(Results in press as of 8 Jul 2012 at http://www.sciencedirect.com/science/article/pii/S0025326X12001828, pdf available upon request.)
Marine plastic debris is an increasing problem in ocean ecosystems. Plastic degrades slowly on land, but in the ocean it persists even longer – if left to its own devices, potentially for hundreds or thousands of years. Also, because plastic is light, it floats or is suspended in the water column and can be carried long distances from its origin by ocean currents. To see just how big of a problem this has become, you need only look a little to the west of our own coastline at the “Great Pacific Garbage Patch” – a mass of trash larger than Texas accumulating at the center of a current system called the Northern Pacific Gyre.
Plastic in marine ecosystems can be extremely harmful to wildlife. Animals can not only become entangled in the debris, but they can also eat the tiny “microplastic” particles that are the result of plastic trash being broken apart in the ocean. Seabirds in particular are known to suffer a great deal from plastic ingestion, which can have serious negative consequences to their health as plastic can accumulate in the gut, reducing stomach capacity, obstructing digestion and causing starvation and reduced growth.
The only good side to this situation is that we can use some seabird species as indicators of marine plastic debris in the environment. Not all seabirds eat or accumulate a lot of plastic – some dive for their food and manage to bypass the surface realms of floating plastic. Some are not so lucky. Procellariids, or “tube-noses” including birds such as albatrosses, petrels, and fulmars, are some of the most extreme accumulators of plastic. This is primarily because they are surface-feeders and are more likely to swallow floating microplastics – presumably as a result of confusing them with food.
Northern Fulmars (Fulmarus glacialis) in particular have been accepted as the best indicator species for marine plastic debris in the northern hemisphere. This is mostly due to their extremely wide range and distribution – they can be found in the North Pacific, North Atlantic, and the High and Low Arctic. They can therefore be used as an international standard indicator of marine plastics. Monitoring projects focusing on microplastics in Fulmars in the Arctic and Atlantic are fairly wide-spread and well-established. However, data for the North Pacific is lacking and outdated since the 1990s. This fall, I made a first attempt at rectifying this lack of monitoring in the Pacific Northwest. I examined the stomach contents of 20 Fulmars: five from Washington (salvaged from the beach in fall 2009) and fifteen from Oregon (supplied by Sharnelle Fee at the Wildife Center of the North Coast: http://www.coastwildlife.org/Home.html).
I found that 90% of specimens contained plastic, with an average of 21 plastic items and 0.34 grams of plastic per bird. Likely due to the high human population density of our area, this is notably more than in the Canadian high arctic, where studies report only 33% of Fulmars containing plastic (Mallory 2008). However, our study showed similar amounts of plastic to recent studies in the North Atlantic – in 2003, researchers reported 95% of Fulmars as having an average of 29 items and about 0.35 grams of plastic (van Franeker et al. 2003).
While a third of a gram of plastic might not sound like a lot to us, who can hold as much in the palm of our hand, this can be a huge burden for birds the size of Fulmars. There aren’t any established standards or goals yet for the United States, but the Oslo & Paris Convention in Europe has established a goal to reach less than 2% of Fulmars in monitoring surveys containing more than ten plastic pieces. 45% percent of Fulmars in my study and 56% in the North Atlantic in 2003 (van Franeker et al. 2003) contained more than ten items. In short, neither the status of marine plastic debris in the Pacific nor the Atlantic is anywhere near a level considered to be manageable and healthy for marine life.
I also found that 95% of plastic items in the Fulmars were user plastics – things like fragments from consumer products, Styrofoam, and the occasional bit of sheet plastic from a grocery bag. Only 5% were pre-production industrial plastics – round pellets usually of white, beige, or brown color that haven’t yet hit the factories. This is similar to recently reported trends in Northern Canada (Mallory 2008), but opposite of trends reported for the North Pacific in the 1990’s, which found primarily industrial plastics in Fulmars and other seabirds (Robards et al. 1995; Blight & Burger 1997). This could either mean that consumer plastic debris has increased in the Pacific, or that industrial plastics have decreased. It seems likely that both may be the case, as increased regulation on shipping companies may have decreased industrial plastic spills while increased human population and consumerism may be causing increased input of litter into the ocean.
Most of the plastic particles in these Fulmar specimens were neutral colors, such as white and beige. This suggests that Fulmars eat plastics that may resemble food items, such as fish, squid, or crustaceans. However, no data is available regarding the color composition of marine plastic debris in the environment, so we can't really tell whether the high proportion of these neutrally-colored plastics in Fulmars are a result of selection by the Fulmars or just a representative sample of what's available in the environment.
In terms of differences in plastic accumulation within my sample, I found that juveniles from Oregon contained significantly more microplastics than the adults (P=0.033). This is consistent with findings of other researchers (van Franeker et al. 2003), and likely a result of the fact that parents regurgitate food to their offspring, probably transferring plastic along with it. Alternatively, the juveniles might be less selective than adults in "prey" selection. The accumulation in juveniles is highly concerning because plastic accumulation is thought to contribute to reduced growth and could have future implications for recruitment of adults in Fulmar populations.
The last variable I looked at was the difference in plastic accumulation between the sexes. I didn’t expect to see any difference, since males and females are a similar size, both contribute to feeding offspring, and presumably have the same feeding habits. Overall, my expectations were confirmed and there was no significant difference (P=0.27). However, when I compared only the contents of the ventriculi, or the bottom portion of the stomach responsible for mechanical digestion, males contained notably (although not quite significantly) more plastic (P=0.095). Further investigation will hopefully clarify this trend, but for now, we are left in some uncertainty and confusion as to why females might accumulate less microplastics than males.
This project was only a first effort to use Northern Fulmars for microplastic monitoring in the Pacific Northwest. Already, other students at the University of Puget Sound are planning to continue this research in the future, which will hopefully lend additional significance and applicability to these results. Most of all, the results of this study will become vastly more useful with continued monitoring in an effort to better understand trends in environmental levels and composition of marine plastic debris and its potential effect on wildlife.
Blight L.K. & Burger A.E. 1997. Occurrence of plastic particles in sea-birds from the Eastern North Pacific. Marine Pollution Bulletin 34: 323-325
Mallory M.L. 2008. Marine plastic debris in Northern Fulmars from the Canadian high Arctic. Marine Pollution Bulletin 56: 1501-1504
Robards M.D., Piatt J.F. & Wohl K.D. 1995.Increasing frequency of plastic particles ingested by seabirds in the subarctic North Pacific . Marine Pollution Bulletin 30:151.157.
van Franeker J.A., Meijboom A. & de Jong, M.L. 2003. Marine litter monitoring by Northern Fulmars in the Netherlands 1982-2003. Wageningen, Alterra, Alterra-rapport 1093
Lydia Kleine, Curatorial Assistant, Slater Museum
Bio of the author: A biology student at the University of Puget Sound, I have worked as an assistant at Slater Museum for a year. This was a final project for a marine biology class. I will be graduating this month and looking for a job.
Result in press as of 8 Jul 2012 at http://www.sciencedirect.com/science/article/pii/S0025326X12001828