Invasive Species

The presence of industrial pellets on beaches free from the influence of petrochemical facilities and pellet processing plants is an indication of long-range marine transport [139]. Like all natural or artificial floating debris, plastic can provide a mechanism for encrusting and fouling organisms to disperse over great distances [140]. Logs, pumice and other flotsam have traversed the open ocean for millennia [59], and the introduction of hard plastic debris to the marine ecosystem may provide an appealing and alternative substrate for some opportunistic colonizers [59,141]. It is estimated that if biotic mixing occurs, global marine species diversity may decrease by up to 58% [142]. Barnes [143] estimates the propagation of fauna in the sea has doubled in the tropics, and more than tripled at high latitudes (>50°), due to the input of anthropogenic debris. The hard surfaces of plastics provide an ideal substrate for opportunistic colonizers. Pelagic plastics are most commonly colonized by bivalve mollusks; however, other encrusting organisms include bacteria, diatoms, algae and barnacles [1,59,70,134,141].

Plastic substrates may also contain multispecies habitats composed of organisms that would normally inhabit different ecological niches [140]. Drifting plastic debris may also increase the range of certain marine organisms or possibly introduce species to new environments which they had previously not inhabited [144]. Sensitive or at-risk littoral, intertidal and shoreline ecosystems could be negatively affected by the arrival of unwanted and aggressive alien species, with potentially damaging environmental consequences [140,145,146,59]. The absence of biological organisms on plastic debris may be an indication that the particles were not present in the marine environment long enough for fouling to occur. Instead, these items probably have a more local, land-based origin (beachgoers, storm-water drainage), than more heavily encrusted debris [134]. Plastic waste also affects beaches.

Plastic waste could encourage the invasion of species who prefer hard surfaces, and as a result, indigenous species may be displaced, particularly those who prefer sandy and muddy bottoms [5]. So-called “wrack” environments consist of national flotsam and jetsam, such as seaweed and driftwood that is washed up on the shore, and often contain plastic waste [5]. Beach cleanups are way to remove plastic waste, but it is often assumed that the beach will return to its previous state once the cleanup is done [5].

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