Brito-Lolaia, M. (2023). Diversidade funcional e isotópica do microzooplâncton de uma região costeira tropical (Baía de Tamandaré, Pernambuco, Brasil), de 2013 a 2019. [Functional and isotopic diversity of microzooplankton from a tropical coastal region (Tamandaré Bay, Pernambuco, Brazil), from 2013 to 2019.]. Tese de Doutorado, Universidade Federal de Pernambuco, Recife, Pernambuco, Brazil. 122 pp. [In Portuguese and English].

485330

Brito-Lolaia, M.

2023

122 pp. [In Portuguese and English]

Publication

https://repositorio.ufpe.br/handle/123456789/53386

Available for editors   [request]

Functional diversity and stable isotope analysis have been widely used additionally to the traditional study of zooplankton ecology. Functional diversity is the measure of the values of species, according to their attributes or characteristics, which influence the functioning of the ecosystem. Stable isotopes are indicative of diet (Carbon) and trophic position (Nitrogen) present in the tissue of organisms. Long-term studies are important in observing seasonal and interannual variations and the effects of climate anomalies on the microzooplankton community. This thesis aimed to evaluate the ecological relationships of microzooplankton through analyses of functional diversity and stable isotopes and their variability influenced by seasonality, interannual and environmental conditions along a time series (2013 to 2019). Samples were collected bimonthly between June 2013 and August 2019 at three stations in Tamandaré Bay (Pernambuco, Brazil), through subsurface tows with 64 μm mesh conical nets. The samples were placed in plastic jars containing 4% formalin, buffered with sodium tetraborate (5 g L−1). Four samples were selected per year (two in the dry season, two in the rainy season), except when there were no samples due to bad weather. The samples were divided, one part was separated for counting, measuring and identifying zooplankton and the other part for stable isotope analysis in the mass spectrometer. For the calculation of functional diversity, the copepod assembly was analyzed regarding their functional attributes and divided into functional groups. The functional diversity analysis showed that a minimal variation in environmental conditions (temperature and salinity) significantly affected the functional groups of copepods (91% of the explained variation) and that the most abundant group presents functional attributes (morphological characteristics and reproductive strategy) that allowed its permanence in an environment in constant variations. The analysis of stable isotopes made it possible to detect the trophic level of key species through a new approach, “species-biomassisotopes-mixture” (SBIM) that analyzes the entire community. The copepod Pseudodiaptomus acutus showed the highest trophic level within the zooplankton community, while small organisms, such as copepod nauplii and polychaete larvae, showed the lowest trophic level. This result would not be possible in studies that analyze only a few pre-selected species. The effects of seasonality and external climate forcing (e.g., El Niño Southern Oscillation) on environmental conditions and the community were also analyzed. The copepod Euterpina acutifrons, the ciliate Favella ehrenbergii and “other ciliates” were indicators of seasonal variation, with high abundance in the rainy season. In view of this study, it is concluded that a small variation in abiotic factors, caused by precipitation in Tamandaré Bay, is the main responsible for the seasonal and interannual variation of microzooplankton, especially in the functional groups of copepods. The SBIM method is an important new approach for discovering which key species are occupying trophic levels based on isotope analysis of the entire community. The studies developed in this thesis offered a glimpse into the ecological factors that drive the variability and trophic relationships of microzooplankton in a tropical coastal ecosystem. Keywords: Zooplankton; Functional diversity; Stable isotopes; Time series; Southwestern Tropical Atlantic.

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