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Nets are towed obliquely at approx. 1 knot, from the surface to approx. 175 m. Towing time is approx. 20 minutes. Zooplankton (weak swimmers >200µm) are collected using oblique tows of a 1 m**2 net (3m length) with 202µm mesh Nitex netting.

We simulated an experimental summer storm in large-volume (~1200 m3, ~16m depth) enclosures in Lake Stechlin (https://www.lake-lab.de) by mixing deeper water masses from the meta- and hypolimnion into the mixed layer (epilimnion). The mixing included the disturbance of a deep chlorophyll maximum (DCM) which was present at the same time of the experiment in Lake Stechlin and situated in the metalimnion of each enclosure during filling. Size-fractionated Bacterial Protein Production (BPP) of particle associated (PA, >3.0 µm) and free-living bacteria (FL, 0.2-3.0 µm) (14C-Leu incorporation) as well as abundances of PA (microscopy of DAPI stained cells on 3.0 µm polycarbonate filters) and FL heterotrophic prokaryotes and picocyanobacteria (flow cytometry of SYBR green I stained cells) were monitored for 42 days after the experimental disturbance event. Mixing increased bacterial abundance and production about 3 weeks after mixing, which was associated to a mixing-induced stimulation of phytoplankton growth in the mixed enclosures compared to the controls. Simultaneously, decreased abundances of picocyanobacteria could be observed in mixed enclosures. Empty cells = NAFurther Project information: Core Facility grant; Award: GE 1775/2-1

The data set has been processed and contains quality flags for different kinds for erroneous data. Flag values are the sum of individual error codes. The value of 0 refers to no error. Quality flag, position: The geographic position is flagged +1 if the drift velocity, as derived from the GPS longitude and latitude, exceeds a threshold of 10 deg latitude or 50 deg longitude per time step; +2 if the position exceeds extreme values, such as longitude > 360 deg; +4 if the position is exactly 0.0. Solar radiation over and under sea ice was measured by radiation station 2014R4, an autonomous platform, installed on drifting Multi-Year-Ice (MYI) in the Arctic Ocean during Oden_AO18. Along with the radiation measurements, this autonomous platform consisted of thermistor chain with 208 sensors, measuring tempeature and heating-induced temperature differences.

Poleward range extensions by warm-adapted sea urchins are switching temperate marine ecosystems from kelp-dominated to barren-dominated systems that favour the establishment of range-extending tropical fishes. Yet, such tropicalization may be buffered by ocean acidification, which reduces urchin grazing performance and the urchin barrens that tropical range-extending fishes prefer. Using ecosystems experiencing natural warming and acidification, we show that ocean acidification could buffer warming-facilitated tropicalization by reducing urchin populations (by 87%) and inhibiting the formation of barrens. This buffering effect of CO2 enrichment was observed at natural CO2 vents that are associated with a shift from a barren-dominated to a turf-dominated state, which we found is less favourable to tropical fishes. Together, these observations suggest that ocean acidification may buffer the tropicalization effect of ocean warming against urchin barren formation via multiple processes (fewer urchins and barrens) and consequently slow the increasing rate of tropicalization of temperate fish communities. In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2021) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation by seacarb is 2021-07-26.