Eukaryotic biodiversity of coastal islands of São Paulo through environmental DNA and metabarcoding

Abstract

Biodiversity plays a fundamental role in the balance and functionality of ecosystems, holding ecological, economic, and social importance. In recent decades, its constant loss has become a critical environmental issue. This loss occurs in various ecosystems, including marine environments, where biological diversity suffers from anthropic actions such as overfishing, pollution, habitat loss, and unregulated occupation. The ocean is a rich and diverse environment, and the decline of its population can cause changes that lead to ecosystem imbalance. In this context, non-invasive techniques that protect the integrity of the environment, such as molecular methods, become essential. Environmental DNA (eDNA), derived from environmental samples and consists of genetic traces released into the ecosystem through excretions such as feces, mucus, skin, gametes, and carcasses, has been employed to conduct biodiversity surveys easily and accurately. Using eDNA metabarcoding, the extracted DNA can be amplified, sequenced, and taxonomically attributed to its species of origin using high-throughput sequencing (HTS). This approach has been used for several purposes, such as detecting threatened, cryptic, exotic, and invasive species, identifying communities, conducting biodiversity surveys, and monitoring specific ecosystems, however, its use is still incipient in the Brazilian marine environment. The state of São Paulo has several coastal islands, many of which are Marine Protected Areas, such as Laje de Santos and the Alcatrazes Archipelago, while others, like Búzios Island and Queimada Grande Island, are unprotected. All are characterized by high biodiversity and proximity to metropolitan areas, along with significant tourism and other economic activities such as fishing. Regardless of the degree of protection of these islands, they all face strong anthropogenic impacts, and there are still gaps in knowledge regarding the biodiversity of these areas. Therefore, this project aims to conduct a survey of the eukaryotic biodiversity of these four islands of São Paulo through environmental eDNA and metabarcoding, as well as to test hypotheses regarding the possible causes of changes in biodiversity, such as oceanographic characteristics, spatiotemporal relationships, and the protection status of the islands. Thus, this project intends to fill gaps in the knowledge of marine biodiversity in protected marine areas and support conservation and management priorities for these ecosystems to ensure the conservation of biodiversity in the coastal islands of the state of São Paulo.