Protistology 4 (3) 251-268 (2006)
Patterns of psammophilous ciliate community structure along the salinity gradient in the
Chernaya River estuary (the Kandalaksha Gulf, the White Sea)
Yuri A. Mazei 1 and Igor V. Burkovsky 2
1 Department of Zoology and Ecology, Penza State Pedagogical
University, Penza, Russia
Summary
Species composition patterns and mechanisms of formation of ciliate community
structure in the Chernaya river estuary (the Kandalaksha Gulf, the White Sea) were
studied in 1996-2000 at stations distributed along the salinity gradient. From the
marine part of the estuary riverwards, salinity decreases and oxidative-reductive
properties of the sediments become more reduced due to organic accumulation. The
greatest variability of salinity, acidity and redox-potential is observed in the brackish
water part of the estuary. All other factors have a more complex distribution in the
intertidal zone, being both gradient and mosaic. During the period of the investigation
altogether 123 species of psammophilous ciliates were found. Psammophilous ciliate
community in the estuary may be considered as rather unified, continual and two-
polar (with marine and brackish-water pool of species). A relative and fuzzy border
between the two poles is situated in brackish water part of the estuary, where the greatest
variability of salinity and redox-potential as well as critical salinity level (3-8‰) are
observed. In the estuary riverwards the complexity of ciliate community in terms of
ciliate density, biomass and species richness decreases significantly. Decrease in species
richness results from congeners. It probably reflects a simplification of niche structure.
Seasonal changes of ciliate community structure in marine zone may be characterized
as rather trended and stable. Changes in community structure in the brackish water
zone of the estuary, on the contrary, are more variable and stochastic. Community in
the intermediate zone of the estuary is both trended and highly heterogeneous.
Community biomass, abundance and species richness are positively connected with
average salinity and redox-potential levels. Variability of integral community
characteristics is related predominately to sediment parameters (amount of organic
matter and relative ability of large size fraction of sand grains). Variability of saline
regime affects that of the total abundance and biomass of the community but not the
variability of species richness and diversity. Analysis of the role of salinity in ciliate
community formation reveals trended changes of species composition and non-linear
modifications of integral community characteristics. All community variants are divided
into two groups with equal complexity but different species composition: marine and
brackish water. Ability of complex marine community to sustain its own structure under
the influence of lower salinity is the first mechanism of community formation in brackish
waters. It predominates at a relatively higher salinity level as well as during terminal
succession stage. Ability of oligohaline ciliates to immigrate from marine to freshwater
estuarine zone is the second mechanism. It determines the community structure in
the initial stages of succession at lower salinity level.
Key words: ciliates, community structure, estuary, salinity gradient, interstitial
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