Tackling Marine Debris in the 21st Century (2009) / Chapter Skim
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2 Understanding Marine Debris and Its Impacts
2 Understanding Marine Debris and Its Impacts
Pages 27-48
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From page 27... ...
and assesses the effectiveness of measures to prevent and reduce marine debris based on this information. Knowledge gaps are identified and recommendations provided on key aspects of monitoring and research that can help improve assessments and prioritize marine debris mitigation efforts.
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From page 28... ...
Plastic materials dominate coastal marine debris in number, volume, and weight at all debris sizes examined to date, particularly on beaches and areas near population centers (e.g., Ribic et al., 1997; Sheavly, 2007)
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UNDERSTANDING MARINE DEBRIS AND ITS IMPACTS 29 FIGURE 2.1 Image of a typical trash-covered beach (used with permission from the National Oceanic and Atmospheric Administration)
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From page 30... ...
Moreover, during this same period, Gulf of Alaska groundfish catches dropped by more than 50 percent; thus, the observed decline in trawl web bing could be due to MARPOL Annex V, a change in fishing intensity, or a combination of factors. Elucidating the contribution of mitigation actions on the abundance of marine debris can only be achieved when there is an opportunity to draw on a series of compatible longitudinal surveys.
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From page 31... ...
. Following the congressional ratification of MARPOL Annex V and the enactment of the Marine Plastic Pollution Research and Control Act (33 U.S.C.
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contained no plastic pellets whatsoever. Because these studies did not examine pelagic debris distributions before and after implementation of MARPOL Annex V, there is no information to deter mine if MARPOL Annex V has contributed to demonstrable changes in the prevalence of pelagic marine debris.
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From page 33... ...
Nylons, aramids, and many carbon fiber compounds used as hightensile cording are neutral to negatively buoyant and sink to the benthos. Moreover, through photodegradation, mechanical breakdown, or fouling with organic matter, even buoyant plastic debris sinks or is transported to the benthos.
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From page 34... ...
Microplastics are the very small (approxi mately ≤5 mm) plastic debris items; sources include preproduction plastic resin pellets used in the manufacture of plastic items (Gregory, 1977, 1978; Shiber, 1979, 1982, 1987; Redford et al., 1997; Moore et al., 2001b)
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Although the effects of plastic ingestion may not currently rise to the level of significantly impacting population-scale dynamics, ingestion of plastic debris may impede the recovery of species listed under the Endan gered Species Act (16 U.S.C.
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From page 36... ...
. Once entangled, mortality rates differ among species from more than 80 percent for Antarctic fur seals, 44 percent for Australian sea lions, and 57 percent for entangled New Zealand fur seals (Croxall et al., 1990; Page et al., 2004)
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From page 37... ...
For example, reported changes in northern fur seal entanglement rates (e.g., Fowler and Baba, 1991) did not account for the effects of radical changes in the structure and organization of the Bering Sea fisheries that took place during the 1980s and 1990s that may have been the ultimate cause of the variations observed in northern fur seal entanglements.
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From page 38... ...
In contrast, for traps, cages, and pots, which are used to target crustaceans and some species of finfish, ghost fishing can persist for as long as the gear remains intact. Thus, a key component of understanding the impact of derelict traps is to determine mortality rates within the traps.
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From page 39... ...
. The following are ways in which marine debris can reduce direct socioeconomic benefits: • sustainable harvests or catch-per-unit-effort of valued fish and shellfish due to ghost fishing (Kirkley and McConnell, 1997; National Research Council, 1999)
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Human behavior is the ultimate cause of marine debris, and the factors that lead to marine debris generation must
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From page 41... ...
Further studies elucidating the role of education level in environmental awareness and human behavior relative to marine debris generation will be needed to ensure a successful long-term solution. Finding: Despite measures to prevent and reduce marine debris, evidence shows that the problem continues and will likely get worse.
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From page 42... ...
As discussed in the previous sections, the available body of information documents the complexity of the marine debris problem but does not reliably track the changes in those problems over time and provides little functional insight into the factors control ling and contributing to the marine debris problem. Many studies that purportedly address the effectiveness of MARPOL Annex V address it a posteriori and are unable to link changes in debris definitively to regula tory actions versus other factors.
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From page 43... ...
There are also opportu nities for researchers to add onto existing research programs, particularly other longitudinal oceanographic monitoring efforts. Research into the distribution and prevalence of microplastics may be particularly well suited for piggybacking onto existing research programs.
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From page 44... ...
Design of Monitoring, Assessment, and Evaluation Programs Effective monitoring, assessment, and evaluation programs are also crucial to providing useful information to assess and improve measures to prevent and reduce marine debris. Thoughtful and scholarly analysis of marine debris monitoring, assessment, and evaluation efforts have been completed and many aspects of these works remain relevant (e.g., Ribic, 1990; Ribic et al., 1992)
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From page 45... ...
For example, airborne synthetic aperture radar is a type of remote sensing instrument that has the potential to identify, map, and guide the removal of plastic debris at sea at very fine scales, particularly for large debris items such as DFG. While synthetic aperture radar is a fairly new technology and not readily available, there are also a variety of similar existing tools available to researchers (e.g., remote sensing instruments mounted on U.S.
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From page 46... ...
used remote sensing to show that Hawaiian monk seal e ntanglement is greater in El Niño years. Marine Debris Information Clearinghouse There is a significant opportunity with regard to the dynamic use of the Internet and other emerging technologies for practitioners whose actions may directly influence marine debris generation and mitigation.
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From page 47... ...
Overarching Finding: Although there is clear evidence that marine debris is a problem, there has not been a coordinated or targeted effort to thoroughly document and understand its sources, fates, and impacts. This confounds the ability to prioritize mitigation efforts and to assess the effectiveness of measures that have been implemented.
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