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New Zealand Journal of Marine and Freshwater Research abstractsEffectiveness of various counting methods in detecting viable phytoplanktonHans W. PaerlFreshwater Section, Ecology Division, DSIR, P.O. Box 415, Taupo, New ZealandAbstract Comparisons of counts from "C microautoradiographs of photosynthetically active natural phytoplankton populations with counts from Utermohl or membrane-filter methods often reveal significant discrepancies in biomass estimates; the viability of armoured species such as diatoms cannot be determined effectively by the latter two methods. Furthermore, nanoplankton < 5 /an in diameter are difficult to distinguish from detrital material, especially when Utermohl methods are used at routine magnifications. Considering that nanoplankton commonly account for between 20% and 50% of total phytoplankton biomass in various lakes, current methods tend to overlook a major segment of the primary producers. In overestimating viable diatoms, dinoflagellates, and armoured green algae by as much as 50% and underestimating nanoplankton by a similar magnitude, conventional counting methods may be inadequate to describe true phytoplankton biomass. These discrepancies can be discovered and corrected by applying microautoradiography.
N.Z. Journal of Marine and Freshwater Research 12 (/) : 67-72.
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