 Oxygen-depleted areas are in red Oxygen depletion is a phenomena observed in aquatic ecosystems which are getting out of oxygen balance and turning to 0 % oxygen saturation (anaerobic) (anoxia) (a status of low concentrations in the range between 0 and 30 % is often called hypoxia. Most fish can not live below 30 % saturation. 100 % is fully saturated water).
The graphic shows the most severe known oxygen depletion of an open ocean area as a consequence of too much input of oxygen consuming chemicals and bioactive nutrients through the Hudson, Raritan and Mullica rivers into the waters off New York and Atlantic City USA New Jersey (100 - 110 % saturation is healthy ocean water, the oversaturation caused by phytoplankton).
If too many nutrients enter the ocean from rivers, strong phytoplankton blooms are triggered. After a few days the cells die, sink to the bottom and are decomposed by bacteria, which can use up all the oxygen dissolved in the water in extreme cases. This process, called eutrophication can cause causes fishkill and even invertebrates like worms and clams may leave the ground and die. New approaches of longterm monitoring of oxygen regime in the ocean observe online the behavior of fish and zooplankton, which changes drastically under reduced oxygen saturations (ecoSCOPE) and already at very low levels of water pollution.
In a very short time the oxygen saturation can drop to zero when offshore blowing winds drive surface water out and anoxic depthwater rises up. At the same time a decline in temperature and a rise in salinity is observed, as below presented from the first ever online longterm ecological observatory in the seas at Kiel Fjord, Germany. It is planned to have such live readouts available for the public to deliver unfiltered and unbiased reports about the real status of the oceans to the interested voter and fisheater.
Underwater video of the seafloor covered with dead or dying crabs, fish and clams
Publications
- KILS U, WALLER U, FISCHER P (1989) The Fish Kill of the Autumn 1988 in Kiel Bay. International Council for the Exploration of the sea C M 1989/L:14
- FISCHER P, KILS U (1990) In situ Investigations on Respiration and Behaviour of Stickleback Gasterosteus aculeatus and the Eelpout Zoaraes viviparus During Low Oxygen Stress. International Council for the Exploration of the Sea C M 1990/F:23
- FISCHER P, RADEMACHER K, KILS U (1992) In situ investigations on the respiration and behaviour of the eelpout Zoarces viviparus under short term hypoxia. Mar Ecol Prog Ser 88: 181-184
The underwater videos of dying fish were released for broadcasting in the primetime TV news TAGESSCHAU (http://www.tagesschau.de) and articles in key newspapers in Germany (against the order of the director of the oceanography institute), with the consequences that the tourism in the area declined drastically, and the research group with all students and instrumentation (http://en.wikipedia.org/wiki/EcoSCOPE) were destroyed by political forces of the that-time quite (http://de.wikipedia.org/wiki/Barschel-Affäre) currupt capitol Kiel.
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