Journal
HYDROBIOLOGIA
Volume 570, Issue -, Pages 53-59Publisher
SPRINGER
DOI: 10.1007/s10750-006-0161-9
Keywords
aquatic macrophytes; reservoir; water level; water hyacinth; aquatic weeds; Upper Parana River; Egeria najas; Eichhornia crassipes; Salvinia herzogii; growth dynamics
Categories
Ask authors/readers for more resources
The biomass and maximum depth of colonization (Z(max)) of Egeria najas Planchon (submerged), and the biomass and area covered by a stand of Eichhornia crassipes (Mart.) Solms and Salvinia herzogii Raddi (floating species) were assessed to measure the effects of a 5 in drawdown in water level of the Itaipu Reservoir (Brazil-Paraguay), which lasted about 3 months. The frequency of occurrence of the two first species, and of Salvinia spp was also assessed in the main arms of the reservoir. A conspicuous decrease of E. najas biomass was observed and this attribute did not reach the previous values even 10 months after the water level had returned to normal. Rapid growth of free-floating species (surface t(doub) = 2.9 and 3.2 days for total biomass of S. herzogii and E. crassipes, respectively, and 2.3 days for surface area covered by both species) was recorded immediately after the water level returned to normal. This fast growth was related to phosphorus increases in water. A clear succession was observed over a period of 103 days, during which S. herzogii was slowly substituted by E. crassipes. The effects of water level drawdown were also observed on E. najas frequency, given that this species occurred in 38% of the stands investigated before the water drawdown, but in only 9 and 6% of stands following 1 and 10 months of water level recovery, respectively. Water drawdown did not affect the frequency of occurrence of the floating species, which remained approximately constant, and lower than 15% in several of the reservoir arms investigated.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available