A study conducted by two graduate students of the Scripps Environmental Accumulation of Plastic Expedition (SEAPLEX) revealed the extent of water and environment pollution caused by man. According to the study, during the voyage undertaken to the North Pacific Subtropical Gyre, more than nine percent of fishes collected had plastic waste in their stomach. That area of the ocean has been named as the ‘Great Pacific Garbage Patch.’
The graduate students, Rebecca Asch and Peter Davison, deduced through their study that every year fishes of the north area of the Pacific Ocean swallow plastic at a rate of about 12,000 -to 24,000 tons. For this research, a group of graduate students travelled aboard the Scripps research vessel-New Horizon, to more than 1,000 miles west of California to the eastern area of the North Pacific Subtropical Gyre. The voyage lasted for roughly more than 20 days and was undertaken in August 2009. During this time, water samples, marine debris and specimens of fish were gathered ranging from the surface, to thousands of feet deep within the sea.
Approximately 9.2 percent of the 141 fishes spanning 27 species which were dissected for the study had plastic debris in their stomachs. The researchers say that the debris found inside the mid-water fishes were broken down into tiny pieces which were smaller than a fingernail. They were so small that their source could not be identified.
“About nine percent of examined fishes contained plastic in their stomach. That is an underestimate of the true ingestion rate because a fish may regurgitate or pass a plastic item, or even die from eating it. We didn’t measure those rates, so our nine percent figure is too low by an unknown amount,” stated Davison.
The author says that, studies conducted on fish and plastic ingestion previously may have featured “net-feeding” biases. Net feeding can result in artificially high cases of plastic consumption by fishes while they are confined to a net which has large amounts of debris. But this study by Scripps was apparently modeled to steer clear of such biases. A surface collecting device called manta net, which sampled for fifteen minutes at one time, collected the highest amount of plastic. Because of the short sampling time, the risk of net feeding is almost eliminated since the amount of time that a fish spends in the net is decreased and plastic does not accumulate in huge numbers.
Explained James Leichter, a Scripps associate professor of biological oceanography who participated in the SEAPLEX expedition, “This study clearly emphasizes the importance of directly sampling in the environment where the impacts may be occurring. We are seeing that most of our prior predictions and expectations about potential impacts have been based on speculation rather than evidence and in many cases we have in fact underestimated the magnitude of effects. SEAPLEX also clearly illustrates how relatively small amounts of funding directed for novel field sampling and work in remote places can vastly increase our knowledge and understanding of environmental problems.”
Since this research only concentrated on the prevalence of plastic ingestion, topics like the composition of plastic or the toxicological impacts on fishes were not included. Out of the 141 fishes, most of them were myctophids which are more commonly known as lanternfish owing to their luminescent tissue. At daytime these fishes stay between 200-1,000meters below the surface of the sea while at night they come up to the surface.
Asch commented, “These fish have an important role in the food chain because they connect plankton at the base of the food chain with higher levels. We have estimated the incidence at which plastic is entering the food chain and I think there are potential impacts, but what those impacts are will take more research.”
The marine debris are scattered across thousands of miles of the North Pacific Subtropical Gyre. For obtaining dimensions and boundaries of the garbage patch, researchers gathered samples in 132 net tows (of which 130 contained plastic) spanning a distance of more than 2,375 kilometers. This was done because it is not possible to map the debris from either air or space. This patch or region full of waste congregations is normally shunned by mariners because of its calm winds and mild currents. Since the North Pacific Subtropical Gyre hasn’t been examined in detail, several questions regarding the marine debris in the area and its effects in the long run on the marine environment remain unanswered as of today.
The results of this study were printed in a journal called the Marine Ecology Progress Series.