Low microplastic abundance in Siganus spp. from the Tañon Strait, Central Philippines

Abstract

Microplastic (MP) occurrence is a major global issue, though data on MP occurrence in the Philippines is limited and the potential effects of MPs on biota are still poorly studied. MP occurrence in fishes remains a concern, especially in economically and ecologically important species such as Siganus spp. This study determined MP occurrence in the gastrointestinal tract of wild rabbit fishes from Tañon Strait, the largest marine protected area in the Philippines. Siganus canaliculatus (n = 65), S. spinus (n = 17), S. guttatus (n = 5), S. virgatus (n = 8) and S. punctatus (n = 1) were sampled from the north and south of the strait. All MPs isolated from the gut of the rabbit fishes except for fibers were chemically analyzed by ATR-FTIR spectroscopy; an established library was used to determine the polymeric identities. Five particles were confirmed as polyester, polyamide, polyethylene or phenoxy resin MPs. The average MP abundance was 0.05 items/individual (S. virgatus > S. guttatus > S. canaliculatus > S. spinus = S. punctatus), which is comparable to studies conducted in other locations using similar methods. Fibers were counted (1556 in total), but not chemically analyzed. The low MP abundance in the samples may be attributed to the capability of rabbit fishes to discriminate food preferences. However, the risks associated with MPs should not be underestimated, especially as all parts of the fishes-including the gut-are utilized as human foods in the Philippines and many other Asian countries.

Keywords: Ingestion; Marine ecosystem; Rabbit fish; Siganids; Synthetic polymers.