НАЙБІЛЬШІ ГЛИБИНИ ПЕРЕБУВАННЯ РИБ У ЧОРНОМУ МОРІ ТА ОСОБЛИВОСТІ ЇХ ХАРЧУВАННЯ БІЛЯ КОРДОНУ СІРКО-ВОДНЕВОЇ ЗОНИ

• Дата: 2023
• Автори: Заїка, В. Є., Гулiн, М. Б.
• Формат: Стаття
• Мова: Ukrainian
• Опубліковано: Marine Ecological Journal 2023
• Теми: придонна іхтіофауна; гіпоксія; верхня межа сірководню; Чорне море; near-bottom fishes; hypoxia; upper bounds of H2S; Black Sea
• Онлайн доступ: https://mej.od.ua/index.php/mej/article/view/276
• Назва журналу: Marine Ecological Journal

Results of underwater visual explorations have been discussed regarding fishes congestions in the near-bottom layer of hypoxic waters of the Black Sea. Observations cover the deep-sea hypoxic layer contacting to the permanent H2S anoxic zone, and also small-size hypoxic zones over the shallow seabed sediments with periodic anoxia which is fueled by methane gas seeps located off the NW-Crimea shore. Massive, up to 14 cm thick detritus-microbial mats was formed in sites of gas seepage from the seabed sediments, content of organic matter in these mats was 7-50 times higher in comparison with adjacent reference stations. At one the most active seep, fish-shoal of surmullet Mullus barbatus ponticus was found. Fishes not only remain for a long time within the seep area above microbial mats but also consume benthic organisms associated with mat. Concentration of O2 at the "water-mat" interface has been on the sharp decreasing to 0.0 – 0.6 mg L-1. On the northwest shelf, in the near-bottom layer of 144 – 145-m depth, two fish-congestions were detected - sprat Sprattus sprattus phalericus and whiting Merlangius merlangus euxinus; oxygen content near sea floor was equal to 0.7 – 1.1 mg L-1. During survey of another NW-area very dense congestion of sprat has been observed in the near-bottom layer at a depth of 163 m, oxygen concentration didn’t exceed 0.1 – 0.4 mg L-1. The upper H2S-interface has property of spatial-temporal instability. Sulphidic conditions in the near-bottom waters occur within the depth range 146-168 m, i.e. discovered fish congestions are located directly above the H2S-zone. In the region adjacent to Bosporus Straits penetration of M. merlangus euxinus was revealed down to 186 m, i.e. quite deeper than for the NW Black Sea. Negative values of Eh-potential in the water column were found in this area beginning with 191-m depth. Location and food resources of fishes in the hypoxic waters as well as their role for chemocline indication are summarized and discussed.