Tracking the microplastic accumulation from past to present in the freshwater ecosystems: A case study in Susurluk Basin, Turkey.

Microplastic pollution in aquatic ecosystems has become a global issue in recent years due to its presence everywhere around the world. Although several studies have explored the impact of the accumulation of those small particles in marine environments, comparisons of freshwater systems with marine environments are scarce. In the current study, due to the lack of long-term data on microplastic pollution, we used paleolimnological approaches to acquire the missing information regarding this hot topic. Two short cores were taken from Bursa province in Turkey, which is the center of industrial and agricultural production with many different sectors such as textile and manufacturing. The first core sample was taken from a relatively pristine environment, Lake Uluabat, and the second one was taken from a delta area where all the discharge coming from the basin flowed through to the Marmara Sea. The sediment core from the lake was dated back to the 1960's and the majority of the sample was dominated by fibers. Despite there being no uniform distribution pattern, the number of the microplastics showed decreasing trend after the lake became a Ramsar site. Due to the continuous mixing in the sampling area, there were obstacles via the dating of the Delta core. Nevertheless, the data showed that a high number and variety of microplastics have accumulated over the last decade in the province. This can be interpreted as microplastic pollution reaching the sea directly from the basin. These findings revealed that a plastic chronostratigraphy would give important temporal data regarding the microplastic accumulation in aquatic ecosystems.

Microplastics composition and load from three wastewater treatment plants discharging into Mersin Bay, north eastern Mediterranean Sea.

Copious quantities of microplastics enter the sewage system on a daily basis, and hence wastewater treatment plants (WWTPs) could be an important source of microplastic pollution in coastal waters. Influent and effluent discharges from three WWTPs in Mersin Bay, Turkey were sampled at monthly intervals over a one-year period during 2017. When data from all WWTPs were combined, fibers constituted the dominant particle form, accounting for 69.7% of total microplastics. Although notable oscillations in microplastic particle concentrations were observed throughout the year influent waters on average contained about 2.5-fold greater concentrations of microplastics compared to the effluent waters. An average of 0.9 microplastic particles were found per liter of effluent from the three WWTPs amounting to around 180 × 106 particles per day to Mersin Bay. This shows that despite their ability to remove 55-97% of microplastics, WWTPs are one of the main sources of microplastics to the northeast Mediterranean Sea.

Virgin microplastics are not causing imminent harm to fish after dietary exposure.

Among aquatic organisms, fish are particularly susceptible to ingesting microplastic particles due to their attractive coloration, buoyancy, and resemblance to food. However, in previous experimental setups, fish were usually exposed to unrealistically high concentrations of microplastics, or the microplastics were deliberately contaminated with persistent organic chemicals; also, in many experiments, the fish were exposed only during the larval stages. The present study investigated the effects of virgin microplastics in gilt-head seabream (Sparus aurata) after 45 days' exposure at 0.1 g kg-1 bodyweight day-1 to 6 common types of microplastics. The overall growth, biochemical analyses of the blood, histopathology, and the potential of the microplastics to accumulate in gastrointestinal organs or translocate to the liver and muscles were monitored and recorded. The results revealed that ingestion of virgin microplastics does not cause imminent harm to the adult gilt-head seabream during 45 days of exposure and an additional 30 days of depuration. The retention of virgin microplastics in the gastrointestinal tract was fairly low, indicating effective elimination of microplastics from the body of the fish and no significant accumulation after successive meals. Therefore, both the short- and the long-term retention potential of microplastics in the gastrointestinal tract of fish is close to zero. However, some large particles remained trapped in the liver, and 5.3% of all the livers analyzed contained at least one microplastic particle. In conclusion, the dietary exposure of S. aurata to 6 common types of virgin microplastics did not induce stress, alter the growth rate, cause pathology, or cause the microplastics to accumulate in the gastrointestinal tract of the fish.

Microplastic litter composition of the Turkish territorial waters of the Mediterranean Sea, and its occurrence in the gastrointestinal tract of fish.

Microplastic pollution of marine environment is receiving increased publicity over the last few years. The present survey is, according to our knowledge, the survey with the largest sample size analyzed, to date. In total, 1337 specimens of fish were examined for the presence of plastic microlitter representing 28 species and 14 families. In addition, samples of seawater and sediment were also analyzed for the quantification of microplastic in the same region. Samples of water/sediment were collected from 18 locations along the Mediterranean coast of Turkey. 94% of all collected plastic microlitter from the sea was in the size range between 0.1 and 2.5 mm, while the occurrence of other sizes was rare. The quantity of microplastic particles in surface water samples ranged from 16 339 to 520 213 per km2. Fish were collected from 10 locations from which 8 were either shared with or situated in the proximity of water/sediment sampling locations. A total of 1822 microplastic particles were extracted from stomach and intestines of fish. Majority of ingested particles were represented by fibers (70%) and hard plastic (20.8%), while the share of other groups: nylon (2.7%), rubber (0.8%) and miscellaneous plastic (5.5%) were low. The blue color of plastic was the most dominant color. 34% of all examined fish had microplastic in the stomach. On average, fish which had microplastic contained 1.80 particles per stomach. 41% of all fish had microplastic in the intestines with an average of 1.81 particles per fish. 771 specimens contained microplastic in either stomach and/or intestines representing 58% of the total sample with an average of 2.36 particles per fish. Microplastic was found in all species/families that had sample size of at least 2 individuals. The number of particles present in either stomach or intestines ranged between 1 and 35. Ingested microplastic had an average diameter ±SD of 656 ± 803 µm, however particles as small as 9 µm were detected. The trophic level of fish species had no influence whatsoever on the amount of ingested microplastic. Pelagic fish ingested more microplastic than demersal species. In general, fish that ingested higher number of microplastic particles originated from the sites that also had a higher particle count in the seawater and sediment.