Conexões entre a pluma do rio amazonas, o carbono orgânico particulado e os padrões biogeográficos bentônicos na margem equatorial do Brasil
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Data
2025-07-14
Autores
Pereira, Araiene Peres
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Universidade Federal do Espírito Santo
Resumo
The Amazon and Guiana continental shelves comprise one of the most dynamic marine systems on the planet, shaped by the interaction between the river discharge of the Amazon and Orinoco Rivers and the regional ocean circulation. This complex hydrodynamics regulates the spatial distribution of particulate organic carbon (POC), a key element in the biogeochemical cycles of the Atlantic Ocean and in the structure of pelagic and benthic communities. Despite its importance, there are still gaps in knowledge about how the Amazon River plume influences the spatiotemporal dynamics of POC along the continental shelf, especially as it disperses toward northern Brazil. Therefore, we investigated this relationship by integrating Amazon River discharge data (Óbidos station), POC estimates derived from MODIS-Aqua imagery (2003–2023), and benthic invertebrate occurrence records from the OBIS database. The analysis revealed a clear pattern of hydrological seasonality, with fluctuations influenced by climatic events such as the El Niño–Southern Oscillation (ENSO), which directly affected COP availability in the region. The highest COP concentrations were observed north of the mouth of the Amazon, driven by the continuous transport of the Amazon plume by the North Brazil Current. In contrast, the Guiana Shelf showed lower concentrations, likely due to the retroflection of the plume toward the open ocean. This COP dynamic appears to be directly reflected in the composition of benthic communities. A total of 4,541 invertebrate occurrences were recorded, distributed across 12 phyla, with Arthropoda, Cnidaria, Echinodermata, and Mollusca predominating. The Mouth of the Amazon stood out for its high taxonomic richness, possibly favored by the high deposition of organic matter and the region's intense hydrodynamics. The dissimilarity observed between the Boca and Norte communities, as well as the similarity between Guiana and the Orinoco, suggest that the combination of river flow and marine circulation patterns strongly influences faunal organization. Species such as Xiphopenaeus kroyeri and Penaeus subtilis were representative of COP-rich environments, while corals and echinoderms were more frequent in areas with lower particulate matter input. These results indicate that COP distribution acts as one of the main ecological determinants of regional benthic structure. Finally, we highlight the impact of extreme climate events, such as the 2015–2017 El Niño, which reduced Amazon flow and COP concentrations by approximately 15%, highlighting the high sensitivity of this coastal system to global climate change.
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Plataformas continentais tropicais , Pluma do Rio Amazonas , ENSO