Taking a group along the shore of the tidal lagoon, yet another huge gelatinous dome lay on the stony strand line, pink-tinged tentacles trailing. Looking down at the translucent jelly, someone noticed definite pulsing where the folded edge of the blue stained umbrella fringe lay on the stones. Carefully avoiding the tentacles, the Common or Moon Jelly was re-floated in the estuary lagoon, though with little hope of long-term survival. Later, a burning sensation on the side of the face demonstrated that not only the tentacles carry venom.
One evening, a clear strip of what looked like thousands of saucer sized warts or lenses formed a dense strand line on the beach, water’s edge thick with Jellies, like wading into frogspawn. Later again, fishing in the estuary mouth, the apparent occasional slow heave of Mullet breaking the surface turned out to be more massive Moon Jellies sucked into the estuary by inflowing tide, diaphanous pinkish clouds pulsing underwater as they floated past.
Taking a diversion past a Sand Martin colony en-route to Samphire beds, several flat, shining, dinner plate-sized lenses lay on wet estuary sand, characteristic brown radial dial marking revealing well named Compass Jellies only recently colonising British waters. Whilst carefully re-floating one still pulsing upside-down in a flooded mud pool high on the salting, a circular mark nearby on the short sea-washed turf demonstrated how little of substance remains after evaporation in hot sun: just a thin translucent brownish crust, like the edge of a well fried egg.
It seems that it is not known what causes these ‘blooms’, population explosion and mass stranding, or if a regular or recent phenomenon. Population explosions of other organisms are often created by habitat disruption with some thought that these simple organisms may be exploiting an ecological imbalance created by over-fishing.
Wildlife Wales Activities: www.wildlife-wales.co.uk