Knysna estuary, South Africa

The Knysna estuary is found along the southern coast of South Africa in an area known as the Garden Route. The estuary is typical of many estuarine systems with its shallow mud banks, eelgrass, Zostera marina, seagrass meadows and oyster beds. And as with many estuary systems it is threatened by an array of human activities.

Estuaries along the South African coast are sheltered from the high-energy coastal waters so become popular recreational areas, harbours, and mariculture areas. In recent years Knysna has developed both residential and tourist areas and become more intensely populated. It is this development and the ensuing pollution that is threatening animals in the estuary. One in particular has become a focus of attention; The Knysna seahorse, Hippocampus capensis, is endemic to South Africa and only found in the Knysna and Swartvlei estuaries. These seahorses are considered the most endangered seahorses in the world and due to their very limited range, low population, and the increasing threat that their habitat is facing they were added to the IUCN Red list as an endangered species in 2001.

South African law protects the Knysna seahorse and nobody is allowed to remove or disturb a Knysna seahorse however the impacts of land run off, sewage discharge, littering and illegal dumping have taken their toll on the estuary as a whole and thus the seahorses. Recent developments between Leisure Isle and Thesen's Island, a popular breeding area for the seahorse, threaten the population further as does their illegal trade for the Chinese medicine markets, aquarium trade, and as curios. Boat propellers, particularly in shallow areas, destroy the seagrass beds where these animals live, as well as killing seahorses in the grasses. Even people wading in the lagoon can inadvertently hurt or kill seahorses by standing on them.