Az Eszterházy Károly Tanárképző Főiskola Tudományos Közleményei. 2004. Sectio Biologiae. (Acta Academiae Paedagogicae Agriensis : Nova series ; Tom. 25)
Makrai, L., Dulai, S., Polyánka, H., Ertli, T. and Lehoczki, E.: Monitoring of the Functional State of Beds of Common Reed (Phragmites australis) in Shallow Lake Balaton (Hungary) by Means of Chlorophyll Fluorescence Studies
Monitoring of Functional state of Reed. .. 145 Balaton. The Rfd results on the southern side varied between 1.58 and 1.44, i.e. no appreciable change in the weaker functional state on the southern side. In contrast, the northern side displayed a significant year-by-year deterioration in functional state: the mean Rfd for this three-year period varied between 1.85 and 1.44. In 1998, the average Rfd values for the northern and southern reeds became similar, in consequence of the gradual deterioration of the reed-stands on the northern side. The linear correlation between the maximum assimilation rate of CO2 fixation and Rfd suggested that the C0 2 assimilation also decreased by 25-30% in this period. From the individual Rfd data of the settlements, we constructed an overall functional state map of the reed areas of Lake Balaton (Lehoczki and Makrai, 1997; 1998). This could be compared with effects relating to the local quality of the lake water, the various forms of chemical contamination, the eutrophication, the age of the reeds, etc. It would be a great challenge to identify the factors with significant impacts on the local differences from the average functional state. Keszthely Bay has been the object of numerous scientific studies, mainly because this is the entry point of the River Zala and the region of most extensive eutrophication. The functional state of the reeds at Keszthely Bay in 1996 (Rfd=1.97±0.23) was outstandingly good, but two years later it had deteriorated to have one of the weakest functional states (Rfd=1.42±0.29). These and other similar results demonstrate that there are dynamic changes year by year, probably caused by different individual factors, which can affect separate regions. Serious problems may be observed in the Szigliget Bay and Becehegy regions (though not much attention is paid to these areas), where the reeds are in the poorest condition of all those on the entire northern side. In summary, the application of chlorophyll fluorescence induction to monitor the functional state of reed-beds provides a powerful means of linking photosynthesis with higher levels of plant functioning and is of significant potential for research on the die-back of reeds and for the quantitative determination of the effects of environmental factors before visual symptoms develop. The presented results can be utilised in further research with the aim of establishing the concrete reasons for the die-back of reeds. Acknowledgement: This work was supported by the Balaton Secretariat of the Prime Ministers's Office.
