Persistent whole-bay red tide of Noctiluca scintillans in Manila Bay, Philippines

概要

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Noctiluca scintillans, which contains a photosynthetic endosymbiont, Pedinomonas noctilucae, formed perennial red tides in Manila Bay, Philippines, occasionally covering almost whole area since 2001. A whole-bay scale red tide of the green Noctiluca in Manila Bay is described as the first step to elucidate the formation mechanism of the large scale blooming of the organism. A field survey was conducted in March 2004, when greenish discoloration due to N. scintillans was observed in the whole bay. The bloom persisted at least for two months from late February to late April 2004 as revealed by SeaWiFS images and sea-truth observations. Chlorophyll a varied from 0.55 to 522μgL^<-1> in the upper 10-m water column, 28 to 94% of which was ascribed to N. scintillans with a mean of 75±17%(n=60) as revealed by HPLC analysis of bio-marker pigments with CHEMTAX interpretation. In-situ specific growth rate was too low for the continuous dominance of N. scintillans in the bay, where potentially fast growing diatoms occurred as secondary dominant species. While the endosymbiosis of P. noctilucae provides competitive advantages for N. scintillans under conditions with low availability of external food supply or insufficient light intensity for photosynthesis of the symbiont, no suitable explanation was obtained for the persistent dominance. Trophic status of the green Noctiluca appears to be crucial.
東京大学の論文
2006-04-28