Insights into the Microbial and Viral Dynamics of a Coastal Downwelling-Upwelling Transition

PLOS ONE, Dec 2019

Although previous studies have described opposing states in upwelling regions, i.e., the rise of cold nutrient-rich waters and prevalence of surface warm nutrient-poor waters, few have addressed the transition from one state to the other. This study aimed to describe the microbial and viral structure during this transition and was able to obtain the taxonomic and metabolic compositions as well as physical-chemical data. This integrated approach allowed for a better understanding of the dynamics of the downwelling upwelling transition, suggesting that a wealth of metabolic processes and ecological interactions are occurring in the minute fractions of the plankton (femto, pico, nano). These processes and interactions included evidence of microbial predominance during downwelling (with nitrogen recycling and aerobic anoxygenic photosynthesis), different viral predation pressures over primary production in different states (cyanobacteria vs eukaryotes), and a predominance of diatoms and selected bacterial and archaeal groups during upwelling (with the occurrence of a wealth of nitrogen metabolism involving ammonia). Thus, the results provided insights into which microbes, viruses and microbial-mediated processes are probably important in the functioning of upwelling systems.

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Insights into the Microbial and Viral Dynamics of a Coastal Downwelling-Upwelling Transition

September Insights into the Microbial and Viral Dynamics of a Coastal Downwelling- Upwelling Transition Gustavo Bueno Gregoracci 0 1 Ana Carolina dos Santos Soares 0 1 Milene Dias Miranda 0 1 Ricardo Coutinho 0 1 Fabiano L. Thompson 0 1 0 1 Departamento de Ciências do Mar , UNIFESP Baixada Santista. Santos, SP , Brazil , 2 Instituto de Biologia, Universidade Federal do Rio de Janeiro (UFRJ) , Rio de Janeiro, RJ , Brazil , 3 Laboratório de Vírus Respiratórios e do Sarampo, Instituto Oswaldo Cruz (IOC)-FIOCRUZ , Rio de Janeiro, RJ , Brazil , 4 Instituto de Estudos do Mar Almirante Paulo Moreira (IEAPM) , Arraial do Cabo, RJ , Brazil , 5 Laboratório de Sistemas Avançados de Gestão de Produção-SAGE-COPPE, Centro de Gestão Tecnológica-CT2, UFRJ, Rio de Janeiro, RJ , Brazil 1 Funding: Financial support by Brazilian funding agencies CAPES , CNPq, and FAPERJ Although previous studies have described opposing states in upwelling regions, i.e., the rise of cold nutrient-rich waters and prevalence of surface warm nutrient-poor waters, few have addressed the transition from one state to the other. This study aimed to describe the microbial and viral structure during this transition and was able to obtain the taxonomic and metabolic compositions as well as physical-chemical data. This integrated approach allowed for a better understanding of the dynamics of the downwelling upwelling transition, suggesting that a wealth of metabolic processes and ecological interactions are occurring in the minute fractions of the plankton (femto, pico, nano). These processes and interactions included evidence of microbial predominance during downwelling (with nitrogen recycling and aerobic anoxygenic photosynthesis), different viral predation pressures over primary production in different states (cyanobacteria vs eukaryotes), and a predominance of diatoms and selected bacterial and archaeal groups during upwelling (with the occurrence of a wealth of nitrogen metabolism involving ammonia). Thus, the results provided insights into which microbes, viruses and microbial-mediated processes are probably important in the functioning of upwelling systems. - Competing Interests: The authors have declared that no competing interests exist. Upwelling regions sustain a high productivity of primary producers, such as diatoms and fish. Although the Brazilian coast is not among the five major upwelling coasts of the world, namely, the Canary current system off the Iberian Peninsula and northwestern Africa, the Benguela current system off southwestern Africa, the Peru current system off western South America, and the western coast of the United States [1, 2], the southeastern portion of the coast includes the South Brazil Bight, a high productivity zone characterized by upwelling events [3]. Within this large area, extending from Cabo Frio (23°S 42°W) to Cabo Santa Marta (28.5°S 48.6°W), the northernmost portion has received more attention and study [2, 3].The Cabo Frio region represents a “turning” point in the Brazilian coast, where the coastline changes from northsouth to east-west, and is thus subjected to the strongest wind driven upwelling events of any location on this coast [2]. NE-E winds from the South Atlantic anticyclone transport surface water away from the coast, causing water from the South Atlantic Central Water (SACW) current to rise, particularly during austral spring and summer seasons [2–4]. The passage of southern (S-SW) cold fronts interrupts the upwelling, and surface waters from the Continental Water and the Brazilian Current (Tropical Water) prevail [2–4]. Longer upwelling events, particularly in the austral spring, allowed the distinction of three phases: 1) an upwelling of cold and nutrient-rich waters; 2) a phytoplankton production phase in which nutrients are incorporated as biomass; and 3) a downwelling phase in which phytoplankton and nutrient concentration decline [4]. In austral summer, the more frequent passage of cold fronts provides shorter and weaker upwelling intermixed with frequent downwelling. Although the distinction of different phases has been clearly shown in previous studies [2, 4, 5], few studies have focused on the transition from one state to the other [6], and to our knowledge, none describe the temporal effect of the transition on the microbial community. A common approach in the study of upwelling events is the description of organisms during upwelling occurrences [4] or in contrasting conditions of upwelling and downwelling [5, 7– 10], while the dynamics of a transition between these extremes is overlooked by most (but see [6]). The aim of this study was the description of how the passage of a summer cold front affects the viral and microbial communities, which was achieved through an integrated approach involving metagenomic analysis via high throughput sequencing as well as measurements of microbial abundance and water chemistry analysis. Material and Methods Sampling site and date (...truncated)


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Gustavo Bueno Gregoracci, Ana Carolina dos Santos Soares, Milene Dias Miranda, Ricardo Coutinho, Fabiano L. Thompson. Insights into the Microbial and Viral Dynamics of a Coastal Downwelling-Upwelling Transition, PLOS ONE, 2015, 9, DOI: 10.1371/journal.pone.0137090