This data was collected as a part of a mesocosm study to investigate the ecosystem impacts of ocean alkalinity enhancement, within the EU H2020 OceanNETs project. Nine mesocosms were deployed in Taliarte Harbour (Gran Canaria, Spain) and were regularly sampled using integrated water samplers between 10th September-25th October 2021. A gradient design was used in this experiment with a total of nine different alkalinity concentrations. Seawater alkalinity ranged between ambient (0 µeq kg-1 added alkalinity, OAE0) and 2400 µeq kg-1 additional alkalinity (OAE2400). The alkalinity levels increased in equal intervals of 300 µeq kg-1 across nine mesocosms (OAE0, OAE300, OAE600, OAE900, OAE1200, OAE1500, OAE1800, OAE2100, OAE2400). This data set contains particulate matter and metazoan zooplankton fatty acid concentrations (nanograms of fatty acids per µgC), percent contribution, as well as specific trophic marker and marker ratios (calculated form percent fatty acids), and nutritional indexes (calculated from fatty acid concentrations). Samples with %esterification of 0 excluded. Samples with less than 95-100µg carbon are included, but were not used in our analyses because they are below the c mass recommendation thresholds of the gas chromatograph. This results in an underestimation of minor, but biologically-relevant, fatty acids. Fatty acid concentrations were normalized by carbon concentration in the sample, which derives from particulate matter carbon measurements (POC) and zooplankton biomass (data sets available in PANGAEA). Phases were not included here, since they differed between metazoan zooplankton and particulate matter (see Sanchez et al. in prep. for more info).

This data set is associated to the submission by Paul et al. (in review) (https://doi.pangaea.de/10.1594/PANGAEA.966941), so we refer to this data set for basic parameters like water temperature, salinity, pH and carbonate chemistry, to avoid repetition. This data set also contains in greater detail the particulate matter carbon mass used to calculate the correspondent fatty acid concentrations. It is also associated with the dataset "KOSMOS 2021 Gran Canaria mesocosm study on ocean alkalinity enhancement: metazoan zooplankton carbon biomass" (https://doi.pangaea.de/10.1594/PANGAEA.971764), which contains in greater detail the zooplankton carbon mass used to calculate the correspondent fatty acid concentrations.