Composition and abundance of octocorals in the Sea of Marmara, where the Mediterranean meets the Black Sea

Species composition and abundance of octocoral assemblages were investigated in the Sea of Marmara, which forms the connection between the Mediterranean and the Black Seas, two semi-enclosed seas with peculiar oceanographic conditions. Fourteen octocoral species were collected in the saline layer of the Marmara Sea (20-40 m), with a mean coral abundance of 5.21±5.11 colonies m –2 (mean ± SD) calculated from a total of 1390 colonies counted in transects. In spite of severe anthropogenic disturbances, dense assemblages of corals/gorgonians were observed during this study. The coralligenous communities—one of the most valuable structures of the Mediterranean Sea—harbored either Eunicella cavolini or Paramuricea macrospina as the dominant gorgonian in the Marmara Sea. Furthermore, the gorgonian assemblages of the Marmara Sea differed from those of the Mediterranean in their high abundance of P. macrospina and Spinimuricea klavereni , two species rarely encountered in the Mediterranean Sea at the studied depth range. The factors behind the observed differences are discussed in regard to the particular oceanographic conditions of the Marmara Sea. Finally, we revised the main threats to corals/gorgonians in the Marmara Sea and provided some insights on management recommendations for coral conservation in this area.

14 octocoral species were collected in the study area at various stations (stations N1 to N17 in the Northern group of Islands and stations S1 to S14 in the Southern group of Islands).Biological samples were deposited at the Octocoral Collection of the University of Istanbul (IUOK).
This sea pen was common on soft substrates of both Prince Islands and Southern Marmara Islands coasts starting from right after the halocline depth.Uncontracted colonies of various sizes (approximately 5-55 cm) were encountered anytime in the day.The density of Veretillum cynomorium varied from 0.2 to 4.2 colonies m -2 among stations.V. cynomorium is a shallow water sea pen found from the first ten meters to 100 meters (Williams 1995, Williams 2011).The species is distributed in the Eastern Atlantic from the Southern Europe to the West Africa coasts and in the Mediterranean Sea (Williams 1995, López-González et al. 2001, Vafidis in Coll et al. 2010: Table S13).
This sea pen was found on soft substrates of only the Southern Marmara Islands coasts at 2 stations between 27-38 m.Its density was about 1-2 colonies m -2 .Pteroeides griseum is a shallow water sea pen found from the first ten meters to 200 meters (Williams 1995, Williams 2011).The species is distributed along the European coasts of the Atlantic and in the Mediterranean Sea (Williams 1995, Vafidis in Coll et al. 2010: Table S13).

Family FUNICULINIDAE Gray, 1870
Genus Funiculina Lamarck, 1816 Funiculina quadrangularis (Pallas, 1766) Material examined: IUOK99 (S2).This sea pen was observed at the limit of observation (41 m) of this study on muddy bottom.Funiculina quadrangularis is a deep sea species that can be found until 2000 m (Williams 1995, Williams 2011) but rarely above 30 m.The species has a cosmopolitan distribution along the Atlantic, Indo-Pacific and in the Mediterranean Sea (Williams 1995, Vafidis in Coll et al. 2010 This encrusting soft coral was found between 18 -26 m among the calcareous bioconcretions of polychaete tubes in both Prince Islands and Southern Marmara Islands coasts.Sarcodictyon catenatum is found from the sublittoral to 100 m on stones and shells in the Mediterranean and the Northeast Atlantic coasts (Vafidis et al. 1994, Ocaña et al. 2000, Vafidis in Coll et al. 2010: Table S13).
This soft coral was the most common octocoral in the study area but did not form dense assemblages.It was found on all types of bottom attached to rocks, stones or shells from the halocline to 40 m depth with densities of 0.1-1.2colonies m -2 .The colours varied from red, orange to yellow but were mainly whitish.The species is found along the Mediterranean and Northeast Atlantic coasts between 20-200 m (Vafidis et al. 1994, Watling and Auster 2005, Vafidis in Coll et al. 2010: Table S13) on sandy/muddy bottoms but attached to stones or shells (Weinberg 1977).
Table S1.-Taxonomic list of collected species with data of the material examined and notes on its ecology.
Alcyonium acaule was found on rocky bottoms and calcareous bioconcretions or attached to stones/shells on sandy bottom in both Prince Islands and Southern Marmara Islands coasts from 30 to 40 m (Fig. S1).This soft coral was rather rare in the northern stations whereas it formed assemblages in the southern stations with densities of 0.8 to 3.4 colonies m -2 .The colours varied from whitish cream to orange but wine red was the most common.Shark egg cases were common observations on this coral (Fig. S1).This species is distributed in the Mediterranean between 12-45 m on rocky bottoms (Weinberg 1977, Vafidis et al. 1994) but also present in the Northeast Atlantic coasts (Watling and Auster 2005).

Alcyonium coralloides was common in both Prince
Islands and Southern Marmara Islands coasts between 20-40 m.The soft coral mainly covered calcareous bioconcretions and Chaetopterid polychaetes tubes but also gorgonian skeletons; besides, lobular forms were observed on pinna and mytilus shells.In the Mediterranean it is found from 2 to 100 m mainly on gorgonian skeletons but also tunicates, shells and stones/ rocks (Weinberg 1977).The species is distributed in the Mediterranean Sea but also present in the Northeast Atlantic coasts (Vafidis et al. 1994, Watling and Auster 2005, Vafidis in Coll et al. 2010: Table S13).This soft coral was common in the Prince Islands coasts with densities of 1-7 colonies m -2 and rare in the Southern Marmara Islands.It was found between 25-38 m on rocky bottom and stones/shells on soft substrates.In the Mediterranean Sea, the species is found between 22-90 m on hard bottom (Weinberg 1977, Vafidis et al. 1994).It is also present in the Northeast Atlantic coasts (Watling and Auster 2005).
Red gorgonian was found on rocky substrates in the study area between 30-40 m but did not form dense assemblages.It was generally below Eunicella cavolini assemblages and associated with Savalia savaglia colonies.All observed colonies had reddish pink coloration and were generally about 20 cm in height.In the Mediterranean, the species is found from 6 to 100 m but is most abundant between 40-60 m mainly on This gorgonian was found on rocky bottoms or attached to stones/shells on sandy bottom mainly in Prince Islands coasts from 21 to 40 m with densities of 0.1-3.9colonies m -2 .The colonies were generally fan shaped but sometimes less branched and the colours varied from creamy white to orange and brownish but were mainly yellow.In the Mediterranean sea, the species is found attached to boulders on detritic bottoms or sometimes sandy/muddy bottoms between 40-100 m until 200 m (Carpine and Grasshoff 1975).The species is distributed in the Mediterranean Sea but also present in the Northeast Atlantic coasts (Grasshoff 1992, Vafidis et al. 1994, Watling and Auster 2005).
Spinimuricea klavereni was found between 23-45 m on rocks, boulders and attached to pebbles/stones/ shells on soft substrates.This gorgonian was common in the Prince Islands coasts with densities of 0.1 to 3.1 colonies m -2 but rare in the South.In the Mediterranean it is found between 25-130 m on similar bottoms (Carpine and Grasshoff 1975, Vafidis et al. 1994, Bo et al. 2012).The species is distributed in the Mediterranean Sea but also present in the Northeast Atlantic coasts (Grasshoff 1992, Vafidis et al. 1994, Watling and Auster 2005).
Eunicella cavolini was found between 30-40 m on vertical walls or large rocks in both Prince Islands and Southern Marmara Islands coasts with densities of 0.1 to 13.9 colonies m -2 .In the Mediterranean Sea, the endemic gorgonian is found between 10-30 m on hard bottoms but can reach 150 m deep (Carpine andGrasshoff 1975, Weinberg 1976).
Eunicella singularis was found at 37 m on small rocks in only one station in the Southern Marmara Sea.The colonies did not harbour zooxanthellae, were bright white and their shape was more branched than generally observed for this species.In the Mediterranean Sea, this endemic gorgonian is found from 7 to 52 m on both hard and sandy/muddy bottoms (Carpine andGrasshoff 1975, Weinberg 1976).
Eunicella verrucosa was found only at two stations in the Marmara Sea on hard bottoms at 34 and 38 meters.The colours were orange-pink in the North and white in the South.The species is distributed in the Atlantic coasts where it is common (from the Scotland to Angola) and in the Mediterranean Sea as a rare occurrence between 35-200 m (Carpine andGrasshoff 1975, Grasshoff 1992).

Fig
Fig. S1.-Red Alcyonium acaule colony on rocky bottom at station S1 (A); colony on bioconcretion at station S9 (B); colony on the crab Maja crispata at station S6 (C); orange colony at station S6 (D); two small colonies on a dead mussel shell at station S13 (E); surface brooder colony at station S1 on august 2013 (F) and shark egg cases attached colony at station S1 (G).