Microplastics in our oceans are
posing a significant risk to
filter-feeding marine animals like manta rays and whale sharks, especially
in pollution hotspots like the Bay of
Bengal, scientists have warned. Researchers from Murdoch University in
Australia and University of Siena in Italy said that microplastics could be hazardous because they contain toxic chemicals.
Plastic-associated chemicals and
pollutants can accumulate over decades and alter biological processes in the
animals, leading to altered growth, development and reproduction, including
reduced fertility, according to the study published in the journal Trends in
Ecology & Evolution.
While a definitive connection
between microplastic ingestion and toxin exposure for filter feeders remains to
be confirmed, studies into sea birds and small fish have found a link, said
Elitza Germanov, a PhD student at Murdoch University. Marine filter feeders are likely to be at risk because they need to
swallow hundreds to thousands of cubic metres of water daily in an effort to
capture plankton.
They can ingest microplastics directly from polluted water or
indirectly through contaminated prey. These
species also tend to congregate in habitats which overlap with microplastic
pollution hotspots, including the Gulf of Mexico, the Mediterranean Sea, the
Bay of Bengal and the Coral Triangle, which is the marine area comprising the waters of South East Asian countries
including Indonesia.
Indigestible plastic particles
may damage the digestive systems of these iconic species, researchers said.
“Despite the growing research on microplastics in the marine environment, there
are only a few studies that examine the effects on large filter feeders,” said
Germanov.
“This is because it is difficult
to assess plastic concentrations via conventional methods such as stomach
analysis, because these are unsuitable for threatened species like whale sharks
and manta rays,” she said. “So we are using non-lethal sampling of small
amounts of tissue, which we are testing for chemical tracers using
sophisticated and sensitive analytical tools,” she added.
Maria Cristina Fossi from the
University of Siena said that studies on whale sharks in the Gulf of California
and on fin whales in the Mediterranean Sea confirmed exposure to toxic
chemicals. “As these areas are hotspots for microplastics, our results could
indicate that filter feeders are taking up microplastics in their feeding
grounds,” she said.
Microplastic contamination had the potential to reduce population
numbers of filter feeding animals, many of which are long-lived and have few
offspring throughout their lives, said Germanov. There are several species
among the filter feeders that are listed
by the IUCN (International Union for Conservation of Nature) as globally
threatened species and are prioritised for conservation.
Credit: Indian Explain Research
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