Temporal variations in transparent exopolymer particles (TEP) associated with a diatom spring bloom in a subarctic ria in Japan

Temporal variations in transparent exopolymer particles (TEP) were studied during a spring bloom (January to April 1998) in a subarctic ria on the nor theast coast of Japan. A diatom-dominated bloom developed from mid-February . Two major peaks were recorded in the first and last week of March, during which chlorophyll concentrations reached the maximum of 12 mug l(-1). The TEP concentration increased sharply after the first peak, the pre-bloom ave rage of 901 rising to 1442 mug xanthan equiv. l(-1). The maximum TEP value of 2321 mug xanthan equiv. l(-1) recorded at the surface coincided with the second bloom peak. After this peak, TEP concentration continued to be rela tively high. The number of particles fluctuated between 1 and 3.4 x 10(5) m l(-1) (size = 4 to 520 mum) with an increase in small-sized particles follo wing the bloom decline. TEP concentrations in this bay were much higher (av g. 1344 mug xanthan equiv. l(-1)) than reported elsewhere (avg. 147 to 308 mug xanthan equiv. l(-1)). Although TEP increased considerably following th e bloom, it was interesting to note the high pre-bloom concentrations despi te low chlorophyll concentrations. This implied that a source other than ph ytoplankton was responsible for the release of exudates leading to TEP form ation. Laboratory experiments confirmed our assumption that the significant ly high background TEP was due to the additional formation of these particl es from the extracellular exudates released by the macroalga Undaria pinnat ifida, cultivated commercially in this bay. Thus, besides providing informa tion from the subarctic coastal waters of Japan for the first time, our stu dy also confirms the role of macroalgal exudates as an important additional source for the formation of TEP.