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Mediterranean Marine Science Vol. 17, 2016 Soft Bottom Molluscan Assemblages of the Bathyal Zone of the Sea of Marmara DOĞAN A. University, Faculty of Fisheries, Department of Hydrobiology, 35100, Bornova, İzmir ÖZTÜRK B. Ege University, Faculty of Fisheries, Department of Hydrobiology, 35100, Bornova, İzmir BİTLİS-BAKIR B. Dokuz Eylul University, Institute of Marine Sciences and Technology, İnciraltı, 35340, İzmir TÜRKÇÜ N. Ege University, Faculty of Fisheries, Department of Hydrobiology, 35100, Bornova, İzmir https://doi.org/10.12681/mms.1748 Copyright © 2016 To cite this article: DOĞAN, A., ÖZTÜRK, B., BİTLİS-BAKIR, B., & TÜRKÇÜ, N. (2016). Soft Bottom Molluscan Assemblages of the Bathyal Zone of the Sea of Marmara. Mediterranean Marine Science, 17(3), 678-691. doi:https://doi.org/10.12681/mms.1748 http://epublishing.ekt.gr | e-Publisher: EKT | Downloaded at 07/10/2021 04:25:58 | Research Article Mediterranean Marine Science Indexed in WoS (Web of Science, ISI Thomson) and SCOPUS The journal is available on line at http://www.medit-mar-sc.net DOI: http://dx.doi.org/10.12681/mms.1748 Soft Bottom Molluscan Assemblages of the Bathyal Zone of the Sea of Marmara A. DOĞAN1,3, B. ÖZTÜRK1, B. BİTLİS-BAKIR2 and N. TÜRKÇÜ1 1 Ege University, Faculty of Fisheries, Department of Hydrobiology, 35100, Bornova, İzmir, Turkey 2 Dokuz Eylul University, Institute of Marine Sciences and Technology, İnciraltı, 35340, İzmir, Turkey Corresponding author: [email protected] Handling Editor: Argyro Zenetos Received: 19 April 2016; Accepted: 21 June 2016; Published on line: 23 September 2016 Abstract This study deals with the soft bottom molluscan species collected from the bathyal zone of the Sea of Marmara in 2013. Replicated samples were taken using a Box Core, sampling an area of 0.1 m2 at 31 stations along two depth transects, 500 and 1000 m. A total of 1229 individuals belonging to 4 classes and 28 species were collected. Two species (Akritogyra conspicua and Liostomia hansgei) are new records for the marine molluscan fauna of Turkey and four species (Benthonella tenella, Odostomia silesui, Syrnola minuta and Crenilabium exile) are new records for the molluscan fauna of the Sea of Marmara. A relatively richer fauna was determined at a depth of 500 m (25 species) compared to 1000 m (17 species).The most dominant species at 500 m and 1000 m depths were Crenilabium exile and Parthenina flexuosa, respectively. Number of species and number of individuals varied significantly only between depths, while number of individuals changed significantly among basins (ANOVA test). A significant difference in species assemblages between the Tekirdağ and the Central Basins was detected (ANOSIM test). Multivariate analysis showed that depth was the main factor influencing the molluscan assemblages in the area. Keywords: Mollusca, Bathyal zone, New records, Taxonomy, Ecology, Distribution, Sea of Marmara. Introduction (1885) recorded certain species of different systematic groups such as Coelenterata, Bryozoa, Polychaeta, Crus- The Sea of Marmara, with a surface area of 11,500 tacea, Mollusca, Echinodermata and Pisces from the in- km² and a maximum depth of 1390 m, is a semi-enclosed fra and the circalittoral zones. Sturany (1895) dealt only basin in the Mediterranean system located between the with molluscan species from the circalittoral and bathyal continents of Europe and Asia. It is connected to the (one station only) zones. Ostroumoff (1896) conducted Black Sea, the largest anoxic basin in the world, and the the most detailed study in the 19th century; he performed Aegean Sea through the İstanbul and Çanakkale Straits. benthic and pelagic samplings at 61 stations and report- The Sea of Marmara has two prominently different wa- ed more than 700 macrobenthic and planktonic species. ter masses; the upper layer originating from the Black Marion (1898) recorded some species of Coelenterata, Sea (from the surface to about 25 m), with brackish wa- Crustacea, Mollusca and Echinodermata from gravelly ter (22–26‰ salinity) and a renewal time of about 5–6 mud bottoms with shell fragments, at a depth of 40-42 months and the lower layer with more saline water (up to m. Later on, further studies on the molluscan fauna of 38.5‰ salinity) originated from the Mediterranean Sea the Sea of Marmara were conducted by different authors. with a renewal time of about 6–7 years (Beşiktepe et al., Among them, Demir (1952) focused on the benthic in- 1994). Because of the outflow of brackish Black Sea wa- vertebrates along the shores of the Bosphorus and Prince ter, there is a strong halocline throughout the Sea of Mar- Islands. Tortonese (1959) worked on the soft bottoms of mara, leading to low-oxygen conditions below the thin the infra and the circalittoral zones and reported some well-mixed surface layer, at 25 m depth (Beşiktepe et al., macrobenthic species of Porifera, Polychaeta, Mollusca, 1994; Kaminski et al., 2002). On the other hand, the Sea Echinodermata and Tunicata. Oberling (1969-1971) in- of Marmara is subjected to high volumes of wastewater vestigated littoral molluscan species between Tekirdağ discharges from land-based sources.The basin receives a and Avşa Island. Yüksek (1989) studied the littoral biota total of 1.9 x 106 tons of TOC (total organic carbon) and of the southern coast of the Sea of Marmara. Balkıs (1992) 2.7 x 105 tons of TN (total nitrogen) per year from the determined the macrobenthic species of the littoral zone Black Sea inflow (Albayraket al., 2006), which is one of of Marmara Island. Albayrak & Balkis (1996a, b) and Al- the important factors threatening biodiversity. bayrak et al. (2004) focused on the benthic prosobranch Studies on the molluscs of the Sea of Marmara date gastropods and the bivalvian species of the hard and the back to the end of 19th century. In that period, Colombo soft bottoms of the infra and the circalittoral zones of the 678 Medit. Mar. Sci., 17/3, 2016, 678-691 http://epublishing.ekt.gr | e-Publisher: EKT | Downloaded at 07/10/2021 04:25:58 | Bosphorus and the Sea of Marmara. Ritt et al. (2010) re- using a Box Core, sampling an area of 0.1 m2. The first 30 ported some macrobenthic species from the three micro cm of the sediment samples were evaluated. Some sam- habitats (bioturbated sediment, reduced sediment and ples could not be taken at some stations (Table 1) due to carbonate crust) near a brackish-water cold seep of the the weather conditions and the bottom structure. No sam- bathyal zone on the North Anatolian Fault. Among the ple could be taken at 500 m depth of station 34, as the above mentioned studies, only Sturany (1895), Ostrou- bottom was covered with rocks. At each station, three rep- mof (1896) and Ritt et al. (2010) identified molluscan licates were taken for benthic community analysis and an specimens in some samples (8-13 samples) collected at additional sample for granulometric and chemical analy- depths exceeding 500 m. sis of the sediment. Samples were sieved with a 0.5 mm The aim of this paper was to elucidate the composi- mesh on board the R/V Yunus-S and the retained material tion and the structure of the molluscan assemblages oc- was placed in jars containing seawater with 4% formal- curring in the bathyal zone of the Sea of Marmara and dehyde solution. In addition to the box-core sampler, we their relationship with environmental variables. also used a bottom-trawl to sample large-sized deep-sea faunal components of the Sea of Marmara. However, no Materials and Methods molluscan specimens were gathered by this bottom-trawl hauling (one in each basin). At the laboratory, the mate- Study Area rial was washed with tap water and specimens were sorted The Sea of Marmara is divided into three major sub- according to taxonomic groups under a stereomicroscope. basins with bathyal zones, namely, Tekirdağ, Central and The sorted specimens were then preserved in 70% etha- Çınarcık. They are about 1200 m deep and separated by nol. The molluscan specimens were identified and counted saddles as shallow as 400–600 m (McHugh et al., 2008). under stereomicroscopes. Bottom-water samples were Among these, the Çınarcık Basin, which is located south taken with a CTD bottle at each station during sampling. of the Prince Islands, has a maximum depth of 1270 m. Temperature, salinity and dissolved oxygen concentra- The Central Basin, which is located between Marmara tions were determined on board the R/V Yunus-S. Water Ereğlisi and Kapıdağ Peninsula, harbours the deepest samples for analysing nitrite, nitrate, ammonia, phosphate point (1268 m) of the Sea of Marmara. The Tekirdağ Ba- phosphorus and silicate were pre-filtered, frozen and im- sin, which is situated in front of the Ganos Mountains, mediately transferred to the laboratory. has a maximum depth of 1133 m (Gazioğlu et al., 2002). Data analysis Data collection Community parameters such as number of species, The benthic material was collected from 31 stations in number of individuals, Shannon–Wiener’s diversity in- the bathyal zone of the Sea of Marmara (Fig. 1; Table 1) dex (log2 base) (H΄) and Pielou’s evenness index (J΄) by R/V Yunus-S in June 2013. All material was collected were calculated for the samples. In order to determine Fig. 1: Map of the investigated area and sampling sites. Medit. Mar. Sci., 17/3, 2016, 678-691 679 http://epublishing.ekt.gr | e-Publisher: EKT | Downloaded at 07/10/2021 04:25:58 | Table 1. Coordinates, sampling dates, number of sample (N) depth and bottom structure of the sampled stations. Stations Latitude Longitude Date

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