Cephalopod biodiversity in the Southeastern Brazil Bight: early life stages and associated ocean processes

• Ano de defesa: 2023
• Autor(a) principal: Araújo, Carolina Costa de
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: análise de séries-temporais; Biodiversity; dinâmica oceânica; long-term variability; ocean dynamics; Paralarva; Paralarvae; Plataforma Continental Sudeste do Brasil; Southeastern Brazil Bight
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/21/21134/tde-20102023-163817/

Cephalopods are commonly known as squid, cuttlefish and octopus and represent a major targeted fisheries resource worldwide. Inhabiting almost all marine ecosystems, cephalopods occupy an intermediate trophic level being considered opportunistic predators feeding on a variety of fishes and crustaceans and important preys of fishes, mammals and seabirds. Their rapid growth, short lifespans and strong life-history plasticity reflect their high responsiveness/sensitivity to environmental changes, particularly during early-life stages. In this regard, surveys of paralarvae abundance and distribution in the water column have been considered crucial to understand the biology, spawning areas and population structure of cephalopods. The present study investigated the abundance and composition of paralarvae from the continental shelf of the Southeastern Brazil Bight (SBB) by revisiting a historical collection of samples from 1974 to 2010. The overarching goal was to determine long-term patterns in oceanographic processes leading to fluctuations in the abundance and composition of cephalopods early life stages. For this purpose this study was divided into three chapters. In the first chapter, the taxonomic richness of paralarvae was assessed and an unprecedentedly high diversity of oceanic paralarvae was revealed in shelf areas of the SBB. In the second chapter, focused on Argonautidae paralarvae, an interplay of cross-shelf and along-shore transport was untangled and suggested as major contributor to spatial and temporal distribution of the cephalopods early life stages over the SBB shelf. The third chapter exploring multivariate time-series depicted a temporal asynchrony in the abundance of paralarvae assemblages over the SBB potentially linked to multi-decadal variability of ocean\'s surface temperature and salinity as well as global climate oscillations. Taken together, these studies revealed biodiversity patterns where the abundance, composition and distribution of paralarvae over shelf areas are intimately associated with the oceanographic dynamics of the SBB. Processes such as meanders and eddies of the Brazil Current, coastal upwelling events of Cape Frio and upwelling jets that flow southwards and along-shore for hundreds of kilometers are key features driving both diversity and abundance of paralarvae assemblages in the continental shelf of the SBB. Each of these processes may distinctively affect the distribution of paralarvae, since they might vary both spatially and temporally (seasonal and interannual variability). Finally, major assumptions about paralarvae ecology and behavior in the present study were based on a multi-decadal and large spatial scale sampling using the ColBio-IOUSP historical collection, which provided insights that could be underrated in studies targeting seasonal or interannual variations.