Description: This data is part of the BMBF project CUSCO (Coastal Upwelling Systems in a Changing Ocean). Here we report carbon and nitrogen uptake rates by phytoplankton collected 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). Samples were spiked with 13C labelled sodium bicarbonate and 15N labelled potassium nitrate. Samples were incubated for 24 hours at light intensities that resemble the light conditions in the mesocosms. After incubation a subsample (150-1000 ml) was filtered onto a 0.7 µm pre-combusted glass-fiber filters (GFF, Whatmann). The filters were acidified, then dried in the oven at 60 °C and later measured using an elemental analyzer (Flash IRMS, ThermoFisher) connected to a mass spectrometer (Delta V Advantage Isotope Ratio MS, ThermoFisher) with the ConFlo IV (ThermoFisher). Carbon and nitrogen uptake rates were calculated based on Slawyk et al. (1977, DOI:10.4319/lo.1977.22.5.0925) and Shiozaki et al. (2009, DOI:10.3354/meps07837) respectively.

Description: This data is part of the BMBF project CUSCO (Coastal Upwelling Systems in a Changing Ocean). Here we report the dissolved organic carbon and total dissolved nitrogen 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). Sub-samples (60 mL) were syringe filtered through two pre-combusted glass fiber filters (5 h, 450 °C). To reduce clogging, one 3.1 µm GMF filter was placed on top of a 0.7 µm GFF filter. The filtrate was acidified to pH 2 with 25% HCl before storing at -20°C until analysis. The DOC and TDN concentrations were measured using a TOC-VCPH analyser (Shimadzu). Instrument accuracy was evaluated by comparison against a deep Atlantic seawater reference (Consensus Reference Material project: D. Hansell, University of Miami, USA).

Description: This data is part of the BMBF project CUSCO (Coastal Upwelling Systems in a Changing Ocean). Here we report the environmental conditions 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. CTD casts were taken between 0 and 12.5m with a CTD167M sensor system (Sea&Sun Technology, Trappenkamp, Germany) to generate depth profiles of conductivity, salinity, density, pH, temperature and photosynthetically active radiation (PAR) as well as oxygen, hydrogen sulphide and Chla concentrations (sensors described in (Schulz and Riebesell, 2013; Bach et al., 2016; doi:10.1007/s00227-012-1965-y, doi:10.1002/2016GB005372). The water sampling and CTD casts of the Pacific took place in the mesocosm field.

Description: This data is part of the BMBF project CUSCO (Coastal Upwelling Systems in a Changing Ocean). Here we report the dissolved inorganic carbon concentration and total alkalinity 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). Dissolved inorganic carbon (DIC) and total alkalinity (TA) samples were obtained by 0.2µm gentle pressure filtration, poisoned with saturated 7.5 % mercury chloride (HgCl2) solution and frozen at -20°C until measurement. Samples for Total Alkalinity (TA) were measured by means of potentiometric titration with 0.05 M HCl using an automated titration device (862 Metrohm Compact Titrosampler). All DIC samples taken until day 17 were measured using an Automated Infra-Red Inorganic Carbon Analyzer (AIRICA) with a LICOR detector (LI-7000 CO2/H20 Analyzer, MARIANDA, Kiel). Certified reference material (Dickson standard for oceanic CO2 Measurements - CRM Batch 142 with salinity = 33.389 and DIC = 2038,07 µmol/kg) was measured and used to correct measured sample values. Additional DIC samples were measured using gas chromatography-mass spectrometry (GC-MS) to determine the 13C signal. The data of the GC-MS was adjusted to the AIRICA data using a linear transformation. Missing days were filled using an average of the day before and after.

Description: 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).

Description: This data is part of the BMBF project CUSCO (Coastal Upwelling Systems in a Changing Ocean). Here we report particulate organic matter concentrations collected 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). Samples (150-1000 ml) were filtered onto a 0.7 µm pre-combusted glass-fiber filters (GFF, Whatman). The filters were acidified and then dried in the oven at 60 °C for 24 hours and total particulate carbon (TPC), particulate organic carbon (POC) and nitrogen (PON) content were measured using a CN analyzer (Euro EA3000, HEKAtech GmbH, Wegberg, Germany). POP filters were autoclaved for 30 min in 100 mL Schott Duran glass bottles using an oxidizing decomposition solution (Merck, catalogue no. 112936) to convert organic phosphate to orthophosphate. Phosphate concentrations were determined spectrophotometrically following Hansen and Koroleff (1999; doi:10.1002/9783527613984.ch10).

Description: This data is part of the BMBF project CUSCO (Coastal Upwelling Systems in a Changing Ocean). Here we report biogenic Silica concentrations in the watercolumn collected 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). Samples (0.15-1L) were filtered onto polycarbonate filters (0.65 µm pore size, Whatman). The filters were then dried in the oven at 60 °C for 24 hours and measured following a modified procedure by DeMaster (1981, doi:10.1016/0016-7037(81)90006-5). A standard water bath (Fisher Scientific Isotemp Water Bath, Thermo Fisher Scientific, Waltham, US) was used to digest BSi samples at 85°C. The BSi analysis was carried out with a 4.5-hour time course alkaline digestion (0.1N Na2CO3) to dissolve the BSi followed by a 48 hour HF acid digestion (2.0M) to release the remaining lithogenic silica (LSi). Spectrophotometric analysis of the solubilized silica was done using a Thermo Scientific Genesys 10 UV- VIS Spectrophotometer (Thermo Fisher Scientific, Waltham, US). Model I linear regression was performed to calculate the concentrations of BSi while accounting for the amount of LSi that leached out during the alkaline digestion. Due to restrictions caused by the COVID-19 pandemic BSi data is only available for day 1 until day 17 and for day 31 until day 35.

Description: This data is part of the BMBF project CUSCO (Coastal Upwelling Systems in a Changing Ocean). Here we report pigment concentrations and the phytoplankton community composition based on CHEMTAX analysis 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). To obtain pigment concentrations 0.15 – 1L of water sampled from the water column were filtered onto glass-fiber filters (precombusted at 450°C for 6h, GFF, 0.7 µm nominal pore size, Whatman) using a low vacuum of 200 mbar. Afterwards the filters were stored in cryovials at -80°C until analysis of photosynthetic pigments using reverse-phase high-performance liquid chromatography (HPLC) following (Barlow et al., 1997; doi:10.3354/meps161303) as described by (Paul et al., 2015; doi:10.5194/bg-19-5911-2022). The phytoplankton community composition was calculated with CHEMTAX, which classifies phytoplankton taxa based upon taxon-specific pigment ratios (Mackey et al., 1996; doi:10.3354/meps144265). The values for the Peruvian upwelling system determined by (DiTullio et al., 2005; doi:10.4319/LO.2005.50.6.1887) as described by (Meyer et al., 2017; doi:10.3389/fmars.2017.00001) were used as pigment ratios. As phytoplankton microscopy revealed high abundances of the raphydophite Fibrocapsa japonica, the initial pigment matrix was complemented by ratios for F. japonica from (Laza-Martinez et al., 2007; doi:10.1093/plankt/fbm069) from the Atlantic.

Description: This data is part of the BMBF project CUSCO (Coastal Upwelling Systems in a Changing Ocean). Here we report oxygen primary production rates 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). Oxygen production as well as respiration rates were measured as described in Ortiz et al. (2022; doi:10.3389/fmars.2021.743105) using the Winkler method. For each mesocosm and sampling day samples for initial oxygen values fixed immediately after subsampling ("Initial"), dark incubations ("Dark") and light incubations ("Light") were measured. All samples were incubated with constant light dark/cycles and temperature was adjusted regularly to mesocosm values. After incubation samples were fixed and titrated by means of an automated, precise titration system with colorimetric end-point detection along with the initials (Dissolved Oxygen Analyzer, SIS Schwentinental, Germany). Community respiration (CR) was calculated as the oxygen consumption during dark incubation per hour. Net community production (NCP) was the oxygen production per hour in the light samples and gross production (GP) the sum of CR and NCP.