Bacteria and phytoplankton of the seasonal surveys of 1972 and 1973 / John C. Ayers.

PHYTOPLANKTON

Techniques
Phytoplankton samples were collected by Niskin bottle at a depth of
1 m, with the exception of the nearshore stations. Nearshore collections
(serial number zero stations) were made by submerging an open 1-liter
bottle 4 inches below the water surface. All samples were 1-liter whole
samples. Each sample was fixed with Utermohl's iodine fixative immediately after collection and stored in an opaque container.
In the laboratory, each sample was concentrated to 100 ml by
settling in a 1000-ml graduate cylinder and siphoning off 900 ml of
fluid. The concentrated sample was stored in a 100-ml opaque bottle.
The samples of April 1972 were prepared and counted by the Utermohl
technique: by placing an aliquot of the concentrated sample in a tubular
combination settling and counting chamber and allowing the aliquot to
settle overnight. The counting chamber containing the settled cells was
then separated from the settling chamber, covered, and placed on the
microscope. The samples were counted on a binocular inverted microscope
at 100OX magnification.
Beginning with July 1972 and continuing since, the method of concentration for species identification and enumeration has been the settlefreeze method as proposed by Sanford et al. (1969). The method entails
an overnight settling of 1000 ml of sample in a graduated cylinder. The
following day the top 900 ml are siphoned off and discarded. Part of
the remaining 100 ml is used for preparation for the microscope slide
and the rest is kept for any possible further references or back checking.
The once settled sample is then diluted if need be and settled again,
this time in 18-ml cylinders. These cylinders are attached with a small
amount of stopcock lubricant (to prevent leakage) to the microscope
slides which rest on an aluminum plate one quarter inch thick. The whole
apparatus is then secured together mechanically. The microscope slides,
prior to having the cylinders placed on them, are treated with Dissicote
to provide a hydrophobic surface to the slide. After the samples have

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