Algal bloom crisis looms over L. Victoria

May 23, 2023

Timothy Mugerwa, the executive director of GCCF, urged the government to support efforts to preserve the lake and improve the sanitation of landing sites.  

Lake Victoria, the lifeblood of East Africa, is Africa’s largest and the world’s second-largest freshwater lake, stretching as far as the eye can see.

Davis Buyondo
Journalist @New Vision

Lake Victoria, the lifeblood of East Africa, is Africa’s largest and the world’s second-largest freshwater lake, stretching as far as the eye can see. 

The crystal-clear surface reflects the brilliant blue sky above, while colorful boats bob gently on the waves. 

The shoreline at Lambu landing site in Bukakata sub-county, Masaka district is alive with the hustle and bustle of fishermen and vendors selling their merchandise to locals and tourists alike. But there is a problem brewing beneath the surface. 

A subtle greenish tint is creeping across the lake, signaling the presence of algal blooms. It is a silent killer that threatens the delicate balance of the lake’s ecosystem, and unless something is done soon, the consequences could be unpleasant. 

Scientists and environmentalists cleaning Lambu landing site.

Scientists and environmentalists cleaning Lambu landing site.

The lake has been the centre of attention after a significant fish kill in 2021. Several landing sites in Uganda, such as Kasenyi, Kigungu, Bugonga, Gguda (greenfields), Lido Beach, as well as Wagagi Flower Farm in Wakiso district, were affected. 

Others were Lambu, Kaziru, Namirembe, and Kachanga in the Masaka district and Kasensero in the Kyotera district, and others in the Greater Masaka region. 

The same impact was felt by Kenya and Tanzania and also several African countries, whose landing sites have been impacted The cause was attributed to environmental or climate change, but scientists, conservationists, and environmentalists in Uganda have come forward to assert that algal and cyanobacterial blooms played a role in the deaths of fish. 

They have warned that these blooms, locally called mubiru, or nkonge, have the potential to cause harm to aquatic life by obstructing sunlight and clogging fish gills. 

The situation often results in fish death, anxiety, and disorientation. 


Fishermen at Bukakata, Lambu, and Kasensero landing sites say they lack the expertise and scientific knowledge in dealing with marine blooms and invasive plant species. 

Antonio Kalyango, the executive director of  Biodiversity Conservation Forum

Antonio Kalyango, the executive director of Biodiversity Conservation Forum

According to Joseph Kimera, a fisherman and councilor for Kasensero Town Council, River Kagera daily brings in tons of numerous invasive plant species from Burundi, Rwanda, and Tanzania. 

However, he says a wide range of pollutants pose a severe threat to the health of the surrounding areas' people, ecosystems, and economies. 

Yasin Sentamu, the chairman of Kagera Cell 10, explains that while some fish species can tolerate the blooms, Nile perch is usually driven away from the infested areas to search for freshwater. 

The excess algae can be fatal to fish. As a result, he adds, fish species that require a higher level of dissolved oxygen may migrate to deeper waters of the lake in search of suitable conditions, which leads to fish scarcity. 

“Tilapia and African lungfish are among the fish species that can survive in polluted waters and coexist with organisms that thrive in such conditions. Despite the presence of algal blooms, these fish can still be caught in a net, unlike Nile perch, which tends to avoid such areas,” he says.

Environment authorities

According to Rose Nakyejjwe, the Masaka district environment officer, algal blooms flourish in areas where there are excess nutrients, such as phosphorus and nitrogen. 

These nutrients are typically introduced into the water due to runoff from land-based sources, such as animal waste, fertilizers, and sewage. 

As a result, the blooms can deplete oxygen levels in the water, leading to the suffocation of fish, particularly those that are sensitive to low oxygen levels, such as Nile Perch, tilapia, haplochromines, and rastrineobola. 

Houses submerged at Lambu landing site in the wake of the rising water levels in Lake Victoria

Houses submerged at Lambu landing site in the wake of the rising water levels in Lake Victoria

“Just like water hyacinth and hippo grass, algal and cyanobacterial blooms are considered invasive plant species that tend to replace native species, leading to ecological imbalances that promote the growth of algal blooms,” said Nakyejjwe. 

The surge in agricultural activities and the utilization of fertilizers, pesticides, and fungicides along the lake’s banks is believed to be the primary cause of the escalating blooms. 

“Such agrochemicals, liquid and solid industrial waste, and soil are commonly washed into the lake, leading to a rise in nutrient levels,” she explained.


Researchers, according to the 2020 study on Harmful Algae, say that Lake Victoria (LV) has undergone a gradual process of eutrophication, resulting in significant alterations in the fish population and recurrent growth of water hyacinth, as well as algal or cyanobacterial blooms. 

Mark Olokotum, a research scientist at the National Fisheries Resources Research Institute (NaFIRRI), and one of the authors of the study, states that the presence of cyanobacterial blooms has two primary effects on fish communities. 

Firstly, it alters the environmental conditions that fish inhabit, which can negatively impact the abundance and diversity of fish populations in Lake Victoria. 

Secondly, it can lead to the accumulation of cyanotoxins in fish, which poses risks for human populations that consume these contaminated fish. 

According to Olokotum, microcystins (MC) concentrations, which are toxins produced by certain species of cyanobacteria (blue-green algae), can be harmful to humans and animals if ingested in high amounts and are a cause for concern in bodies of water experiencing cyanobacterial blooms. 

“When bacteria break down organic matter produced by cyanobacteria in lakes, it can lead to severe oxygen depletion at the bottom of deep lakes or throughout the water column in shallow lakes,” he says, adding that this can cause harm to the fish community and other organisms living in the lake The study further highlights a lack of information regarding the potential health risks to people who use Lake Victoria water directly for activities such as cooking, washing, or recreation, during cyanobacterial bloom events. 

Kasensero Town Council Councillor Joseph Kimera

Kasensero Town Council Councillor Joseph Kimera

Apart from the potential risks associated with consuming untreated or treated water and contaminated fish, the researchers note that cyanobacterial blooms can also have direct and indirect effects on the cost and availability of drinking water produced by treatment plants. 


Environment advocates from Biodiversity Conservation Foundation (BCF), Green Climate Campaign Africa (GCCF), and Fridays for Future Uganda recently launched a campaign to relieve Lake Victoria of pollutants, including invasive aquatic weed, algal blooms, and plastics. 

The campaign, launched at the Lambu landing site in Bukakata sub-county, Masaka district, aims to increase solid waste collection at various landing sites across the Greater Masaka region to ensure proper sanitation and safety of the water. 

Despite efforts of the Uganda-Egypt Aquatic Weed Control project to eradicate water hyacinth, there remains a significant and overlooked challenge of algae in Lake Victoria. 

Antonio Kalyango, the executive director of the Biodiversity Conservation Forum (BFC), has noted that the government has not allocated enough resources to eliminate invasive algae species and address other issues affecting the lake and its ecosystems. 

To combat this problem, he says, environmentalists and NGOs are partnering to educate communities around the lake on the importance of protecting the lake from bloom contamination. 

A survey conducted by the BCF following massive fish deaths revealed alarming levels of lake pollution due to solid waste dumping and encroachment on catchment areas by farmers, who use chemicals that end up in the lake. 

For instance, the Lwera and Lutembe catchment areas were allocated to investors for development, exacerbating the problem. 

While plastic pollution remains a significant challenge, people should also be aware of other factors contributing to lake pollution. 

Authorities should reconsider discussions that permit the use of chemicals in catchment areas and take appropriate measures to prevent harmful substances from entering the lake. 

Timothy Mugerwa, the executive director of GCCF, urged the government to support efforts to preserve the lake and improve the sanitation of landing sites. 

According to him, the lake is not only affected by climate change but also by human activities, which must be considered. 

Recent research suggests that plastic waste and climate change are the primary causes of the lake’s degradation, leading to the presence of toxic chemicals and solid waste that have affected the water quality.

Way out

Despite the severity of the situation, experts say that something can be done to protect the lake, fish, and water quality. 

They emphasize the need to invest in solutions, such as early warning systems, to detect algal blooms, effective management of the agricultural and industrial sectors to reduce nutrient runoff, and the promotion of sustainable fishing practices. 

They also stress the need for increased public awareness of the dangers of consuming poisonous algae, which can harm both fish and humans. 

By taking these steps, experts believe it is possible to combat algal blooms and protect Lake Victoria’s ecosystem for future generations. 

Other solutions include reducing nutrient pollution: 

Algal blooms thrive on nutrients, such as nitrogen and phosphorus, that come from agricultural and urban runoff. 

Reducing nutrient pollution can limit the growth of harmful algae and prevent them from taking over the lake’s ecosystem. 

They say that promoting sustainable fishing practices, such as using selective gear and avoiding fishing during breeding seasons, can help maintain healthy fish populations and support long-term fish production.

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