Long - Term Dynamic Patterns and Diversity of Phytoplankton Commun Ities in a Large Eutrophic River (The Case of River Danube, Hungary

Abstract

Verasztó et al.: Long-term dynamic patterns and diversity of phytoplankton communities in a large eutrophic river - Abstract. In this paper we present the composition, seasonal dynamics and fluctuations in diversity of the phytoplankton in the Danube River over 24 years. Weekly samplings were conducted at one section of the river at Göd, in the 1669 river kilometer segment. The change in the phytoplankton community structure was analyzed in relation of water temperature and discharge means. Our findings support the opinion that the Danube is very rich in species, although many of the species are rare and could be described only as coloring species. Results indicate trends in the phytoplankton abundance, which are only detectable in long-term studies. By the help of diversity indices we have observed an increase in the phytoplankton community diversity. With the relevant information, an explanation of the significant changes in diversity and richness was formed. Our goals were a construction of a solid database of the phytoplankton, examining the seasonal dynamics of the phytoplankton through a 24 year long study and to see the most important changing factors of the community. The results of this study are to assist and help future model developments to predict the phytoplankton seasonal dynamic patterns.

Simulation modeling of phytoplankton dynamics in a large eutrophic river, Hungary — Danubian Phytoplankton Growth Model (DPGM)

“…In addition, each year is followed by the next one in the ordination plot till the end of the 1980s, where we suspect a great change in the phytoplankton composition. The results of Cluster analysis also support the patterns observed on the ordination plot, moreover the authors got similar results during the multivariate analyzes based on the binarization of the data matrix (Verasztó et al 2010).…”

“…Results of temporal coenological patterns constructed from phytoplankton database supported this scenario (Verasztó et al 2010), where change in phosphorus load goes hand in hand with phytoplankton clusters in ordination plot. Assuming that high level of nutrient excess serves a different kind of environment for algae than does low level of nutrient oversupply, purely temperature variation improves simulation of algal biomass without building a nutrient variable into the model.…”

“…Generally, the model estimates biomass variation within years quite well, however, underestimation of phytoplankton biomass in early years and overestimation in the last four yearsthe extent of which lags behind those of the underestimations in the early years -suggest drastic change in environmental variables beyond temperature over the study period. Although mean water temperature in the Danube River experienced some variation over the study period, no remarkable increase was demonstrated (Tóth 2007), whereas discharge peaks reported over 4-6-year cycles increased to a certain degree (Verasztó et al 2010). The trend in phytoplankton biomass variation over the study period, however, cannot be attributed to those observations.…”

“…Theoretically, increasing release of inhibitors of algal growth, or other human pollutants may account for decreased algal biomass as was documented in some case studies (Barinova et al 2008) however, long-term record of water chemical variables in the Danube River does not indicate such profound variation (Tóth 2007). Another rational assumption includes variation in discharge, which can have profound effect on phytoplankton biomass development (Kiss & Schmidt 1998), although discharge variation during the study period does not imply such trend as was observed in algal biomass (Verasztó et al 2010), thus, discharge variation cannot serve as a true predictor of algal biomass.…”

Comunidade fitoplanctônica no monitoramento de rios do estado de São Paulo

“…A comunidade fitoplanctônica do presente estudo apresentou uma riqueza muito elevada de táxons, porém com uma alta proporção de espécies raras (67%), resultados similares foram obtidos em outros estudos com o potamoplâncton (VERASZTÓ et al, 2010;RODRIGUES et. al.…”