Original ArticlesThe role of annual periodic behavior of water quality parameters in primary production - Chlorophyll-a estimation

•Spatiotemporal variability of periodic behavior of water quality parameters assessed.•Wavelet spectrum analysis was used to obtain periodicity indices.•A statistical relationship was found between the periodicity indices and chlorophyll-a.•Phytoplankton biomass was successfully estimated using the periodicity indices.

Since phytoplankton is an autochthonous primary producer, it plays a vital role in driving the water quality of rivers and lakes. Therefore, in cases where measurements are lacking, its estimation is of the essence. In the present study, Morlet wavelet spectrum (periodicity) and multiple regression analyses were conducted on 15 chemical, biological and physical water quality variables sampled at 14 sites along the Hungarian section of the River Tisza and 4 sites from artificial tributary channels for 1993-2005. Results show that annual periodicity was not always to be found in the water quality parameters, at least at certain sampling sites. Periodicity was found to vary over space and time, but in general, an increase was observed in the company of higher trophic states of the river heading downstream. Based on the spatial distribution of the periodic behavior of the water quality parameters (runoff, ions, and nutrients given in so-called periodicity indices), an improved model was constructed which was capable of explaining about half (adjusted R2 = 0.5) of the phytoplankton variance in the study area.

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