From lake to fisheries: Interactive effect of climate and landuse changes hit on lake fish catch?

Global warming and unpredictable nature possess a negative impact on fisheries and the daily activities of other habitats. GIS and remote sensing approach is an effective tool to determine the morphological characteristics of the lake. The present study addresses the interactive effect of climate and landuse changes hit on fish catch in lake fisheries. We used a combination of the landscape disturbance index, vulnerability index, and loss index to construct a complete ecological risk assessment framework based on the landscape structure of regional ecosystems. The results indicate an increase from around 45%-76% in the percentage of land susceptible to moderate to ecological severe risk in the landscape from 2004 to 2023. Since 1950, temperature changes have increased by 0.4%, precipitation has decreased by 6%, and water levels have decreased by 4.2%, based on the results. The results indicate that landuse, water temperature, precipitation, and water depth significantly impact the aquaculture system. The findings strongly suggest integrating possible consequences of environmental change on fish yield for governance modeling techniques to minimize their effects.

Microplastics abundance, distribution and composition in surface waters, sediments and fish species from Amir-Kalayeh Wetland, Northern Iran.

Microplastics (MPs) pollution is considered as a globally pervasive threat to aquatic ecosystems and many studies reported this pollution in different aquatic ecosystems. However, studies on MPs pollution in wetlands are still scarce. Therefore, the aim of present study was to investigate the presence of MPs in the surface water, sediment and different fish species of Amir-Kalayeh wetland, Northern Ian. Surface water and sediment samples were collected from six stations during June to July 2022. Moreover, the gills and gastrointestinal tract (GIT) of 54 fish specimens belonging to four species including Cyprinus carpio, Tinca tinca, Esox lucius and Silurus glanis were analysed. MPs were detected in all samples with an average of 2.15 ± 1.98 items/m3 for surface water, 51.66 ± 32.20 items/kg dry weight for sediments, 0.17 ± 0.17 items/individual for fish GIT and 0.12 ± 0.12 items/individual for fish gills. There was no significant relationship between MPs abundance in surface waters and sediments as well as between MPs abundance in environmental matrices and fish (P > 0.0.5). In terms of feeding habit, no significant differences were observed between the number of MPs found in omnivorous and carnivorous fish species (P > 0.05). Moreover, no significant relationship was detected between the MPs abundance in fish tissues and body size (P > 0.05). MPs were mainly fibers, mostly transparent, and in a range size of 70-5000 µm. The dominant MPs type was nylon in all samples. This study will help increase our knowledge about MPs pollution in inland freshwater systems and suggests that management policies take essential steps to reduce this insidious problem in freshwater ecosystems.

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.

Spatial distribution of microplastics pollution in sediments and surface waters of the Aras River and reservoir: An international river in Northwestern Iran.

Microplastics (MPs) in freshwater environments have been recognized as one of the important sources of plastic contamination in marine ecosystems. Reducing the amount and spatial distribution of MPs reaching the sea through accumulation behind dams remains unclear. In this study we analyzed the spatial distribution of sediment and surface water MPs in the Aras Dam and from nineteen upstream and downstream locations of the Dam in the Aras River. The MPs abundance ranged from 32 to 528 items/kg dry weight (mean 217.8 ± 132.6) and 1 to 43 items/m3 (mean 12.8 ± 10.5) in the sediment and surface water stations, respectively. MPs abundance in surface waters collected within the Dam reservoir was significantly higher than those found either upstream or downstream (P < 0.05). For sediments, reservoir MPs concentration was generally higher than upstream and downstream, although their differences were not significant. High MPs concentration was observed in the vicinity of urban areas. Moreover, MPs abundance was positively correlated with total organic carbon (TOC) and clay content (P < 0.01). GAM analysis revealed that clay is the most important variable with lowest Akaike information criterion (AIC) and explained 61.3 % of deviance (R-sq.(adj) = 0.344) in MPs abundance. MP particles ranged from 0.1 to 5 mm in size and were dominated by fibers (53.5 %), black color (24 %) and PE polymer (36.6 %). Our results highlight the high MPs distribution in the Aras River and demonstrate that they accumulate in the surface waters behind the Dam. Consequently, the fate and effects of MPs in international rivers is one of the most politicized issues between countries with a common boundary and therefore needs joint management policies that help mitigate this insidious problem.

Assessing the relationship between the abundance of microplastics in sediments, surface waters, and fish in the Iran southern shores.

The purpose of this study was to investigate the microplastic (MP) pollution in sediments, surface waters, and four fish species in the northern coast of the Persian Gulf. Sampling was conducted in seven important regions during December 2019. The abundance of MPs was respectively 190 ± 35.5 items/kg dry weight for sediments, 9.28 ± 2.1 items/km2 for surface waters, and 0.33 ± 0.05 items/individual for fish. There was no correlation between MP abundance in surface water, sediment, and fish samples. Except for Cynoglossus arel, abundance of isolated MPs did not show significant relationships with body weight, body length, and gastrointestinal tract weight (P > 0.05). MPs were ranged from 0.3 to 5 mm in size and were prevailed by fiber in shape; black, red, and blue in color; and polypropylene and polyethylene in polymer. This study may help in increasing our knowledge regarding MP pollution in marine water systems and biota.

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.

Microplastics in different tissues of some commercially important fish species from Anzali Wetland in the Southwest Caspian Sea, Northern Iran.

The aim of this study was to investigate the occurrence of microplastics (MPs) in the gastrointestinal (GI) tract, muscle and gonads of 193 individuals of nine commercially-important fish species from Anzali Wetland between May and July 2018. Tissues were removed, digested by 10% KOH for 24 h at 60 °C, filtered on cellulose nitrate filter and then dried. MPs were found in all tissues. There were significant differences between the numbers of isolated particles from GI tract and control groups (procedural blank containing Milli Q water without tissue), while their abundance in the muscle and gonads did not display significant differences with control groups. Higher abundances of MPs were recorded in omnivorous fish (2.26 ± 2.93 items/individual) than carnivorous species (1.10 ± 1.10 items/individual) (P < 0.05). MPs were ranged from 20 to 4800 µm in size and were dominated by fiber-like in shape, polyethylene in polymer and black in color.

Identification and distribution of microplastics in the sediments and surface waters of Anzali Wetland in the Southwest Caspian Sea, Northern Iran.

The occurrence, abundance and distribution of microplastics (MPs) were studied in sediments and surface waters of the Anzali coastal wetland, southwest of the Caspian Sea. Sediment and surface water samples were taken at 11 and 6 stations in June 2018 and January 2019 respectively. The abundances of MPs in sediment samples were 140-2820 and 113-3690 items/kg dry weight while in surface waters were 0.40-4.41 and 0.19-2.85 items/m3 in June and January respectively. Fiber was the most common shape, followed by fragment and film. Red, black and blue were the most frequent colors. Particles 1-2 mm were the dominant size. SEM/EDS and ATR-FTIR analyses were used to identify MPs. Polypropylene, polyethylene and polyester were the most frequently found polymers. Our results highlighted the widespread dispersion of MPs in Anzali Wetland which in turn might be a pathway of MPs pollution transporter to the adjacent and connected Caspian Sea.