Incubation experiments to assess the physiological and molecular response of subsurface phytoplankton communities to a simulation of the Upwelling Conveyor Belt Cycle (UCBC) conducted in summer 2019 onboard the R/V Oceanus (OC1905b)

The primary objective of this study was to assess the physiological and molecular response of subsurface phytoplankton communities to a simulation of the Upwelling Conveyor Belt Cycle (UCBC). To capture this phenomenon, we performed on-deck incubation experiments that spanned different time points representing the different stages of growth (initial deep-water community at T0, and stimulated growth phases at T1 and T2). We further subjected the incubations to various Fe-related treatments to test how Fe might play a role in determining their physiological and molecular response to upwelling.

The first incubation was conducted from 27 May to 01 June 2019 in a wide continental shelf, and the second incubation was conducted from 02 June to 06 June 2019 in a narrow continental shelf. For each time point, the incubation was harvested and analyzed for chlorophyll, nutrients, particulate organic carbon and nitrogen, and dissolved and particulate Fe and Sc concentrations. 6-hour incubations using trace concentrations of stable isotopes of 13C and 15N were also conducted to assess uptake kinetics of dissolved inorganic carbon (DIC) and nitrate (NO3) in bulk-size fractionated phytoplankton communities. PUPCYCLE I (Phytoplankton response to the UPwelling CYCLE) took place in summer 2019 onboard the R/V Oceanus (OC1905b), led by Chief Scientist Adrian Marchetti.