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The expedition to the Galapagos Islands was made in October 2021, when the Covid-19 infection numbers were still leading most of the headlines.
Five researchers, among whom were members of the Galapagos National Park, from the Escuela Superior Politécnica del Litoral de Ecuador (ESPOL), Guayaquil, and the Ecuadorian biologist Juan José Alava from the University of British Columbia (UBC), Canada, landed in them just like the iconic Charles Darwin did 186 years ago.
Despite time, these islands remain a living laboratory.
A place that provides many answers.
In this case, the scientists had the mission of knowing if the Galapagos penguins (
Spheniscus mendiculus
) were being affected by microplastics floating in the ecosystem and which, globally, have reached an average of 170 trillion particles.
Why penguins?
“Because they are what we call the canary in the coal mine
,
” says Alava, referring to a common practice that English miners had in the last century of interning a canary in the mines they wanted. explode to find out if there were toxic gases or not.
If the canary survived, they could enter;
If not, they left the mine alone.
Something similar happens with the Galapagos penguin: being in one of the highest steps of the food chain, its health can also indicate how healthy or contaminated the ecosystem is.
The problem, the researcher continues, is that “it is not ethical to go and sacrifice a penguin to open it.”
These penguins, those of the Galapagos, are rare.
A unique species, but endangered.
It is estimated that there are currently only around 1,200 individuals and they are known to be the only tropical penguin in the world that exists above the equator.
What they had to do, then, was collect samples of everything around these birds to predict, through ecosystem modeling, whether microplastics were bioaccumulating and biomagnifying in the penguins.
And here we have to pause, because there is a difference.
While bioaccumulation refers to the increase that microplastics have in an organism through everything that is exposed in the ecosystem over time - not just its prey -, biomagnification implies knowing how the contaminant is amplified in each organism or level. trophic through the marine food web.
The hypothesis, the study says, is that “organisms at higher trophic levels or apex predators show higher concentrations compared to organisms at lower trophic levels.”
They were in the Galapagos for 15 days.
There, moving between the most inhabited islands, such as Santa Cruz, and the almost pristine ones, such as Isabela, they took samples of water, zooplankton, fish that penguins eat and that they obtained in the markets, and two samples of their excrement. seabirds, all with the permits given to them by the Galapagos National Park.
The idea, as Alava says, was to use the data on microplastics that they found in each of these samples and then incorporate them into a complex modeling system that would not only tell them if the microplastics were bioaccumulating and biomagnifying, but would allow them to play with certain variables and scenarios to know how these criteria would change if there were more or less microplastics around the Galapagos.
Karly McMullen and Eduardo Espinoza collect Galapagos penguin feces on Isabela Island.Dr.
Juan José Alava
Getting the results of the samples was an international task.
In the facilities of the Galapagos National Park on the islands, they filtered the water samples.
In the Espol Ecotoxicology and Environmental Health laboratory, led by Paola Calle, another of the co-authors of the study that was published in Plos One, they processed the samples to eliminate organic material.
Finally, at the Ocean Pollution Research Unit (OPRU) at the University of British Columbia (UBC), where Alava is the principal investigator, the plastic particles were identified in collaboration with the UBC Department of Chemistry.
Some of these primary data that were important for the investigation are remembered by the Ecuadorian.
“The average concentration of microplastics observed in the water was 400 particles per cubic meter,” he explains, most of them fibers.
“And there was in a single specimen of a species of fish, the devil or milkfish (Chanos chanos), in which 27 particles were found per fish,” he points out.
In the other cases, the average was five particles per fish as in the mullets (
mugil spp
).
But this information was only a first input that they used to feed the modeling system.
How this second part of the investigation worked is perhaps the most difficult to explain.
However, it could be summarized as follows: to an
ecosystem modeling
software known as
Ecopath with Ecosim
they added not only the results of the samples, but also static data – such as the place where the ecosystem is located with the species matrix and their diet – and a dynamic simulation component of the species or functional groups of the marine network that do vary over time – such as the trend in the biomass of the organisms.
Then, through another tool called
Ecotracer
, they were able to predict how microplastics accumulate through the food chain.
The model allowed them to play with four scenarios to see what would happen if certain variables were changed over time.
“There was the standard scenario, the current one, which served as a reference baseline with the average concentration observed (400 microplastics per cubic meter).
But simulations were also made with a scenario with a high concentration of microplastics, a low concentration of microplastics and, another, assuming that the elimination rate of microplastics in the penguins was 99%.
That is, assuming that the microplastics do not stay in the body, but are released,” says Avala.
The conclusions were several.
For example, they found that the increase in the accumulation of microplastics in organisms was constant until approximately the fifth year of simulation, at which time the absorption rate began to gradually increase until finally becoming a plateau.
As expected, the penguin also presented the highest level of microplastic per biomass, followed by barracuda, anchovy, sardine, herring and salema, and predatory zooplankton.
But the most important conclusion is mentioned by Avala: “Galapagos penguins are facing a great exposure to microplastics through their food chain.”
Zooplankton sample collected in marine waters of the Galapos Islands that was analyzed for microplastics at the University of British Columbia (Canada). Karly McMullen
Although through the research, the experts also predicted that there is a biomagnification of microplastic through the food chain, they were left wondering what role the excretion rate plays in this issue, that is, how much the plastic comes out. through excrement or remains in the digestive tract and tissues of penguins.
“The model predictions highlight that there is a key knowledge gap in microplastic science, specifically in the accumulation behavior and residence time of microplastics in the intestine,” 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 pollutant of the oceans and enter the environment daily, so there is increasing concern for marine and coastal fauna and their food webs.
For this reason, future research must address how these various plastics behave after ingestion,” he says in a statement.
The important thing, as Avala says, is that this information becomes a warning signal to take action against plastics, not only in the Galapagos – where single-use plastics have already been banned – but internationally.
“Plastic pollution does not respect any corner of the ocean and is everywhere, from the Arctic to Antarctica.”
And although the Galapagos are a milestone in the history of evolution and science, a Natural Heritage of Humanity and a UNESCO Biosphere Reserve, they have not been immune to the floating plastic particles that seem to flood everything
.