Terrestrial and freshwater inputs are major forces in coastal ocean ecosystems, affecting nutrient cycles, microbial communities and food webs. The equatorial Atlantic Ocean is greatly influenced by freshwater inputs from the Amazon and Orinoco River plumes in the west, upwelling on the western boundary of Africa, and Aeolian dust inputs throughout the basin. The region is characterized by a strong east-west gradient in water temperature and productivity, where warm lower-salinity waters in the western basin merge with cooler nutrient poor waters of the eastern basin within the equatorial counter-current. Metagenomic and metatranscriptomic samples were collected during an oceanographic research cruise on the R/V Seward Johnson across the Amazon River plume to the eastern Equatorial Atlantic Ocean. Size-fractionated samples were collected to analyze gene expression patterns from Eukaryotes (particularly diatoms) and microorganisms (bacteria and cyanobacteria), as well as symbiotic microorganisms (e.g. the heterocyst-forming cyanobacteria that form symbioses with diatoms). The goal of this project is to determine the patterns of gene expression across the gradient of productivity in the Equatorial Atlantic driven by the Amazon River influence, and to determine how general microbial community composition and gene expression corresponds to nitrogen-fixing microbial populations.
Microbial community gene expression across a productivity gradient of the Amazon River plume
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