Effect of DMSP and DMS on Marine Phytoplankton, Climate, and Plankton-Climate Feedback Interactions(2008)

Project Description:This project focuses on the factors that regulate seawater concentrations of dimethylsulfide (DMS), a volatile sulfur compound produced by microscopic marine algae (phytoplankton) that influence cloud formation and global climate. DMS produced by phytoplankton diffuses into the atmosphere where it is transformed by natural chemical reactions into small sulfuric acid particles, which provide nucleation sites for the formation of cloud droplets. The resulting clouds influence global temperatures by reflecting sunlight back into space, thereby lowering solar heating of the earth’s surface. Consequently, factors that regulate DMS production by marine plankton influence global temperatures and climate. DMS is produced from the enzymatic breakdown of a precursor molecule, dimethylsulfoniopropionate (DMSP), which occurs at high concentrations in many phytoplankton species. Researchers at CCFHR have found that phytoplankton produce DMSP and DMS at least partly in response to oxidative stress, including that caused by solar UV-radiation and nutrient limitation. These scientists have proposed a new conceptual model for biological regulation of global climate. They note that increased global warming increases the thermal stratification of ocean water, which in turn leads to nutrient limitation and increased exposure to solar UV for phytoplankton residing in the surface layer of the ocean. The resultant increase in DMS release to the atmosphere promotes the formation of more reflective clouds, which decrease solar heating of the ocean’s surface. These findings indicate the existence of a negative feedback loop in the global climate system which has important implications to any future warming of global climate. The research project focuses on the factors that regulate cellular DMSP concentrations and DMS release in phytoplankton. The research has both laboratory and field components. Laboratory experiments will be conducted to examine the effect of nutrient limitation on cellular DMSP concentrations and DMS production rates in marine algal cultures. The field research consists of time-series measurements the concentration of dissolved DMS, particulate and dissolved DMSP, and the activity of the DMS producing enzyme (DMSP lyase) in Gallents Channel off the CCFHR laboratory dock. Data are also being collected for environmental parameters that can influence DMS concentrations: water temperature, salinity, chlorophyll a (Chl a), the taxonomic composition of the phytoplankton community (via measurement of diagnostic algal pigments), and concentrations of nutrients. The data will be compared with previous time series data collected at the Bermuda Atlantic Time Series (BATS) station in the Sargasso Sea to determine fundamental differences in DMS behavior between coastal and oceanic environments.

Expected Outcome:This research will provide a better understanding of the physical, chemical, and biological factors that regulate DMS concentrations in surface ocean water, and resultant DMS flux to the atmosphere. It will provide a conceptual framework for elucidating large scale ocean/atmosphere biological feedback interactions that influence the earth’s climate and the structure and composition of marine phytoplankton communities. The research will be used to refine theoretical and numerical models for global climate change, and thus will help scientists and regulators to more accurately predict the rate of planetary global warming linked to increased atmospheric levels of CO2 and other greenhouse gases.

Completion Date:
9/2007
Fiscal Year: 2008
PI: Sunda, William -NOAA/NOS/NCCOS/CCFHR
Center: CCFHR
Location of Activity:
All International
NC
Stressor:
Global Warming
HABs
Ecosystem:
Coastal Ocean
Estuaries
SE US Atlantic Ocean