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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.
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.
Hourly means of temperature and oxygen as logged in the tanks.
Abundances (numbers) of major grazer species in the tanks as assessed by subsamples taken at three time points (before upwelling 2 and 3 and between the two upwelling events).
The depletion of dissolved oxygen in lakes (hypoxia) is an ongoing phenomenon that put under risk ecological systems and impact sedimentary environments. This phenomenon is driven by the increasing anthropogenic pressure on such environments. This dataset contains high-resolution sedimentological, geochemical and biological depth series of selected short sediment cores from lake Tiefer See (NE Germany). Those cores cover the recent transition from homogeneous to laminated sediments (~100 years ago), a transition that reflect the onset of hypoxic conditions in the lake. The cores were taken from different locations and water depths across the lake and allow to trace the spatiotemporal evolution of hypoxia spread in the lake.
Temperature, pH, salinity and oxygen logged and measured in the tanks.
Control measures of temperature, pH, salinity and oxygen as taken by WTW multimeter daily 3h after sunrise.
Grazing rates of the isopod Idotea sp. on the macroalga Fucus vesiculosus during upwelling 3 in response to warming and upwelling.
Impact of warming and upwelling on macroalgal growth (expressed as anomaly or z-growth).
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