Over the course of the past few weeks, visitors to Cape Town’s beaches have noticed a large number of jellyfish washing up – particularly on Milnerton Beach, Bloubergstrand, LagoonBeach, and False Bay.
The most prevalent species in our area is the compass jellyfish – which gained its name for the distinct brown marking which cover its bell; these markings closely resemble a compass.
Three specific species are found in South African waters – the Benguela compass jellyfish, the purple compass jellyfish, and the Cape compass jellyfish.
The majority of the jellyfish washing up on Cape shores appear to be of the Cape compass variety.
Jellyfish are planktonic – meaning they drift around in the ocean – and the cause of these mass wash-ups may be attributed to a combination of wind and current.
“This poses no problem to their species as a whole,” Two Oceans Aquarium cautions. “They are very abundant offshore.”
The large number of compass jellyfish found around Cape Town’s shores indicate that our waters are very rich in nutrients, and as a result rich in phytoplankton. These are the microscopic plants which form the base of the ocean’s foodchain, and feed the small fish and crusteceans jellyfish feed on.
Sometimes, a large number of jellyfish washing up on shores may also be indicative of pollution adding nutrients to the ocean’s waters. At this point, however, it is not yet clear why the Cape’s compass jellyfish are washing up in such massive numbers.
“When these nutrient influxes are particularly high, ocean plants can grow so rapidly that they deplete the oxygen causing a phenomenon called ‘red tide’,” Two Oceans Aquarium said. “No red tide warning has been issued by the Department of Agriculture, Forestry and Fisheries (DAFF), so no need to be concerned!”
The sting of a compass jellyfish is comparable to that of a bee. “Other than being very painful, there is little danger to humans, unless you are allergic or get stung over a large portion of your body,” the Aquarium said. “Jellies that wash up and are exposed to dry air lose their ability to sting once they are dried out, but can still give you a nasty sting as long as they remain moist. Luckily, the tentacles of compass jellies are fragile and most of the washed-up specimens we’ve seen seem to have lost their tentacles, so those that are found on the beaches are unlikely to pose much risk to children, bathers and pets that may accidentally touch one.”
Source: Two Oceans Aquarium Blog