r. patimar

Diatom species diversity and cell abundance are influenced by environmental factors. The effect of physico-chemical factors on interseasonal dynamics of planktonic diatom community structure was examined along Noor shore of Caspian Sea to determine which of the variables impact more on the diatom diversity, distribution and cell number. Overall, 144 samples were collected during four sampling campaigns along four transects of 2 km long each with three sampling sites in 2014 (February, May, July and November). In total, 62 diatom species were identified, of which 27 species were typical marine or brackish-water and the rest were marine-freshwater or freshwater. In the present study, diatom species diversity was highest in winter. As a result, Shannon-Wiener Index was 3.5 in winter, while in spring it was reduced to 0.8. Among the revealed species, the centric Thalassiosira caspica was the most abundant (up to 2.75×106 cells L-1). Comparison of species and their abundances between coastal, middle and offshore stations, as well as all stations as a whole, showed that they differed (Test χ 2, p<0.05) except for Navicula sp. (in summer) and Ulnaria ulna (in autumn and winter). Canonical correspondence analysis results showed that in particular temperature and salinity, in the second place transparency, phosphates and to a lesser extent dissolved oxygen and pH can affect diatom species diversity and abundance. Diatoms Thalassiosira fasciculata, T. caspica and Melosira caspica may be recommended as biological indicators along the shore of Caspian Sea.

The problem of pollution in the Caspian sea has attracted increasing scientific concerns in recent years, but still, there is limited data relevant to the Gorgan bay. The current study aimed to evaluate the organic pollution of the Gorgan Bay, using Palmer Algal Index. Sampling was conducted seasonally in triplicate from summer 2017 to spring 2018. Phytoplankton samples were collected from surface water (maximum depth of 50cm), using a one-liter sampling bottle and fixed in 2.5% formaldehyde buffer solution. A total of 23 stations were selected including, seven stations in the eastern areas, eight stations in the centre, and eight stations in the western part of the bay. The Palmer Index indicated that all parts of the bay are highly polluted, in the four seasons. Comparison of the index among the three parts of the bay indicated that the central areas are more polluted than other areas in the three seasons, from summer to winter, while only in the spring, the western area of the bay showed the highest value of the index. The predominance of the pollution resistant Phyto-genera such as Oscillatoria, Euglena, Cyclotella, Navicula, Nitzschia, and Synedra supports the classification of the bay as eutrophic. Generally, the results of the algal index revealed that the water quality of the bay has reached a critical level.

A study in order to evulated to do the effects of different levels of organic carbon supplement on biofloc formation, inorganic nitrogen and phosphat situation, feed efficiency and growth performance of common carp (Cyprinus carpio) in biofloc system for 42 days. After of acclimatization period, 180 common carp fingerlings with (weight average ± SD, 5/78 ± 0/10 g) were stocked in roundel tank with water capacity of 40 l. Determain of C/N different ratios 15:1 (CN-15) and 20:1 (CN-20) were determined by the content of C/N in commercial feed and the amount of carbon in wheat meal that it was daily used to experimental treatments. Wheat meal don’t added to control treatment (≈ C/N ratio, 10:1). Increasing of carbon to nitrogen ratio was increased water quality parameters such as turbidity, total suspended solid (TSS), total dissolve solid (TDS), Biochemical oxygen demand (BOD), alkalinity and nitrat concentration, but it was decreased total ammonia nitrogen (TAN) and phosphat during the experimental period (p<0/05). Water exchange was reduced 50 % in biofloc treatments than control. Growth performance of common carp fingerlings in different treatments indicated that the fingerlings of CN-15 treatment had the highest of body wieght, specific growth rate, protein efficiency rate (PER) and the lowest of feed conversion rate then both of CN-20 and control treatments. The results of this study suggest that carbon to nitrogen ratio 1:15 a positive impact on water quality parameters, improve food consumption and growth performance of common carp in biofloc system and reduces the amount of water Consumption in the system.

In present research biomass, frequency and distribution of macrobenthos in Gorgan Bay was studied in 8 stations in 4 seasons in 2009. Sampling was done by Van Ven Grab in 3 replicates in each station. Identified macrobenthos belonged to 13 families. The most abundant family was Ampharetidae (76%) compared to total population of macrobenthos. Balanidae (10%), Cardiidae (6%) and Nereidae (4%) had the next abundance. Maximum biomass of macrobebthos was observed in Cardiidae (45%), Balanidae (44.78%), Nereidae (5.8%) and Tubificidae (5.27%), respectively. The greatest frequency of macrobenthos was found in spring with 4110/m2 and the least was in winter with 29.25/m2. Maximum and minimum of biomass was observed in spring (33.568 g/m2) and winter (.080 g/m2) respectively.

In this study, some of biological parameters of Vimba vimba from February 2009 to June 2010 were examined. In total, 281 fish samples were caught by gill- net. In two regions had of five age groups that, the most frequent age groups were related to 2+. Sex ratio of male to female were in Gorganrud population 67% ♂ to 33% ♀ and in Mahmoudabad population 57% ♂ to 43% ♀ (p 0.05). There was no significant differences (p>0.05) between the average length and weight of the two populations,. Growth pattern for populations of Gorganrud and Mahmoudabad were negative allometric and isometric, respectively. Within the two populations, the asymptotic length (L∞) in males was higher than females, but the growth rates (K) in females were relatively higher. Mean absolute fecundity in Gorganrud and Mahmoudabad populations were 11970.8±8381/03 and 6728.49±2488.5 eggs per fish, respectively. There was significant difference between the two populations (p≤0.05) in mean absolute fecundity, average egg diameter and condition factor. The results showed that, in many biological parameters, there were significant differences between the two populations due to environmental differences in two regions.

During the study, which was conducted to determine fish species diversity in coastal areas of the Gomishan wetland on the basis of twice per season from autumn 2006 to summer 2007, 13555 specimens belonging to 15 species and 8 families were caught. Total diversity and frequency of species and frequency of each species were different among the seasons. Atherina boyeri was dominant in spring, summer and winter, Gambusia holrooki in autumn. Alburnus albulnus had the lowest quantitative abundance in the study area. Out of six Gobiid fishes, Neogobius fluviatilis and Bentophilus stellatus showed the highest and the lowest abundance respectively. In the coastal areas of the Gomishan wetland, the highest Shanon and diversity indices were observed in winter, the highest richness index in spring and the highest evenness index in winter.