The use of stranded aquatic-associated bird surveys for plastic litter monitoring in Portugal

Plastics durability and persistence, combined with their high production and low rates of recovery, are causing a net accumulation of plastic debris along shorelines, surface waters, throughout the water column and in bottom sediments. Pollution by plastic debris is an increasing environmental concern all around the globe, accounting for up to 90% of marine debris. Wildlife has been severely impacted by plastic debris in coastal and aquatic environments. Macroplastics (> 20 – 100 mm) pose a health risk to several aquatic animals, including fish, turtles and birds, because of possible entanglement and ingestion. When in the environment, macroplastic debris can brittle and break through UV radiation, mechanical action and biodegradation into small sized plastic particles, designated as microplastics (1 – 5 mm), that become more bioavailable to organisms throughout the food web. However, microplastic debris can also reach aquatic environments in their original form that were manufactured for particular industrial or domestic applications, such as plastic particles used in exfoliating facial scrubs, toothpastes and resin pellets used in plastic industry. Birds are top-predators, exposed to all threats affecting these environments and this makes them ideal sentinel organisms for monitoring ecosystem changes. Considering the knowledge gap existing in southern Europe, in particular in Portugal, about the use of stranded aquatic-associated bird surveys for plastic litter monitoring, this study tries to fill this gap by: (1) set a baseline assessment of the prevalence of plastic litter affecting multispecies populations of aquatic birds in Portugal and (2) test if species, gender, age and condition of the birds influence type and quantity of ingested plastics. In this study, the plastics accumulated in the stomachs of stranded aquatic birds collected across the Portuguese territory will be quantified and characterized. A total of 310 birds samples comprising four species sourced from five different wildlife rescue centres (Parque Biológico de Gaia, CERVAS, CERAS, LxCRAS and RIAS) were collected and examined for the presence of plastic litter. Of these, 15.48% were found to ingest plastic litter. The average number and mass of ingested plastics was 1.62 items per individuals and 0.0771 g, respectively. Results show that aquatic-associated birds in Portugal do ingest plastic litter, as in many other countries in the world. Monitoring plastic litter ingested by aquatic-associated birds has the potential to be a part of a wide monitoring programme that can help to inform mitigation and management measures for aquatic litter.À medida que os plásticos se tornaram num produto indispensável no nosso quotidiano, a sua rápida produção tem sido consequentemente acompanhada por um aumento da acumulação de plásticos no meio ambiente. A durabilidade e persistência dos plásticos, combinada com a sua elevada produção e baixas taxas de recuperação, causam a acumulação de detritos plásticos ao longo das costas, águas superficiais, ao longo da coluna de água e sedimentos. A poluição por detritos plásticos é uma crescente preocupação ambiental em todo o mundo, representando cerca de 90% dos detritos marinhos. Devido ao uso excessivo e à eliminação inadequada de produtos plásticos, a vida selvagem tem sido severamente afetada pelos detritos plásticos em ambientes costeiros e aquáticos. Os macroplásticos (> 20 – 100 mm) representam uma ameaça para vários animais aquáticos, incluindo peixes, tartarugas e aves marinhas, devido à possibilidade de enredamento e ingestão. Quando no meio ambiente, os macroplásticos podem fragmentar-se através da radiação UV, ação mecânica e biodegradação em partículas plásticas mais pequenas, designadas de microplásticos (1 – 5 mm). Estas novas partículas tornam-se mais biodisponíveis para todos os organismos da cadeia alimentar e podem libertar substâncias químicas tóxicas durante o processo de degradação. As aves aquáticas são predadores expostos a todas as ameaças que afetam estes ambientes, tornando-os organismos sentinelas ideais para monitorizar mudanças nos ecossistemas