Temperature regimes (ºC) implemented in the experiment for the four temperature treatments: ambient ('constant'), warm ('constant'), ambient sinusoidal and warm sinusoidal. The treatment regimes were based on 15 years (2000–2014) temperature data measured by GEOMAR weather station (Data source: GEOMAR, Ocean Circulation and Climate Dynamics - Marine Meteorology (http://www.geomar.de/en/service/weather; published in: doi:10.1594/PANGAEA.888599). Data gathered during the summer months June to September (experimental period) were taken into consideration only. The eight warmest years (reaching maximum values above 20°C in summer) were chosen and fitted to a polynomial (4th degree), representing today's average warm summer conditions (Ambient ('constant')). The 'Warm' treatment represented the identical polynomial function but with the offset of +4°C (projected future warming the Baltic Sea). Around these two 'constant' but seasonally fluctuating treatments, sinusoidal temperature fluctuations of 3°C amplitude were modelled ('Ambient sinusoidal' and 'Warm sinusoidal').