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Algae censors biodiversity formation in the North Russian rivers Sergei Komulainen Institute of Biology, Karelian Research Centre, Russian Academy of Sciences Pushkinskaya 11, 185610 Petrozavodsk, Republic of Karelia, Russia Introduction Lists of species provide the basis for the study of the biota structure and the factors that affect it. It is important to make systematic analysis more complete, but it is equally important to improve diagnoses, to revise classifications and phylogenetic schemes, and to change the concept of a species. Besides, one should bear in mind that species are not equivalent in their “contribution” to biota structure. They can differ in evolution status, the extent of phylogenetic isolation, and functional role in ecosystems. Therefore, assessment of diversity solely as an arithmetic sum of species without considering the fact that they are not equivalent is hardly acceptable, and does not reflect changes in a coenoses. Changes in the species number and its relatively abundance in periphyton communities can be used to survey water quality. Many richness, evenness and diversity indices have been developed to characterize communities. But more often have been suggested that the best means for detecting shift in the environment is Shannon-Weaver diversity index, which is an integral characteristic of assemblages. The purpose of this paper is to summarize and discuss, with specific examples, the variations in species diversity not only after changes in abiotic factors, but also in watercourses that differ in geographic position. The hypothesis that changes in species diversity can be used as an indicator of changes in water quality was tested Material and methods Attached communities have been studied at 49 streams located within north-western Russia from Ladoga Lake to Barents Sea. It allows to estimate the climatic and the hydrological regime influence on phytoperiphyton communities structure and abundance. Biodiversity indices have been tested with materials collected from natural and artificial substrata. In all the rivers studied, samples were collected during a short summer low-water period. In some rivers characteristic of each region observation was conducted during an open water period (April-October) or rivers were studied throughout the season. The sample form of Shannon-Wiever formula H =− ( N i / N ) ln( N i / N ) was used as an index of species diversity. It was calculated separately for diatoms and for communities in whole, for rivers and separate locations and communities. The diatom database software “OMNIDIA” (Lecointe et al. 1993) was used to calculate trophic diatom index (TDI), the values of which varied more at low concentrations (Eloranta 1999). 170 ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ The Finnish Environment 485 Results and discussion The most important characteristics of the phytoperiphyton in studied rivers is underline its belonging to the flora of boreal type, as true high latitude elements even in the rivers of the Barents Sea Basin occupy, as a rule, a subordinate position (Komulainen 2002). Taxonomic structure of periphyton displays a tendency for the concentration of inter- and intraspecies taxons in a small number of genera and families while at the same time forming a considerable amount of genera and families comprised of few species which reflects the complexity of florogenetic processes. This trend suggests that a significant role in the formation of periphyton, in studied rivers is played by the allochthonous way of development. Taxonomical structure of algal communities is formed either due to the introduction of new taxons into them or at the expense of combinatorial change within the same species. The first is determined for periphyton by entering of allochthonic species from plankton and bottom algae communities. Floristic diversity is also maintained due to the succession asynchronism in various sites of the river system and algal drift explains simultaneous presence of spring, summer and autumn species in algocenosis at that, the formation rate is mainly regulated by light conditions. Some “northern” traits, characteristic of algal periphyton flora, are apparent at the different levels of taxonomic analysis (Komulainen 1998). With predominance of diatoms, blue-green algae become less diverse northwards than green algae. Species that show a high phosphorus and nitrogen demand are the first to drop out of algal coenoses. Forms that are accidental for the periphyton are less common than true attached forms. Nostocales/Oscillatoriales ratio increases from 1.6 for the rivers of the Ladoga Lake basin to 4.0 for those of the Barents Sea basin. Assessing the impact of climate changes on biodiversity is difficult due to the spatial and temporal scale and the complexity of the problem, and its interactions with other environmental factors. In spite of marked north-south variations in taxonomic composition of phytoperiphyton in study rivers, the diversity indices values remain practically the same ranged from 2.0 to 3.0 for most rivers (Fig. 1). This shows that the algal coenoses of periphyton are highly developed in the rivers studied that have high vital activity, self-regulation and stability. Fig. 1. Correlation between river location (latitude) and phytoperiphyton species diversity indices (H). The Finnish Environment 485 ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ 171 At the same time the heterogeneity of habitat in each river is very high and significant for the formation of periphyton diversity. Firstly differences in species composition have been observed between pool, run and riffle habitats. Current is the main “taking” factor determining mosaic character of the periphyton communities distribution and regulating the periphyton succession. It is noted that during floods, a large quantity of attached material is irretrievably removed from the ecosystem, and the formation of biodiversity begins from the very beginning. Species diversity peaked quickly during colonisation and decreased as the length of exposure increased. Pool zone showed greater diversity indices during the first few days exposure than did slides exposed in riffle zones. After week diversity of algaecoenoses was significantly (p<0.05) greater at 0.1 m c-2 than at 1.0 m c-2. Later on this brief conditioning period, however, the riffle slides showed more rapid cell growth and accommodation rates, particularly. That is why in the rapids with poorly sorted mosscovered rocky substrates diversity values were generally greater than at the pools. But for both cases the negative relations of an index Shannon-Wiever with phytoperiphyton biomass was very weak (r = 0.30, F = 3.50, P < 007). Besides, phytoperiphyton diversity was observed to increase in rivers with large basin areas (Fig.2) and decreased in communities were filamentous algae have become very abundant. Fig. 2. Correlation between river size (length, km) and phytoperiphyton species diversity indices (H). Variations in diversity are caused not only by the variability of hydrological regime. Lake factor is of great importance, by the removal of allochthonous species from swamps and running-water lakes (Komulainen 1999). Structure and abundance of allochthonic algae flora changes in dependence on the number of lake their morphometry, trophic status and seasons. In attached communities, in addition to euperiphytonic forms, which have adjusted to the attached mode of life and are scarce in other algocenotic types, periphyton was found to include planktonic and benthic algae. Allochthonous forms are clearly dominated by colony-forming planktonic diatoms, such as Aulacosira spp, Melosira spp, Fragilaria spp. and Tabellaria fenestrata (Lyngb.) Kütz. A particularly substantial contribution to the formation of periphyton in large lakes is sometimes made by planktonic green (Palmodictyon viride Kütz., Hyalotheca mucosa ( Merth.) Ehr. ) 172 ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ The Finnish Environment 485 and the blue-green (Gloeotrichia echinulata (J. S. Smith.) P. Richt., Microcystis aeruginosa Kütz., Aphanizomenon flos-aquae (L.) Ralfs, Anabaena spp., Woronichinia naegeliana (Ung.) Elenk., and Oscillatoria agardhii (Gom. )) algae, that cause waters “blooming”. Migration of a large number of algae from one assemblage to another and from lakes to rivers leads to significant indices of diversity changes, which constant fluctuations indicate the low organization and stability of algal communities in these locations. As a result of such “mutual enrichment” the classical continuum has been interrupted and local increase/decrease changes in phytoperiphyton communities diversity constantly observed . Most of the rivers are not affected by human activities. The impact of man on the water bodies is basically caused by the discharge of domestic and agricultural waste water rich in nutrients. The increase of anthropogenic effect leads to slightly increased bottom species diversity and structural trivialization, followed by a decline in the number of dominant species. The halophobic-acidophilic-indifferent composition of diatoms is enriched in alkaliphilic and halophilic species. Leading oxiphilic xenosaprobic diatoms of the genera are observed to drop out, and the role of Tabellaria becomes less important. TDI values calculated for river in which same human impact was observed varied rather widely but correlation between the TDI and index of biodiversity was significant (r=0.46; F=19.0; P<00004). There are problems with using species diversity indices to indicate pollution trend to be related to predicting decrease in diversity in response to decrease in water quality. But in our experiments with artificial substrates it has been found that at the initial stages of contamination, the structure changes by introduction of new species and the large-scale reproduction of the species that were earlier scarce in phytocenosis. Fig. There are changes in diversity index for periphyton communities in Lizma River developed on slides which were placed to points where there was sewage water input in river, after three months exposure in clear water (Fig. 3). With an increase in anthropogenic impact an oligodominant complex of species is formed and structural trivialization followed by a decline in the number of dominant species and the communities become less diverse and structurally more simple. Fig. 3. Box plot of species diversity indices (H) for phytoperiphyton developed in point of sewage water input. The Finnish Environment 485 ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ 173 The minimisation of anthropogenic effect and the stabilization of hydrological regime lead to the rapid reconstruction of the natural structure of algal cenosis. It has often been noticed that algal flora has a natural structure even at a short distance from the place of wastewater discharge. This is favoured by alternation of zones differing in hydrological regime, when a riffle-pool complex acts as “a natural water treatment facility”. References Eloranta P. 1997. Application of diatom indices in Finnish rivers. - 3rd European Workshop “Use of algae for monitoring rivers”. France: 138-144. Komulainen S. 1998. Climate changes and some peculiarities of periphyton development in streams - Climate and waters. Helsinki. Finland: 527-532 Komulainen S. 1999. The influence of lake on algal communities structure and dynamics in lake-river systems.- Proceeding of 8th International Conference on Conservation and Management of Lakes. Copenhagen. Denmark. S12C-2 Komulainen S. 2002. Features in periphyton in some rirers of northwestern Russia. -Verh. Intern. Verein. Limnol. 27: 3159-3161. Lecointe C, Coste M & Bukowska J. 1993. “Omnidia”: software for taxonomy, calculation of diatom indices and inventories management. - Hydrobiologia 269/270: 509-513. 174 ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ The Finnish Environment 485