Abstract
Deep-water meiobenthos of Turkish shelf has been evaluated at the Black Sea exit of İstanbul Strait (Bosphorus) and off Sinop peninsula as a result of three scientific cruises. Taxonomic diversity of meiobenthos communities was studied at the Black Sea exit of Bosphorus on a transect with a depth range of 75-300 m. The bottom sediments were collected at the area during two cruises, on board RV "Arar'' (of Turkey) and ''Maria S. Merian" (of Germany) in November 2009 and April 2010, respectively. Data on meiobenthos inhabiting both normoxic and extreme conditions was collected in the studied area and meiobenthos composition included 26 high level taxa. In addition, 2-3 morphotypes of benthic fauna were recorded as incertae sedis, which require further study. The number of higher taxa decreased from 22 to 14-8 when switching from oxygenic conditions (50-125 m) to the anoxic hydrogen sulphide environment (226-300 m). The constant components of meiobenthos included protists (Ciliophora, Gromiidea and soft-shelled Foraminifera), and metazoans were constantly represented by Nematoda and Harpacticoida. In 2011, a quantitative study on meiobenthic composition of the oxic/anoxic interface at the western part off Sinop Peninsula (Southern Black Sea) has also been investigated. The material was collected by ROVs during the expedition (Black Sea Leg) of the exploration vessel (E/V) Nautilus. Results showed that the taxa composition of meiobenthos ranged from 4 to 10 major groups. Free-living marine nematodes were numerically the dominant taxon at each station. Total abundances decreased in parallel to increasing water depth, hence decreasing oxygen levels.
Highlights
The Black Sea is a deep marginal meromictic sea
Detailed studies of deep-water meiobenthos have been conducted at the Black Sea exit of Bosphorus within the framework of the EU 7th FP project HYPOX (In situ monitoring of oxygen depletion in hypoxic ecosystems of coastal and open seas, and land-locked water bodies, EC Grant 226213)
The present paper summarizes the results of the analysis of meiobenthos samples obtained at the Black Sea exit of Bosphorus (75-300m) during the cruises RV "Arar" in November 2009, RV "Maria S
Summary
The Black Sea is a deep marginal meromictic sea. It has an oxygenated surface water layer overlying an anoxic deep-water layer. It is a unique marine water body where the dissolved oxygen disappears at a depth of about 200 m while hydrogen sulphide is present at all greater depths (Zaitsev 2008). The shallow sill depth at the Bosphorus, together with the positive water balance, produce a strong pycnocline/chemocline at -100 to -150 m in the Black Sea, separating the aerated brackish waters (17-18 ‰) from anaerobic, H2S-rich more saline waters (22.5 ‰; 8.9°C) (Özsoy & Ünlüata 1997). 100 m and the suboxic zone is at 85- 120 m near the head of the Bosphorus canyon. The suboxic zone is important for Ecologica Montenegrina, 14, 2017, 60-73
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