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The expedition to the Galapagos Islands took place in October 2021, when Covid-19 infection numbers were still dominating most of the headlines. Five researchers, including members of the Galapagos National Park, from the Escuela Superior Politécnica del Litoral de Ecuador (ESPOL), Guayaquil, and Ecuadorian biologist Juan José Alava from the University of British Columbia (UBC), Canada, landed in them Just like it the legendary Charles Darwin did 186 years ago. Despite the passage of time, these islands remain a living laboratory. A place that provides many answers. In this case, the scientists were tasked with finding out whether Galapagos penguins (Spheniscus mendiculus) were affected by microplastics floating in the ecosystem and containing an average of 170 billion particles worldwide.
Why penguins? “Because they are what we call the canary in the coal mine,” says Alava, pointing to a common practice by English miners in the last century of interning a canary in the mines they planned to explode to find out if there were toxic gases there were present or not. If the canary survived, they could enter; If not, they left the mine alone. Something similar happens with the Galapagos penguin: because it is at one of the highest levels of the food chain, its health can also indicate how healthy or contaminated the ecosystem is.
The problem, the researcher continued, is that “it is not ethical to sacrifice a penguin to open it.” These penguins, those of the Galapagos Islands, are rare. A unique species but threatened with extinction. It is estimated that there are currently only about 1,200 individuals and is the only tropical penguin in the world to exist above the equator. What they then had to do was collect samples of everything around these birds in order to use ecosystem modeling to predict whether microplastics would bioaccumulate and biomagnify in the penguins. And here we have to pause, because there is a difference. While bioaccumulation is the increase in microplastics in an organism from everything it is exposed to in the ecosystem over time – not just its prey – biomagnification is the knowledge of how the pollutant is present in any organism or at any trophic level is reinforced by the marine food web. The hypothesis, the study says, is that “organisms at higher trophic levels, or top predators, have higher concentrations than organisms at lower trophic levels.”
They were in the Galapagos Islands for 15 days. There, they shuttled between the most heavily inhabited islands, such as Santa Cruz, and the nearly untouched islands, such as Isabela, taking samples of water, zooplankton, fish that penguins eat and bought at markets, and two samples of their excrement. Seabirds, all with permission from Galapagos National Park. The idea, Alava says, was to take the data on microplastics that they found in each of these samples and then integrate it into a complex modeling system that would not only tell them whether the microplastics were bioaccumulative and biomagnifying, but would also allow them to play with certain variables and scenarios to see how these criteria would change if there were more or less microplastics around the Galapagos Islands.
Karly McMullen and Eduardo Espinoza collect poop from Galapagos penguins on Isabela Island.Dr. Juan Jose Alava
Obtaining the results of the samples was an international task. They filtered the water samples in the Galapagos National Park's facilities on the islands. In the Espol Laboratory of Ecotoxicology and Environmental Health, led by Paola Calle, another co-author of the study – along with Karly McMullen, Félix Hernán Vargas, Omar Alvarado and Evgeny Pakhomov – which was published in Plos One, they processed the samples to remove organic material. Ultimately, the plastic particles were identified in collaboration with the UBC Department of Chemistry at the Ocean Pollution Research Unit (OPRU) at the University of British Columbia (UBC), where Alava is the principal investigator.
The Ecuadorian remembers some of this primary data that was important for the investigation. “The average concentration of microplastics in the water was 400 particles per cubic meter,” he explains, most of them fibers. “And in a single specimen of a fish species, the devil or milkfish (Chanos chanos), 27 particles per fish were found,” he points out. In the other cases, the average was five particles per fish, as in the case of mullets (Mugil spp.).
However, this information was only an initial input that they fed into the modeling system. How this second part of the investigation worked is perhaps the most difficult to explain. However, it can be summarized as follows: To an ecosystem modeling software called Ecopath with Ecosim, they added not only the results of the samples, but also static data – such as the location where the ecosystem is located, the species matrix and their diet – and a dynamic one Simulation component of the species or functional groups of the marine network that change over time – such as the evolution of organisms' biomass. Using another tool called Ecotracer, they were then able to predict how microplastics accumulate in the food chain.
The model allowed them to play with four scenarios to see what would happen if certain variables changed over time. “There was the standard scenario, the current one, which served as a reference base with the observed average concentration (400 microplastics per cubic meter). However, simulations were also carried out with a scenario with a high microplastic concentration, a low microplastic concentration and another scenario with the assumption that the elimination rate of microplastics in the penguins was 99%. “Provided that the microplastics do not remain in the body but are released,” says Alava.
The conclusions were varied. For example, they found that the increase in the accumulation of microplastics in organisms remained constant until around the fifth year of the simulation. At this point, the absorption rate gradually began to increase until it finally reached a plateau. As expected, the penguin also had the highest microplastic content per biomass, followed by barracuda, anchovy, sardine, herring and salema, as well as predatory zooplankton. But Alava calls the most important conclusion: “Galapagos penguins are exposed to high levels of microplastic pollution through their food chain.”
Zooplankton sample collected in marine waters of the Galapos Islands and analyzed for microplastics at the University of British Columbia (Canada). Karly McMullen
Although the experts also predicted biomagnification of microplastics through the food chain through the research, they were left with the additional task of investigating what role the excretion rate plays in this question, i.e. how much plastic comes out through excrement or remains in the digestive tract and tissues of penguins.
“The model predictions highlight that there is a large knowledge gap in microplastics science, particularly with regard to the accumulation behavior and persistence of microplastics in the gut,” says Karly McMullen, who led the research as part of his master’s thesis at the University of British Columbia. “Microplastics are becoming a major ocean pollutant and are released into the environment on a daily basis, causing increasing concern for marine and coastal fauna and their food webs. For this reason, future research must address how these different plastics behave after ingestion,” he says in a statement.
Importantly, Alava says, this information becomes a warning sign to take action to curb plastics, not just in the Galapagos Islands – where single-use plastics are already banned – but internationally. “Plastic pollution respects no corner of the ocean and is everywhere, from the Arctic to Antarctica.” And although the Galapagos Islands are a milestone in the history of evolution and science, a natural heritage of humanity and a UNESCO Biosphere Reserve, they are not immune to it the floating plastic particles that seem to flood everything..