Recent reports suggest that approximately 40% of the water surface of the Hartbeespoort Dam in the North-West is covered by invasive hyacinth.
However, there is a glimmer of hope as the plants show signs of stress caused by the Megamelus bugs—according to the Centre for Biological Control (CBC).
The dense mats of hyacinth have created significant ecological challenges at the dam. A surge in fish deaths has occurred along its shores in recent weeks.
According to Casper Kruger from Hartbeespoort Fisheries, these fatalities are due to oxygen deprivation beneath the thick hyacinth layers.
“There are currently lots of young fish and if the wind suddenly blows a thick hyacinth mat over the schools of fish, it cuts off oxygen,” Kruger told Hartbeespoort community paper Kormorant.
“We have been installing aerators at various points to assist where fish were dying.
Latest images
On Sunday social activist Yusuf Abrmajee posted a recent photo of water hyacinth choking a section of the dam filled with boats.
This was followed up with a post by energy expert Chris Hart, showing an extensive mat of hyacinth near the dam wall.
Magalies Water (MW), who are leading the Hartbeespoort Dam Remediation Project, is currently investigating both the fish deaths and the overall condition of the dam.
The entity has also been manually removing the invasive plant, and this continued during the festive season.
“It is a well-known fact that the regrowth rate of the hyacinth increases during the summer months as a result of persistent heat,” added MW spokesperson Bulelwa Mbali-Khoele.
“The biggest challenge is upstream pollution. We can only manage growth by curbing the rate at which the plant is growing.”
What is water hyacinth?
Common water hyacinth is an aquatic plant native to South America, that has naturalised throughout the world and is often invasive outside its native range.
The main reason for its rapid growth at Hartbeespoort has been an influx of nutrients into the dam. Sources include untreated sewage from surrounding settlements, agricultural runoff, and fertiliser from golf courses and gardens. These nutrients create ideal conditions for the hyacinth to flourish.
The water hyacinth also causes substantial danger to small craft users at Hartbeespoort dam, and the NSRI have previously advised boat users against entering the mats.
Water bugs become an ally
Meanwhile, the CBC has been closely monitoring the impact of the introduction of Megamelus bugs on the invasive hyacinth.
Based on an inspection last week, the bug population is growing. These biological control agents have helped curb the spread of hyacinth by eating through and killing off the plant.
“The [insect] population is spreading through the hyacinth mat and the bugs are mating, meaning their numbers will grow exponentially,” noted Dr. Kelby English from the CBC.
“It is expected that the plants will die in late February as they did last year.”
Have you visited Harties recently? How bad is the hyacinth invasion?
Let us know by clicking on the comment tab below this article or emailing info@thesouthafrican.com or sending a WhatsApp to 060 011 021 1.
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