Attention towards microplastic (MP) pollution in various environments is increasing, but relatively little attention has been given to the freshwater-riverine environment. As the biggest city in the eastern Indonesia region, Makassar can be a potential source of MP pollution to its riverine area. This study aimed to determine the spatial trends, seasonal variation, and characteristics of MPs in the water and sediment of Tallo River, as the main river in Makassar. Water samples were collected using a neuston net and sediment samples were collected using a sediment corer. The samples collected contained MPs with an abundance ranging from 0.74 ± 0.46 to 3.41 ± 0.13 item/m3 and 16.67 ± 20.82 to 150 ± 36.06 item/kg for water and sediment samples, respectively. The microplastic abundance in the Tallo River was higher in the dry season and tended to increase towards the lower river segment. Fragments (47.80–86.03%) and lines (12.50–47.80%) were the predominant shapes, while blue (19.49–46.15%) and transparent (14.29–38.14%) were the most dominant color. Polyethylene and polypropylene were the common MP polymers found in the Tallo river. Actions to prevent MP pollution in the Makassar riverine area are needed before MP pollution becomes more severe in the future.

There is growing awareness and concern on microplastics pollution in marine environments. Seagrasses are among the most productive shallow water ecosystems, serving a diverse assemblage of fish and invertebrates. Sediment and benthic animal samples collected from small islands at Spermonde archipelago confirmed the presence of microplastics with different levels of contamination. The occurrence of microplastics for up to 28.29% and 25% of contamination level in sediments and benthic animals, respectively, clearly indicated an alarming state of the microplastics pollution in rich and productive shallow water seagrass ecosystem of tropical seas. Moreover, all positively contaminated microplastics of benthic animals are for human consumption and therefore pose threats for microplastics transfers which may facilitate pathways for a wide spectrum of organic pollutants entering the food web and affecting human health.

Microplastic pollution is so widespread and rising a great concern all over the globe. The seagrass ecosystem is commonly known to play significant roles in biodiversity support. The occurrence of microplastics (MPs) in sediments, surface water, fish, and benthos collected from the seagrass ecosystem at Kodingareng Lompo island of Makassar City were observed. From 29 sediment samples collected the range of MPs abundance was 2.96-28.3 item.kg−1 dried sediment. Meanwhile, MPs abundance in surface water was 0.023 item.m−3, exceptionally lower compared to the sediment value. Of 4 fish species observed, Siganus canaliculatus was the species with the highest number of ingested MPs. On the other hand, sea urchin Tripneustes gratilla ingested more MPs compared to other benthos species. There was no consistent MPs abundance in sediments found at present studies. Similarly, there were no statistically significant differences seen on MPs abundance within all components examined using non-parametric Kruskal-Wallis analysis. However, the presence of MPs in all components observed has clearly shown a wide dispersion of MPs contamination in the marine food web, as seagrass is a well-known productive ecosystem with high marine biodiversity assemblage in the tropical region.

The riverine environment is known as the main pathway of microplastic entering the ocean. Recent studies show that the barricading of water flow in the riverine environment can influence the microplastic load to the ocean. The Jeneberang River, which is located in Makassar City, is prone to microplastic pollution. There are three weirs located in this river as water barricades. The aim of this study was to measure the microplastic abundance upstream and downstream of each weir flow. Microplastics in the water compartment were measured using the volume-reduce towing method and were measured in the sediment compartment using a density separator method. The results show that microplastic abundance in the water prior to passing each weir was higher (1.43 – 3.19 item/m3) compared by the flow after each weir (1.20 – 2.10 item/m3). The same pattern was also apparent in the sediment compartment where the microplastic abundance prior to the weirs tended to be higher (28.33 – 56.67 item/kg DW) compared to the compartment after the weir (30.00 – 53.33 item/kg DW). Based on microplastic shape, there is no evidence that weirs in the Jeneberang River are blocking any specific shape of microplastic. In conclusion, weirs that are commonly found in the riverine environment could act as microplastic retention devices in the riverine environment.

Aquaculture is a growing fisheries sector. Along with the growth of aquaculture, water quality problems become one of the main factors that need to be considered, especially related to pollution pressure. Microplastic (MPs) is a pollutant sourced from anthropogenic activities and is currently in the spotlight and has been widely studied in aquatic environments around the world. However, in Indonesia, research related to MP especially in term of aquaculture activities is still lacking. The presence of MP in aquaculture activities can originate from internal sources such as the use of unmaintained aquaculture equipment/facilities and the use of feed contaminated with MP. Then, the external source of MP at the cultivation location can come from water sources that come from an environment that has been previously polluted by MP. Maintenance of aquaculture equipment/facilities, search for alternative feed raw microplastic free materials and protection of the aquatic environment from MPs are some of the ways to reduce the presence of MP in aquaculture sites. The existence of MP in aquaculture activities is related to food safety of aquaculture commodities.