شناسه هاي افزوده :
افرائي بندپي، محمد علي ، همكار طرح , نادري جلودار، مهدي ، همكار طرح , كيهان ثاني، عليرضا ، همكارطرج , نصراله تبار آهنگر، عبداله ، همكارطرج , تهامي، فاطمه سادات ، همكارطرج , لالوئي، فرامرز ، همكارطرج , مرتضائي، رضا ، همكارطرج , پورنگ، نيما ، همكارطرج , صفري، رضا ، همكارطرج , روشن طبري، مژگان ، همكارطرج , خداپرست، نوربخش ، همكارطرج , سالاروند، غلامرضا ، همكارطرج , نظران، مجيد ، همكارطرج , رجبي ساسي، ايرج ، همكارطرج , شكوري، متين ، همكارطرج , رضواني، زيبا ، همكارطرج , رضائي نصرآبادي، علي ، همكارطرج , مكرمي رستمي، علي ، همكارطرج , دشتي، علي ، همكارطرج , عقلمندي، فرهاد ، همكارطرج , احمد نژاد،احد ، همكارطرج , سجادي، اسداله ، همكارطرج , كاردر رستمي،، محمد ، همكارطرج , داودي ، ايوب ، همكارطرج
چكيده انگليسي :
Since, the Caspian Sea has special conditions due to its strategic location, so knowledge of biological groups including phytoplankton, zooplankton and ctenophore will be of particular importance. Because, the Caspian Sea in recent decades has experienced emerging phenomena such as the introduction of non-native species, the flourishing of some species and the decline of commercial fish. Non-native and invasive comb jelly (Mnemiopsis leidyi) is one of the prominent examples of this species that entered the Caspian Sea from the Black Sea in 2000 through the balanced waters. From 2001 to 2009, this animal spread in all areas of the sea with a lot of biomass and after that it remained at a low level.
This study was conducted to investigate the biological groups (plankton and macrobenthos) as primary and secondary producers, biological indicators of water quality and environment during four seasons (autumn and winter 2018, spring and summer 2019) at the 8 semi transects of Astara, Anzali, Sefidrud, Tonekabon, Nowshahr, Babolsar, Amirabad and Turkmen at depths of 5, 10 and 30 meters in the southern Caspian Sea. The aim of this study was to evaluate the distribution, temporal and spatial changes of phytoplankton, zooplankton, macrobenthos and comb jelly as well as species diversity, species richness and species dominance of plankton and macrobenthos and determining biological quality indicators, the interrelationships of planktonic communities in the southern Caspian Sea. Phytoplankton samples were collected by water bottle (Neskin), zooplankton and comb jelly was done using plankton net with the mesh of 100 and 500 microns and 50 cm diameter, respectively. Macrobenthos sampling was also performed by Grab Van dorm of 0.0225 m2.
A total of 125 phytoplankton species were identified beloged to 7 phyla: Bacillariophyta (61 species), Pyrrophyta (21 species), Cyanophyta (15 species), Chlorophyta (16 species), Euglenophyt, (9 species), Chrysophyta, 2 species), Haptophyta (1 Species). Examination of temporal changes in phytoplankton abundance showed the maximum and minimum phytoplankton abundance were in winter with (358±43+106.m-3) and summer (45±7+106.m-3), respectively, showed a decreased from 5 m to 30 m depth (ANOVA, P <0.05). Spatial changes in abundance at different regions (east, middle and west) showed an increase in its amount from east to middle in the southern Caspian Sea. 17 zooplankton species were determined belonged to Copepoda (3 species), Rotifera (3 species), Cladocera antennae (1 species), Protozoa (2 species), Balanidae (1 species), Neridae (1 species), Annelidae (3 species), Nematoda, Chironomidae and Bivalva larvae (1 species each). The mean abundance and biomass of zooplankton were 1767.9±52.03 ind.m-3 and 11.6±3.7mg.m-3, respectively. Maximum abundance and biomass were recorded with 3370.6±1063.0ind.m-3 and 30.7±11.2mg.m-3, while the mimimum was 789.1±204.6 ind.m-3 and 3.2±0.7mg.m-3, respectively. The highest average abundance and biomass of zooplankton were recorded in winter with 3370.6 ±1063.0 ind. m-3 and 30.7±11.22mg.m-3, respectively, while the lowest average abundance and biomass with 789.1±204.6 ind.m-3 and 3.2±0.7 mg.m-3 in summer, respectively (ANOVA, P <0.05).
The dynamics of the total amount of organic matter in the substrate ranged at least 0.78% at a depth of 10 m in Tonekabon in winter to 6.34% at a depth of 30 m in Anzali in summer. Mean (standard error) percentage of organic matter showed the coasts of Gilan had an increasing of average percentage of organic matter from Astara to Sefidrood with a a decreased in Mazandaran (Tonekabon), then an increasing in Nowshahr until in Golestan (Turkmen) showed a decreasing trend. The percentage of sand particles (63-1000µ) and silt and clay particles (<63 µ) showed a normal distribution.
Macrobenthic invertebrates of the southern Caspian Sea belong to 16 species of 8 families belonged to 5 classes of Olygochaeta, Polychaeta, Malacostraca and Hexanauplia, crustacean and Bivalvia in which Crustaceans consited of 65%, polychaetes 24% and bivalves and Olygochaeta with 6%. The mean abundance of macrobenthos showed the lowest and highest densities in Sefidrood and Babolsar of 931±187.1 ind.m-2 and 477±88.2 ind.m-2, respectively. Mean minimum and maximum biomass were recorded in Sefidrood and Turkmen with 0.6±0.2 g.m-2 and 43.6±15.1 g. m-2 with the highest biomass of Cerastoderma glaucum and the highest abundance of Streblospio gynobranchiata (T-test, p<0.05).
The annual average abundance and biomass of Mnemiopsis leidyi were recorded of 12.0±2.9 ind.m-3 and 0.3±0.1 g.m-3, respectively. The highest mean comb jelly abundance was observed in autumn with 21.8±0.8 ind.m-3 and the highest average of biomass was 0.5±0.1 g.m-3. The lowest mean abundance and biomass were 2.5±0.4 ind.m-3 and 0.03±0.0.006 g.m-3 in spring, respectively, which showed a significant difference between abundances and biomasses during different seasons (ANOVA, P<0.05). Seasonally abundance and biomss in different water columns showed the highest in coastal layer (0-5 m). The structure of the length groups (size) frequency of Mnemiopsis leidyi showed comb jelly of less than 5 mm was 64%, 6-15 mm with 14% and the adult (>16 mm comprised approximately 22% of the population. The maximum size of comb jelly was recorded of 35 mm during the whole research period in autumn. Statistic analysis of comb jelly data showed a positive relationship with water temperature (r=0.789, P<0.06) and no relation with salinity (P>0.05). Therefore, with increasing of water temperature in summer, the frequency of comb jelly increases rapidly, and vice versa in winter. Therefore, the highest abundance of M. leidyi was observed in summer with a temperature of 25-30 °C and the lowest at a temperature of 8-10 °C.
