ABSTRACT
The quantitative assessment of the carbonate system represents one of the biggest challenges toward the "Sustainable Development Goals" defined by the United Nations in 2015. In this sense, the present study investigated the Spatio-temporal dynamics of the carbonate system and the effects of the El Niño and La Niña phenomena over the Cabo Frio upwelling area. The physical characterization of the site was carried out through data on wind speed and sea surface temperature. Water samples were also collected during the oceanographic cruise onboard the Diadorim R/V (Research Vessel). From these samples, the parameters of absolute and practical salinity, density, pH, total alkalinity, carbonate, calcite, aragonite, bicarbonate dissolved inorganic carbon, carbon dioxide, partial pressure of carbon, calcium, and total boron were obtained. The highest average concentration of bicarbonate in S1 (2018 µmol/kg) seems to contribute to the dissolved inorganic carbon values (2203 µmol/kg). The values of calcite saturation state, aragonite saturation state, and carbonate were higher on the surface of each station (calcite saturation state = 4.80-5.48; aragonite saturation state = 3.10-3.63, and carbonate = 189-216 µmol/kg). The mean values of pH were similar in the day/night samples (7.96/7.97). The whole carbonate system was calculated through thermodynamic modeling with the Marine Chemical Analysis (AQM) program loaded with the results of the following parameters: temperature, salinity, total alkalinity, and pH parameters. This manuscript presents original data on the carbonate system and the "acidification" process influenced by the Cabo Frio upwelling, which directly depends on the El Niño and La Niña phenomena oscillations in the sea surface temperature.
ABSTRACT
To evaluate the impacts of the interaction between bacteria and microalgae has been the object of study by many research groups around the world. However, little is known about the interference that pigments produced by bacteria, such as the pyoverdine siderophore, can cause to microalgae like Isochrysis galbana. Pyoverdine is a fluorochrome produced by certain Pseudomonas strains, such as P. fluorescens, which plays a role in capturing and transporting iron ions from the environment to the cell. Unlike the oceans where Fe concentrations are extremely low (< 10-15 µM), in a ballast tank it is expected that there is a great supply of iron to the cells and that the absence of light is the main limiting factor until the water is discarded. Interestingly, under certain conditions, bacteria such as P. fluorescens absorb most of the water soluble iron ions and prevent the growth of phytoplankton even if there is sufficient light. Changes in the patterns of light distribution in aquatic environments may affect the physiological characteristics of certain microalgae. This study aimed to evaluate the impacts of the presence of P. fluorescens on the survival and growth of I. galbana inside the tank. For the study, an experiment was carried out to study the interaction between P. fluorescens and I. galbana under simulated conditions of a vessel in the presence/absence of Pseudomonas and light. The results showed that the presence of the bacteria is not the main limiting factor for microalga growth. The effect of the light factor was determinant on the reproduction rate. It is believed that pyoverdine produced by P. fluorescens affected I. galbana stock either by increasing mortality or decreasing growth rate as revealed by laboratory experiments. However, it was not possible to check if the pigment concentration was affected by the growth of microalgae.
