Recent
research has shown that many larval fish species from various ocean habitats
are ingesting large quantities of microplastics within their preferred nursery
habitat.
Approximately 300
million tons of plastic gets manufactured per year, with around 5 to 13 million
tons of it ending up in our oceans. Much of this is in “macro” form such as
plastic packaging, fishing nets, and buoys that are quite easy to spot
littering shorelines or swirling around the enormous circular currents of the
world's oceans. Microplastics constitute pieces of plastic too small in size to
be filtered out of sewage systems: synthetic fibers, microbeads commonly used in cosmetics and
industrial cleaners, as well as minuscule scraps that are broken off from any
type of plastic.
Polyethylene beads extracted from cosmetic products,
as shown in an electron micrograph, regularly pass through sewage and treatment
plant filters, later ending up in open waters.
Image courtesy of Adil Bakir and Richard Thompson
(Plymouth University, UK)
A growing number
of research as of late have been dedicated to investigating precisely where
microplastics are found and their effects on marine life. While much evidence
has shown that adult fish are ingesting plastic, recent studies show that fish
at their larval stage are also consuming plastics, as early as mere days after
they have been spawned. Larval fish make up the next generation of adult fish
of who will supply resources of protein and nutrients to populations around the
world, yet little is understood as to the ocean processes that affect the
survival of these quintessential organisms.
Surface slicks are
naturally occurring, ribbon-like, smooth patches of water on the ocean surface.
These water features typically contain high densities of larval fish as well as
aggregate plankton, which are an important food source for them. In addition,
surface slick nurseries concentrate lots of planktonic prey, providing an oasis
of food that is critical for the development and survival for fish in their
larval stages. However, NOAA’s Pacific
Islands Fisheries Science Center and an international team of scientists
conducted a field study sampling coastal waters of Hawaii and discovered that
the same ocean processes that were allowing for the aggregation of prey for
larval fish also concentrated passively floating microplastics. “We were
shocked to find that so many of our samples were dominated by plastics,” said
study co-lead Dr. Jonathan Whitney, a marine ecologist for the Joint Institute
for Marine and Atmospheric Research and NOAA. Plenty of times, plastics found
in surface sinks, and therefore larval fish nurseries, can be on average eight
times higher than plastic densities found in other ocean habitats.
Larval fish lay
a foundation to ecosystem function, representing the future of adult fish
populations. These organisms are highly sensitive to environmental and food
changes. With nurseries and larval fish populations being surrounded by and
ingesting toxin-laden plastics that provide no nutrition at their utmost
vulnerable life-history stage, it indicates a call for attention and cause for
alarm. Plastics ingested by adult fish induce malnutrition, stemming from gut
blockages and accumulation of toxins. As a more unfamiliar subject, researchers
are not fully aware of the exact harm plastics cause to larval fish, however,
they can predict that microplastics may play a role in negative impacts to
development and even reduce survivorship of those that ingest them.
Despite calls for
classification of plastics to be categorized as hazardous, there has been a
lack of legislation to restrict marine debris accumulation as it is still
hindered by a lack of evidence to show the exact ecological harm caused. The
productivity of fisheries, as well as overall marine biodiversity, are currently
threatened by a large number of anthropogenic stressors including climate change,
habitat destruction, and overfishing. Modern studies have suggested that
pollution of microplastics to fish nurseries and ingestion of them at larval
stages are now emerging as a novel issue and have since become the lists’ newest
addition.
References
Galloway, T., & Lewis, C. (2016). Marine
microplastics spell big problems for future generations. Proceedings of
the National Academy of Sciences of the United States of America, 113(9),
2331-2333. Retrieved February 19, 2020, from www.jstor.org/stable/26468516
Katsnelson, A. (2015). News Feature: Microplastics
present pollution puzzle: Tiny particles of plastic are awash in the oceans—but
how are they affecting marine life? Proceedings of the National Academy
of Sciences of the United States of America,112(18), 5547-5549.
Rochman, C., Browne, M., Underwood, A., Van Franeker,
J., Thompson, R., & Amaral-Zettler, L. (2016). The ecological impacts of
marine debris: Unraveling the demonstrated evidence from what is
perceived. Ecology, 97(2), 302-312. Retrieved February 19,
2020, from www.jstor.org/stable/24703091
University of Hawaii at Manoa. (2019, November 11).
Prey-size plastics are invading larval fish nurseries. ScienceDaily.
Retrieved February 17, 2020 from www.sciencedaily.com/releases/2019/11/191111150636.htm
No comments:
Post a Comment