First characterization of marine litter collected on Fort Dauphin and Sainte Marie island, East Coast of Madagascar

, Thibault Margot, Ramanampamonjy Aina, Saloma Anjara.

Madagascar has a high degree of endemism. This biodiversity is threatened by pollution, especially by marinelitter along the coasts. So far, no research has been carried out on marine pollution in this island. This study focuses on the first characterization of marinelitter on the east-coast of Madagascar in order to describe the quantity of marine and land-based inputs. Data were collected in October 2019. An accumulation survey of macro-litter (¿ 2.5 cm) was carried out for 10 consecutive days on inhabited and uninhabited sites in Ford-Dauphin (FD) and Sainte-Marie Island (SMI). The abundance of the marine litter per category was noted according to the SST manual and an origin determination was undertaken. A total of 4 005 pieces of marine debris were collected at FD (uninhabited site: 0.0173 item.m2 . d1; inhabited site 0.0893 item.m2 . d1) and 15 666 at SMI (uninhabited site: 0.225 item.m2. d1; inhabited site: 0.0699 item.m2. d1). Globally, the frequency of daily occurrence of stranded marine litter decreased for each site, however, the quantity varied inter day. Hard plastic was the main category found at the uninhabited sites for 50% (n=310) at FD and 76% (n=6,202) at SMI, mainly plastic fragments and bottles. A total of 111 brands were identified for SMI with the largest number being 54% of Indonesian origin (n=368) for the uninhabited site and 11% (n=85) of Malagasy origin for the inhabited site. This first study confirms that the majority of the marine waste stranded on the east coast of Madagascar comes from the East Indian Ocean via the securrent and to a lesser extent from Madagascar's land-based input. Light and durable, hard plastic can resist degradation and travel the ocean. To preserve Madagascar's biodiversity and human health, the implementation of a waste management program is more than a necessity.

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