Possible evidence of a red tide was observed in the Knysna Heads on Sunday afternoon (the 19th January 2014). Authorities (SANParks, Knysna Municipality and the Knysna Basin Project) are cautioning against the collection of shellfish from the Knysna estuary until further notice.
Common types of red tide can kill shellfish, abalone, black and white mussels and oysters. Other blooms can be stored in mussels until they become poisonous if eaten by humans.
What are these phytoplankton organisms?
Phytoplankton are ‘microscopic, single-celled organisms that float in the sea, according to a Marine and Coastal Management Guideline from the Department of Environmental Affairs. They are able to photosynthesise and form the basis of food chains in the oceans. There are three types of red tide organisms, dinoflagellates, diatoms and ciliates.’
Dinoflagellates usually lie dormant on the seabed until they are lifted to the surface during upwelling where the ideal conditions of temperature and light trigger their germination.
Paralytic Shellfish Poisoning (PSP), which produces toxins that disrupt normal nerve functions, can be associated closely with dinoflagellate. Symptoms of PSP appear anytime between one and five hours after eating contaminated seafood.
Issued by : South African National Parks (SANParks) Corporate Communications:
Tel: 044 302 5633