certified standards, for those measurements where standards are available. Certified standards were run with each analytical run and compared to long term control charts for respective analyses. For those analyses where there are no standards (e.g., flow cytometric cell counts) data were assessed for reasonableness based upon extensive experience of the PI’s.

Data processing was performed using mostly Microsoft Excel. Further statistical analyses and graphing were performed with SigmaPlot. All samples collected are included in the report. Any occurences of "nd" in the data mean those samples were not collected. 

BCO-DMO Processing:
- modified parameter names to conform with BCO-DMO naming convetions (removed units, replaced spaces with underscores);
- replaced blank cells with "nd" ("no data").

Description from NSF award abstract:
The Indian Ocean accounts for nearly a fifth of global ocean photosynthesis and is likely a key component in global ocean nutrient and carbon cycles. However, the Indian Ocean may be the least studied major marine body on the planet. Our limited understanding suggests extensive variations in physical and chemical environmental conditions, but how this variation influences biodiversity, nutrient stress, and more broadly regional differences in the functioning of phytoplankton is unknown. To help address these gaps, the investigators will conduct a study by joining an already-funded major research cruise to this region. It will cover a northern region with some of the highest temperatures recorded in open ocean waters, an area around 10°S of predicted (but not tested in situ) iron stress, and a southern subtropical gyre with unique nitrogen to phosphorous(or N:P) ratios. The focus of this project is to quantify and synthesize the interconnectedness of environmental conditions, phytoplankton diversity and genome content, and nutrient biogeochemistry, with the goal of understanding how these may lead to unique biogeochemical regions in Indian Ocean. The research will have broader impacts on many levels. First, it will increase public awareness of the role of phytoplankton on ocean functioning, climate, and people's lives through a new partnership with the Aquarium of the Pacific (AOP), which is the fourth most-attended aquarium in the nation. Secondly, the project will train a postdoctoral scholar as well as a graduate and undergraduate students. Third, the research will dramatically increase our basic knowledge ocean biogeochemistry and in many cases will be the first measurements of their kind made in the Indian Ocean.

This project will address two major questions: How do environmental conditions, phytoplankton diversity, phytoplankton physiology, and biogeochemistry vary across the central Indian Ocean? Are there distinct biogeochemical regimes in the central IO? The researchers hypothesize that environmental conditions, including the relative availability of nitrogen (N) and iron (Fe), lead to three distinct phytoplankton communities and biogeochemical regimes. They will employ a series of advanced analytical tools including high sensitivity measurements of dissolved and particulate nutrients (nitrogen, phosphorus, and iron), genomics, bioassays to test for nutrient stress, and cell-sorting of specific taxa followed by measures of nutrient content and uptake. A focus of this project is to quantify and synthesize the interconnectedness of environmental conditions, phytoplankton diversity and genome content, and nutrient biogeochemistry, and how these lead to unique biogeochemical regions in Indian Ocean. This extensive set of observations can ultimately be linked to ocean models and satellite data to provide a comprehensive view of regional differences in chemistry, biodiversity and phytoplankton biogeochemical functioning in the Indian Ocean.