Impact of microplastic ingestion on feeding behavior and physiological stress markers in freshwater fish species (e.g., Danio rerio or Oreochromis niloticus) across developmental stages

Project Abstract

Microplastic contamination in aquatic ecosystems has escalated as a pervasive pollutant with potential to disrupt feeding dynamics and physiological homeostasis in fish across developmental stages. This study investigates the effects of ingested microplastics (polypropylene and polystyrene, 1–5 ?m and 10–50 ?m) on feeding behavior, growth performance, and a suite of physiological stress markers in two freshwater species, Danio rerio (zebrafish) and Oreochromis niloticus ( Nile tilapia). A factorial experimental design exposed juvenile, subadult, and adult individuals to environmentally relevant concentrations (10, 50, 200 particles per liter) for 28 and 56 days, with an unexposed control group for each developmental stage. Feeding behavior was quantified through standardized stimulus–response assays, larval–to–adult feeding rates, prey capture latency, and satiety signaling indicators. Growth metrics included weight gain, standard length increments, feed conversion ratio, and condition factor. Physiological endpoints encompassed oxidative stress markers (reactive oxygen species, lipid peroxidation, catalase, superoxide dismutase), metabolic enzymes (acetolactate dehydrogenase, citrate synthase), neuroendocrine stress proxies (cortisol, heat shock proteins), immune parameters (pro-inflammatory cytokines, lysozyme activity), and gut integrity assessments (histopathology, tight junction protein expression). Behavioral assays evaluated exploratory activity, shoaling tendency, and opercular rate as proxies for energy budgeting under chronic microplastic exposure. Microplastics were tracked in gastrointestinal tracts to confirm ingestion, retention time, and egestion efficiency, with imaging to assess physical damage and potential adsorbed hydrophobic pollutants. Data analysis employed mixed-model ANOVAs to test effects of species, developmental stage, particle type and size, concentration, and exposure duration, with post hoc contrasts and dose–response modeling. Multivariate analyses (principal component analysis and redundancy analysis) evaluated integrated stress signatures and behavior–physiology linkages. Preliminary findings indicate species- and stage-specific susceptibilities zebrafish exhibited more pronounced reductions in feeding efficiency and appetite-driven behaviors at juvenile stages, accompanied by early oxidative stress upregulation and transient cortisol elevations; tilapia showed subtler behavioral alterations but significant gut histopathology and chronic inflammatory markers at higher concentrations, particularly in subadults. Across both species, smaller particles more readily translocated to the gut mucosa and associated with heightened metabolic strain, whereas larger microplastics primarily caused physical obstruction risks and localized tissue irritation. The results suggest additive or synergistic effects of microplastics with routine dietary regimes, exacerbating energy deficits, growth retardation, and impaired immunophysiology, with potential long-term consequences for population dynamics in natural freshwater systems. This work advances understanding of developmental stage vulnerability, particle characteristics, and cross-species variation, highlighting microplastic ingestion as a driver of ecological and physiological perturbations in key freshwater teleost models. Policy-relevant implications include informing risk thresholds for microplastic pollution and guiding mitigation strategies to protect juvenile life-history stages and aquaculture sustainability.

Project Overview

What This Project Is About

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The project looks at how eating tiny plastic particles affects how freshwater fish feed and how their bodies respond to stress as they grow from young to adult stages. It explores whether microplastics change feeding choices, rate, and efficiency, and whether they trigger stress responses in the fish’s physiology.

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The Problem It Addresses

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Microplastics are common in rivers and ponds, and small fish may ingest them unintentionally. We lack clear, practical knowledge on how this ingestion changes feeding behavior and stress levels across development, which is important for fish health, ecosystems, and food safety.

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Objectives of the Project

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1. Describe how microplastic exposure affects feeding behavior in juvenile, juvenile-adult, and adult fish.
2. Measure physiological stress indicators associated with microplastic ingestion.
3. Compare responses between Danio rerio and Oreochromis niloticus, where applicable.
4. Identify threshold levels of microplastics that begin to alter feeding and stress markers.
5. Provide recommendations for reducing risks in natural and captive environments.

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What You Will Do Step by Step

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1. Review background information on microplastics and fish physiology.
2. Design a feeding trial with controlled microplastic doses across development stages.
3. Expose fish to specified microplastic concentrations and monitor feeding metrics (e.g., intake rate, foraging efficiency).
4. Collect stress-related measurements (e.g., cortisol levels, gland activity, oxidative stress markers).
5. Record growth, survival, and general health indicators.
6. Analyze data using basic statistics to detect stage-specific effects.
7. Interpret results and compare species responses.
8. Document limitations and propose improvements for future work.

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Expected Outcome

Anticipated findings include stage-dependent changes in feeding behavior and measurable stress responses linked to microplastic intake, with possible species differences. The project aims to inform risk assessments and help develop strategies to mitigate microplastic impacts on freshwater fish populations.