Organisms in intertidal zones experience fluctuations in environmental stressors such as hypoxia and temperature. These stressors and their fluctuations often appear in combination. Combination of stressors can have different effects compared to single stressors. In this study, we investigate the physiological effects of intermittent hypoxia in combination with different temperature regimes on the Pacific Oyster Crassostrea (Magallana) gigas. The oysters were exposed to hypoxic cycles (12h hypoxia by emersion/12h submersion) at normal (15°C), elevated (30°C) or fluctuating (15°C submersion/30°C emersion) temperature for 10 days. After the last submersion phase, the gills and digestive gland were sampled. We measured markers for bioenergetics and redox-balance in the gills and digestive gland using colorimetric methods as well as a set of metabolites (predominantly amino acids, osmolytes, anaerobic end products and energetic metabolites) in the gills using LC-MS/MS. Oysters kept submerged for up to 10 days were used as controls.
These data were produced in two experimental studies. The first experiment was conducted on September 22, 2018. Over a five-week period, mussel shell-length (mm d-1), mass, and tissue dry weight growth (both mg d-1) were assessed in response to twelve temperature scenarios composed of constant versus daily fluctuating regimes using Kiel Indoor Benthocosms (KIBs). In the second experiment, started on November 20, 2018, filtration (feeding) and respiration rates of different mussel individuals were recorded in seven temporally repeated trials of one-day thermal fluctuations using the Fluorometer and Oximeter-equipped Flow-through Setup (FOFS; Vajedsamiei et al., 2021).
Climate change will shift mean environmental conditions and also increase the frequency and intensity of extreme events, exerting additional stress on ecosystems. While field observations on extremes are emerging, experimental evidence of their biological consequences is rare. Here, we introduce a mesocosm system that was developed to study the effects of environmental variability of multiple drivers (temperature, salinity, pH, light) on single species and communities at various temporal scales (diurnal - seasonal): the Kiel Indoor Benthocosms (KIBs). Both, real- time offsets from field measurements or various dynamic regimes of environmental scenarios, can be implemented, including sinusoidal curve functions at any chosen amplitude or frequency, stochastic regimes matching in situ dynamics of previous years and modelled extreme events. With temperature as the driver in focus, we highlight the strengths and discuss limitations of the system. In addition, we examined the effects of different sinusoidal temperature fluctuation frequencies on mytilid mussel performance. High-frequency fluctuations around a warming mean (+2°C warming, ±2°C fluctuations, wavelength=1.5 days) increased mussel growth as did a constant warming of 2°C. Fluctuations at a lower frequency (+2 and ±2°C, wavelength=4.5 days), however, reduced the mussels' growth. This shows that environmental fluctuations, and importantly their associated characteristics (such as frequency), can mediate the strength of global change impacts on a key marine species. The here presented mesocosm system can help to overcome a major short-coming of marine experimental ecology and will provide more robust data for the prediction of shifts in ecosystem structure and services in a changing and fluctuating world.
Mit einer zehnjaehrigen, lueckenlosen Erhebung praeziser, quantitativer Vegetationsdaten soll gezeigt werden, wie die Zusammensetzung der bis zu 75 Arten vergandeter und traditionell genutzter Magerwiesen auf die Veraenderlichkeit des Wetters reagieren. Korrelationen zwischen Ertrag, Artfrequenz und Klimaparametern werden bestimmt, um zu ueberpruefen, ob verschiedene 'funktionelle' Artengruppen verschiedene Schwankungsmuster in der Zeit zeigen. Im weiteren wird die Reaktion der Artenzusammensetzung gemaehter und vergandeter Magerwiesen auf eine veraenderliche Nutzung untersucht.