Zooplankton of the open Baltic: Extended Atlas - IOW

Cnidaria, Ctenophora, Chaetognatha, Mysidacea, Euphausiacea, Decapoda,
Polychaeta and others) (Lenz, 2000).
The sub-division of zooplankton into micro- and mesozooplankton size
classes used in this book is (to a certain extent) not a traditional one: we
consider all rotifers as mesozooplankton, applying the term
“microzooplankton” to planktonic ciliates. This is another conventionality
determined by the fact that the authors want to draw special attention of the
readers to the chapter “Ciliates of the Baltic Sea”. It is the first attempt to
provide updated illustrated information on biodiversity of these protists in the
Baltic ecosystem. Unlike the dominant mesozooplankters, ciliates are usually
not considered in the regional monitoring programs; nevertheless, they are
good indicators of water quality. They play an important role in the
zooplankton communities, and contribute significantly to energy fluxes
(through the microbial loop, for example) and water purification in the Baltic
Sea ecosystem. The chapter provides a checklist of 811 species of planktonic
and benthic ciliates (which may also be numerous in plankton) that inhabit
both open and coastal waters of the Baltic Sea. This part of the atlas is
illustrated by the original photographs of live ciliates collected in the Gulf of
Finland, eastern Baltic Sea and cultured in the laboratory for the purpose of
precise species identification.
Aquatic ecologists know that species identification of zooplankton
organisms is a tedious and time-consuming work which requires certain
taxonomic skills, understanding of the general principles of species
identification, and knowledge of taxonomically-important morphological
characteristics of zooplankters from different groups. On a regular basis,
species determination should be performed with the help of taxonomic
identification keys. Additionally, illustrated atlas books with drawings and
photos of live and preserved planktonic organisms can be also helpful;
however, they can not substitute the classical taxonomic guides.
Nowadays, it is a common problem worldwide that professional
taxonomists with the deep knowledge of the systematic of different groups of
aquatic invertebrates become extinct (Costello et al., 2006). For the Baltic Sea
region, taxonomic training of the professional staff in hydrobiological
laboratories storing their results in joint databases is of exceptional
importance for harmonising the methods and improving the skills necessary
to identify the zooplankton species. These training courses for Baltic
zooplankton identification are essential for acquiring and maintaining the
quality assurance of the laboratories participating in the joint international
monitoring programmes in the Baltic Sea region. Unfortunately, such
taxonomic training courses are rare so far.
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