Effects of microplastic exposure on the feeding behavior and gut microbiota of freshwater tilapia (Oreochromis niloticus).

Project Abstract

Freshwater tilapia (Oreochromis niloticus) were exposed to environmentally relevant concentrations of microplastics (polyethylene and polystyrene, 1–5 µm) dissolved in aquaria for 28 days to evaluate shifts in feeding behavior and gut microbiota composition, coupled with histopathological assessments of the digestive tract. Feeding behavior was quantified using a standardized two-choice feeding assay, latency to feed, and bite rate, recorded daily under controlled light and temperature conditions. Microplastic uptake and distribution in gut tissues were assessed via Raman spectroscopy and confocal microscopy, while gut microbial communities were characterized using 16S rRNA gene sequencing and metagenomic shotgun analysis to capture taxonomic and functional shifts. Endpoints included body condition factor, condition index, fecal pellet analysis for egestion rate, and growth performance to detect sublethal effects. Behavioral assays revealed a dose-dependent reduction in feeding vigor, with increased latency to feed and lower bite rates in higher microplastic exposure groups, suggesting irritant or orexigenic disruption. Histological examination showed microplastic-associated mucosal damage, villus atrophy, and inflammatory cell infiltration, potentially impairing nutrient absorption. Microbiome analyses demonstrated significant alterations in alpha diversity and beta diversity, characterized by enrichment of opportunistic pathogens and a relative decline in fiber-degrading and probiotic taxa (e.g., Lactobacillus and Bacteroidetes members). Functional profiling indicated a shift toward pathways linked to stress responses, xenobiotics degradation, and altered short-chain fatty acid production, indicating disrupted gut metabolic potential. Correlation analyses connected specific microplastic burdens with altered feeding metrics and microbial dysbiosis, while histopathology scores correlated with microbiome instability, suggesting a mechanistic link between physical gut injury, microbial community disruption, and feeding suppression. Water chemistry parameters (dissolved oxygen, pH, conductivity) were continuously monitored and remained within optimal ranges, ensuring observed effects were attributable to microplastic exposure rather than abiotic stress. The study integrated a multi-omics approach with ethological and histological assessments to provide a holistic view of microplastic impacts on an ecologically and economically important tropical freshwater species. The findings reveal that even short-term, environmentally pertinent microplastic exposure can compromise the feeding behavior and gut microbial ecology of Oreochromis niloticus, with potential downstream consequences for growth, health, and disease resistance, thereby highlighting risks to aquaculture productivity and ecosystem function in microplastic-polluted freshwater systems. Recommendations include adoption of microplastic mitigation strategies in aquaculture, development of feeding regimens that minimize ingestion risk, and the incorporation of gut microbiome monitoring as an early indicator of environmental stress in tilapia culture.

Project Overview

What This Project Is About

---

The project looks at how tiny plastic particles, called microplastics, affect a common freshwater fish, the tilapia. It examines whether eating microplastics changes how the fish feeds and how it hosts bacteria in its gut.

---

---

The Problem It Addresses

---

Microplastics are now found in rivers and lakes. We don’t fully understand how these particles influence fish behavior or their gut bacteria, which can affect health, growth, and food safety for humans who rely on fish as a protein source.

---

---

Objectives of the Project

---

1. Describe how microplastics are present in tilapia habitats.
2. Test whether microplastic exposure changes feeding rate and feeding choices.
3. Assess changes in gut bacteria composition after exposure.
4. Link feeding changes to gut microbiota shifts.
5. Evaluate potential health and growth indicators in fish.

---

---

What You Will Do Step by Step

---

1) Review basic literature on microplastics and fish gut microbiota. 2) Design a simple feeding trial with different microplastic levels. 3) Measure feeding behavior (how much/how fast). 4) Collect gut samples and analyze bacterial communities with basic sequencing data. 5) Compare results across treatments. 6) Look for correlations between feeding and gut changes. 7) Interpret findings in plain terms and note limits.

---

---

---

---

Expected Outcome

We expect to see changes in feeding behavior and a shift in gut bacteria with higher microplastic exposure. The study should clarify potential risks of microplastics to tilapia health and offer simple guidance for minimizing exposure in farming and waterways.