In situ determination of cellular DMSP and pigment quotas in a Prorocentrum minimum bloom near the Falkland Islands

Abstract

Marine phytoplankton play critical roles in the biogeochemistry of open and coastal oceans. However, the impact that individual species have on an ecosystem-wide scale can strongly depend on the production of cellular compounds, especially those that are climatically active such as dimethylsulfide (DMS). Herein, we use sorting flow cytometry to separate a distinct phytoplankton population from four samples taken along the Patagonian shelf near the Falkland Islands. Morphological, genetic, and biochemical analyses demonstrated that three of the sorted samples were dominated by a bloom of the dinoflagellate Prorocentrum minimum. Cellular quotas of the DMS-precursor dimethylsulfoniopropionate (DMSP) ranged from 1.23–4.11 pg cell⁻¹ in the same population at different sampling stations. Causes of this variability may be due to different growth stages of the P. minimum bloom or changes in other environmental variables. Overall, in situ intracellular DMSP concentrations were lower than what would be expected based on previous, culture-based measurements. We demonstrate the difficulties inherent in sorting individual phytoplankton species from natural samples in order to determine in situ species-specific cellular quotas of important biogeochemical compounds.

Keywords:

• dimethylsulfoniopropionate
• Patagonian shelf
• dinoflagellate
• pigments
• sorting flow cytometer

Acknowledgements

We thank COPAS ’08 expedition Chief Scientist Barney Balch and the Captain and crew of the R/V Roger Revelle. We would also like to thank our fellow scientists on each expedition for their assistance, and in particular, Bobbie Lyon for her assistance with sample collection. We would like to acknowledge Dr Steve Morton (NOAA Hollings Marine Laboratory) for preparation and collection of the SEM images, Dr Mike Janech (Medical University of South Carolina) for help with the phylogenetic analyses, and the Clemson University Genomics Institute (CUGI) for running the DNA sequences. This paper is contribution No. 426 from the Grice Marine Lab.

Funding

This work was supported by the U.S. National Science Foundation (0848882 to G.R.D. and ANT-0739446 to P.A.L.).