Seawater carbonate chemistry and mass fluxes and elemental composition of particulate export in KOSMOS mesocosm experiments (2010-2014)

• Main Authors: Taucher, Jan, Bach, Lennart Thomas, Prowe, Friederike, Boxhammer, Tim, Kvale, Karin F, Riebesell, Ulf
• Format: Dataset
• Language: English
• Published: PANGAEA 2022
• Subjects: Alkalinity; total; Aragonite saturation state; Arctic; Area/locality; Bicarbonate ion; Biogenic silica; flux per day; Biomass/Abundance/Elemental composition; Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; organic; particulate; Carbon/Nitrogen flux ratio; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Coast and continental shelf; DATE/TIME; Day of experiment; Elemental analyzer; Entire community; Event label; Field experiment; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Gullmar Fjord; Skagerrak; Sweden; Kongsfjorden-mesocosm; KOSMOS_2011_Bergen; KOSMOS_2012_Tvaerminne; KOSMOS_2013_Sweden; KOSMOS_2014; KOSMOS_2014_GranCanaria; KOSMOS 2013; Measured spectrophotometrically after alkaline leaching of particulate matter; MESO; Mesocosm experiment; Mesocosm or benthocosm; Nitrogen; North Atlantic; OA-ICC; Kongsfjord*; Kongsfjorden; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.946304; https://doi.org/10.1594/PANGAEA.946304

Diatoms account for up to 40% of marine primary production and require silicic acid to grow and build their opal shell. On the physiological and ecological level, diatoms are thought to be resistant to, or even benefit from, ocean acidification. Yet, global-scale responses and implications for biogeochemical cycles in the future ocean remain largely unknown. Here we conducted five in situ mesocosm experiments with natural plankton communities in different biomes and find that ocean acidification increases the elemental ratio of silicon (Si) to nitrogen (N) of sinking biogenic matter by 17 ± 6 per cent under pCO2 conditions projected for the year 2100. This shift in Si:N seems to be caused by slower chemical dissolution of silica at decreasing seawater pH. We test this finding with global sediment trap data, which confirm a widespread influence of pH on Si:N in the oceanic water column. Earth system model simulations show that a future pH-driven decrease in silica dissolution of sinking material reduces the availability of silicic acid in the surface ocean, triggering a global decline of diatoms by 13–26 per cent due to ocean acidification by the year 2200. This outcome contrasts sharply with the conclusions of previous experimental studies, thereby illustrating how our current understanding of biological impacts of ocean change can be considerably altered at the global scale through unexpected feedback mechanisms in the Earth system.