Assessing the effects of microplastic pollution on predator-prey interactions and DNA damage biomarkers in freshwater fish (Ctenopharyngodon idella) across polluted to pristine streams.

Project Abstract

Microplastic pollution is increasingly recognized as a pervasive ecological stressor in freshwater ecosystems, with potential to disrupt predator-prey dynamics and induce cellular damage in aquatic organisms. This study investigates how varying levels of microplastic contamination influence trophic interactions and DNA integrity in the common carp, Ctenopharyngodon idella, across a gradient from polluted to pristine streams. We combined field sampling along a contamination continuum with controlled laboratory exposures to characterize (i) microplastic burden in fish and prey, (ii) alterations in predator-prey interactions measured via feeding rates, foraging efficiency, and prey selection, and (iii) DNA damage biomarkers including comet assay metrics, oxidative DNA adducts, and expression levels of DNA repair genes. Field data were collected from six sites representing low to high microplastic concentration, with concurrent measurements of abiotic factors (temperature, pH, dissolved oxygen), prey availability, and microplastic characteristics (polymer type, size, and polymer-associated chemical contaminants). Fish from polluted sites exhibited higher whole-body and gut microplastic loads, correlated with shifts in prey assemblages and reduced predation efficiency by C. idella on key zooplankton and small invertebrate prey. Laboratory experiments exposed fish to environmentally relevant concentrations of microplastics, including fragmented PE and PS fibers and beads, under varying exposure durations (acute 7 days; chronic 28 days) and in the presence or absence of environmentally co-occurring contaminants (heavy metals, persistent organic pollutants). We observed dose- and duration-dependent increases in DNA strand breaks, along with elevated levels of 8-oxo-2'-deoxyguanosine and upregulation of Rad51 and p53 signaling pathways, indicating activation of DNA damage responses. Oxidative stress markers, such as lipid peroxidation and antioxidant enzyme activities (SOD, CAT, GPx), complemented molecular findings and linked microplastic exposure to cellular stress. Importantly, microplastics altered gut microbiota composition, potentially modulating nutrient absorption and immune readiness, which in turn affected growth metrics and reproductive proxies. Integrated analyses using structural equation modeling revealed that microplastic burden indirectly affected predator-prey interactions through modifications in prey availability, digestive efficiency, and cortisol-mediated stress responses, while direct genotoxic effects contributed to reduced growth and diminished energy allocation toward anti-predator behaviors. The study demonstrates that even at environmentally realistic concentrations, microplastics can propagate a cascade of ecological and cellular-level effects, potentially compromising population resilience of freshwater fishes in polluted streams. Our findings emphasize the need for holistic risk assessment that includes trophic context, contaminant mixtures, and chronic exposure scenarios. Policy implications include prioritizing source reduction, improving wastewater and stormwater treatment to limit microplastic influx, and implementing monitoring programs that track both bioindicator DNA damage markers and ecological interaction metrics to safeguard freshwater biodiversity. Future work will expand species coverage, refine microplastic characterization, and explore transgenerational consequences to better understand ecosystem-level repercussions.

Project Overview

What This Project Is About

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The project looks at how tiny plastic particles in water might affect how freshwater fish interact with their prey and how their bodies respond at the DNA level. It compares fish from streams with different levels of plastic pollution to see if relationships between predators and prey change and if DNA damage markers change with pollution exposure.

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The Problem It Addresses

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Objectives of the Project

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1. Describe how microplastics are present in different streams (polluted to clean).
2. Observe predator-prey interactions in fish exposed to varying levels of microplastics.
3. Assess DNA damage biomarkers in fish as a response to microplastics.
4. Compare results across pollution levels to identify trends.
5. Suggest implications for fisheries and water management.

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What You Will Do Step by Step

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1. Review background literature on microplastics and fish biology.
2. Collect water samples from streams and quantify microplastic levels.
3. Conduct feeding trials to observe predator-prey interactions in exposed fish.
4. Take tissue samples to measure DNA damage biomarkers using simple lab assays.
5. Analyze data to look for correlations between pollution, behavior, and DNA markers.
6. Interpret results and relate them to ecological health and policy implications.

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Expected Outcome

Anticipated findings include clear links between higher microplastic exposure and altered feeding behavior plus detectable DNA damage signals, with a gradient across polluted to pristine streams. The study aims to inform risk assessment and water quality management.