Macrobenthic echinoderm fauna of the littoral zone of the Gulf of Antalya and some ecological factors effecting their seasonal distribution

The aim of this study is to investigate the species diversity, abundance and biomass of the echinoderm fauna in the littoral zone of the Gulf of Antalya and to determine some ecological factors affecting their distributions. Samplings were carried out seasonally in soft substrates at six stations, between the depths of 0-200 meters between August 2009 and April 2010 and in hard substrates at seven stations, between the depths of 0-30 meters, between August 2010 and May 2011. A commercial bottom trawler called Akyarlar was used for the samplings in the soft substrates. A total of 117 trawl hauls were carried out at six depth levels (25, 50, 75, 100, 150, 200 m) and 165 sledge hauls and grab (van Veen grab) samplings at eight depth levels (5, 10, 25, 50, 75, 100, 150, 200 m) in soft substrates. 32 SCUBA dives were conducted at four depth levels (0-5 m, 5-10 m, 10-20 m ve 20-30 m) to count and sample the echinoderm specimens inside 1 m2 quadrates located at equal intervals in the transects of hard substrates. Sea water and sediment samples were taken from the sampling points.As a result of the examination of the sampled specimens, 5 classis, 14 orders, 30 families, 39 genera and 50 species (1 Crinoid, 18 Asteroid, 14 Ophiuroid, 12 Echinoid, 5 Holothurid) belonging to the phylum of Echinodermata were determined in the study area.According to the literature 12 species (Astropecten spinulosus (Philippi, 1837), Chaetaster longipes (Retzius, 1805), Hacelia attenuata Gray, 1840, Hymenodiscus coronata (G.O. Sars, 1872), Luidia ciliaris (Philippi, 1837), Luidia sarsi sarsi Düben & Koren, in Düben, 1845, Sclerasterias richardi (Perrier, 1882), Ophiacantha setosa (Bruzelius, 1805), Ophiura grubei Heller, 1863, Echinus melo Lamarck, 1816, Genocidaris maculata A. Agassiz, 1869, Spatangus purpureus O.F. Müller, 1776) are new records for the Mediterranean coasts of Turkey and Sclerasterias richardi (Perrier, 1882) is a new record for Turkey. Among the total of 50 species found in this study, most species (42) have an Atlanto-Mediterranean distribution, while 4 are Mediterranean endemics, two are cosmopolitan and two are Lessepsian immigrants in the Mediterranean Sea. The Mediterranean endemics are A. mediterranea, A. jonstoni, A. spinulosus ve P. microtuberculatus and Lessepsian immigrants are O. savignyi and S. reciprocans.Significant differences were found between the echinoderm communities sampled by different sampling methods. 24 echinoderm species were sampled by trawl, 32 by sledge, 22 by grab and 7 by SCUBA diving. According to Soyer's frequency (F) index, E. sepositus was `continuous?, A. mediterranea, A. placenta, C. longispinus, S. affinis, P. regalis, P. lividus and S. reciprocans were `common? and the other 18 species sampled by trawl, 32 species sampled by sledge, 22 species sampled by grab and the other 5 species sampled by SCUBA diving were rare species. The most frequent species were E. sepositus in trawl samplings, C. longispinus in sledge samplings, A. filiformis in grab samplings and P. lividus in the hard substrates.According to the importance values of the species, the first five species were S. affinis, S. granularis, E. sepositus, A. mediterranea, P. regalis in the trawl samplings; H. tubulosa, A. filiformis, H. mammata, P. microtuberculatus, A. mediterranea in the sledge samplings and A. filiformis, E. cordatum, O. ophiura, A. mediterranea ve O. setosa in the grab samplings.Significant differences were found between the stations in the number of echinoderm species sampled by all different sampling methods and in the communities sampled by trawl and sledge. In soft substrates, 30 echinoderm species were found in the station A, 37 in B, 18 in C, 17 in D, 39 in E and 35 in F. In hard substrates 1 species were found in the station 1, 2 in 2, 3 in 3, 5 in 4 and 3 in 7. No echinoderm species was found in the stations 5 and 6. The overall average abundance were high in the stations of B, E, F, A, D, and C in trawl samplings; stations of C, A, B, E, F and D in sledge samplings and E, F, A, B, C, and D in grab samplings, respectively. The overall average biomass were high in the stations of E, B, A, F, D, and C in trawl samplings; stations of C, B, E, F, D and A in sledge samplings and B, E, F, A, C and D in grab samplings, respectively.The lowest species numbers of the stations C and D, located in the Kaleiçi Marina ve Great Harbour of Antalya, in comparison with those of other stations should mainly be attributed to the high anthropogenic effects present in these stations. The low species number of the station A, where is located in the mouth of Manavgat River, should be a result of the very peculiar oceanographic conditions prevailing in the area, especially the low salinities and terresterial material carried by the river to the sea.Significant differences were found between the depth levels in the number of echinoderm species sampled by all different sampling methods and in the communities sampled by trawl and sledge. In soft substrates, 8 echinoderm species were found in the depth of 5 m, 15 in 10 m, 25 in 25 and 50 m, 34 in 75 and 100 m, 26 in 150 m and 19 in 200 m. In hard substrates 3 species were found in the depth of 0-5 m, 2 in 5-10 m, 4 in 10-20 m and 3 in 20-30 m. The reason of the highest species numbers of the depths of 75 and 100 m was found to be mainly related to the high calcium carbonate levels (CaCO3) in these depth levels.The overall average abundance were high in the depths of 75 m, 100 m, 150 m, 200 m, 50 m, and 25 m in trawl samplings; depths of 10 m, 75 m, 100 m, 25 m, 150 m, 50 m, 200 m, and 5 m in sledge samplings and 75 m, 25 m, 100 m, 50 m, 10 m, 150 m, 200 m, and 5 m in grab samplings, respectively. The overall average biomass were high in the depths of 100 m, 75 m, 200 m, 150 m, 50 m, and 25 m in trawl samplings; depths of 10 m, 25 m, 75 m, 200 m, 100 m, 5 m, 50 m and 150 m in sledge samplings and 75 m, 25 m, 100 m, 10 m, 150 m, 50 m, 200 m and 5 m in grab samplings, respectively.No significant seasonal differences were found in the number of echinoderm species and communities sampled by trawl and sledge. However, significant seasonal differences were found in the number of echinoderm species sampled by grab. In all samplings, 45 echinoderm species were found in summer, 43 in autumn, 35 in winter and 43 in spring. The overall average abundance were high in summer, spring, winter, and autumn in trawl samplings; autumn, spring, summer and winter in sledge samplings and summer, spring, autumn, and winter in grab samplings, respectively. The overall average biomass were high in summer, spring, autumn, and winter in trawl samplings; autumn, winter, spring, and summer in sledge samplings and summer, spring, autumn, and winter in grab samplings, respectively.Although many parameters in sea water differ seasonally, no significant seasonal differences were found in the epifauna. However, Ophiuridae, possessing the highest species number and abundance in endofauna, showed seasonal difference and exibited low species number, abundance and biomass in winter.For the echinoderm abundance data in trawl samplings, the model that achieved the lowest value of AIC (and therefore was the best model on the basis of this criterion) had seven variables of environmental parameters (depth, salinity, NH4-N, total CaCO3, %pebble, %mud and %sand (0,5- 0,25mm)) explaining 25.4% of the variability in the data cloud. For the echinoderm biomass data, the best model had six variables of environmental parameters (depth, salinity, NH4-N, total CaCO3, total organic carbon and %pebble) explaining 24,1% of the variability.For the echinoderm abundance data in sledge samplings, the best model had three variables of environmental parameters (dissolved oxygen, %sand (1-0,5mm) and %sand (0,125-0,063 mm)) explaining 8,9% of the variability. For the echinoderm biomass data, the best model had two variables (dissolved oxygen and %sand (0,125-0,063 mm)) explaining 7,1% of the variability.For the echinoderm abundance and biomass data in grab samplings, the best model had two variables of environmental parameters (depth and %sand (0,125-0,063 mm)) explaining 10,3% and 9,5% of the variability, respectively.Echinoderm species constitutes a significant percentage of the benthic biomass. By determining the echinoderm fauna of the Gulf of Antalya and environmental parameters best explaining the changes in the community structures, this study provides a database for the further research and monitoring programmes.