Microplastic pollution
General Studies Paper III (GS-3) – Environment and Ecology
Context: Recent study found alarming microplastic contamination in commercial fish along Goa’s coast, threatening estuarine fisheries and human health.
What is Microplastic?
| Aspect | Details |
| Definition | Plastic particles <5mm, including fragments, fibers, films, beads. |
| Origin | – Primary: Microbeads in cosmetics, pellets. – Secondary: Breakdown of larger plastics. |
| Persistence | Do not biodegrade; remain for centuries in ecosystems. |
| Entry into Ocean | Via runoff, wastewater, wind, direct littering, rivers and estuaries. |
Goa Study: Estuarine Fisheries Under Threat
- Analyzed 251 fishes (nine species) from Mandovi estuary by feeding type: filter feeders, secondary consumers, carnivores.
- Aim: Trace microplastic bioaccumulation, identify ingestion pathways, assess risks for fish and humans.
- Bamboo shark (apex predator) and shellfish (71 samples) included.
Key Findings
| Metric | Details |
| Microplastic Count | 4,871 total particles, 3,369 plastics from 19 polymers (11 toxic); 120 MP/litre in water. |
| Per Fish Species | Anchovies (8.8 MP/fish), Catfish (>10 MP/fish), Bamboo shark (3.5 MP/fish). |
| Distribution | Higher in benthic zone (sea floor/sediment); benthic fish (catfish) had most contamination. |
| Bioaccumulation | Shellfish: 66/71 had poor nutrition; particles mostly in digestive tract (fish) vs. gills. |
Sources of Microplastics
- Discarded fishing gear and nets.
- Wastewater and urban runoff from settlements.
- Tire residue and e-waste.
- Packaging and textile fibers identified via shape/color analysis.
Biological & Ecological Effects
Impact on Fish
- Genetic disruption, oxidative stress, and reproductive damage.
- Lower growth and nutritional value; respiratory issues due to gill blockage.
- Filter feeders most affected; benthic species highly susceptible.
Impact on Humans
- Consumption of contaminated seafood linked to immune dysfunction, cancer risk, and neurotoxicity.
- Threat to livelihood if fish quality and demand decline.
Bioaccumulation & Biomagnification
- Microplastics accumulate in organism tissues and increase up the food chain, reaching humans.
Estuaries: Importance and Vulnerability
- Mandovi-Zuari system produces 97% of Goa’s fish; estuaries act as sinks for upstream microplastics.
- Benthic sediments trap microplastics, exposing bottom-dwelling species to high contamination.
- Support diverse finfish, shellfish, filter feeders—especially vulnerable to pollution.
Specific Results
| Sample Data | Details |
| Species Sampled | 30 each: mackerel, sardine, anchovy, bamboo shark, sole, catfish, clams, oysters; 11 green mussels. |
| Particle Ingestion | More microplastics found in digestive tracts than gills; confirms intake from contaminated prey/water. |
| Trends | Benthic fish highest accumulation; lower in longer-bodied fish. |
| Shellfish | 66/71 with poor nutritional status, indicating ecosystem-wide stress. |
Shape and Color Analysis
| Shape / Color | Potential Sources & Notes |
| Fiber (53%) | Fishing nets, textiles. |
| Fragment (29.9%) | Packaging, e-waste. |
| Film (13.1%) | Degraded plastic. |
| Bead (4%) | Cosmetics, industry. |
| Blue (37.6%) | Nets/gear—most common color. |
| Black (24.3%) | Tire residue, e-waste. |
| Red (12%) | Packaging, textiles. |
Risk Assessment
| Aspect | Details |
| Fish/Ecosystem | Highest hazard to benthic life (category IV–V). |
| Human Consumers | Medium–high risk, especially from highly toxic polymers. |
| Shellfish | Most affected; poor nutritional status, direct risk to humans. |
Key Concepts Table
| Term | Meaning |
| Bioaccumulation | Toxin buildup in tissues via direct exposure/diet. |
| Biomagnification | Increased toxin levels at higher trophic levels. |
| Benthic | Bottom-dwelling zone/species. |
| Pelagic | Open-water zone/speci |
