Abstract
The evaluation of abiotic and biotic variables can provide information for understanding the structure and function of lotic systems. To obtain this information, measurements of 15 chemical and physical variables and of phytoplankton were conducted at two sampling stations. The present study aims to evaluate the temporal and spatial variation of planktonic diatoms in terms of abiotic variables and the trophic level of the river water and to select diatom species as descriptors of the physical and chemical conditions of the water upstream (S1) and downstream (S2) of the Iguassu River over an annual cycle. Sampling station S1 was classified as oligotrophic to mesotrophic, and S2 was classified as ultra-oligotrophic to oligotrophic. A total of 98 diatom species distributed among 39 genera was recorded, showing no dominant species but 36 abundant species. Although the differences of chemical and physical variables between S1 and S2 were limited to greater turbulence and turbidity, processes triggered by heavy rainfall exerted a significant influence on community structure, and a temporal change in composition was observed. At the end of the dry period, due to the recovery of nutrients and high transparency, there was an abundance of Cocconeis placentula var. lineata. In the rainy period, with increased turbulence and turbidity processes resulting from higher rainfall, there was an abundance of Aulacoseira granulata var. granulata.
Highlights
IntroductionThe growth of qualitative and quantitative impacts (agriculture, livestock, industry and tourism), isolated or not, leads to the deterioration of water quality and affects the biological integrity of aquatic ecosystems
The growth of qualitative and quantitative impacts, isolated or not, leads to the deterioration of water quality and affects the biological integrity of aquatic ecosystems
Considering the lack of ecological information on large rivers, this study aims to conduct the following: i) evaluate the temporal and spatial variation of planktonic diatoms in terms of abiotic variables and the trophic level of the river water upstream and downstream of the Iguassu falls in the Iguassu River; ii) and select diatom descriptors of the physical and chemical conditions of the water in these two sampling stations and identify factors determining the community structure
Summary
The growth of qualitative and quantitative impacts (agriculture, livestock, industry and tourism), isolated or not, leads to the deterioration of water quality and affects the biological integrity of aquatic ecosystems. Among the activities impacting affecting Brazil’s major rivers, the construction of numerous dams and waterways stands out (Tundisi, 2003). Based on this assumption, it was seen by Ward and Stanford (1983) that a lotic environment undergoing impoundment may suffer substantial changes in patterns of abiotic processes, and biotic processes, both upstream and downstream of the impoundment. The river is divided into three parts: the high, middle and low Iguassu. This last part of the river is in the Iguazu National Park, and because this area is of great importance for biodiversity, it was designated a National Heritage by Decree-lawn 1035 – January 10, 1939 (UNESCO, 2002)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
