Sandspit “Seasnot” Degenerating for the Winter

It looks like the sea snot, or Australian droplet tunicate, is slowly degenerating for the winter, but there are large numbers of juveniles which may stay in a dormant state until the spring.

The Australian droplet tunicate is still abundant at Sandspit, but appears to be degenerating with the onset of winter and cooler temperatures.  Photo: 1 May 2014.

The Australian droplet tunicate is still abundant at Sandspit, but appears to be degenerating with the onset of winter and cooler temperatures. Photo: 1 May 2014.

The larger adults are infested with fine red algae on the lower parts of the colonies, and the upper parts of the larger colonies are becoming dissected with furrows and grooves as they slowly fall apart.

The larger colonies are starting to break up, with grooves and furrows dissecting their surface.  This makes them look even more ugly than normal!  Photo: 1 May 2014.

The larger colonies are starting to break up, with grooves and furrows dissecting their surface. This makes them look even more ugly than normal! Photo: 1 May 2014.

It is currently not known how the tunicate copes with the winter, but clearly there is a dormant stage which survives then springs to life again when the water warms. There are huge numbers of juveniles only two or three millimetres across, close to the larger colonies beginning to break up.

There are enormous numbers of juvenile colonies only two or three millimetres across scattered among the degenerating adults.  This may be part of the survival strategy of the tunicates over the cooler winter months.  The larger colonies are infested by fine red algae on their lower parts.  Photo: 1 May 2014.

There are enormous numbers of juvenile colonies only two or three millimetres across scattered among the degenerating adults. This may be part of the survival strategy of the tunicates over the cooler winter months. The larger colonies are infested by fine red algae on their lower parts. Photo: 1 May 2014.

Having invaded Northland in 2007, the Australian droplet tunicate, Eudistoma elongatum, has been present in increasing numbers at Sandspit since 2010. Throughout the summer it has been abundant on the wharf piles, sandstone ledges toward low tide, in the subtidal channel, and scattered on shells around the estuary edge. It is also present on some moored vessels, mooring ropes and piles.

So far the Australian droplet tunicate has not been seen at Whangateau Harbour. Unconfirmed reports indicate that the tunicate may already have reached the Mahurangi Harbour and is infecting oyster farms. Unless special care is taken, it is inevitable that sooner or later it will reach Auckland where it will be a very unpopular addition to the beaches at Takapuna and Mission Bay! It can only move such distances when assisted by human intervention, on boats, tugs, barges, or dumped dredgings.

Comments

  1. Many thanks Ian!

    Roger    

    ________________________________

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