Relationship between phytoplankton abundance, available nitrate, ammonium, and temperature at Station ALOHA, and the R/V Roger Revelle Cruise RR1604.

Abstract

The goal of the project was to assess the relationship between phytoplankton abundance, various available nutrient concentrations (𝑁𝑂3, 𝑁𝐻4) and temperature (C), based on data collected at station ALOHA, a time-series station located in the North Pacific subtropical gyre, and aboard the R/V Roger Revelle Cruise RR1604, conducted in a transect of the Indian Ocean. The cell counts, to gage abundance, were deemed through a Flow Cytometer, and temperature was measured using a CTD sensor. Linear regression models were generated for the analysis process, thereby directly depicting the correlation between each of these factors and phytoplankton abundance. The overall relationship between phytoplankton abundance and the concentration of nitrate indicated a negative correlation between the two factors, for both diatom and dinoflagellate biomass. The overall relationship between phytoplankton abundance and the concentration of ammonium, conversely, showed a moderate, yet positive correlation between the two factors, for both diatom and dinoflagellate biomass. For temperature, there exists a positive relationship (directly proportional) between dinoflagellate (phytoplankton) abundance and sea – surface temperature. Under non-limiting nutrient conditions, an increase in water temperature usually correlates to an increase in phytoplankton nutrient uptake. In the data sets under study however, both these factors seem to have a drastic effect on abundance, not in correlation with each other (an increase in temperature does not necessarily lead to an increase in nutrient uptake, vice-versa). The differences in the derived correlations between phytoplankton abundance and the concentration of ammonium and nitrate, lead to the possibility that nitrate may be a limiting nutrient in the sampling environment, and is used by either class of phytoplankton at a time, but not together.