Factors (type, colour, density, and shape) determining the removal of marine plastic debris by seabirds from the South Pacific Ocean: Is there a pattern?

Abstract

1. While floating near the sea surface plastic debris interacts with a number of external factors, including many different organisms. Seabirds have the most extensive documented history of interactions with plastics, through ingestion, entanglement, and nest construction. 2. In the present study, eight seabird species from the South Pacific Ocean were used as a proxy to determine potential patterns of removal of marine plastic debris, and three hypotheses were tested in relation to their feeding habits and nesting areas. 3. Plastics from abiotic compartments (Chilean continental coast, South Pacific Gyre, and Rapa Nui beaches) and biotic compartments (surface-feeding seabirds, diving seabirds, and nesting areas) were compared, according to their type, colour, shape, and density. 4. Continental beaches had a relatively wide range of colours and shapes, with many non-buoyant plastics. Samples from the South Pacific Gyre (SPG) and Rapa Nui (Easter Island) beaches comprised mainly hard, rounded, buoyant, and white/grey plastics. 5. These results indicate that the composition of floating plastics from terrestrial sources changes during transport with oceanic currents, reducing the proportion of prey-like plastics present in the subtropical gyres. 6. The stomach contents of surface-feeding and diving seabirds were dominated by hard, white/grey, and round plastic items, similar to plastics from the SPG, suggesting non-selective (accidental or secondary) ingestion. 7. Nesting areas had a more variable composition of brightly coloured plastics, suggesting a pattern of selective removal of plastics by seabirds, probably from oceanic sources. 8. The present study reveals extensive interactions of seabirds with plastics on a broader scale, which is highly relevant given that the impacts of plastics on seabirds are increasing worldwide, compromising their efficient conservation.

Sea-Surface Slicks and Their Effect on the Concentration of Plastics and Zooplankton in the Coastal Waters of Rapa Nui (Easter Island)

“…This suggests that organisms within the slicks are susceptible to ingestion of plastics (Gove et al, 2019), and transfer to higher trophic level organisms could be a result. Slicks play an important ecological role in food retention and aggregation, where the risk of ingestion of plastics by mistake (confusion with their natural prey) or indirectly (with their prey organisms) appears to be high in visual predators such as seabirds, fish, and megafauna species that feed in these areas (Ory et al, 2017(Ory et al, , 2018Gove et al, 2019;Hidalgo-Ruz et al, 2021).…”

Plastic Debris in Nests of Two Water Bird Species Breeding on Inland Saline Lakes in a Mediterranean Biosphere Reserve

“…Due to the scarcity of studies on plastics in wetland bird nests, we cannot determine whether a pattern was occurring in other breeding colonies of these species. However, there is evidence for an active selection of brightly colored plastics by eight seabird species in nest areas of the South Pacific Ocean [ 18 ], a preference for white and black debris shown by the brown booby ( Sula leucogaster ) [ 52 ], the collection of hard and white items by the Caspian tern ( Hydroprogne caspia ), and the use of greenish fishing gear in the nests of the great cormorant ( Phalacrocorax carbo ) [ 53 ]. In our study, both species apparently used plastic and other anthropogenic items as ornaments (most of the nest material comprised sticks and other plant debris, including pebbles and olive pits in many cases).…”

“…The association between plastic debris and organisms is shaped by plastic properties (type, size, and color), but it also depends on each species and the habitat. In seabirds, there is evidence for the ingestion of hard, white or gray, and round plastics, while plastics used as materials to build nests have a different composition and are bright in color [ 18 ]. Similarly, there is evidence of more use of plastic strings in nests of great grey shrikes ( Lanius excubitor ) that breed on farmland compared to conspecifics inhabiting more naturalized areas [ 19 ].…”

Ecological Traits Influencing Anthropogenic Debris Ingestion by Herbivorous Reef Fishes

“…Rotjan et al (2019) demonstrate through laboratory experiments that for the coral Astrangia poculata, fiber contamination predominates over microbeads, while in the Red Sea (Baalkhuyur et al, 2018) and the Southeastern Atlantic (Macieira et al, 2021), fibers are more common than fragments for reef fishes (Baalkhuyur et al, 2018;Macieira et al, 2021). But for seabirds, however, it does not seem to be relevant (Hidalgo-Ruz et al, 2021). Notwithstanding, fibers were the most common shape of debris found in different studies worldwide (Rochman et al, 2015;Savoca et al, 2019;Macieira et al, 2021) and may take longer to be egested after ingestion by fishes.…”