Phytoplankton carbon biomass estimated from the size-fractionated chlorophyll alpha concentration and cell density in the northern coastal waters [of Japan] from spring bloom to summer
1993
Odate, T. (Hokkaido Univ., Hakodate (Japan). Faculty of Fisheries) | Yanada, M. | Mizuta, H. | Maita, Y.
Phytoplankton carbon biomass (PC) was estimated from size-fractionated concentration of chlorophyll alpha (CHL) and cell density in Funka Bay, Hokkaido, from February to August 1989, using the conversion equations from cellular CHL content to cell volume, cell volume to cellular PC, and the cellular PC conversion factors taken from literatures. The temporal variations of phytoplankton biomass and size composition based on the measured CHL were compared those based on the estimated PC, and then discrepancies arising from differences of size composition and of cyanobacterial abundance in estimating PC from CHL data were recognized. The phytoplankton biomass in terms of CHL was predominated by the 10 micron size fraction during a spring phytoplankton bloom and by the 2-0.2 micron size fraction after the bloom. Cell density of cyanobacteria largely increased in the thermally stratified water column from June to July and reached the maximum in August. The total CHL during the spring bloom was 37-fold higher than after the spring bloom. The former total PC was 61-fold higher than the latter one. After the bloom the abundance of the 2-0.2 micron size fraction was 61% of the total CHL while it was 35% in the PC based comparison. On the other hand, the total CHL in summer was 80% of that observed after the bloom. It the comparison was conducted based on the PC, the abundance of total phytoplankton in summer was 25-fold larger than that observered after the bloom. The predominance of the 2-0.2 micron size fraction based on PC in summer was further emphasized (98%) compared to 60% based on the CHL. It is concluded that high occurrence of cyanobacteria with high PC:CHL creates a larger discrepancy than a dominance of small-sized eukaryotic cells with low PC:CHL when PC is estimated from CHL in this bay
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