Abstract:

Hydrilla verticillata invasion at Pongolapoort Dam: is it a crisis?

Jabulile Sithole¹, Rene Glen², and Ryan Brudvig³

¹Early Detection and Rapid Response Programme (EDRR),  South African National Biodiversity Institute, P.O Box 52099, Berea Road, 4007, Durban, South Africa.
²School of Biological Sciences, University of KwaZulu-Natal, Durban, South Africa
³Natural Resources Management, Department of Environmental Affairs,  South Africa

The ecological damage and economic loss caused by invasion of Hydrilla verticillata in other countries meant that the discovery of Hydrilla in South Africa at Pongolapoort Dam in 2006 caused widespread concern. Pongolapoort Dam is widely known for tiger-fishing competitions and there is a frequent movement of boats by sport-fishermen between Swaziland, South Africa and Mozambique – where Hydrilla was first recorded in 1961. The purpose of the study was to monitor Hydrilla invasion in this artificial impoundment over a period of three years, understand the processes involved in its invasion and assess how much damage it is causing. During the spring of 2009 Hydrilla comprised 47% of the submerged aquatic flora (2779 ha): Compared with the 600ha extent which was reported when it was first discovered in 2006, this is a marked increase. In 2010 the Hydrilla contribution decreased to 35% and then increased slightly to 39% in 2011. In the early summer of 2011 water was released which dropped the water level about 1m. This encouraged more Hydrilla invasions which increased to 67%. Temperature and depth show a positive correlation with Hydrilla coverage. A high concentration of NO3 and PO4 from fertilizer run-off was also recorded. The management of Hydrilla requires the involvement of all stakeholders. The release of water from the dam needs to be carefully planned as it has had negative consequences for the management of Hydrilla in this impoundment.

Presentation Topic

Hydrilla verticillata invasion at Pongolapoort Dam: is it a crisis?

 

Contact Ms Sithole: South African National Biodiversity Institute, P.O Box 52099, Berea Road, 4007, Durban, South Africa.

 

Email Ms Sithole