چكيده انگليسي :
Abstract:
The phytoplankton, zooplankton, Macrobenthos and ctenophore Mnemiopsis leidyi with Physico-chemical parameters and pollutants of water were investigated in the Caspian Sea during 2007-2008. The sample station located between 48°to° 54° longitude and 36° to 39° latitude. The samples were gathered in four seasons and eight transects (half-line perpendicular to the coast) in Astara, Anzali, Sefidrud, Tonekabon, Noshahr, Babolsar, Amirabad and Turkmen. Sampling was done of 5, 10, 20, 50 and 100M depth of different layers. Nonparametric test and multivariate analysis (PCA) were used for statistical methods.
Physico-chemical factors: The results showed that the changes of physico-chemical factors, includes: water temperature, salinity, organic nitrogen and inorganic nitrogen (ammonium) are most important than other factors. The lowest sea surface water temperature was recorded in winter (7.2 oC) and highest in summer (29.8 oC) (p<0.05). However, there was not significant difference at 50 and 100m depths in different seasons (p>0.05). The lowest salinity was recorded in winter (10.42±0.14ppt) (p<0.05) and the rest of the seasons, there was not significant difference (p>0.05). The most inorganic nitrogen was determined (ammonium ion: 40.8±2 µg.l-1) in winter and the highest organic nitrogen (660.6±92 µg.l-1) in summer (p<0.05). The concentration of inorganic nitrogen was evident from the surface layer to a depth of 100 meters (p<0.05), but this trend was not observed in inorganic nitrogen (p>0.05).The maximum concentrations of total nitrogen were measured at the near-shore stations (640.6±28 µg.l-1). The annual average water transparency was 4.91±0.24 m and increased in away from the beach (p<0.05).
Phytoplankton: in total, 191 species of phytoplankton were identified. The phylum of phytoplankton include: Bacillariophyta with 97 species (50.8%), Chlorophyta with 28 species (14.7%), Pyrrophyta with 26 species (13.6%), Cyanophyta with 25 species (13.1%) and Euglenophyta with 15 species (7.9%). Bacillariophyta and Euglenaphyta were had the most (51.49%) and the lowest (0.39%) abundance respectively. Nevertheless, Pyrrophyta and Chlorophyta were having the most (53.14%) and the lowest (0.54%) biomass respectively. Mean abundance and biomass of phytoplankton in the photic and the aphotic layers were a significant difference (p<0.05). The average abundance and biomass decreased with increasing depth (p<0.05). The most abundant and biomass phytoplankton was determined in the photic layer. Abundance and biomass of phytoplankton in the different seasons have been significant differences (p<0.05).The most abundance of phytoplankton was in winter, fall, summer and spring respectively (p<0.05) and the most biomass of phytoplankton was in winter, fall, spring and summer respectively (p<0.05).
Zooplankton: Also, 14 species of zooplankton include: 2 species of Copepoda, 5 species of Rotatoria, 2 species of Protozoa, 3 species of Cladocera, 2 species of newborn and larvae of Balanus and larvae of Bivalvia from meroplankton group were identified. However, the dominant zooplankton population was divided into three groups of copepoda, Rotatoria and meroplankton. Mean abundance and biomass of zooplankton in different seasons and layers showed significant different (p<0.05). The most abundance and biomass of them in winter and the photic layer was determined. The mean abundance of Rotifera, Cladocera and protozoa in different depth was having not significant differences (p>0.05). However, there was significantly in other groups (p<0.05). The most abundance of them was in photic layer.
Ctenophore: Average abundance and biomass of Mnemiopsis leidyiwere recorded 63±7 ind.m-3 and 7.70±2.34 g.m-3, respectively. The maximum seasonal average of abundance was 150 ± 17 ind.m-3 while the maximum biomass was 26.59± 4.61 g.m-3 in summer (p<0.05). The lowest seasonal average of M. leidyi abundance and biomass were in the winter (6±2 ind.m-3 and 0.07±0.02 g.m-3, respectively) (p<0.05).The average annual abundance and biomass of ctenophore were not significant difference in the 8 transects (p>0.05). The maximum of ctenophore abundance and biomass were belonged to the depth of low than 20m (p<0.05). The maximum of ctenophore abundance and biomass were recorded in the 5m depth of Anzali with 639 ind.m-3 and 158 g.m-3, respectively.
Results of biological and non-biological factors showed that significant changes between euphotic and aphotic layers (p<0.05).There were the most seasonal changes in the euphotic layer. The results showed that the presence of ctenophore is highly related to the presence of the zooplankton and phytoplankton and some non-biological factors. The water temperature is a limiting factor in the ctenophore Fluctuation at the winter, because of food presence (phytoplankton, zooplankton and Nutrients), M. leidyi have had the lowest abundance.
Macrobenthos: Three phyla of macrobenthos (arthropoda, annelida and mollusca) include: 5 classes (crustacea, insecta, polycheata, oligocheata and bivalvia), 8 orders, 11 families, 26 genera and 24 species were identified. The most abundance and biomass of orders in the different seasons were belonged to polycheata (annual average: 2452±258 g.m-2) and bivalvia (annual average: 25±6 g.m-2), respectively. Macrobenthic abundance in all orders except insecta and oligocheata in different seasons was significant difference. The amount of seabed total organic mater (TOM) from the 5m to 100m stations was with an increasing trend and the highest percentage had in the 50m and 100m stations (P<0.05). The percentage of seabed TOM was not significant difference in the different transect (P<0.05). However, seabed grain size had significant difference (P<0.05) and seabed grain size from the 5m to 100m stations was with a decrease trend in the size (P<0.05). Macrobenthos and physico-chemical parameters of correlation matrix showed that macrobenthos abundance in the between parameters have a positive correlation with TOM. However, it biomass with pH (positive), inorganic phosphorus (positive) and organic phosphorus (negative) have a correlation.
Heavy metals: The levels of heavy metals (Cd, Cr, Cu, Fe, Pb, and Zn) of water had lower than standard and acceptable for aquatic life. Significant accumulation of metals such as Co, Cu and Cr in the sediment was observed at transect Sefidrud and Anzali and Ni at transects Sefidrud and Astara in comparison with six other transects (P<0.05).
Petroleum compounds (16PAHs): Concentration levels changes of petroleum compounds in seawater in different seasons was significant (P<0.05) and in seasons of spring, summer, fall and winter was 56.5, 9.3, 14.9 and 19.3 of percent respectively. However, the concentration values in sediments of the sea in different seasons and transects were not significant difference. Maximum concentrations in summer and in Astara transects (8.02 mg.kg-1) were determined. In correlation matrix, observed positive correlation between petroleum compounds and Cr, Ni and Pb in sediments of seabed and between petroleum compounds and Zn in seawater.
Organochlorine pesticides (OCPs): The OCPs concentration of seawater in different seasons had significant difference (p<0.05). The pesticides groups of DDT, BHC, Drin and Endosulfan in seawater in different seasons had significant difference (p<0.05), but, it was not found in Heptachlor group (p>0.05). The maximum concentration values of OCPs in all groups in seawater were determined in winter (99%) (p<0.05). The seawater OCPs concentration in comparison of regional and stations were not had significant differences (p>0.05). The only DDT group in the seabed sediment had significant difference in different seasons (P<0.05) and the maximum of seasonal average, it was determined in summer (Average: 0.88±062 mg.Kg-1 and Max: 4.5 mg.Kg-1). However, in comparison of regional were not had significant differences (p>0.05). In correlation matrix, the groups of Endosolfan and Drins in seawater and sediment were had equal variance and the changes were included. There was high correlation of between Endosulfan and Drin with DDT group in seawater and with Heptachlor group in the sediment of seabed.
Surfactant: Mean surfactant concentration (LAS) between different seasons had significant difference (P<0.05). The maximum concentrations of LAS were in spring and summer (Anzali transect) was 0.084 mg.l-1 and 0.082 mg.l-1, respectively. Also, average concentrations in the spring: 0.06±0.003 mg.l-1, summer: 0.059±0.004 mg.l-1, winter: 0.042±0.003 mg.l-1 and fall: 0.031 ± 0.013 mg.l-1 was determined. Nevertheless, there was no significant difference in the study area and station (p>0.05). Based on existing standards, Surfactant concentration in the southern Caspian Sea region was not critical
