Different land uses influenced on characteristics and distribution of microplastics in Qarasu Basin Rivers, Gorgan Bay, Caspian Sea.

Concerns about the negative effects of microplastics (MPs) on human health have led to increasing attention to the occurrence of MPs in the aquatic environment. Recent studies have focus on the spatio-temporal distribution of MPs in rivers for residential and agricultural areas. Qarasu River Basin, watershed to Gorgan Bay, is the site of many permanent rivers and the levels of MP pollution in those rivers are unknown. This research was conducted in three different types of land use: forest, residential, and agricultural along 8 different rivers. A total of 9 fish species were identified and the presence of MPs in 87% of fish was confirmed. The prevalence of MP among species was Liza sp. > Carassius gibelio > Gambusia holbrooki > Rutilus rutilus > Neogobius melanostomus > Cyprinus carpio = Vimba vimba > Rutilus frisii > Barbus sp. The highest frequency of MPs was observed in Qarasu River (1880 ± 251 n/kg) and Mohammadabad River (184 ± 1340 n/kg) in agricultural land use, and the lowest frequency was related to Baghu and Ziarat Rivers with 660 ± 77 and 600 ± 91 n/kg found in forest land use respectively. The highest type, color, and size of MP sediments were fragment, black, and 1-2 mm, respectively. The highest type, color, and size of MP in fishes were fiber, black, and 0.5-0.1 mm respectively. Overall according to the source tracing result, agricultural land use was the main source of MP pollution of Gorgan Bay. The Bay is strongly affected by the incoming rivers, the Qarasu River Basin as the most important river supplying water.

Optimization of macrophage isolation from the Persian sturgeon and the Caspian kutum fish: a comparative study.

The aim of this research was a comparative study on the isolation and culture of head kidney macrophages derived from Acipenser persicous and Rutilus frisii kutum as teleost and chondrostei species of fish. The macrophages were isolated by density gradient sedimentation, followed by adherence to a plastic surface. They exhibited strong phagocytic activity against bacteria. The effect of cell density, incubation time, FBS percentage, pH and temperatures on the cell number and viability were determined and compared. Also, the effect of light/dark regimen on viability, adherence, release of reactive oxygen species (ROS) and nitric oxide (NO) in the macrophages was determined. The results showed that the Caspian kutum macrophages were more sensitive to FBS percentage and cell density whereas the Persian sturgeon macrophages were more sensitive to pH of the cell culture media. The adherence and viability of the macrophages from both fish species firstly increased (P < 0.05) after exposure to a light/dark regimen, but then significantly decreased as did ROS and NO productions. For the first time, this study has determined the optimal conditions for primary culture of macrophages derived from sturgeons, and shows the unique effect of light on the biology of fish immune cells.