Monday, June 25, 2012

Swatting a Fly with a Sledgehammer

If you like to swim in the Chesapeake, but don’t like being stung by jellyfish, a new high-tech bay buoy system can help.

The National Oceanic and Atmospheric Administration says the Chesapeake Bay Interpretive Buoy System can tell when conditions are right for jellyfish, also known as sea nettles. NOAA says sea nettles are found from Cape Cod to the Caribbean but abound in the Chesapeake.

NOAA says observations have found concentrations of jellyfish are normally found in water between 79 and 86 degrees and in a specific salinity range. The buoys are listed on an online map, which shows data for each buoy, including sea nettle probability.
Using the buoy system to predict the probability of finding Sea Nettles (Chrysaora quinquecirrha, the incredibly abundant and highly annoying stinging jellyfish of the East Coast) with multimillion dollar buoy system strikes me as the acme of overkill.  If it's summertime in Chesapeake Bay, there's a really excellent chance of finding yourself wading or swimming with Sea Nettles.  Sure, they have preferred salinity range (pretty broad, but they won't be found in very fresh water), and it takes them a while to get going as the bay heat up, and their most important prey, the comb jelly to get going, but really, it's a pretty wide range of both time and space.

Now of course, that's not really all the buoys are doing; they're collecting a wide range of oceanographic data.  The "sea nettle probability" is just generated from some regression model from a suite of these values.

I  looked for the buoy closest to me, Gooses Reef, and indeed, there on line 19, nestled between relative humidity, and ocean acidity, was sea nettle probability, 27.8%.  What that means is unclear to me.  Does that mean if I go out to the Gooses Reef buoy (about 30 minutes by boat, or a long, wet walk from my beach), would I find a sea nettle in sight 25.7% of the time (using some calibrated system for looking for one)?  Gooses reef is so far from me, and anyone swimming except from a boat near Gooses Reef (a favorite fishing spot, but not considered a swimming hole).  How does that apply to my beach?  Sometimes the nettles are thick on the shore, and sometimes quite rare; I think it has a lot to do with wind moving the surface waters around, myself.

But, on the other hand 25% seems like a reasonable number.  I've seen nettles this year, but not too many yet.  Is my intuition as good as a million dollar buoy?

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