David Caron and Darcy Lonsdale
WHOI
Methodology for microplankton counts

Duplicate samples for the enumeration of microplankton were preserved with a
10% final concentration of acid Lugols and also with 1% buffered formalin. Both
samples were stored in 0.5L amber glass bottles and kept in the dark at 4
degrees C (Stoecker et. al., 1994a). Samples with low microplankton abundance
were presettled and concentrated 5 to 10-fold before final settling in counting
chambers for the enumeration of 20-200 micrometer organisms using inverted
microscopy.  Microplankton were grouped by major taxa (diatoms,
dinoflagellates, non-loricate ciliates, tintinnid ciliates,
silicoflagellates)and colonial Phaeocystis antarctica cells. Although
individual Phaeocystis antarctica cells are in the nanoplankton size range
(2-20 micrometer), colonies generally fall in the range of microplankton
(20-200 micrometer) or larger. Thus flagellated, single cells of P. antarctica
were enumerated as phototrophic nanoplankton, and non-motile cells associated
with colonies were included in the counts of microplankton. Samples preserved
in 1% buffered formalin were used for distinguishing phototrophs from
heterotrophs by autofluorescence. 
 

Microplankton biovolumes were determined from measurements of their linear
dimensions using volume equations for appropriate geometric shapes. Biovolume
estimates were converted to carbon biomass for each of the plankton categories
using published conversion factors. 
 

References


Stoecker, D. K., D. J. Gifford and M. Putt  (1994a)  Preservation of marine planktonic ciliates:
losses and cell shrinkage during fixation.  Marine Ecology Progress Series, 110, 293-299.