Banca de DEFESA: LEONARDO CAPITANI

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : LEONARDO CAPITANI
DATE: 26/04/2021
TIME: 14:00
LOCAL: Natal
TITLE:

RESOURCE AVAILABILITY AND TEMPERATURE: NEW INSIGHTS FROM WESTERN ATLANTIC REEF ECOSYSTEMS

KEY WORDS:

reef ecosystems, prey-predator interactions, temperature, primary productivity, funcional response, Western Atlantic Ocean

PAGES: 144
BIG AREA: Ciências Biológicas
AREA: Ecologia
SUBÁREA: Ecologia de Ecossistemas
SUMMARY:

Reef ecosystems are complex, biodiverse and productive marine systems. Although they represent less than 0.09% of the surface of the oceans, these ecosystems provide fundamental ecological processes, such as nutrient recycling, feeding, reproduction and evolution of many species. In these ecosystems there are non-linear relationships between physical variables (temperature, acidity, salinity, dissolved oxygen) and biotic components (primary production and species abundance). On physical side, water temperature is a crucial factor that can affect the phenology, growth and trophic interactions of many reef species. On the side of biological interactions, it is known that the colonization of shallow waters by herbivorous fish may have facilitated the formation of reefs as we know them today, leading to specific changes in the trophic relationships of these environments. Surprisingly, there is a lack of general understanding on how temperature, resource availability and trophic interactions jointly shape reef environments in the western Atlantic Ocean. The study with a mathematical approach of the reef trophic interactions and their dependence on temperature and resource availability offers enormous potential for the consolidation of ecological theories or the discovery of new macro-ecological patterns. This thesis is organized in three chapters, in which we explore the relationship of temperature and available resources on reef species abundance in three different ways. In the first chapter, using a controlled field experiment on the reef of Rocas Atoll, we tested mechanistic models of the functional response of the fish Acanthurus chirurgus with its resource algae Digenea simplex. The results indicate that the herbivory process by A. chirurgus is best described by a model where the amount of algae and the density of A. chirurgus are equally important to define the per capita resource consumption. These results shed new light on the dynamics of herbivorous fish-algae interactions in the western Atlantic, highlighting the fundamental importance of considering the effect of consumer density on herbivore- plant models for reef ecosystems. In the second chapter, we modeled the food web of Rocas Atoll reef ecosystem and we analyzed the changes in standing biomass at all trophic levels as a response to the rise in sea water temperature over the 21st century, based on IPCC scenarios. The results of the simulations indicate that, by the end of the century, the total biomass of the ecosystem should decrease by 1%, 8% and 44% in low, medium and high emissions scenarios. As the total biomass decreases, the trophic structure of the ecosystem will change, favoring primary producers (algae turfs), invertivorous fish, while hard corals will severely decrease. In the third chapter, we will use data on reef fish length over 61° degrees of latitude in the Western Atlantic (from North Carolina, USA to Santa Catarina, Brazil). We will test for the existence of a linear relationship between the average fish body size, sea water temperature and resource availability (primary productivity). The results expected for this chapter (not yet finalized) should strengthen a general ecological rule: greater availability of resources, greater individual body size regardless of temperature. With this thesis, I hope to contribute to the construction of a more solid and general basis on the factors (physical and biological) that influence one of the most important biological processes in reef ecosystems: resource intake (predation) and the consequent conversion of resources into new living biomass.

BANKING MEMBERS:
Presidente - 1177742 - RONALDO ANGELINI
Interno - 2319234 - GUILHERME ORTIGARA LONGO
Externo à Instituição - MARIANA BENDER GOMES - UFSM
Externo à Instituição - PAULO INÁCIO DE KNEGT LÓPEZ DE PRADO - USP
Externo à Instituição - RONALDO BASTOS FRANCINI-FILHO - USP
Externo à Instituição - SERGIO RICARDO FLOETER - UFSC