Banca de DEFESA: DANDHARA ROSSI CARVALHO

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : DANDHARA ROSSI CARVALHO
DATE: 25/11/2022
TIME: 09:00
LOCAL: on-line
TITLE:

β-taxonomic and functional diversity as tools for evaluating the effects of Small Hydroelectric Power Plants on the ichthyofauna of a tropical river

KEY WORDS:

Anthropogenic impacts, aquatic ecosystems, dams, non-native species

PAGES: 53
BIG AREA: Ciências Biológicas
AREA: Zoologia
SUBÁREA: Zoologia Aplicada
SUMMARY:

Dams construction blocks lotic systems, creating physical barriers that modify the physical-chemical local conditions and alter the flow regime. The new environment formed prevents the free migration of the ichthyofauna and other aquatic organisms that inhabits the lotic environment that need to pass through the filters of the lentic environment. This environment, with lentic characteristics, facilitates the entry of non-native species, which may lead to the extinction of native species, especially those that are more specialized and more sensitive to new environmental conditions. Damming of tropical rivers has been one of the main threats to aquatic biodiversity, and it has occurred on an unprecedented scale. One way out for medium and small rivers is the construction of Small Run-of-Run Hydroelectric Power Plants (SHPs), as they present reduced flooding areas and do not form large reservoirs. However, the real influence of SHPs has been questioned as to their effects in ichthyofauna compared to large dams. In this context, the present study aimed to evaluate the influences on the ichthyofauna of two PCHs built in the middle section of the Paraíba do Sul River, a lotic system of great importance for the water supply of the state of Rio de Janeiro. This study aimed to assess influences on the ichthyofauna of two Small Power Plants (SPPs), built in the middle section of the Rio Paraiba do Sul. Three periods were selected: 1) a period with a totally lotic scenario, before the construction of the two SPPs (2008 - Pre); 2) a period immediately after the construction of the PCHs (2012 - Post); and 3) a period of a decade after the construction of these dams (2021 - Current). Seasonal comparisons were also made among three hydro-environmental conditions: 1) wet, between January and March; 2) dry, between July and August; and 3) transition, between September and October. To assess these changes in ichthyofauna, taxonomic and functional β-diversity were used, since they assess changes in species occurrence and serve to assess both species/function replacement (turnover) and species/function loss (nestedness) in relation to the pool available regionally. For the determination of 10 functional tracts, 12 quantitative morphometrical measures related to habitat use, feeding and locomotion of the species were taken. That ichthyofauna composition varied between periods, although seasonal variations were less conspicuous. Higher richness was recorded in the Post and lower in the Current period. Abundances decrease considerably in the Current period. The taxonomic and functional β-diversity increased over the three periods, with the taxonomic having increased significantly in the Post period and remained without significant differences in the Current period. On the other hand, the functional β-diversity was similar between the pre and post period, with a significant increase in the current period. The replacement component (turnover) was the one that most influenced the results of taxonomic and functional β-diversity, whereas no significant temporal differences were observed in the loss of species component (nestedness). There was a process of the ichthyofauna heterogenization over the periods, with an increase in taxonomic and functional B-diversity associated with a decrease in richness and abundance. Our study indicates that the ichthyofauna is undergoing a re-structuration process, due to the appearance of tolerant species and the replacement of native and sensible species, which results in function replacement after one decade of operation of the SPPs. This suggests that small-scale enterprises such as PCHs are harmful to the ichthyofauna, due to the changes in habitat, or the appearance of non-native and generalist species. Little is known about the real effects of PCHs on ichthyofauna and our results suggest that it is important to understand these changes, as they can be harmful to ichthyofauna. It is suggested to expand these studies in order to provide a basis for biodiversity conservation measures in environments affected by these projects.

COMMITTEE MEMBERS:
Externa à Instituição - BIANCA DE FREITAS TERRA - UFC
Interno - 387200 - FRANCISCO GERSON ARAUJO
Interno - 1728466 - JAYME MAGALHAES SANTANGELO
Externa à Instituição - MARCIA CRISTINA COSTA DE AZEVEDO - UFRRJ
Externa ao Programa - 058.429.537-57 - TAYNARA PONTES FRANCO