فصلنامه بوم شناسی آبزیان
سال دوازدهم شماره 1 (پیاپی 44، تابستان 1401)

One way to reduce the use of chemical fertilizers without harming plant nutrition and increase the absorption of nutrients in crops is to use biostimulants. Seaweed extracts is one of the plant biostimulants that is used in agricultural systems because of their potential for improving nutrient use efficiency, resistance to stressors, and product quality. In this study, the effects of aqueous extract of a green  macroalgae (Ulva flexuosa) and a brown macroalgae (padina) at four levels (dilutions 5, 10, 20 and 40%) as well as NPK chemical fertilizer at one level (concentration 0/625 mg/ml) on the growth of basil (Ocimum basilicum L.) was examined for 45 days. The results showed that the effect of brown algae extract on germination was more significant while 5% dilution of green algae increased plant root length. Treatment with both green and brown macroalgae extracts improved biochemical parameters. The highest amount of chlorophyll, carotenoids and anthocyanins was observed in dilution of 20% and the highest amount of flavonoids, phenol and reducing power was observed in 10% dilution of brown macroalgae extract.

In recent years, Kani Borazan wetland in Mahabad has been at risk due to the drought crisis in the watershed of Urmia Lake, which mostly connected with human societies. Considering the importance of this environmental issue as well as the lack of grounded data using remote sensing technology and geographic information system, changes can be made in the region. Four Landsat 8 satellite images during 2013 to 2016 were investigated.for this purpose. The NDVI maps analysis was done within ArcGIS. Finally, small changes in the water range, dense vegetation, poor vegetation (marshland) have been estimated over the past four years. The results showed that vegetation cover increased in 2016 compared to 2013, while wetland area has decreased in recent years. Wetlands are indicator of climate change in a region. Due to the decrease in the extent and water level of the wetland, it is suggested that more precise conservation plans be applied to reduce and control water consumption in the catchment area of the area. It is also necessary to provide sustainable vegetation monitoring in the wetland.

In the present study, the effects of startup and addition of ammonium chloride (NH4Cl) and sodium nitrite (NaNO2) salts for 4 weeks before fish stocking on efficiency of biofilter for removal of total ammonia nitrogen (TAN) from water, survival rate, growth performance, ammonia metabolizing and urea cycle enzymes activities as well as mucosal immunity of African cichlid (Labidochromis lividus) fingerling. The experimental unit was a recirculating aquaculture system (RAS) with water holding capacity of 200 L in which 20 fingerling fish with average weight of 3.06±0.07 g were stocked and cultured for 30 days. The experimental groups included the RAS without startup and adding salts (control, group 1), startup of RAS before fish stocking (group 2) and startup RAS with adding salts (group 3). Water from each experimental unit was sampled after 0, 10, 20 and 30 days of fish stocking. The results showed that the TAN concentration in the groups 2 and 3 was significantly lower than the control group (P<0.05). Nitrate concentration in the groups 2 and 3 was higher than the control group (P<0.05). The highest nitrate concentration was observed in the group 3 (P<0.05). Growth performance including final weight, weight gain, specific growth rate (SGR%), daily growth index (DGI) and body weight increase (BWI%) were higher in the groups 3, 2 and control, respectively (P<0.05). The food conversion ratio (FCR) in the groups 2 and 3 was lower than the control (P<0.05). The activities of glutamate dehydrogenase, glutamine synthetase and ornithine carbamyl transferase enzymes in liver and muscle tissues increased in the control and group 2 compared to the group 3 (P<0.05). The total immunoglobulin, lysozyme and alternative complement pathway activity (ACH50) of skin mucus increased in the groups 2 and 3 compared to the control; the highest levels were observed in the group 3 (P<0.05). The findings indicate that the startup of RAS with the addition of salts before fish stocking can be an effective way to improve the efficiency of biofilter in converting water ammonia to nitrate, survival rate, growth performance and health of the fish.

Deltas of Rud-e-Shur, Rud-e-Shirin and Rud-e-Minab, consisting of mangroves and coastal mudflats, is one of the most important bird habitats on the shores of the Persian Gulf and are protected as an international wetland. In this study, a list of weland birds was prepared based on the data of the results of the semi-winter census of waterbirds, expert reports and field studies. Also, the trend of changes in the waterbird population in the period of 1988-2021 was calculated using the TRIM statistical package with the possibility of application in R ver3.6.3 software called RTRIM. The results showed that, a total of 156 species of 97 genera, 45 families and 18 orders including 98 species of waterbirds, 21 species of prey and 37 species of terrestrial species were identified. The population of waterbirds has a strong increase with a slope of 7.7% per year. In the last ten years, a moderate decline in population has been recorded with a slope of -4.1% per year. The average population of waterbirds in the wetland was 15,479 ± 2,669 and the average number of species was 41.6 ± 3.39. The largest population was in 2019 with 54,356 individuals and the highest number of species was in 2005 with 64 species. Although annual population fluctuations and diversity depended on census-related factors such as program support, bird-watching tools, number of sites, census coverage levels, and the experience of bird counters, the impact of habitat threats such as overfishing aquaculture and the increase in environmental pollution have also increased in recent years. A program to increase stakeholder awareness and strengthen participatory conservation can be effective in reducing wetland threats.

In this study, frequency and diversity of benthic foraminifera of 44 samples from a 14C dated sediment core were used to assess the effects of human activities on pollution and creating hypoxic conditions in coastal sediments of Bandar Abbas. The results showed that during the last century, the construction of coastal infrastructures and expansion of the city caused 5% elevation of  sand input to the area. Variations of frequency and diversity of benthic foraminifera during the last decades also follows the above-mentioned changes. During the recent decades, the relative abundance of opportunistic hyaline taxa such as Cribroelphidium, Asterorotalia and Ammonia, and also conical species such as Bolivina and Bulimina which show higher ability to survive in polluted environments with lower oxygen content increased 100 to 200%. On the other hand, more than 150% reduction of species with thicker walls (Milliolids such as Massilina and Quinqueloculina) in this time show the intense environmental changes caused by human activities in coastal areas of Bandar Abbas. Altogether, significant increase in sewage runoff due to urban and industrial development of Bandar Abbas has had a great impact on the coastal ecosystem of the city, which should be mitigated by taking the right management decisions

Silver carp, Hypophthalmichthys molitrix, is a plankton filter feeder fish and introduced to Chitgar Lake since 9 years ago. In this study, the effect of silver carp stocking was evaluated on the phytoplankton structure of Chitgar Lake at different seasons in 2018. Samples were caught with gill-net, beach seine and cast-net gears. The results obtained from 51 individuals with a total length of 111-473 (average total length of 325.8±134.6) mm showed that coefficient of vacuity, averages of relative gut length and feeding intensity were 0.00%, 5.91±1.65 and 628.4±274.7, respectively and therefore it showed over eating, herbivory and good feeding intensity in this fish. Silver carp fed on 32 phytoplankton and 11 zooplankton genera and phytoplankton and zooplankton were observed in 100% and 88% of studied specimens, respectively. Synedra, Navicula, Staurastrum and Cyclotella were the dominant phytoplankton genera (30.0, 22.2, 13.8 and 12.1%, respectively) and Bosmina and Alona were the dominant genera of zooplankton (84.0 and 7.2%, respectively). There were no seasonal changes in feeding intensity but there were seasonal changes in food items dominance. Releasing of 20000-30000 individuals of silver carp with a weight 50-100 g is suggested in order to protect water quality of Chitgar lake annually.

Gashtrudkhan River is located in the western drainage basin of Guilan Province. Monthly sampling of macroinvertebrates was carried out in five stations by using a surber sampler with Dimensions of 30.5 cm ×30.5 cm and 360 micron mesh size for eight months in different seasons from autumn 2019 to spring 2020. Moreover, some physicochemical parameters of water, i.e., pH, EC, TDS, DO, temperature and salinity were measured, so that these parameters showed significant differences in different seasons. In addition, diversity indices (Simpson and Shannon), species richness, EPT, EPT/Chir, biological indices (Hilsenhoff and BMWP) and the WQI index were studied and calculated. During the sampling period, a total of 1017 macroinvertebrates were isolated and identified from different stations, belonging to one Phylum, one Kingdom, four orders, 19 families and 22 genera in this river. EPT and EPT/CHIR indices were the highest in spring and the lowest in winter. Also, the highest and lowest values of Shannon's diversity and species richness indices were observed in autumn and spring, respectively. The water quality status in the studied period was classified as good to excellent based on the Hilsenhof biological index. Furthermore, the water quality status was evaluated based on the BMWP and WQI indicators as clean and average, respectively. According to the investigated area in Gashtroudkhan River, located in a forest area with gravel and stone beds, no significant differences were observed in many of the studied indicators.