Marine protected areas invaded by floating anthropogenic litter: An example from the South Pacific

Abstract

Oceanic marine protected areas (MPAs) that are close to the litter accumulation zones in the subtropical gyres receive large amounts of plastic litter, both as micro‐ and as macroplastics. The macro‐litter accumulating on the islands in the Easter Island Ecoregion (Rapa Nui and Salas y Gómez) can be traced back to the high seas industrial fishery operating in the South Pacific. Seabirds nesting in the MPAs in the South Pacific are affected by both microplastic ingestion and macroplastic in their nests, but there was no evidence of entangled birds. Conservation of seabirds (and other species) in these oceanic MPAs requires efficient measures to reduce plastic contamination in the ocean. Observations made in the South Pacific coincide with those from other oceanic MPAs, calling for global actions.

Rapid increase in Asian bottles in the South Atlantic Ocean indicates major debris inputs from ships

“…This represents 7.3 macrodebris items weighing ∼5 kg·m −1 , because of the many large debris items from fisheries (floats, fish trays) and shipping-related activities (ship's hawsers, buffers, etc.). This is among the highest levels recorded at an oceanic island globally (7,9), despite the paucity of small items (<2 cm) recovered because they disappear into crevices between the cobbles and boulders.…”

“…Oceanographic models and empirical observations of debris at sea both indicate that debris floating at the ocean surface tends to accumulate in the center of ocean gyres in so-called garbage patches (3)(4)(5). As a result, the shores of oceanic islands close to these zones often suffer exceptionally high levels of plastic pollution, despite being located far from major source areas for plastic waste (6)(7)(8)(9). The accumulation of plastic on remote island shores is a useful tool to monitor marine plastics (8), but the origins of most plastic items washing ashore are hard to infer, because they are too small to attribute to specific sources based on manufacturers' marks or functional attributes.…”

In search for the sources of plastic marine litter that contaminates the Easter Island Ecoregion

“…Many studies show markedly higher levels of plastic ingestion for fish species (as high as 80% of sampled fish) near Easter Island due to its environment of high microplastic concentration and low food availability 24,25 , relative to other regions of the South Pacific. Birds, marine mammals and sea turtles are also frequently affected by plastic ingestion 26,27 . Beach surveys report extraordinarily high plastic debris density 28 .…”

“…Such densities are equivalent to or higher than densities observed on another island of the South Pacific, the inhabited Henderson Island, where extensive surveys were carried out 29 . It is difficult to determine the potential continental origin of plastic litter because the vast majority of identifiable objects found on the island’s beaches (Easter Island and Salas y Gómez) are from fishing activity 26–28,30 (e.g. nets, buoys, crates…) with the rest consisting of fragmented debris.…”

“…It has been suggested that contamination by litter is likely inversely proportional to the distance to the nearest gyre centre that corresponds to the region with highest litter density 26,33 , implying that these “garbage patches” are the main source of contamination. However, this approximation does not consider potentially important pathways of marine litter operating at shorter timescales (seasonal, or multiyears) and assumes that plastic litter accumulates within the garbage patch prior to contaminating neighbouring regions, which may not be the case when island locations intersect the main routes of plastic litter.…”