Rare giant sea eggs have become the latest victims of the algal bloom still affecting inshore waters from Bream Bay to the Hauraki Gulf.
The death of scallops, unable to survive on the deoxygenated seabed, has already been linked with the bloom. [they died from being suffocated by stringy planktonic algae, JFA] This week divers at Leigh have found rare sea eggs the size of small pumpkins but, like the scallops, they have also died of the conditions. Dr John Walsby, the marine biologist studying the effects of the bloom at Leigh, said the discovery of the sea eggs was probably related to the bloom. "Only the shells of these sea eggs have been found", he said. "Although some of the specimens still had a few spines attached, none of the shells had any marine growth on them. "They had clearly died only recently"
Dr Walsby said the eggs, identified as Brissus gigas, were rare in New Zealand. [nobody knew where they occurred, but they are not rare, JFA] The first was discovered in 1947 and seven more were found in 1965. All were from the Bay of Islands. [and all were fragments, JFA] The largest ever recorded was found this week. It was 19 cm long and 16 cm wide.
"Sea eggs like these, unlike the familiar kina, have all their spines laid back like well-combed hair," Dr Walsby said. "The animals move about below the surface of soft sediments, probably where the bottom is of deep, muddy sand. [they live in coarse broken shell or loose sand, JFA]. "The backwardly directed spines help to propel the animal forward as it burrows just below the surface." [the giant heart urchin hardly moves, and it is burrowed rather deep 20-30cm, JFA]
Dr Walsby said the eggs, which lived permanently buried, had probably surfaced on to the seabed in a last desperate effort to stay alive. But they had perished along with other life in the blanket of decay. "It is quite possible," he said, "that other interesting news may turn up as a result of the freak conditions occurring at the moment."
Dr Floor Anthoni (left) and Mr Marcel Scholtens
examining the sea eggs.
(Photo NZ Herald)