Table of Contents

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

Size Fractionation of retinal, bacteriochlorophyll and chlorophyll:
Samples for quantification of light harvesting pigments in eukaryotes and prokaryotes were collected at a number of depths within the euphotic zone (see field study sites). Seawater were collected from each CTD depth using Niskin bottles and immediately filtered. Size fractionated samples were collected using a series of in-line filters using a peristaltic pump (flow rate < 50 ml per minute). Filters of different pore-size (0.2 um for picoplankton, and 3.0 um for nanoplankton) were used for the fractionation. Particulate samples were immediately stored at -80 degrees C until analysis. For analysis, samples were extracted with methanol (retinal, chla, and Bchl) and with hydroxylamine (oxime) and analyzed by liquid chromatography/tandem mass spectrometry (LC/MS/MS). The LCMS system consists of a ThermoTSQ Quantum Access electro-spray ionization triple quadrupole mass spectrometer, coupled to a Thermo Accela High Speed Liquid Chromatography system (Seegers et al., in preparation). The mobile phase conditions for the LCMS method for chlorophyll and bacteriochlorophyll analyses were adapted from Goericke (2002). All retinoid samples were analyzed in triplicate using an external calibration curve, though not presented, precision was typically in the 5-15% range.

Energy Benefit [kJ/cell/day] = Pigment concentration [molecules/cell] × Photosynthetic unit [per cell] × Maximum rate [electron/RC/s] /(PAR [umol photons/m2/s] + Half saturation [umol/photons/m2/s]) / Avogadro constant [/mol] × 12 [hours] × 60 [min] × 60 [sec] × Energy per photon [kJ/mol]

BCO-DMO Processing Notes:
- Replaced blanks (missing data) with 'nd' to indicate 'no data';
- Modified parameter names to conform with BCO-DMO naming conventions;
- Added ISO_DateTime field using original date and time values provided.

Description from NSF award abstract:
Rhodopsins are the simplest energy-harvesting photoproteins and community metagenomics have revealed that their synthesis genes are ubiquitous throughout the world oceans. These include microbial rhodopsin (proteorhodopsin (PR)), which occur in an estimated 75% of marine bacteria and archaea in oceanic surface waters. The discovery of this abundant and widespread photoprotein in the surface ocean has challenged the notion that solar energy can only be converted into chemical energy for growth in marine ecosystems through chlorophyll-based photosynthesis. Although the potential of light-driven energy flux in ocean ecosystems through PR could be significant, the physiological and ecological functions of this type of rhodopsin remains undetermined, mainly due to the lack of a technique for a direct measurement of this photoprotein. To evaluate the ecological relevance of PR in the marine environment, the investigators have developed a new analytical technique to measure the concentrations of the light-sensitive pigment in the PR, the chromophore retinal. Because rhodopsins have a single retinal chromophore associated with the polypeptide opsin, the total number of retinal molecules is equivalent to the total number of PR.

This project will employ the PI's newly developed protocol to examine the effects of light, organic carbon and trace metals availability on PR and bacteriochlorophyll synthesis using field and laboratory manipulations. Such experiments will establish the impact of abiotic factors on the two known bacterial photoheterotrophic metabolisms. The laboratory studies will be complemented with the analyses of those pigments in field samples collected along spatial and temporal gradients in light intensity, organic carbon and trace metals in different oceanographic regimes. Gene expression patterns will be determined in concert with changes in retinal and bacteriochlorophyll concentrations and microbial growth responses in the field and in the laboratory. Therefore, the combination of observational and manipulative approaches, will address fundamental questions in regard to the impact of retinal-based photochemical energy transformation in the ocean, a process that still is not well understood.