Because of their numbers, recreationists are seen as major contributors to the marine debris problem. 



seabird species — and two invertebrates 

 have been reported to ingest debris. 

 But it's unclear whether ingestion is a 

 more serious threat than entanglement 

 because the effects are largely unmea- 

 sured. Seabirds and turtles appear to be 

 more affected than mammals. 



Ingestion is perhaps best under- 

 stood for seabirds, which are at risk of 

 eating debris because of their general- 

 ized diets and foraging at the water sur- 

 face. Petrels, storm-petrels, phalaropes 

 and some albatrosses and auks rarely 

 regurgitate indigestible pellets; rather, 

 they accumulate large loads in their 

 digestive systems. 



Turtles are also likely to eat debris 

 because of their indiscriminate feeding 

 habits. And once they've swallowed a 

 piece of trash, the papillae lining their 

 esophagus prevents regurgitation. 



Turtles, birds and marine mammals 

 that eat debris suffer a variety of ail- 

 ments. Debris damages the digestive 

 track; causes starvation by blocking 

 food and increasing buoyancy in turtles; 

 creates a false sense of satiation, affect- 

 ing their long-term fitness and ability to 

 grow, molt, reproduce and survive ad- 



verse conditions; and perhaps releases 

 toxic pollutants as they digest. Physical 

 damage from sharp items appears to be 

 rare and an unlikely threat to significant 

 proportions of marine animals. Diges- 



Plastics have emerged 

 as the dominant problem worldwide. 

 Still, our understanding 

 of marine debris is incomplete. 

 Twenty years into our research, 

 efforts to identify sources 



are still crude. 

 And only a few studies 

 have looked at sources 

 with an eye toward tracing trends 

 and reducing debris. 

 Collecting data on waterborne 

 garbage for the sake of 

 having data isn't enough. 

 Nor are beach cleanups 



a cure-all— at best 

 they are a temporary fix 



to a complex 

 and persistent problem. 



tive tract blockages usually occur in 

 turtles, the West Indian manatee and 

 some cetaceans, but it's hard to estimate 

 the proportion. 



An unknown and perhaps large 

 portion of debris eaten by turtles and 

 mammals is excreted. But it can kill an 

 animal that swallows large or several 

 items that block the intestinal tract. 



On the economic side of impacts, 

 we know that waterborne debris fouls 

 ships and other marine equipment, com- 

 petes with fishermen when castaway 

 gear continues to "ghost fish," reduces 

 the value of fisheries products and 

 causes loss of tourism and recreational 

 business. These impacts have only re- 

 cently emerged from behind the consid- 

 erable shadow of biological impacts, but 

 they are much easier to measure. We 

 look at them in terms of financial costs. 



There are hundreds of reasons why 

 marine debris is a problem, each with a 

 common refrain: debris is not a natural 

 part of the marine system. It hurts 

 aquatic animals and plants. And it hurts 

 beach communities and fishermen try- 

 ing to make a living from the sea. As 



Continued 



COASTWATCH 7 



