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SOURCES, FATES, AND EFFECTS OF SHIPBORNE GARBAGE 33 (disposal requirements are outlined in Chapter 1, Figure 1-1). Therefore, an unknown amount of garbage continues to be discharged overboard legally, adding to the accumulation of debris already in the marine environment. IDENTIFYING VESSEL GARBAGE IN THE MARINE ENVIRONMENT The amounts and precise characteristics of garbage thrown overboard, either before the ratification of Annex V or since, are unknown. Vessel discards are difficult to isolate and identify in the marine environment, due to the littering of coastal waters by land-generated wastes left on beaches, continuing domestic and industrial sewer discharges, and previously discharged waste transported via offshore winds, rivers, and coastal runoff. However, there is at least one way to approximate the level of vessel debris as distinct from other wasteâby selecting particular types of sampling sites and then monitoring certain types of debris appearing there. Plastics, which for all practical purposes are indestructible1 under marine environmental conditions, may provide a reliable measure of vessel discards if sampled in sediments and on beaches distant from the influences of recreational activities and sewer outfalls. However, because newly discarded plastic items float, they may be transported to locations far from the site of discharge, confounding attempts to identify vessel-generated debris on the basis of location alone. Plastics also may sink over time as they break apart, weather, or accumulate organic coatings, tar, shells, or sand. Sunken items may not be observed. To complicate monitoring efforts further, it is impossible to distinguish plastics tossed overboard lawfully before 1989 from those discarded illegally since then. Still, worldwide, there probably has been a meaningful (albeit unknown) level of compliance with the ban on discharge of plastics. The types of items discarded from vessels are reflected in beach debris, which encompasses a wide variety of materials. The characteristics of debris items larger than 1 inch (2.5 centimeters) have been summarized from the literature by Ribic et al. (1992). These items include glass, plastic, metal, paper, and a telling variety of fisheries gear, cloth, foodstuffs, wood, rubber, and packaging materials. With the exception of plastics, all these materials may be discharged overboard in certain areas under Annex V. The selection of indicator items for 1 At present, biodegradable plastics are used only on a very limited basis and their ultimate fates in the marine environment are unknown (Palmisano and Pettigrew, 1992). The Environmental Protection Agency (EPA) has published rules setting standards of degradability for plastic six-pack rings (40 C.F.R. Â§238), and commercial ring carriers appear to meet the standards (Craig Vogt, EPA Oceans and Coastal Protection Division, personal communication to Marine Board staff, July 7, 1994). Even so, overboard disposal of all plastics, including biodegradable varieties, is prohibited.
SOURCES, FATES, AND EFFECTS OF SHIPBORNE GARBAGE 34 One way to estimate amounts and types of vessel garbage thrown overboard is to examine beach debris, which may vary by geographical area. Milk jugs are a common sight along Gulf of Mexico beaches. Credit: Tony Amos. measuring vessel discards depends in part on the location of the debris sampling site. Table 2-1 lists items that might be used as indicators for vessel discards washed ashore in the Gulf of Mexico; it should be possible to identify comparable indicator items for vessel garbage in other regions. To date, the monitoring of debris under the Marine Plastics Pollution Research and Control Act (MPPRCA) has been confined to beach surveys and near-shore urban surveys of harbors, where debris may include materials from wastewater treatment plants and combined sewer overflows and stormwater drains (Trulli et al., 1990). The literature includes occasional reports on underwater surveys or cleanups of sunken debris from harbors or around oil platforms (Debenham and Younger, 1991; Minerals Management Service, 1992). Sinking debris receives little attention, yet the long-term and perhaps most insidious effects may be upon the benthic biota. Plastics and other wastes are entering the benthos in continuous fluxes. The material may reside for a near- infinite time in the surface sediments. Debris on the coastal sea floor could be monitored by divers or through the use of side-scan sonar imaging, photographic surveys, submersibles, or trawls. In summary, techniques for monitoring vessel garbage in the marine environment have not been well defined. Improvements are in the offing (Miller, 1993, 1994). Systematic efforts have been made to monitor marine debris2, but to 2 For example, the National Park Service conducted a five-year sampling program at selected parks (Cole et al., 1990, 1992; Manski et al., 1991; Miller, 1993), and sampling programs have been carried out in Alaska (Merrell, 1980, 1985; Johnson and Merrell, 1988; Johnson, 1990a, 1990b), Hawaii (Henderson et al., 1987), and Texas (Amos, 1993b).