Bermuda Bio-Optics Project

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 determination of underwater light availability in the open ocean is of importance because of its role in understanding climate-related biogeochemical cycles, including the carbon cycle, as well as its role in phytoplankton and bacterial productivity. Furthermore, 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). The BBOP project therefore entails the isolation of these 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. Understanding of 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.

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.