THE ROTIFERS OF VAYA LAKE
MARIETA STANACHKOVA1*, DIMITAR KOZUHAROV1, ELENA NENOVA2
1 – Department of General and Applied Hydrobiology, Faculty of Biology, Sofia University “St. Kliment Ohridski”, Sofia, Bulgaria
2 – Faculty of Biology, Department of Zoology and anthropology, Faculty of Biology, Sofia University “St. Kliment Ohridski”, Sofia, Bulgaria
*Corresponding author: etipost@dir.bg
Keywords: Rotifera, plankton, coastal wetlands, anthropogenic influence
Abstract: The Vaya Lake is a Ramsar site, a protected area in the Bulgarian legislation and part of the European ecological network Natura 2000. It is part of the ‘Via Pontica’ bird migration route. At the same time it is situated near Bourgas city – comparatively big harbor and industrial center. The Lake is shallow, holo-polimictic water basin.
The aim of the present investigations was to determine the qualitative structure of the rotifer complex of Vaya Lake in the changed conditions of the lake due to the anthropogenic impact and to compare the results with previous research data. The study was carried out during the summer and autumn seasons of four consecutive years: 2004, 2005, 2006 and 2007. A comparison of nowadays obtained results with results for the period 1953-1957 was made. All samples were collected from the central part of the lake. In result of the provided investigations thirty five rotifer taxa what belongs to 18 genera were recorded in Vaya Lake during the both investigated periods. During the period 2004-2007 – 28 rotifer taxa were established in the Lake. Common for the two periods of research is just one taxa. The increasing number of the Rotifers and mainly these, that prefer eutrophic waters, indicates advanced eutrophication in the basin. The Jaccard similarity index was used for comparing the similarity into rotifer complexes. Similarity was too low – 3%, which indicates continuous changes into the rotifer complex. All types of results show the general negative trend in the evolutional development of the Vaya Lake with increasing of eutrophication.