KOSMOS 2020 Peru mesocosm study on ecosystem responses to different light and upwelling intensities: inorganic nutrient concentrations of water samples

This data is part of the BMBF project CUSCO (Coastal Upwelling Systems in a Changing Ocean). Here we report the inorganic nutrient concentrations during a 35-day experiment, where we enclosed natural plankton communities in in-situ mesocosms off Peru. The experiment investigated the interactive effects of light and upwelling on the Humboldt upwelling ecosystem by mimicking a gradient of upwelling intensities (0%, 15%, 30%, 45% and 60%) under summer-time high light and winter-time low light. Integrated seawater samples from a depth between 0 and 10m were collected using a 5L Integrating Water sampler (IWS; Hydro-Bios, Kiel). Water samples for inorganic nutrients were filtered (0.45 µm PTFE syringe filter, Merck Millex) and analysed in triplicates. Dissolved inorganic nutrients (nitrate, nitrite, phosphate, and dissolved silica were determined using a spectrophotometer (ShimadzuV-1800) and standard colorimetric methods (Grasshoff et al., 2009; DOI: 10.1002/iroh.19850700232). Ammonium was determined fluorometrically. Due to the COVID-19 lockdown, we were not able to determine inorganic nutrients after day 17, and instead samples were frozen at -20°C after filtration and analysed with an autosampler (XY2 autosampler, SEAL Analytical) and a continuous flow analyzer (QuAAtro AutoAnalyzer, SEAL Analytical) connected to a fluorescence detector (FP-2020, JASCO).