Banca de DEFESA: IRMA CARVALHO E SILVA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : IRMA CARVALHO E SILVA
DATE: 22/08/2024
TIME: 14:00
LOCAL: DOL - DEPARTAMENTO DE OCEONOGRAFIA E LIMNIOLOGIA
TITLE:

Interaction between periphyton microalgae and submerged macrophytes in a changing world

KEY WORDS:

Interaction; Resource; Grazing; Climate change; Allelopathy.

PAGES: 128
BIG AREA: Ciências Biológicas
AREA: Ecologia
SUMMARY:

Periphytic algae and submerged macrophytes are directly related, so that in a scenario of climate change, local interactions between both communities may be intensified by competitive processes, reflecting changes in patterns of diversity and functioning of aquatic ecosystems. The thesis is structured in three chapters that experimentally evaluate ecological issues related to periphyton-submerged macrophyte interactions. In the first chapter we experimentally tested how temperature, nutrients and substrate type affect the interaction between periphyton and the macrophyte Egeria densa Planch. It was observed that heating at 3°C reduced the biomass and increased the number of lateral branches of the macrophyte, but these were smaller in size and biomass compared to the room temperature treatment. The presence of periphyton also had a significant effect, reducing the size of lateral branches. For the periphyton, variations in total richness were observed depending on the type of substrate, with greater richness in the natural substrate. Total richness was influenced by the interaction between temperature, nutrients and substrate type, with differences over time. In the second chapter, using the same experiment, we focused on analyzing the effect of controlled variables on the composition and structure of the periphytic community, exploring species and taxonomic groups. The abundance of cyanobacteria was higher when associated with the artificial substrate, under conditions of temperatures heated to 3°C and a higher concentration of nutrients. On the other hand, we found a higher density of the epiphytic community in scenarios with ambient temperature, low nutrient concentration and association with macrophytes. This trend is reversed in the scenarios with warming, artificial substrate and high nutrient concentration. In the third chapter, we carried out field experiments to test the effects of allelopathy and herbivory on periphytic biomass, considering the type of substrate, as well as surface and total extracts of E. densa in the control of periphyton. A significant reduction in periphytic biomass was observed in natural substrate and in relation to total extract of E. densa, with herbivory being the most influential factor in controlling the increase in this biomass. Understanding these relationships in current and future scenarios is critical to establishing restoration measures that promote the resilience and conservation of aquatic ecosystems. The maintenance of ecosystem services is directly dependent on these interactions, so a thorough understanding of these processes is essential to guide effective management and conservation strategies. The thesis highlights the importance of laboratory and field experiments that address fundamental aspects of understanding and conserving aquatic ecosystems in the face of environmental change. 

COMMITTEE MEMBERS:
Externa à Instituição - FABIANA SCHNECK - UFPA
Externa à Instituição - THAISA SALA MICHELAN - UFPA
Interno - 2319234 - GUILHERME ORTIGARA LONGO
Presidente - 2412921 - JULIANA DEO DIAS
Externo à Instituição - NADSON RESSYE SIMOES DA SILVA - UFSB