Keep an eye out for jellyfish
Swimmers warned of an abundance of stinging creatures
The National Institute of Water and Atmospheric Research (Niwa) is urging swimmers to be cautious this summer as jellyfish swarm Waikato’s beaches in search of plankton.
Stings from jellyfish can induce symptoms that include burning sensations on the skin, accompanied by numbness at the sting’s site, which may also turn red or purple.
Niwa Emeritus researcher and jellyfish expert Dr Dennis Gordon says it is common to start seeing more jellyfish at the beach at this time of year.
“As soon as the days start to get longer and there’s more daylight, you get a bloom of more plankton.
“When there is more plant plankton, there’s more animal plankton, which means you get more shrimps and things — and jellyfish feed on those small crustaceans.”
Most jellyfish lurk in shallow water, with around 35 species found in New Zealand waters.
According to Waikato Regional Council, warm sea temperatures and an increase in salinity, nutrients and oxygen all contribute to increases in the abundance of jellyfish.
Several species of jellyfish are commonly seen in coastal areas of the Waikato region.
These include moon jellyfish, which are whitish and have a fringe of short tentacles on the outer margins of the bell.
Lion’s mane jellyfish in Waikato waters measure up to 50cm across, although there have been frequent sightings around the Coromandel of Lion’s Mane jellyfish measuring more than 1m in diameter and specimens larger than 2m have been found in the northern hemisphere.
Dome-shaped spotted jellyfish have reddish-brown dots on the top of the bell and boast eight groups of long tentacles.
Although not a true jellyfish, bluebottles are probably the bestknown jellies in New Zealand waters, and Auckland’s west coast beaches have recently been swamped with strandings.
Jellyfish often wash up and become stranded on beaches in dense groups said Dr Gordon.
“The wind steers the majestic creatures on to the shore because they are light and have a gas-filled float.”
Gordon said water users should be aware of the ferocity of a jelly’s sting:
“Despite being really beautiful, the lion’s mane and spotted jellyfish can produce a very painful sting, as can the bluebottle.”
Stinging is caused by the thousands of microscopic stinger capsules, or nematocysts, on the surface of the tentacles. Upon contact, the nematocysts simultaneously discharge their venom, delivering a nasty sting — so it is best not to touch the tentacles. It is safe to touch the top of the bell.
“Those who do plan on getting in the water should be cautious and wear a wetsuit if it is known that there may be jellyfish in the area,” Dr Gordon said.
Common symptoms of a jellyfish sting include a burning sensation on the skin, a tingling or numbness where the sting occurred, and the sting area turning purple or red.
If a person is stung, NIWA advises flushing the sting area with seawater to remove the tentacles, followed by a dry towel to remove the remaining tentacles.
The affected area should then be immersed in hot (but comfortable) water for 15 to 20 minutes and pain relief or antihistamines can be used if required.
Using urine to relieve a jellyfish sting is a popular misconception. As there is no way of telling the ph and chemical makeup, it could worsen the pain.
Gordon encourages common sense when encountering jellyfish:
“Jellyfish are enchanting, delicate creatures that should be appreciated, just not too close.”