If you attended one of my MESSENGER Space Science workshops at the School District of Palm Beach County Science Symposium, and you are looking for online resources, you are almost there! Just click the “NASA MESSENGER Workshops and Resources” link just above here and you will be on your way. Hope you enjoyed the workshop!
To my MESSENGER Fellow friends, the part of this post you are looking for is way down at the end, after I ramble on about diving for a bit. In no way will my feelings be hurt if you skip down to the UV part!
Last week was Florida’s lobster mini-season, and it was strangely quiet. I generally have the job of captain of the Piratical while its owners Greg and Bill do the lobster hunting underwater – which sounds like a bum deal except that A) it is their boat and B) they are way better at snatching those big crustaceans than I am. I like going just because I enjoy being out on the ocean. They usually let me get a sightseeing dive in on one of the two days, so I always end up happy.
And the flat ocean and huge reduction in the number of boats out this season only made me happier. In addition I had company on the boat both days in the form of Greg’s daughter Savvy, and Bill’s son Brantley, both of whom are smart and fun to hang out with.
So the lobster hunting was so-so, 21 in two days. The marine patrol officers we were inspected by on Thursday told me that they hadn’t seen many divers get their max of 12 lobsters. We have had years where we have had 40+ lobsters per day, but this was not one of those years for us or for many others. My dive on Thursday at Queen Anne’s Reef was beautiful though, and I got to see my first Lionfish – exciting in a bad way.
Our boat saw a total of 6 of them in the two days of diving. Why are lionfish a big deal? Because they are not supposed to be here. They are an invasive species introduced by boneheads with salt water tanks who released them into the ocean when they were done with them. They are fast reproducers, voracious eaters, and due to their poison spines, have no natural predators in our waters. Yes, this is the recipe for disaster on the reef.
There is a great article in the Palm Beach Post about a possible solution to the lionfish population explosion, based on a simple fact that I was not aware of… lionfish are quite tasty! The article even compares them to hogfish – one of my favorite things to order when I am in the Keys. Some folks are trying to start a “Lionfish Derby” where prizes are given for the most lionfish speared or netted in a day. Local restaurant owners are saying that they would buy lionfish from a dealer or licensed fisherman if they were available. For once, we really need to overfish our population!
As I got ready to ascend from the dive, I conducted a little investigation that came from a conversation at the MESSENGER Fellows workshops I attended early in July. We were playing with Ultraviolet light sensitive beads as part of an investigation in the properties of light and how it can be detected and shielded by spacecraft (like MESSENGER) and my group tried submerging some beads in a small cup of water. The water seemed to have no effect on UV light, and in our discussion after the activity I asked if anyone knew how deep the water would have to be to have any measurable effect on the UV. Nobody really knew, and I realized that this was a question I could try to answer myself next time I went diving.
So here is what happened. Put 7 purple UV beads on a string along with a colored key that I ordered from Educational Innovations and laminated and punched a hole in. The key showed %UV absorbtion that was related to different shades of purple that the beads would progress through. I pulled the string of beads out at 50 feet a few minutes before I started to ascend and noticed no real change in them until I got to about 30 feet where I would say that they matched the 20% swatch. When I stopped at 20 feet to begin my 3 minute decompression stop, the bead had darkened to about 50% and stayed there for the duration of my stop. I hurried a bit to get up after my stop so I didn’t get a good read on the way up, but once on the surface the beads darkened all the way to 100%.
So I have three data points, and without taking into consideration the clarity of the water on that day (not super clear) and making the assumption that the UV-blocking properties of the water were approximately linear (is it? Not really sure…) I’m going to say that every 10 feet of water blocks about 25% of the UV originally hitting the surface. More research is probably needed… darn, I’ll need to go diving again!