Journal of the Persian Gulf (Marine Science)/Vol. 5/No. 17/September 2014/ 11 / 37-48 Distribution of Molluscs in the Eastern Persian Gulf, PG-GOOS Cruise Amini Yekta, Fatemeh*; Jalili, Mahshid; Pourjomeh, Fatemeh Hakim Elahi, Maryam; Rezaei, Hamid Iranian National Institute for Oceanography and Atmospheric Science (INIOAS), IR Iran. Received: February 2014 Accepted: July 2014 © 2014 Journal of the Persian Gulf. All rights reserved. Abstract Distribution of molluscs in the eastern part of the Persian Gulf were studied during the PG-GOOS cruise (Oct-Nov 2012), using the 250 cm2 Van Veen grab for sampling. Sixty gastropod and 23 bivalve taxa in addition to one scaphopod taxon were identified. Gastropods constituted 80% of molluscs. The abundance of molluscs averaged 1398.36 (±261.95) ind./m2. Costellaria sp. was the most abundant gastropod and Ervilia scaliola, the most abundant bivalve species. Abundance of molluscs in different stations showed significant differences (p<0.05). Station C, located near Abu Musa Island, with an average abundance of 8040 (±1625.30) ind./m2, was the most abundant site. Average values for Shanon and Simpson indices were 2.08 (±0.11) and 0.81 (±0.02), respectively. The average abundance of molluscs was significantly correlated with depth, sediment temperature (p<0.01), salinity and TOM (p<0.05). Mollusc diversity showed significant correlation with sediment temperature, salinity, depth (p<0.05) and TOM (p<0.01). Keywords: PG-GOOS cruise, Mollusca, Persian Gulf, Distribution, Diversity 1. Introduction its young age (Sheppard et al., 2010). Mollusca with almost 100,000 species constitute The Persian Gulf is a shallow semi-enclosed basin the second largest animal phylum (Barnes et al., connected to the Gulf of Oman through the Strait of 2009). Many mollusc species are used as bio- Hormuz. The Iranian shore of the Persian Gulf has indicators (Saeedi, 2012; Astani et al., 2012; steeply sloping sections and Arabian shore is mostly Mohammad Karami et al., 2014). Despite the high sedimentary (Siebold, 1973). In most of the Persian diversity in the Persian Gulf, little is known about Gulf water salinity is more than 39 psu (Sheppard et subtidal mollusc species of mentioned area both in al., 2010). Depth of the Persian Gulf is 35m in terms of biodiversity and ecology. Some studies on average and maximum depth of 90m and in the Strait molluscs of the Iranian coasts of the Persian Gulf have of Hormuz exceed 100m (Pous et al., 2004). been conducted (e.g. Tadjallipour, 1974; Rezai et al., Biologically, the Persian Gulf is impoverished 1995; Hosseinzadeh et al., 2001; Sadeghi Nassaj et al., because of harsh environmental conditions as well as 2010; Shokat et al., 2010; Asgari et al., 2012), but * mostly focused on specimens greater than about 5 mm Email: [email protected] 37 Amini Yekkta et al. / Distribution of Molluscs in the Eastern Persrsian Gulf, PG-Goos Cruise in size and, therefore, study on small species has Abu Musa, Farur, Siri, Kish, Hendorabi and Lavan always been neglected. Islands. Stations varied from 13 to 90 m in depth The PG-GOOS (the Persian Gulf and Gulf of (Table 1). Oman Oceanographic Study )cruise was launched in October 2012 aboard Nayband Hydrography Vessel to 2.2. Field Sampling cover the oceanographic data gap in the Iranian side of the Persian Gulf and the Gulf of Oman by collecting Sampling was done in Occt-Nov 2012 with a 250 marine physical, chemical, geological, biological and cm2 Van Veen grab in 3 replications in each site. environmental data as well as meteorological Twenty nine stations were sampled in this cruise. parameters. In biological section, macro- and meio- Samples were sieved throughh 1 mm mesh and fixed in benthic inverteebbrates, phytoplankton and zooplankton 10% neutralized formalin. By using stereomicroscope, communities were studied. The present study is focuseed mollusc specimens as well as other benthic groups on the eastern part of the Persian Gulf. were sorted and abundance and diversity of specimens were calculated. By using reliable local references, 2. Materials and Methods samples were identified up to possible taxonomic level. Species which could not be identified, were 2.1. Study Area designated temporary code names to be included in analyses as separate species until further efforts on Twenty nine stations from Bushehr to the Strait of their identification. Factors such as salinity, sediment Hormuz were sampled (Fig. 1). The study arrea temperature, total organic matter (TOM; Heiri et al., included Iranian islands of the Persian Gulf such as 2001) and sediment grain size (Laser particle analyzer, Homuz, Qeshm, Larak, Greater Tonb, Lesser Tonb, Fritsch) were measured as well. Fig. 1: Sampling stations, Eastern part of the Persian Gulf, 2012 38 Journal of the Persian Gulf (Marine Science)/Vol .5/No .17/September 2014/ 11 / 37-48 Table 1. Geographical coordinates for sampling stations pattern in assemblage structure of mollusc. Species Latitude Longitude Depth diversity was evaluated with diversity indices including Stations (N) (E) (m) Shannon–Wiener, Simpson’s and Margalef’s as well as 125 27° 05' 44.8" 56° 22' 14.2" 13 Buzas and Gibson’s evenness measure using PAST 128 26° 50' 17.4" 56° 26' 29.7" 59 software (Hammer et al., 2008). Correlation between 130 26° 41' 33.2" 56° 28' 43.4" 68 environmental factors and mollusc diversity and 123 26° 40' 34.9" 56° 20' 53.5" 71 abundance was assessed to identify the environmental 121 26° 50' 42.9" 56° 15' 42.5" 49 factors that best explained the spatial variation in A 26° 39' 21.5" 56° 04' 56.4" 60 mollusc assemblages (SPSS program version 17). 118 26° 28' 03.0" 55° 55' 24.6" 59 116 26° 37' 11.7" 55° 49' 31.4" 34 3. Results B 26° 29' 28.9" 55° 33' 41.9" 21 TS 26° 12' 26.8" 55° 09' 26.9" 107 In total, 2565 mollusc specimens including 2043 114 26° 04' 41.1" 55° 16' 35.5" 85 gastropods, 515 bivalves and 7 scaphopods were C 25° 54' 47.8" 55° 07' 22.0" 68 108 26° 07' 10.0" 54° 55' 47.0" 85 sampled. Gastropods constituted 80% of molluscs. 106 26° 21' 40.0" 54° 50' 30.5" 63 The abundance of molluscs averaged 1398.36 98 26° 27' 47.2" 54° 28' 29.7" 27 (±261.95) ind./m2. Among stations, station C 99 26° 19' 44.4" 54° 28' 10.0" 79 (located near Abu Musa Island) with an average 101 26° 03' 27.8" 54° 27' 32.1" 81 abundance of 8040 (±1625.30) ind./m2 was the most 102 25° 54' 10.2" 54° 27' 25.9" 74 abundant site followed by station 114 (5600 104 25° 40' 48.6" 54° 25' 23.5" 59 ±1785.72 ind./m2). No mollusc specimens were D 25° 43' 53.9" 54° 05' 23.5" 63 found in station situated near Lesser Tonb (TS), the E 26° 34' 49.2" 54° 00' 27.3" 26 deepest station (107 m; Fig. 2). 88 26° 35' 02.1" 53° 49' 42.3" 54 Excluding stations G and 90, gastropods dominated 90 26° 19' 08.0" 53° 47' 54.6" 90 molluscs in all stations. Scaphopods were just found in 92 26° 03' 13.0" 53° 45' 51.2" 75 F 26° 40' 11.8" 53° 40' 34.3" 20 stations 102 and 130. The most abundant gastropod 84 26° 41' 16.5" 53° 36' 25.2" 58 taxa were species of genus Costellaria and the most G 26° 44' 34.8" 53° 12' 58.3" 84 abundant bivalve species was Ervilia scaliola. Atys 71 27° 22' 25.9" 52° 30' 32.5" 63 cylindrica in gastropods and Nuculoma layardii in 67 27° 35' 54.6" 52° 07' 08.7" 72 bivalves had the widest distribution in sampling the area; they were present in 21 and 7 out of 29 stations, 2.3. Data Analysis respectively. Kruskal-Wallis test yielded significant differences in Plots of average molluscs abundance were analyzed abundance of molluscs in different stations (p<0.05). using EXCEL 2007. Kruskal-Wallis test (SPSS Cluster analysis based on similarities in their program version 17) was used for the differences in assemblage structure, separated station TS from other mollusc abundance among sites as normality could not stations since no mollusc specimens were reported from be obtained by transformation. Cluster analysis based this station. In about 43% similarities, two other groups on Bray- Curtis similarity matrix of fourth root- are formed clearly that nearly separate stations located transformed abundance data was used in PRIMER 5 around Larak, Hormuz and Qeshm Islands from other (Clarke and Warwick, 1994) to depict the spatial stations (Fig. 3). 39 Amini Yekkta et al. / Distribution of Molluscs in the Eastern Persrsian Gulf, PG-Goos Cruise Fig. 2: Average density (ind./m2) of molluscs in different stations Fig. 3: Cluster analysis based on Bray- Curtis similarity matrix of fourth root- transformed abundance data 40 Journal of the Persian Gulf (Marine Science)/Vol .5/No .17/September 2014/ 11 / 37-48 In total, 84 mollusc taxa were identified (±0.28) psu. The sediment temperature ranging (Appendices I and II), including 60 gastropod (36 between 21.50 °C (stations 90 and G) and 28 °C taxa up to species, 18 taxa up to genus, and 5 taxa up (station B), averaged 25.02 (±0.37)°C. TOM content to family levels), 23 bivalve (13 taxa up to species, 6 of sediments was in range of 4.50% in station F to taxa up to genus, and 4 taxa up to family levels) and 16.75% in station A.