Considering that all higher aquatic life depends on oxygen, it is an alarming finding that low oxygen conditions in aquatic ecosystems are increasing in number, duration and extent due to global warming and eutrophication. The subsequent increase of “dead zones” leads to losses in ecosystem functions and services including biodiversity and may induce the emission of greenhouse gases. For understanding hypoxia causes and consequences, present and past hypoxia needs to be investigated at a global scale.
As a first step of addressing this big challenge, a consortium involving 16European research institutes and Universities specialized in marine ecosystems was established. The project, funded by the European Commission Seventh Framework program (FP7-ENV), was coordinated by the Max Planck Institute for Marine Microbiology MPIMM, located in Bremen (Germany).
Sites investigated in the project included open seas with high sensitivity to global warming and high oxygen contents (Artic sea), semi enclosed basins with permanent anoxia (Black Sea, Baltic Sea), and seasonally or locally anoxic land-locked systems (fjords, lagoons and lakes). Different types of sensing devices (observatories) were used to monitor oxygen and associated parameters (e.g., hydrodynamics, temperature, salinity, and other gases) at the appropriate spatial and temporal scales. Additionally, in situ studies and sampling of water columns and sediments where made, in order to analyse biological and biogeochemical processes and understand their role in hypoxia development and the changes that ecosystems undergo when oxygen gets depleted. In addition longer time scales were addressed by analysis of existing data sets and by investigations of proxies for past oxygen conditions in the sediment record (including biotic and abiotic proxies). Numerical modelling of hypoxia-related processes has been carried out for some of the target sites to generalize the findings and to build predictive capacities.
Recommendations on standardized oxygen measurement procedures were developed and investigations of oxygen sensor performance and calibration were carried out. Issues of quality control and measures against biofouling were addressed in order to facilitate long term oxygen observations. These issues were discussed in an Oxygen Sensor Workshop in 2011 with scientists and representatives from international manufacturers of oxygen sensors.
The obtained results can raise awareness of the effects of anthropogenic activity and climate change on oxygen depletion in water bodies, and the consequences for ecosystems. While the main target of the project is the Scientific Community, the obtained results can also be helpful for promoting new policy measures for marine ecosystems preservation. Moreover, all the obtained data have been kept in compliance to the standards of the Global Earth Observation System of Systems (GEOSS) and are published at the World Data Center for Marine Environmental Sciences (http://www.wdc-mare.org/). Open access to all data will be granted at the latest 3 years after the end of the project. Parts of the project, for example methods for oxygen determination and data flow from a cabled observatory in the Swedish Koljoe Fjord to the data portal and repository, clearly reach a level 9 on the TRL scale.