Here is a report from Jenny Edwards and Jane Elek from the Nature Coast Marine Group about the recent phenomenon of millions of bluebottles washing up around Narooma and Far South Coast NSW.
Anyone walking on our beaches or even reading the local papers will have noticed that huge numbers of bluebottles have been washed up on our beaches during the last few weeks, into marinas and piling up in any rocky cove.
Photos of a dense mat of bluebottles washed up on the rocks south of Batemans Bay went viral earlier this month.
There is nothing rare or endangered about bluebottles. They are about the most common animal we find washed ashore on our beaches and are relished by children who love to stomp on them to make them pop.
They tend to be washed onto our shores by onshore northeasterly winds and is a sign that the water has warmed up.
If they are washed up on the beach and still fresh, it may usually means that they are also floating in the surf, so it is quite likely that swimmers will get stung.
Even when they are washed up on the beach they can still sting. If anyone gets stung, pick off the tentacles, as the skin on your fingers is usually too tough for the stingers to penetrate.
Then wash the area with salt water to remove any remaining stinging cells and apply a hot pack or water, as hot as you can stand without scalding.
If a hot pack is not available, use an ice/cold pack to relieve the pain. Do not use vinegar as this may cause more stinging cells to discharge. If it the sting is still causing a lot of pain and distress, or is covering a large area of skin, take the patient to hospital or call an ambulance.
Bluebottles (Physalia spp.) may not be everyone’s favourite but they are worth a closer look.
Each blue bottle is a colony of animals related to corals, jellyfish and sea anemones since they all use stinging cells to catch their food.
One individual swells up with gas and becomes the float. It is oriented at 45 degrees, half the population to the right and half to the left so that not all colonies will drift in the same direction.
The underside of the float is an oval disc which secretes the gas, a slightly different composition in every bluebottle and different to air. The oval disc also has a cavity which acts as a common stomach for all the other individuals in the colony.
The rest of the colony is made up of many groups of polyps suspended from the float. Each group has three types of polyps.
One is a feeding polyp with a sucker-like mouth at the end furthest from the float. Another is the fishing polyp which is long and string-like with stinging cells.
These cells are triggered by touch, firing a barbed dart and poison into the small animals on which the colony preys or the swimmer.
The fishing tentacles retract to deliver their catch of small fish or zooplankton to the feeding polyps which digest the food and share it with the colony.
The third polyp is branched with two types of branches. One type produces sperm and the other type eggs. A fertilized egg develops into a larval polyp which grows into a float for a new colony. Buds from it develop into all the other types of polyps.
If you look closely at a mass of blue bottles on the beach often you will also find a lovely fragile, violet snail, sometimes with a froth of bubbles still attached (Janthina spp.) as well as some curious goose barnacles.
This snail uses its raft of bubbles to float upside down under the surface of the water along with the blue bottles on which it feeds. Each snail is born as a male and later transforms into a female.
The Nature Coast Marine Group has an extensive program of activities where members can have fun learning about our marine environment. To find out more about the group visit the website www.ncmg.org.au
