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Section 1: Impacts of marine debris on biodiversity
It is clear from these reports that numerous individuals and species have died or become harmed as a consequence
of entanglement and ingestion encounters with marine debris. It is, however, likely that a much larger number
of individuals are compromised by sub-lethal effects that have not been fully reported. For example, debris on
beaches has been shown to affect behaviour of intertidal organisms such as the gastropod Nassarius pullus (Aloy
et al., 2011) and adversely affect the ability of turtle hatchlings to reach the sea (Ozdilek et al., 2006).
It seems inevitable that entanglement and ingestion of marine debris will alter the biological and ecological
performance of individuals. A number of possibilities have been suggested, including compromising an
individual’s ability to capture food, digest food, sense hunger, escape from predators, and reproduce—as well
as decreasing body condition and compromising locomotion, including migration (e.g. Ryan, 1988; Spear et al.,
1995; Laist, 1987; Laist, 1997; Derraik, 2002; Gregory, 2009; Aloy et al., 2011). It has also been widely suggested
that ingestion of debris, and in particular microplastic debris, might provide a pathway facilitating the transport
of harmful chemicals to organisms (Oehlmann et al., 2009; Teuten et al., 2009). (see also Section 1.4.3 below).
The consequences of ingestion are not fully understood. There are concerns that microplastics may cause physical
disruption for example, by interfering with feeding and digestion. Little is known about such physical effects,
although there is evidence that particles can be retained for several weeks after ingestion (Browne et al., 2008).
1.4.3 Microplastics
Marine debris, and in particular plastic debris, is fragmenting in the environment. Much of the debris collected
during survey trawls (Law et al., 2010; Thompson et al., 2004) and on shorelines (Browne et al., 2010) consists
of tiny particles of microplastic (Figure 8). This material has been defined as pieces or fragments less than 5
mm in diameter (Arthur et al., 2009; Barnes et al., 2009). The abundance of microplastics is increasing in the
oceans (Thompson et al., 2009, Goldstein et al., 2012), and data presented here indicate that around 10 % of all
reported encounters are with microplastics.
FIGURE 8: A) Marine debris on a strandline where it fragments into smaller pieces. B) A fragment of microplastics next to a grain of
sand found on a beach in Cornwall, UK. C) Scanning electron microscope image of microplastic fragments. Source: R.C. Thompson.
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