SPLAT CAM: mapping plankton distributions with bioluminescent road-kill

The most common sources of planktonic bioluminescence are dinoflagellates, copepods, euphausiids, ostracods and gelatinous zooplankton. Each of these has very distinctive flash characteristics that make them easy to distinguish from each other. Using an intensified video camera mounted on a mid-water submersible we have developed the Spatial Plankton Analysis Technique (SPLAT) that identifies and maps the 3-dimensional microscale distribution patterns of bioluminescent plankton. The unique temporal and spatial characteristics of luminescent displays permit identification of many sources to the species level, and the exceptional signal-to-noise ratio afforded by a self-luminous source means that even microscopic organisms, such as a 50 μm dinoflagellate, can be identified in a field of view of 1 m. Recently we have adapted the SPLAT CAM for deployment on the HIDEX-BP (High Intake Defined Excitation BathyPhotometer). This vertical profiling system was developed for the U.S. Navy (Naval Oceanographic Office-NAVOCEANO) for routine monitoring of bioluminescence in the oceans. The high pumping rate of this BP (18 l/s) assures a high statistical significance and a high-resolution profile of bioluminescence potential in the water column. By combining this capability with the plankton identification afforded by the SPLAT CAM, the utility of both systems is greatly enhanced. The resulting data should prove valuable for a wide range of applications such as defining the geographical boundaries of dinoflagellate blooms, tracking movement patterns of bioluminescent vertical migrators, monitoring temporal changes in the abundance of grazers as a function of environmental variables and primary production, assessing the production of primary sources of nutrition for commercially important fish species and providing data needed for NSW nowcasts and forecasts.