Banca de QUALIFICAÇÃO: PAULO IVO SILVA DE MEDEIROS

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : PAULO IVO SILVA DE MEDEIROS
DATE: 17/07/2020
TIME: 15:00
LOCAL: WEBCONFERÊNCIA - https://meet.google.com/ync-fhqn-vra
TITLE:

Effects of water level reduction on the dynamics of zooplankton and their predators in two shallow lakes semi-arid tropical


KEY WORDS:

Extreme drought;trophic interaction;eutrophication;water turbidity;biomanipulation;


PAGES: 28
BIG AREA: Ciências Biológicas
AREA: Ecologia
SUMMARY:

The reduction in the volume of lakes and reservoirs due to the increase in water deficit during periods of drought, should affect the structure and trophic dynamics of these ecosystems, increasing the concentration of organisms, the rates of encounter between predators and prey and, consequently, pressure of predation. The objective of this work was to investigate the effects of water level reduction caused by extreme drought events on the densities of zooplanktonic organisms and their predators in two reservoirs in the Brazilian semi-arid tropical region. The tested hypothesis is that the densities of zooplankton predators increase with the reduction of the volume of water caused by drought, favoring zooplankton prey less vulnerable to predation over the most vulnerable. To test this hypothesis, the densities of zooplanktonic organisms (rotifers, cladocerans and copepods) and their main predators (fish larvae and juveniles, shrimp larvae, hydracarina mite and chaoboridae larvae) were monitored for 24 months in two shallow artificial lakes of the Brazilian semi-arid region during a drought period (2012-2014). In one of the lakes, about 5.8 tons of adult fish were to remove to prevent massive fish mortality when the volume of water and oxygen reached a critical level. Zooplanktonic organisms were collected monthly by means of vertical trawls with a plankton net with a 68 µm opening and their predators were collected monthly by means of horizontal trawls with an ichthyoplankton mesh with a 500 µm mesh opening and a flow meter to measure the filtered volume. The organism densities were to analyze over the study period and Spearman correlations were to perform to evaluate the possible interactions between zooplanktonic organisms and their predators and the effects of reduced water volume on the studied organisms. In both lakes, rotifers dominated zooplankton and chaoboridae larvae were the most abundant predators. In the lake where there was no removal of adult fish, the densities of fish larvae to increase, the densities of chaoboridae larvae decreased and those of copepods increased with the reduction of the water level. On the other hand, in the lake where adult fish were remove, the densities of fish larvae, shrimp and rotifers decreased while the densities of chaoboridae larvae increased with the reduction of the water level. These results indicate that the water level reduction caused by drought tends to vary the abundance of predators, changing the relative importance of predation by vertebrates and invertebrates and causing changes in the structure of zooplankton communities depending on local conditions.


BANKING MEMBERS:
Presidente - 1362202 - JOSE LUIZ DE ATTAYDE
Interno - 1714892 - ADRIANO CALIMAN FERREIRA DA SILVA
Interna - 1345773 - RENATA DE FÁTIMA PANOSSO
Notícia cadastrada em: 16/07/2020 14:58
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