Impacts of plastic on tropical fishes around Bangka Island, North Sulawesi
Plastics are one of the major contemporary problems for marine life. Several harmful effects on biota result from plastic debris in the sea. Plastics can get ingested by fishes and may defile our seafood. We need to understand the reasons, the impacts and preferences for plastic uptake on fishes to be able to increase their protection and to prevent humans from eating possibly defiled seafood. This study investigated the plastic ingestion phenomenon in tropical fishes in Bangka Island, North Sulawesi. Coral reef associated fishes were in focus. The area is a hotspot for marine biodiversity, that exist in contrast to enormous amounts of marine plastic debris. This is the first approach on the evaluation of plastic from fishes in Indonesia that applied spectrometric methods on all found items (except fibers) and did not relied purely on visual identification or subsample plastic type analyzes. Furthermore, the study examined the impacts of plastic on the respiratory system of fishes. Several precautionary measures and different isolation steps were applied during the analyzes of plastics from gastrointestinal tracts. 80 fishes with different feeding characteristics were examined to find possible plastic ingestion preferences and point out worst affected groups of fishes. 10 % of visually identified potential plastics from digestive tracts were synthetic polymers. In total 37 plastic films, 7 plastic fragments and 62 fibers were evaluated. Fishes of all investigated feeding characteristics were affected. 6 % of all investigated fishes had plastic films and fragments and 19 % of all fishes had fibers in their digestive tract. Plastic films and fragments were exclusively found in 45 % of investigated individuals of Acanthurus mata. 37 % of analyzed ambush predators ingested fibers. Affected ambush predators showed a preference for black fibers. A single parrotfish contained 28 fibers. Planktivores were the only fishes that contained blue fibers. Mobile predators were less and sediment feeder (goatfishes) were least impacted from fiber ingestion. Respiratory tract analyzes were made in 28 fishes. Two of them contained in total three plastic films and one plastic fragment with a maximum size of 4.7 mm. The study points out, that tropical fishes from the area around Bangka Island are impacted from marine plastic debris and show indications for a feeding characteristic specific plastic ingestion. The plastic films and fragments uptake by fishes rose with the increasing availability of plastic. The amount of planktivorous fishes with microplastic around Bangka Island is higher than some investigated areas in the south-east Pacific Ocean, parts of Europe and Australia.