A red tide that has spread to the Garden Route is just the latest marine headache for Knysna, where residents have expressed alarm over the deterioration of their once pristine estuary. Chemicals entering the water are to blame for the rampant growth of algae and sea lettuce in the estuary - often incorrectly referred to as a lagoon - despite R55.5-million being spent on pollution prevention measures.The salt-water estuary is the biggest and most ecologically important in the country, acting as a linefish nursery and hosting 43% of the country's estuarine life."The estuary is continuing to deteriorate due to a continual algal bloom caused by too many chemicals entering the water," said Mike Hampton, a blogger and community activist.Professor Brian Allanson, who started the Knysna Basin Project, an NGO that monitors the estuary, agreed that sea lettuce was a problem but said this year's "bloom" was not as serious as before.story_article_left1A red tide occurs when algal blooms deplete oxygen and as they die off, discolour water. It is harmful to filter feeders such as mussels, oysters and shellfish, but this weekend's Rotary Splash festival and the Lagoon Mile swim would go ahead, a committee representing SANParks, the Knysna Basin Project, Knysna Municipality and the Eden District Municipality's health division has decided .Greg Vogt, head of Knysna Tourism, said the area was hit regularly by red tides. "Conservation agencies provide the usual alerts that one should not eat shellfish during this time and they warn against eating dead fish."Allanson expressed concern about Knysna's development and expanding population, which he said were placing strain on infrastructure, in turn leading to water contamination."If we didn't have millions of cubic metres of water flooding the estuary every day, we would be in serious trouble," he said."The sea lettuce is one of the biggest problems, because it causes shading that is killing off the organisms that grow in the lower strata of the water and that form the basis of the food chain."A resident, who did not want to be named, said the sea lettuce was becoming a problem for boaters. "It got caught up in the intake of my outboard motor recently, causing it to burn out," he said.Municipal manager Grant Easton said Knysna Municipality had spent R48-million on wastewater works upgrades, and R6.5-million on installing restaurant fat traps...