Zooplankton of the open Baltic: Extended Atlas - IOW

Feeding modes and strategies
Different feeding modes can be distinguished in ciliates. Most ciliates
are heterotrophic organisms, but there are some exceptions. Some planktonic
ciliates (especially oligotrichids) are capable of mixotrophic feeding.
Myrionecta rubra is noted for obligate autotrophy: it contains cryptophycean
endosymbionts, which are capable of photosynthesis. In the south-western
Gdańsk Basin, the potential annual production of M. rubra comprised 6 to 9%
of the total primary production. These ciliates were the main contributors to
the total biomass of autotrophs also in the Bothnian Bay (Jaanus et al., 2007).
Heterotrophic ciliates can be attributed to groups with different feeding
types: microphagous (feeding on bacteria, detritus), phytophagous (feeding on
phytoplankton), and predatory carnivorous ciliates (feeding on other ciliates
and small metazoans). In the Baltic Sea, ciliates with all feeding modes are
present: microphagous (genera Balanion, Cyclidium, Mesodinium),
phytophagous (Strombidium, Strobilidium), and carnivorous (Didinium).
Each ciliate species shows a specific food particle size preference
pattern. Most ciliates are known to prefer prey size 2 to 10 µm (Kivi & Setala,
1995; Samuelsson et al., 2006). The overall ciliate food size spectrum covers
the most abundant food items in the Baltic summer plankton. Most species of
the Baltic planktonic ciliates effectively ingest nanoflagellate-size food; a
minority showed effective grazing on the smallest particles, suggesting a
possible ability to utilize bacteria-size prey (Kivi & Setala, 1995).
Among the ciliates, two different feeding strategies appear to be valid:
specialistic and generalistic, where the ciliates either concentrate on feeding
on a narrow size range of food organisms (Tintinnopsis lobiancoi,
Strombidium conicum and Strobilidium sp.), or use food particles of a wide
size range, with little or no preferences within this range (Lohmaniella
oviformis, Strobilidium spiralis, Strombidium sp., Tintinnidium fluviatile,
Tintinnopsis beroidea) (Kivi & Setala, 1995).
Abundance, biomass, distribution
As in the case of community structure, the abundance and biomass of
Baltic ciliates show a high degree of spatial and season variability. Spatial
variability of ciliate abundance consists of distinctions between different
regions of the Baltic Sea, between coastal and open waters, between different
layers studied in the water column (euphotic and deep-water layer).
The abundance of ciliates in the Baltic Sea ranges from 1x10 3 to 88x10 3
ind./l and biomass varies from 0.023 to 0.3 mg C/l. The seasonal succession
of ciliates showed peaks during spring in the northern Baltic Proper
(Johansson et al., 2004), during spring and autumn in the northern and
western Baltic Sea (Smetacek, 1981; Samuelsson et al., 2006), the Neva Bay
(Khlebovich, 1987) and during spring and summer in the south-western
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