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From: Nick Shears
Date: 25-04-08
Time: 13:14
Hi Wade,
Hope all is well in NZ and you guys are squeezing the most out of summer!
I am currently writing up the research I did at Leigh on the dinoflagellate blooms that result in the kina losing their spines (and in some cases dying). I was wondering if I could post some pics on your site and send a message asking your diving audience to let me know when and where they might have seen such events.
There was discussion and some pictures on this phenomenon posted on the site a while back, but here is some background information: The dinoflagellate (Ostreopsis siamensis) is a benthic species so spends most of its time on the reef rather than drifting around in the water column. It was first recorded in New Zealand in 1995 and seems to have increased in occurrence over the last 10 years. It is highly visible and appears as a rusty brown filamentous layer or “fuzz” covering the reef and seaweeds (see pics). The blooms normally occur in shallow water (<8 m) in mid-late summer when the sea temperatures are warm (>20C) and usually after it has been calm for a week or so. The blooms are quickly dispersed by any significant wave action.
One of the main characteristics and consequences of these blooms is areas of sea urchins (kina) that have lost their primary or guard spines (they look like they have had number 2 haircuts). Initially the urchins will appear with all their spines folded over, and after a few days the spines will begin falling out. Eventually, under extreme bloom conditions the urchins will lose all of their spines and can die as a result of the bloom (if they are not eaten first). Once a bloom has subsided or been dispersed by waves the surviving urchins generally regenerate their spines over about a 3 month period. As a result, it is common to see a patch of urchins with short spines but no signs of the dinoflagellate on the reef.
At the moment I am trying to establish where such events have been observed around NZ. If any divers have seen these blooms or sick looking urchins it would be very helpful if they could email me (shears@msi.ucsb.edu) with the location, date, and a general description of what was observed. Also any photos of the specific observations would be much appreciated.
Thanks a lot and I will keep you posted on the results, Nick Shears
Bald Urchin and ostreopis
High conc of ostreopis on C_plumosum
Urchin with spines folded ostreopis visible on spine tips
Urchins losing spines Surrounded by ostreopis small
Last changed: 25-Apr-2008