KOSMOS 2018 Gran Canaria mesocosm study on artificial upwelling. KOSMOS_2018

The KOSMOS 2018 mesocosm experiment was carried out in the framework of the Ocean Artificial Upwelling project, which studied the effect of artificial upwelling on the carbon cycle through a multidisciplinary approach. The experiment was carried out in the autumn of 2018 in the oligotrophic waters off Gran Canaria (27° 55′ 41′′ N, 15° 21′ 55′′ W). During the 39 days of experiment nutrient-rich deep water from the upper mesopelagic was added to the mesocosms with four levels of intensity (low, medium, high, extreme) in two upwelling modes (singular vs recurring additions). Singular upwelling treatments received deep water on day 4, while recurring treatments received it on days 4, 8, 12, 16, 21, 24, 28 and 32. Once additions were completed, equivalent intensity levels in the two upwelling modes had received similar amounts of nutrients, yielding comparable treatments. An extra mesocosm received no deep water, acting as control. Ambient waters outside of the mesocosms were regularly sampled and the collected deep water itself was also monitored. Within the sampling effort, samples for the sequencing of the 16S rRNA gene were collected and filtered through a set of polycarbonate filters, yielding a size fractionation of 0.2–3.0 μm and 3.0–200 μm.