Winter storms have once again brought large rafts of kelp onto the beach.
The bladders which give this seaweed its name can be clearly seen. They keep the blades of kelp floating near the surface of the sea, so the plants can easily photosynthesise.
The kelp is related to the giant kelp found in the North Pacific. But ours Macrocystis pyrifera,can grow just as fast - some websites report half a metre a day, others a mere 30cm, but of course that will be at the height of the growing season - in summer!
There is a report on the anatomy of kelp-fish by F.J. Knox, where he dsecribes in August 1870, how there were 'vast submerged forests with stems two or more feet in circumference fixed to the bottom of the sea, [which] is often used by Cook's Strait fishermen and captains of small coasting vessels to secure their crafts to in a gale of wind.'
All I can say is that if you had secured your boat to these specimens you'd have been in for a nasty shock, they were clearly not big enough to secure any-sized boat.
Reference: "Observations on Coridodax pullus" by F. J. Knox, L.R.C.S.E., Transactions & Proceedings of the Royal Society of New Zealand, vol 3, 1870
