Os efeitos das mudanças climáticas nas relações tróficas microbianas em diferentes regiões dos oceanos.

Abstract

The relationships between microorganisms and phytoplankton are the foundation of the planetary carbon cycle. Photosynthesis removes atmospheric carbon, producing energy that is consumed by bacteria. As in other ecosystems, microorganisms are also susceptible to temperature increases. Primary production, the decomposition of organic matter, and the entire carbon cycle can undergo catastrophic changes due to this phenomenon. In this study, we investigated the impact of climate change on microbial and phytoplankton communities using oceanic vortices in the Brazil-Malvinas Confluence (BMC) region as a natural experimental system. To this end, we integrated flow cytometry, metagenomics, phytoplankton abundance and composition, and physicochemical variable data. This experimental system enabled simulations of warming in two ocean regions: one warm, with waters of equatorial origin, and another cold, with waters from polar regions. Our results reveal that warming induces a 50% decrease in phytoplankton abundance and a 60% increase in bacterioplankton abundance. Additionally, we found a change in the structure and composition of the phytoplankton and bacterial communities. For example, we identified a sixfold increase in the abundance of Karlodinium, a toxin-producing dinoflagellate, in the warmed waters. Conversely, we observed a twofold reduction in Minidiscus, an important diatom for oceanic carbon sequestration, in cold waters. These changes, along with observed differences in fluorescence, suggest a reorganization of microbial and phytoplankton communities, with the replacement of primary producers from eukaryotic phytoplankton to bacterioplankton. This shift has the potential to affect nutrient cycling and primary production, possibly impacting the amount of sequestered carbon, the biomass available for other organisms' consumption, and long-term carbon storage.