Comparison of SeaWiFS images with ballast water quality

It has become a great concern among the international communities that the ship's ballast water causes marine environmental disturbances of coastal ecosystem. And the regulations and prohibitions of ballast water discharge have already been executed by some coastal countries and discussed by the International Maritime Organization. Since Japan is the one of the largest exporting countries of ballast water, it is important to investigate how the ballast water is exchanged at open seas and influences the surrounding waters. In collaboration with a LNG carrier of 110,000 gross tons onboard sampling and plankton analysis of the ballast water have been carried out during the six cruises between Japan and Qatar from May, 2002 to July, 2003. SeaWiFS images including the ballast water exchange areas along the ship's route were acquired and processsed by using SeaDAS. Based on the plankton analysis phytoplankton and zooplankton species were identified and their numbers of cell were counted for each ballast water exchange. Skeletonema costatum was identified as a species for most of the cruises. Prorocentrum minimum and Prorocentrum micans were also identified in one of the cruises. Furthermore it is found out that the observed cell density is highly correlated with the corresponding SeaWiFS-derived diffuse attenuation coefficient at 490nm.