Ecologia trófica e uso de habitat de espécies de um sítio arqueológico local vs. Espécies recentes – o que mudou?

Mestrando:

Guilherme Burg Mayer

Resumo:

The use of stable isotopes analysis (SIA) has been an increasingly popular technique used in ecology studies in which one can examine diet, trophic position and movement patterns in many organisms. Obtaining this information from large apex predators is difficult, especially marine ones. However, SIA is an excellent technique to address these questions in these animals. There are many alternative sources of biological material that can be incorporated in ecology studies of this sort, such as shark teeth and vertebra from museums, as well samples from collections in many institutions.

The present project aims to assess the trophic ecology and movement patterns of up to eleven species[1] of sharks found at an archaeological site, Rio do Meio, located in the north of Florianópolis, SC – Brazil. The site’s most recent layer is dated to be from 1296-1478 A.C (After Christ), however its lower layers are still undergoing work on datations, and the site is probably older. The shark species were identified through morphology of shark teeth and vertebrae. This same material will be used for analysis of 13C and 15N isotopes, which will give us information of the animal’s niche, regarding trophic ecology and habitat use. Some species are of rare occurrence to Brazil, in fact, Carcharodon carcharias is not found nowadays in ‘our’ coast and SIA might help us understand if this animal was using our coast at that time. Moreover, this project aims to compare the data from the archaeological remains with recent shark specimens found at our coast, through literature information of stomach contents and tissue samples that have been collected accompanying fishing journeys and obtained in scientific collections. Thus, we can compare data from pristine environments of the past and compare to the recent specimens data.

The results will be represented as parts per thousand (‰) of international standards: PDB (Peedee Belemnite limestone) for carbon and atmospheric air for nitrogen. The isotopic ratio (R) of each element in the sample and in the standard will be calculated to establish the isotope standards by the equation: δX = [(Ratio / Standard Ratio) – 1] * 1000. Generalized linear models (GLMs) will evaluate the relationship between the δ13C and 15N values for sharks.

[1] Carcharias taurus, Carcharhinus plumbeus, Carcharhinus altimus, Carcharhinus leucas, Carcharhinus longimanus, Carcharhinus brachyurus, Carcharhinus obscurus, Isurus paucus, Negaprion brevirostris, Galeocerdo cuvier, Carcharodon charcharias.