Post #2

One of our first priorities was to deploy a SeaFET, a newly designed underwater instrument programmed to measure the sea water’s pH every 10 minutes.  Along with the SeaFET we attached a tidal height recorder and a temperature recorder.  These data loggers help provide researchers with a better picture of the dynamic environment to which organisms are exposed.  Here is a happy Emily with the equipment hose-clamped to a sunken cement piling.  We will recover these in March before we leave and download the stored information.

A second priority was to collect Acanthaster planci, the crown-of-thorns sea star.  This sea star feeds on corals and periodically (about every 20 years or so) experiences huge population explosions where they can become so numerous that they literally can eat almost all the available corals in an infected area.  The reef out front of the labs here suffered such a population explosion in  ~2007, and now instead of having about 60% live coral cover has less than 10%, so it looks pretty dead at the moment.  It reminds me of the seemingly dead areas after forest fires, and like new seedlings growing in burned areas, the seemingly barren reef areas out front are loaded with tiny coral “recruits” less than 3 cm across.   Thus the cyclical “destruction” and regrowth of the coral community continues.  This has been going on for decades, if not centuries.  Interestingly, the local Polynesians see this periodic rebirth of the coral reef as a good thing, and even have a traditional song about it.

However, this means that with little live coral around, the crown-of-thorns is pretty rare right now here.  I have found no more than 2 in any given scuba dive or snorkel.  Here is a picture of one I found on my second dive.

Unfortunately, every one so far has not had ripe gonads.  (I need to get their eggs and sperm for my experiments.)  At first I determined that they were not “sexy” by dissecting them back at the labs by simply making a cut in the “armpit” area where the gonads are.  This should not kill them for they are good at regenerating.  Now I take my dissecting scissors into the water with me and open them up in situ.  Here is a male after being opened up.  The orange-brown organ is digestive gland.  The testes in this animal were tiny and not easily discerned here.  Bummer!

Perhaps the sea stars do not have large gonads because they are starving now that there is very little for them to eat.  Thus tomorrow we hope to snorkel on the west side of the island where the live coral cover is reported to be much higher.  Wish us luck!