Dynamics of Primary Productivity and Oceanographic Parameters under Influence of the Amazon River Plume

Abstract

The watershed of the Amazon River discharges about 120,000 m 3 •s −1 of freshwater into the adjacent platform and oceanic region. The aim of this work was to analyze the distribution of oceanographic parameters, chlorophyll a and primary productivity under the influence of the Amazon River plume, during the period of greatest extension of the Amazon plume. Collections were carried out in September 14 in 16 stations including continental platform and oceanic region. It was possible to observe superficial currents along the coast in the northwest direction, but with less intensity and currents with greater speeds towards the east due to the North Brazil Current retroflexion at this time of the year, transporting the plume to the central Atlantic Ocean. The spatial influence of the plume was observed in the salinity, which ranged from 28 to 36.75, although the high precipitation in the region may also have contributed as a source of freshwater. However, the sampled region showed strong negative linear correlation of silicate, chlorophyll a and primary productivity with salinity. The primary productivity values ranged from 0.04 to 18.81 mg C m −3 day −1 , whereas chlorophyll a concentrations ranged from 0.15 mg•m −3 to 1.83 mg•m −3 , decreasing their values as they move away from the coast. The Amazon River plume can reach and influence the oceanographic and biological parameters in a large area of this oligotrophic region. However, the results also suggest that the export of material from the adjacent coastal region is another determinant of the region's productivity.

Amazon river plume influence on planktonic decapods in the tropical Atlantic

“…Extremely high values of phytoplankton and zooplankton biomass were recorded for stations E09 and E10 by Araujo et al (2017). High phytoplankton productivity rates were also recorded for the area of these stations during the retroflection period in 2014 by Otsuka et al (2018), which related the high productivity of the retroflection region to the transition zone of the ARP, regions of abrupt variation of water transparency and high concentrations of nutrients, conditions that favor phytoplankton blooms. Huge numbers of diatoms and diazotrophic bacteria (such as Trichodesmium sp.)…”

“…Huge numbers of diatoms and diazotrophic bacteria (such as Trichodesmium sp.) were recorded for the retroflection region, which may lead to greater abundance of planktonic organisms (Araujo et al, 2017;Otsuka et al, 2018).…”