Assessing phytoplankton growth in River Tisza (Hungary)

摘要

Riverine phytoplankton can play an important role in the car-bon metabolism of flowing water (SELLERS & BUKAVECKAS 2003). Their role in material fluxes depends on the growth and loss processes they achieve, so the net growth rate of phyto-plankton is a key factor of the whole riverine ecosystem. How-ever, in situ detection of net growth rate of entrained algae in rivers is complicated because they are continuously travelling downstream with the broader water environment as well as reacting to the local conditions along the journey.Fluctuations in the environmental variables (light avail-ability, nutrient supply, and turbulence) make rivers dynamic habitats for phytoplankton. The characteristic organisms of a specific river reach might transiently find preferable condi-tions within the quickly changing bulk flow to maintain their population (VANNOTE et al. 1980), or instead use the more-or-less isolated, slowly moving bodies of water as recruitment sources. The latter areas have been called "dead" or "inshore retention" zones by REYNOLDS & DESCY (1996) and SCHEMER et al. (2001), respectively. These recruitment sources would typically affect all passing water, thus their impact can be identified by looking for phytoplankton growth bound to spe-cific locations.River Tisza is the largest tributary of River Danube. The Hungarian section is about 600 km long, with most of the lower part regulated for flood protection in the 19~(th) and early 20~(th) century. We estimated phytoplankton growth along the river based on high frequency phytoplankton measurements and hydraulic modeling and relate the results to river morphology.