When analyzing the faeces of the whales, the researchers found, on average, the presence of 21 micro-fragments of plastic for every six grams of excrement
When analyzing the faeces of the whales, the researchers found, on average, the presence of 21 plastic microfragments per six grams of excrement.
For the work, published in the journal Science of The Total Environment , the research team collected the droppings of cetaceans such as Bryde’s fin whale ( Balaenoptera brydei ) and the Boreal whale ( Balaneoptera borealis ) in the Harauki Gulf, near New Zealand’s largest city, Auckland.
Although the presence of microplastics has been detected in all marine ecosystems studied to date, calculating the average daily amount to which these marine animals are exposed is difficult to estimate.
Large consumers of microplastics
The marine predators that feed through the filtration of sea water are perfect for the analysis of their exposure to these compounds, both from the environment in which they live and through the food they eat.
Each cetacean analyzed consumes around 25,000 microplastic fragments each time it swallows the water where the krill is found
“The whales are constantly collecting samples, both from the environment and from the prey they consume during feeding,” explains one of the authors, Laura Zantis from the University of Leiden (The Netherlands ).
This feature makes them a perfect element to monitor the severity of microplastic contamination in the area where they feed. “We wanted to understand how much microplastics they consume per day, and if these were in the food itself, or in the water they filter during the process,” adds the researcher.
Using DNA analysis , the research team determined that the whales were mainly eating zooplakton (krill), and calculating the amount of food the whales extracted For each bite, they estimated that each cetacean analyzed consumed around 25,000 microplastic fragments each time it swallowed the water where the krill was found.
Most of those 25,000 micro-fragments of plastic that whales collect are in krill. Only one out of every thousand fragments comes from water
Emma Carroll (University of Auckland)
“Most of those 25,000 micro-fragments of plastic that whales collect are in krill. Only one out of every thousand fragments comes from water, which shows how plastic is progressively concentrated in the food chain ”, explains Emma Carroll , from Aukland University (New Zealand), and another of the study’s signatories.
To estimate the amount of microplastics consumed per day by these sea giants, the researchers drew on previous work by the biologist Rochelle Constantine (University of Auckland ), which determined that whales in the Hauraki Gulf feed continuously during the day, which translates into about one hundred bites of food over the course of a day.
When comparing this last data with the previous one, the research team estimated that whales consume an average of three million plastic fragments per day.
New way to measure the concentration of pollutants
“In the future, studies on the risk of exposure to microplastics will have to take into account the importance of taking samples from both water as well as marine food, if you want to correctly determine the levels of these pollutants ”, warns Zantis.
The work thus provides a new way of measuring contamination by microplastics in all filter feeders, as a way to better understand the impact of this global threat.
“The conclusions of the study demonstrate the need to act in the Hauraki Gulf to reduce plastic pollution, which affects whales and other large animals that filter the water to feed themselves, such as stingrays”, Constantine concludes.
Rights: Creative Commons.