The determination of underwater light availability in the open ocean plays an important role in understanding climate-related biogeochemical cycles, including the carbon cycle, as well as phytoplankton and bacterial productivity. A comprehensive knowledge of these processes allows for improved accuracy of global satellite-based measurements of ocean chlorophyll and primary productivity. Transmittance of light through the water column is regulated by the absorption of radiation by various components, including phytoplankton, detritus and other particulate matter, and the chromophoric fraction of dissolved organic matter (CDOM). Understanding CDOM cycles and the processes by which they are regulated is especially important because of the role CDOM plays in ocean photochemistry, including processes of direct and indirect photolysis to produce such compounds as reactive oxygen species (ROS), and the photooxidation of others such as dimethyl sulfide (DMS). These reactions can ultimately lead to the photobleaching of CDOM itself, thus in turn, altering the underwater light availability.
The Bermuda Bio-Optics Project (BBOP) is a long term study of the factors contributing to the regulation of the underwater light field in the open ocean and the resulting biogeochemical impact. These studies are done, on average, once a month in conjunction with the Bermuda-Atlantic Time Series (BATS) in the Sargasso Sea. The BBOP project entails the isolation of compounds from the water column and their spectrophotometric/fluorometric determination in order to create a comprehensive model of their seasonal/annual cycles in open ocean waters.
Another faction of BBOP acquires radiometric data to corroborate NASA’s Seawifs (Sea-viewing Wide Field-of-view Sensor) project satellite measurements, which employ ocean color algorithms to determine optical properties in ocean waters. Because these ocean color data provide an understanding of primary productivity and ocean biogeochemistry, confidence in their accuracy is invaluable. Therefore, on monthly cruises, a multichannel profiling radiometer is deployed in the water, in conjunction with a surface reference radiometer and overhead passes by an earth-orbiting ocean color sensor. Please visit the BBOP Data Page for a variety of online data resources, including radiometric profile and surface data, PAR data, and pigment data.
Areas of Active Research
Using bottle samples collected by a CTD, scientists analyze suspended particles (including CDOM) and phytoplankton to increase our understanding of open-ocean primary productivity and nutrient cycles.
We measure light at the surface of the ocean and at various depths to calculate a variety of parameters, including how much light is hitting the sea surface, how fast that light disappears with depth, and how much light is being scattered back by particles within the water column. These measurements help calibrate satellite measurements and improve mathematical algorithms for obtaining additional data.
BBOP scientists continue to work to improve algorithms for obtaining a variety of information (including cholorophyll concentration, CDOM, and particulate backscatter spectra) from ocean color satellite data. Time-series observations from the BBOP are submitted to various NASA databases.
We are interested in the effect of small amounts of Saharan dust on the remote sensing signal near Bermuda. To this end, BBOP scientists participated in a research expedition in the equatorial Atlantic as part of the US-AMMA program.