Fragile seahorses under threat

21 June 2017 - 07:48
Seahorse. File photo.
Image: Gallo Images/iStockphoto Seahorse. File photo.

The endangered Knysna seahorse, and the sea grass it depends upon, could be unlikely victims of the recent fires.

Safe from the heat of the infernos that ravaged the area, the seahorse could come under threat from the inflow of ash and eroded topsoil from the surrounding land, said the Endangered Wildlife Trust.

Just 12cm long, the seahorse lives in the estuaries at Sedgefield and Keurbooms, with its stronghold in the Knysna Estuary.

The organisation's Grant Smith said concern about the species is related to the health of the "eel grass" on which seahorses and 90 other estuary species rely.

"The seahorse holds onto the eel grass with its tail and feeds on small invertebrates that float past. The eel grass is already under pressure from the nutrient load in the estuary as a result of development and sewage spills," said Smith.

"The worry is that this new inflow of silt will increase the nutrient load on the eel grass, reducing its ability to photosynthesise and flourish as it needs to."

The trust will be working together with the authorities, the Knysna Basin Project, and the estuary management forum to implement solutions.

This will include stabilising fire-ravaged banks and installing traps to filter out the sediment inflow of topsoil, ash and other debris, said Smith.

The Knysna Basin Project's Louw Claassens said it was assumed that erosion and estuary sedimentation would occur because of the fires but critical areas now needed to be identified.

The Knysna Municipality is running this task with the help of the Endangered Wildlife Trust, SANParks and local NGOs.

"If the sea grass and especially eel grass habitat is lost as a result of the sedimentation it will have a direct negative impact on the seahorse and many other species including the critically endangered limpet Siphonaria compressa," said Claassens.