Zooplankton of the open Baltic: Extended Atlas - IOW

procedure of sample preparation is described in Gifford and Caron (2000),
Strüder-Kypke et al. (2003).
All fixatives do not necessarily preserve the cell shape and size of live
specimens, it is important to note that fixatives shrink cells. So, investigators
will use a conversion factor (for aloricate ciliates, which are preserved with
2% Lugol's - 190 fg C µm -3 ) (Putt & Stoecker, 1989). Biomass of planktonic
ciliates can be determined by multiplying the species abundance by the
individual mass of ciliates. Calculation of the volume and mass of the cell
may be performed by establishing the similarity of the ciliate cell to different
geometric figures.
Additional methodological information on ciliates can be obtained from
manuals for microzooplankton sampling, fixation, and staining (e.g. Gifford
& Caron, 2000; Strüder-Kypke et al., 2003; http://www.liv.ac.uk/ciliate/
intro.htm).
3.4. Identification and counting of meso- and macrozooplankton
Species identification and counting are the basis of any community
analysis. These procedures are time-consuming and require considerable
professional experience. This fact often restricts the number of samples that
can be analysed with an acceptable effort within a reasonable time span.
Attempts to overcome these difficulties by the automatic counting methods
may help to solve the problem of under-sampling (Wiebe & Benfield, 2003).
However, application of the automatic methods is limited to uniform samples
(e.g. cultures in laboratories), to certain size-class specific analyses, or to a
coarse separation of organisms from larger taxonomic groups with significant
differences in general body morphology. Coupling of such procedures with
computerised image analysis may be helpful; however, it is still linked with
sophisticated technical equipment and a need of special software.
Routinely, for monitoring purposes counting is performed for the
dominant organisms from easily identifiable taxonomic groups, and their
developmental stages. More taxonomic skills are required for the
identification of certain species. The species names should be used according
to the International Code of Zoological Nomenclature (http://www.iczn.org).
Information on the validity of names and actual taxonomic classification can
be given, for example, after the Integrated Taxonomic Information System
(http://www.itis.gov) and The European Register of Marine Species
(http://www.marbef.org/data/erms.php).
The laboratory procedure of sorting mesozooplankton starts with
removing the carcinogenic formalin from the sample by its filtration through
meshes smaller than the mesh size of the sampling gear. The filtrated
preservative is used again after the analysis for any further storage. The
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