KOSMOS mesocosm experiment Gran Canaria 2019 on testing the effect of nutrient composition (Si:N) during artificial upwelling: mesozooplankton trophic level and fish biomass and feeding

Mesozooplankton trophic position (via copepod δ15N) to approximate food web length as well as fish production (via biomass increase) and feeding rate (via stomach content) during the mesocosm experiment in the Canary Islands in autumn 2019. Copepods >200µm were sampled depth-integrated (0-2.5m) on day 13. At this time, copepods represented the top of the food web as fish were not yet present. Individuals were picked in groups into tin capsules and δ15N measured in a mass spectrometer. Particulate organic matter(>0.7µm) δ15N was also measured to calculate an autotroph baseline. The difference between copepod and autotroph δ15N was used as trophic level proxy. A small pelagic fish (silverside, Atherina presbyter) was introduced to the mesocosms on day 15. On day 18, for a subset of fish, stomachs content was assessed to estimate feeding success. On day 21, all fish were sampled for biomass and abundance. The upwelling treatment started on day 6. Methodological details in Goldenberg et al. (doi:10.3389/fmars.2022.1015188) and Goldenberg et al. (under review).