The impact of carp on a rhizomatous macrophyte was examined in two consecutive years using three outdoor aquaculture ponds with naturally established beds of Potamogeton tricarinatus. Each pond was divided with wire fencing to form a carp (500 kg ha-1) and control treatment. After 6 weeks, plant biomass had declined to the same extent in the carp and control treatments, indicating that direct physical disturbance by carp was not reducing the biomass of P. tricarinatus. In a second experiment, carp were added to two of the same ponds when plants were regenerating after a 9-11 month drying period. After 8 weeks, P. tricarinatus biomass in the carp treatments was between one half and one tenth of the biomass in the control treatments and one control treatment supported more Najas tenuifolia than the paired carp treatment. The lower biomass of Potamogeton in the carp treatments was a result of fewer shoots and less growth per shoot. Rhizomes had been undermined in the carp treatment with less than 1% of plants growing from rhizome compared to 36% in the control treatment. Accumulation of sediment into traps was significantly higher in the carp treatments (2.5 to 77.5 times more than the control). On average, carp resuspended 662 kg dry sediment ha-1 for each 100 kg ha-1 of carp or 6.6 times their wet weight biomass in dry sediments each day. Some implications of high sediment resuspension are discussed. The research demonstrates that well anchored macrophyte species can show tolerance to the physical disturbance associated with carp benthic feeding, however, these same species are vulnerable during regenerating and recruitment stages. It is suggested that anchorage is the most important factor for determining plant tolerance to carp. The implications for aquatic plant and riverine management are discussed, including the importance of excluding carp from newly flooded wetlands and the role of carp in determining alternative stable states.

Artificial ponds are excellent for the study of phytoplankton ecology. They permit repeatable initial conditions and sufficient replication of independent experimental units in complex experiments to test hypotheses about the control of structure and function in natural communities. There were 20 experimental ponds constructed in Kokoř nsko Protected Landscape Area, from which samples were taken and analyzed. This study was part of the EU BIOPOOL. During the first two years after the filling of the ponds the colonization and the seasonal development of phytoplankton communities in the ponds were examined. The phytoplankton species composition was determined, then species richness and relative abundance of individual taxa were quantified. Species composition data were compared with the environmental parameters measured (temperature, oxygen concentration, pH, transparency, conductivity, depth, chlorophyll-a concentration, and zooplankton). In the spring 2007, the ponds were periodic, and followed a similar trend over time (February- April). There were dominated by the following taxonomic groups: Dinophyta, Chrysophyta, Cryptophyta, and Euglenophyta. After installing foil on the bottom of the ponds, the ponds were of permanent character. In terms of environmental parameters, the individual ponds...

Macroinvertebrate communities inhabiting an exotic, Myriophyllum spicatum, and a native, Heteranthera dubia macrophyte were studied from March 1999 to June 2000 in experimental ponds. Although macrophyte architecture explained some variation in macroinvertebrate abundance between the two macrophytes, most variation was explained by the sampling months. Total number of macroinvertebrates was found to be positively correlated with epiphyton biomass which differed significantly between the two plant types and among sampling months. Taxa richness did not vary between the two plant types. Chironomid larvae were the most abundant organisms and dominated by Apedilum elachistus on both plant communities. Annual production of five chironomid species was estimated by the size-frequency method. Production estimates (P) in g dry wt m-2 yr-1 of plant surface area for the predator Tanypodinae larvae were: Larsia decolarata, P= 0.77 and 0.67, Labrundinia virescens, P= 0.59 and 0.35 on M. spicatum and H. dubia, respectively. Larvae of Cricotopus sylvestris and Psectrocladius vernalis were collected from M. spicatum from March to mid-June. Production of C. sylvestris was found to be 0.46 g dry wt m-2, whereas it was 0.07 g dry wt m-2 for P. vernalis for this period. Apedilum elachistus exhibited the highest productivity: 9.9 g dry wt m-2 yr-1 of plant surface area on M. spicatum, and 8.5 g dry wt m-2 yr-1 on H. dubia. These production estimates are among the highest production values reported for a single species. Additionally, post-ovipositing development times for five chironomid species collected from Myriophyllum and Heteranthera were determined. Three different temperatures (15°, 20° and 25°C) were chosen to rear eggs under 12L: 12D photoperiod. Egg development times ranged between 1-4 days. Larval development times ranged from 44 days at 20°C for Tanypus neopunctipennis to as few as 9 days at 20°C for Larsia decolorata.