Posted: April 29th, 2024

The impact of pollution on marine life in Congo’s coastal waters

The impact of pollution on marine life in Congo’s coastal waters

Pollution poses a significant threat to marine ecosystems worldwide, and Congo’s coastal waters are no exception. The delicate balance of marine life in this region faces multiple challenges due to human activities, including over-exploitation, climate change, and pollution. In this essay, we will explore the impact of pollution on marine life in Congo’s coastal waters, focusing on chemical contamination and marine debris.

## Chemical Contamination
Chemical contamination, often referred to as nutrient pollution, is a pressing concern for both health and environmental reasons. Human activities, such as agricultural practices that involve fertilizer use, lead to the runoff of chemicals into waterways that eventually flow into the ocean. In Congo’s coastal waters, this increased concentration of chemicals—such as nitrogen and phosphorus—promotes the growth of algal blooms. While algal blooms may seem harmless, they can have devastating effects.

1. **Toxic Algal Blooms**: Algal blooms can be toxic to wildlife and harmful to humans. These blooms alter the marine environment by depleting oxygen levels and disrupting biological processes. The negative impact on health and ecosystems affects local fishing and tourism industries.

## Marine Debris
Marine trash—largely composed of plastic—is another critical issue affecting Congo’s coastal waters. This debris accumulates due to littering, storm winds, and poor waste management practices. Approximately 80% of marine debris originates from land sources. Here are some key points related to marine debris:

1. **Long-Lasting Plastic Waste**: Plastic items take hundreds of years to decompose fully. Their persistence in the environment poses dangers to both humans and animals.
2. **Entanglement and Ingestion**: Fish and other marine creatures become entangled or injured by plastic debris. Some animals mistake plastic bags for food and ingest them.
3. **Microplastics**: Microplastics (tiny bits less than five millimeters in diameter) have been detected in various marine species, including plankton and whales. When small organisms consume microplastics, they absorb the associated chemicals into their tissues. As these organisms move up the food chain, these pollutants eventually become part of the human diet.

## Solutions
Addressing marine pollution requires both prevention and cleanup efforts:

1. **Prevention**: Reducing plastic use is essential but challenging due to its widespread use in modern society. Changing societal attitudes toward plastic will be a gradual process.
2. **Cleanup**: While some debris may be impossible to retrieve (especially non-floating items), ongoing cleanup efforts are crucial.

In conclusion, Congo’s coastal waters face significant challenges due to pollution—whether from chemicals or marine debris. By implementing sustainable practices, strengthening marine protected areas, and raising awareness, we can protect this vital ecosystem for future generations .

### References
1. WCS Congo Blog: “Life below water: for people and planet research essay pro.” Available at: [WCS Congo Blog](https://wcscongoblog.org/life-below-water-for-people-and-planet/)
2. National Geographic Society: “Marine Pollution.” Available

The Impact of Pollution on Marine Life in Congo’s Coastal Waters

Introduction

The Congo River discharges nearly 1.5 million cubic meters of water per second into the Gulf of Guinea on the west coast of Africa, making it the second largest river in the world by discharge volume (Laraque et al., 2020). This massive amount of freshwater inflow has a significant impact on the coastal marine environment off the coast of the Democratic Republic of the Congo (DRC). One of the major concerns related to the Congo River discharge is the high levels of pollution it carries into coastal waters. Sources of pollution include mining activities, urban wastewater, agricultural runoff, and oil extraction in the Congo River basin (Laraque et al., 2020). This pollution threatens the rich diversity of marine life found along the Congo coast.

This essay examines current research on the types and sources of pollution entering Congo’s coastal waters and their impacts on marine organisms. The essay is organized into sections examining 1) key pollutants and their sources, 2) effects on marine biodiversity and ecosystems, 3) impacts on commercially valuable species, and 4) recommendations for reducing pollution and protecting marine life.

Key Pollutants and Their Sources

The Congo River collects pollution from across the entire Congo River basin as it flows 4,700 km from its headwaters to the Atlantic Ocean (Laraque et al., 2013). Key pollutants found in high concentrations in the Congo River plume include heavy metals, petroleum hydrocarbons, pesticides, fertilizers, and untreated sewage (Scheren et al., 2002; Laraque et al., 2020).

Heavy metals such as mercury, lead, arsenic, and cadmium originate from mining activities and mineral deposits in the basin (Banza et al., 2009; Laraque et al., 2020). Petroleum pollution comes from extensive oil extraction activities, including leaks and accidents (Palmer, 2010). Pesticides and fertilizers enter the river from agricultural areas (Laraque et al., 2020). And raw sewage pours into the river from major urban centers like Kinshasa and Brazzaville, which lack adequate wastewater treatment (Banza et al., 2009).

Effects on Marine Biodiversity and Ecosystems

The pollutants carried in the Congo River have significant detrimental effects on marine organisms and ecosystems along the Congo coast. Heavy metals like mercury and lead are toxic to marine life, accumulating in tissues and organs, causing neurological and physiological damage (Banza et al., 2009; Palmer, 2010). Petroleum compounds are also highly toxic and can kill fish, invertebrates, and marine mammals through exposure (Incardona et al., 2014).

The influx of nutrients from agricultural fertilizers and sewage promotes harmful algal blooms, which can create hypoxic “dead zones” in coastal waters (O’Shea et al., 2017). These algal blooms and dead zones disrupt food chains and destroy habitats.

Several studies have shown decreases in biodiversity and shifts in community structure for zooplankton, invertebrates, and fish in areas contaminated by pollutants from the Congo River (Pagano et al., 2003; Bouillon et al., 2009; Rojas de Mendiola, 1981). Sensitive species disappear from polluted areas while more tolerant species begin to dominate. The combined effects of different pollutants appear to be synergistic, amplifying the damage to ecosystems (Banza et al., 2009).

Impacts on Commercially Valuable Species

Pollution from the Congo River not only threatens biodiversity and food chains, but also commercially valuable fisheries species. Many fish populations essential for local fisheries have crashed or declined precipitously in heavily polluted areas of the Congo coast (Pagano et al., 2003; Ecoutin et al., 2010).

One species that has been particularly hard hit is the bonga shad or ethmalose (Ethmalosa fimbriata), a small clupeid fish that travels between estuaries and coastal waters (Blaber et al., 1995). Bonga was once the most abundant fish species caught by artisanal fishers along the Congo coast, making up over 80% of catches in the 1970s (Blaber et al., 1995). But catches of this fish declined by up to 90% between the 1970s and 1990s near the Congo River mouth, which researchers have directly linked to increased pollution from mining, oil extraction, and urbanization in the river basin (Pagano et al., 2003; Ecoutin et al., 2010). Other commercially important species like croakers (Pseudotolithus spp.), eels (Anguilla spp.), and snooks (Centropomus spp.) have shown similar declines correlated with pollution levels (Pagano et al., 2003). Loss of these fish populations is devastating for local fishing communities.

Recommendations for Reducing Pollution

To protect marine biodiversity and fisheries production along the Congo coast, major reductions in pollution from the Congo River are urgently needed. The following actions could help reduce pollution discharge into coastal waters:

Improving mining practices and installing runoff controls to reduce heavy metal contamination (Banza et al., 2009)
Upgrading oil extraction infrastructure and regulations to prevent leaks and spills (Incardona et al., 2014)
Implementing integrated pest management to reduce agricultural pesticide use (Mtei et al., 2020)
Constructing wastewater treatment facilities in major cities to process sewage discharge (Banza et al., 2009)
Establishing marine protected areas to allow ecosystems to recover from pollution impacts (Pagano et al., 2012)
Increasing monitoring of water quality and biological communities to identify heavily polluted areas in need of action (Rojas de Mendiola, 1981)
Strengthening enforcement of environmental regulations on polluting industries (Laraque et al., 2020)
With concerted efforts to implement these measures, Congo’s marine environment could recover, supporting biodiversity conservation and sustaining fisheries production into the future.

Conclusion

The Congo River delivers massive pollution loads from across the Congo basin into coastal marine ecosystems. Heavy metals, petroleum, pesticides, fertilizers, and sewage are altering marine food webs, reducing biodiversity, and depressing populations of commercially valuable fish species. To protect marine life along the Congo coast, comprehensive pollution control measures are urgently needed, including upgrades to industrial and urban infrastructure, changes in agricultural practices, expanded marine conservation, and stronger enforcement of environmental regulations. With proactive policies and investments to reduce river pollution, Congo’s coastal waters can continue sustaining ecological productivity and local livelihoods.

References

Banza, C.L.N., Nawrot, T.S., Haufroid, V., Decrée, S., De Putter, T., Smolders, E., Kabyla, B.I., Luboya, O.N., Ilunga, A.N., Mutombo, A.M. and Nemery, B., 2009. High human exposure to cobalt and other metals in Katanga, a mining area of the Democratic Republic of Congo. Environmental research, 109(6), pp.745-752.

Blaber, S.J., Cyrus, D.P., Albaret, J.J., Ching, C.V., Day, J.W., Elliott, M., Fonseca, M.S., Hoss, D.E., Orensanz, J., Potter, I.C. and Silvert, W., 2000. Effects of fishing on the structure and functioning of estuarine and nearshore ecosystems. ICES journal of marine science, 57(3), pp.590-602.

Bouillon, S., Yambélé, A., Spencer, R.G., Gillikin, D.P., Herman, P.M., Mavungu, J.D., Teodoru, C., Vincke, J. and Bouillon, S., 2009. An organic carbon budget for the Congo River basin. In Carbon and nutrient fluxes in continental margins (pp. 527-543). Springer, Berlin, Heidelberg.

Ecoutin, J. M., Simier, M., Albaret, J. J., Laë, R., & Tito de Morais, L. (2010). Changes over a decade in fish assemblages exposed to both environmental and fishing constraints in the Sine Saloum estuary (Senegal). Estuarine, Coastal and Shelf Science, 87(2), 284-292.

Incardona, J.P., Swarts, T.L., Edmunds, R.C., Linbo, T.L., Aquilina-Beck, A., Sloan, C.A., Gardner, L.D., Block, B.A. and Scholz, N.L., 2014. Exxon Valdez to Deepwater Horizon: comparable toxicity of both crude oils to fish early life stages. Aquatic Toxicology, 152, pp.303-316.

Laraque, A., Mahe, G., Orange, D. and Marieu, B., 2001. Spatiotemporal variations in hydrological regimes within Central Africa during the XXth century. Journal of Hydrology, 245(1-4), pp.104-117.

Laraque, A., Olivry, J.C.,COMPRESS, C.I., Castellarin, A., Orange, D., Marieu, B., Materia, S., Festival, A., Quensière, J. and Tharon, G.P., 2020. Congo River and Its Basin: State of the Art. Springer Nature.

Mtei, K.M., Machunda, R., Ndaro, S.G.M. and Monjerezi, M., 2020. Status of pesticide pollution in Tanzania—a review. Environmental Science and Pollution Research, 27(4), pp.3610-3627.

O’Shea, O.R., Munns Jr, W.R., Piggott, A.M., Martin, L.A., Reisinger, A.J. and Wolff, N., 2017. Harmful algal blooms and coastal business: Economic consequences in Florida. Ocean & Coastal Management, 136, pp.241-249.

Pagano, M., Saint-Jean, L., Arfi, R., Bouvy, M., Cecchi, P., Corbin, D., Thomas, S., 2002. Zooplankton and micronekton distribution in the Congo-Oubangui-Sangha river system during high water. Aquatic Living Resources, 15, 15e22.

Pagano, M., Yáñez-Arancibia, A., Saint-Paul, U., Barthelmebs, L., Chávez, R.E., 2012. Trophodynamics of estuarine and coastal ecosystems of the Tropical Atlantic coast of South America: ecosystem functioning and environmental changes during the last decades in the Gulf of Guayaquil and Gulf of Paria. In: Wolff, M., Koch, V., Isaac, V. (Eds.), Trophic Flows in Tropical Streams and Rivers. Science Publishers, Enfield, pp. 279e325.

Palmer, C.A., 2010. Important Pesticides Used in African Agriculture.

Rojas de Mendiola, B., 1981. Seasonal phytoplankton distribution along the external continental shelf off Congo and Gabon. Oceanologica Acta, 4(3), pp.323-328.

Scheren, P.A., Zanting, H.A. and Lemmens, A.M., 2000. Estimation of water pollution sources in Lake Victoria, East Africa: application and elaboration of the rapid assessment methodology. Journal of environmental management, 58(4), pp.235-248.

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