Many commercial fish species are unable to survive at depths greater than 30 meters in Turkey’s inland sea due to a significant decrease in oxygen levels, which have dropped to one-fourth of what they were four decades ago, according to data from METU.
https://m.bianet.org/english/environment/282083-experts-warn-of-impending-disaster-in-marmara-sea-due-to-oxygen-depletion
