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''5 days ago Philippines Earthquake: Deaths Reported After 7.6 Shake
Takashi Fujioka, a Hakodate Fisheries Research Institute researcher, said he has heard of similar phenomena before, but it was his first time to see it.
He said the fish may have been chased by larger fish, become exhausted due to a lack of oxygen while moving in a densely packed school, and were washed up by the waves. The fish also may have suddenly entered cold waters during their migration, he said.''
Introduction
The Black Sea is known for its peculiar vertical structure: a strong stratification prevents deep-water ventilation, leading to complete absence of oxygen and abundance of hydrogen sulphide and ammonia in its deep layers [1,2,3]. The oxycline is quite shallow (~100 m) and coincides approximately with the halocline and winter convection depth [4, 5]. Consequently, most biological activity, light and oxygen dependent, is confined to the first 100 m from the surface, while the deeper layers constitute an unfavourable environment for photoautotrophic microorganisms [6, 7]. Since 2013 several Bio-Argo autonomous profiling floats were deployed in the Black Sea, providing real-time profiles to a depth of 1000 m for several variables (http://www.oao.obs-vlfr.fr/bioargo/PHP/basbio001d/basbio001d.htm). The floats consistently measured a chlorophyll a (Chl a) concentration increase between 100 and 1000 m depth, not visible in the corresponding profiles for the Mediterranean Sea and the Atlantic Ocean. This increase of red fluorescence well below the euphotic zone was firstly described in the early 1980s [8, 9], during oceanographic research in different areas of the Pacific Ocean: from the subtropical (off Mexico, between California and Hawai [1, 9]) to the North Pacific [10]. This scattering in the visible wavelengths at around 415 nm, termed “deep red fluorescence”, has been found associated with the oxygen minimum zone (OMZ) [9, 11] and was described as a feature of the global oceans, since it was reported across different oceanic regions [12].
https://www.nature.com/articles/s41396-019-0378-z
an earthquake could release a pocket of this species of water
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