Plastics on the menu: Microplastics Present in Indonesian Manta Ray Feeding Habitats

              Microplastics have emerged as a major threat to the marine environment. Recent research advances have shed light on global microplastics estimates, threats to biodiversity, and key focal regions for... [ view full abstract ]

              Microplastics have emerged as a major threat to the marine environment. Recent research advances have shed light on global microplastics estimates, threats to biodiversity, and key focal regions for intervention. Yet there are few reports assessing the potential for microplastic ingestion by threatened large filter feeders, such as mobulid rays, in regions heavily impacted by plastic pollution like Indonesia. Here, we evaluate the microplastic concentrations found in critical feeding habitats for manta rays (Mobula alfredi) in two areas fraught with marine plastic pollution, Nusa Penida and Komodo National Park, Indonesia. Using a 200-micron plankton net, we assessed microplastics found in the top 0.5m of the water column during the predominantly wet and dry months over two years (2016-2018). Microplastic abundance in manta rays feeding grounds appears to be seasonally influenced in Nusa Penida, with higher concentrations of microplastics during the wet as compared to the dry season (0.48 pieces/m³ Vs 0.03 pieces/m³, respectively). Conversely, microplastic abundance did not change significantly with season in the manta ray feeding grounds in the Komodo National Park. Given the large quantities of water manta rays must filter to meet their daily energy demands, feeding activity in these locations will likely result in microplastic ingestion that over time may expose these vulnerable animals to associated treats, including toxins. A seasonality trend in the microplastic abundance in Nusa Penida points to an ideal time for concentrating marine debris intervention and prevention efforts from land based sources such as rivers.