KOSMOS Finland 2012 mesocosm study: Phosphorus pool sizes and uptake

• Main Author: Nausch, Monika
• Format: Dataset
• Language: English
• Published: PANGAEA 2016
• Subjects: -; Adenosine triphosphate per volume; Adenosine triphosphate uptake rate; fractionated; BIOACID; Biological Impacts of Ocean Acidification; Day of experiment; Deoxyribonucleic acid per volume; KOSMOS_2012_Tvaerminne; MESO; Mesocosm experiment; Mesocosm label; Phase; Phosphate; Phospholipids; Phosphorus; adenosine triphosphate; dissolved; uptake rate; deoxyribonucleic acid; organic; particulate; phospholipid; ribonucleic acid; total; total dissolved; Phosphorus uptake rate; Ribonucleic acid per volume; Size fraction; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.884748; https://doi.org/10.1594/PANGAEA.884748

Studies investigating the effect of increasing CO2 levels on the phosphorus cycle in natural waters are lacking although phosphorus often controls phytoplankton development in many aquatic systems. The aim of our study was to analyse effects of elevated CO2 levels on phosphorus pool sizes and uptake. The phosphorus dynamic was followed in a CO2-manipulation mesocosm experiment in the Storfjärden (western Gulf of Finland, Baltic Sea) in summer 2012 and was also studied in the surrounding fjord water. In all mesocosms as well as in surface waters of Storfjärden, dissolved organic phosphorus (DOP) concentrations of 0.26 ± 0.03 and 0.23 ± 0.04 µmol/l, respectively, formed the main fraction of the total P-pool (TP), whereas phosphate (PO4) constituted the lowest fraction with mean concentration of 0.15 ± 0.02 in the mesocosms and 0.17 ± 0.07 µmol/l in the fjord. Transformation of PO4 into DOP appeared to be the main pathway of PO4 turnover. About 82% of PO4 was converted into DOP whereby only 18% of PO4 was transformed into particulate phosphorus (PP). PO4 uptake rates measured in the mesocosms ranged between 0.6 and 3.9 nmol/l/h. About 86% of them was realized by the size fraction < 3 µm. Adenosine triphosphate (ATP) uptake revealed that additional P was supplied from organic compounds accounting for 25-27% of P provided by PO4 only. CO2 additions did not cause significant changes in phosphorus (P) pool sizes, DOP composition, and uptake of PO4 and ATP when the whole study period was taken into account. However, significant short-term effects were observed for PO4 and PP pool sizes in CO2 treatments > 1000 µatm during periods when phytoplankton biomass increased. In addition, we found significant relationships (e.g., between PP and Chl a) in the untreated mesocosms which were not observed under high fCO2 conditions. Consequently, it can be hypothesized that the relationship between PP formation and phytoplankton growth changed with CO2 elevation. It can be deduced from the results, that visible effects of CO2 ...