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A Plastic World

Pictured: Caddisfly, mayfly and chironomid larva surrounded by microplastics

Plastic pollution has been acknowledged as a long lasting and far-reaching environmental issue. With the gradual break down of plastic items smaller plastics are produced and as a result now exist virtually everywhere on earth. Microplastics (plastic particles smaller than 5 mm) pose a threat as they are easily transported around the environment, and their small size allows for uptake and ingestion by a wide variety of organisms. In terms of aquatic environments, studies have shown the presence of microplastics in oceans, lakes, and rivers. There can be a number of sources distributing microplastics into aquatic environments. Of particular interest, wastewater treatment facilities perform an important role in removing contaminants from wastewaters yet may still behave as a source by contributing microplastics back into waterways in effluent. Therefore, monitoring the environmental levels of microplastics and their presence in diverse organisms is of high importance for understanding risks. To do this, our study focuses on emergent insects

Why emergent insects?

Pictured: Adult mayfly and a UV light used to attract insects

Some aquatic insects are in their larval form and will grow and change through metamorphosis into flying terrestrial adults. Common examples of these aquatic insects include dragonflies, mayflies, caddisflies, midges, and mosquitos. We call these emergent insects.

Aquatic insects are often used as bioindicators to assess pollution and water quality due to their diversity, limited movement within home ranges, relatively long residence times and range of sensitivity to environmental disturbances such as pollution. Being easy to collect and available in high abundance is also a benefit! Given their advantageous use as bioindicators, why not use aquatic insects to also monitor microplastics in rivers? The unique aspect here is that we plan to not only consider insects in their larval aquatic forms, but also see if they may be carrying microplastics through to their emerged adult life stage.

The Food Web Aspect

Pictured: Nearshore spider on its web

Emergent insects in both their aquatic and terrestrial life stages are important forage for various predators, including fish, spiders, bats, birds, and small mammals. Contaminants can be passed from one organism to another within a food web; this is called this trophic transfer. What we don’t currently know much about is the potential for emergent insects to carry microplastics from their aquatic to terrestrial life stage, and pass microplastics onto predators such as nearshore spiders. We also don’t fully understand the implications microplastics may have on food webs.

Pictured: Emergent insect collection set up at dusk

Overall, the risks posed by microplastics may not only remain with aquatic organisms. Our project will investigate microplastic ingestion by emergent insects up and downstream wastewater treatment facilities, and the transfer of microplastics to nearby terrestrial predators.

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