February 1st to 5th 2016
Olhão, Portugal
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Complex global change: multifactorial pressure, multivariate response and the role of fluctuations in a benthic community

Oral Presentation
Future Oceans
Wednesday, February 3, 2016 -
11:30 to 11:45

Wahl, M. 1

1GEOMAR, Kiel, Germany

Simultaneous and sequential impacts of the global change factors warming, acidification, nutrient enrichment and hypoxia were investigated in all seasons with regard to multivariate responses of a benthic community of the Western Baltic Sea. The factors were generally applied as "delta.treatments, i.e. as offsets from the ambient conditions. The latter, and consequently the applied treatments, were naturally fluctuating at different temporal scales (seasonal, circadian, sporadic). We assessed the responses of the community components macroalgae, epibionts and grazers, at the individual level and regarding the shifts of interactions among species.The emerging pattern showed that effects differed strongly among seasons, acidification plays a minor role at most, warming and hypoxia are the strongest drivers of change, nutrient enrichment may modulate some stress effects, interaction shifts show a substantial potential for the enhancement or the buffering of environmental stress, and genetic diversity favors adaptation. The latter, however, only holds true when sensitivites towards single stressors correlate positively. Anti-correlation of sensitivites will accelarate the decline of a population. Most effects were strongest in summer. Indirect effects were often stronger than any direct impacts. In our effort to understand the ecological impact of complex global change we should strive for experiments of appropriate complexity including multiple global, regional and local factors, multiple responses, multiple scales, natural fluctuations, all seasons, all ontogenetic stages, shifts of biotic interactions, plasticity and adaptation.
keywords: 
global change, fluctuations, benthos, fluctuations

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