Assessment of wetland landscape changes based on landscape metrics and trophic state index (case study: Anzali International Wetland).

Wetlands play an important role in conserving biodiversity, the hydrosphere's equilibrium, and the maintenance of daily livelihood; therefore, the trophic process hastens the succession procedure in them, resulting in structural changes in the landscape. The study aimed to monitor and investigate the impact of the trophic procedure on landscape structural changes in Anzali Wetland, specifically domains related to vegetation canopy and water bodies, over 24 years. The TSI (trophic state index) of the Anzali Wetland, a vital habitat in the south of the Caspian Sea, was estimated by using the Carlson TSI for 1994, 2002, 2014, and 2018. Based on satellite data for these years, the structural landscape changes were also measured using metrics such as the number of patches (NumP), class area (CA), mean patch size (MPS), and mean shape index (MSI) of the measured patch using in Patch Analyst. The Spearman rank correlation coefficient was then used to calculate the correlation between the two variables of trophic index modifications and landscape metrics. Results showed that the TSI of the wetland touched 59.51 in 1994 and then reached 65.10 in 2018. Its water body area, which was 5283.90 ha in 1994, decreased to 4183.92 ha in 2018, indicating the greatest decrease in the area from 2002 to 2018. In addition, the maximum area of vegetation canopy in 2018 was 11696.31 ha. The trophic exhibited a positive correlation of 0.8 with the area of the vegetation canopy and a positive correlation of 0.4 with the NumP of the vegetation canopy. It also had an inverse correlation of -0.4 with the area and NumP of the water body. Based on the study findings, changes in the trophic level of Anzali Wetland can be regarded as a direct factor influencing the vegetation canopy and water body.

Microplastic Pollution in the Gastrointestinal Tract and Gills of Some Teleost and Sturgeon Fish from the Caspian Sea, Northern Iran.

The increasing microplastic pollution in the marine environment has raised global concern. The main risk of microplastics in aquatic ecosystem is their bioaccumulation in aquatic organisms. A few studies have reported microplastic pollution in the digestive system of Caspian Sea fish species, but there is no research on sturgeon species, nor on fish gills. We investigated the occurrence of microplastics in the gastrointestinal tract (GIT) and gills of 62 specimens belonging to four species including three teleosts (Cyprinus carpio, Rutilus kutum, and Chelon aurata) and one sturgeon (Acipenser persicus, a valuable endangered species) from the Caspian Sea between January and March 2022. Fish tissues were removed, exposed for 24 h to 10% KOH, and then dried on filter paper. Particles were observed under a stereomicroscope and analyzed by Raman microspectrometry, scanning electron microscopy, and energy-dispersive spectroscopy. A total of 91 microplastics were detected in the GIT (average of 1.46 ± 1.17 items/individual) and 63 microplastics in the gills (average of 1.01 ± 0.62 items/individual). A significant correlation was not found between the number of microplastics found in both tissues and fish body length, body weight, GIT weight, and gill weight (p > 0.05), except between microplastics isolated from gills and gill weight in C. carpio (rs = 0.707, p = 0.022). The abundance of microplastics in fish followed the order of A. persicus > C. aurata > R. kutum > C. carpio. The microplastics were in the size range of 45 to 5000 µm, with particles of 300 to 1000 µm being the most prevalent; 74.68% of the particles were shaped like fibers, 30.53% were red, and 70.6% were composed of nylon polymer. Environ Toxicol Chem 2023;42:2453-2465. © 2023 SETAC.

Characteristics and Seasonal Distribution of Microplastics in the Surface Waters of Southwest Coast of the Caspian Sea (Guilan Province, Iran).

The aim of this study was to investigate the occurrence, abundance and distribution of microplastics (MPs) in the southwest coast of the Caspian Sea in four seasons. Three stations were chosen and their surface waters were sampled between April 2019 and February 2020. The average number of MPs was 1.37 ± 0.47 items/m3 and the predominant frequency in different seasons were as follows: summer > autumn > spring > winter. MPs were dominated by fiber in shape. Black and blue were the most common colors respectively. The size was in the range of 0.3-5 mm with a mean of 1.44 ± 1.08 mm. Due to Fourier-transform infrared spectroscopy equipped with attenuated total reflection (ATR-FTIR), four different polymers were identified dominating by polypropylene. The low MP concentrations detected in the present study can be related to lower sewage inlet and more MPs sedimentation in the investigated stations.