Warning signs – effects of oxygen deficiency on the species composition in the oceans:
Our oceans change rapidly: empirical data and models have shown that temperature has increased during the last decades, oxygen concentration has decreased, and increasing CO2 in the atmosphere reduces pH in the water.
The majority of marine organisms is poikilothermic, which means their body temperature follows environmental temperature. Changes in temperature and oxygen thus have a direct impact on the metabolism of the species, and organisms try to avoid such unfavorable conditions.
Rapid temperature and oxygen changes will lead to emigration of species from their traditional habitats, and immigration and proliferation of new species with larger tolerance for low oxygen levels. In other cases it may have an impact on growth, reproduction and survival performance. As a consequence these developments mostly lead to an impoverishment of the diversity.