Diel Migration

So, many times I use this blog as a space to "warm up" as a writer.  Tonight I have to put together a proposal for an upcoming panel on integrating research and teaching.  This made me think of diel migration.

Plankton is a word that means "drifter."  In other words, any plankton, from tiny microscopic guys to huge things like jellyfish are at the mercy of the current.  The horizontal current, that is.  As long as there are no strong vertical currents, plankton have limited control over their place in the water column.

This control is important because fish that eat plankton are usually visual predators.  This means that zooplankton (tiny animal plankton) need to stay out of the top of the water column during the day, when its light and fish can see them in the water.  However, because phytoplankton (tiny plant plankton) need light to photosynthesize, they are at the top of the water column also.  This is problematic, because zooplankton eat phytoplankton.  The solution?  The zooplankton stay at depth, where its dark, during the day, and migrate up closer to the surface at night to eat.  There are some special circumstances (other predator types) where this migration pattern is reversed, but we don't need to worry about that right now.

The reason I bring this up, is that years ago while I taught the ecology of lakes laboratory, we set up two or three major projects, rather than isolated weekly labs.  One project was always on phytoplankton, which we did in a lab setting, and the other was on zooplankton, which we did in the field.

The first year I was a TA, we actually monitored zooplankton populations at various depths for 24 hours.  The second time I taught this class, we broke the class into groups and each group came with me out to Lake Somerville at a different phase of the moon.

See, the zooplankton respond not to "time" per say, but to light levels.  Therefore, our expectation was that during the full moon, we would see less zooplankton at surface levels than during other phases of the moon.

I have to say, I don't particularly remember our results.  It was a memorable experience though, especially the night that I couldn't get the boat started.  See, ecology of lakes was a course taught in the Wildlife and Fisheries Sciences Department, which some refer to as the "hooks and bullets" kids.

This means, that I was out in the middle of Lake Somerville at 2:00 am, with male students who grew up fishing and hunting.  Not being able to start the boat (who do you call to come haul you off the lake at 2 am?) does not increase your ethos when you're a small woman who neither hunts nor fishes (not that I'm against either... I just didn't grow up hunting or fishing).  I did get the boat started, after a few muttered pleas for deliverance, but it certainly left an impression in my mind!

Well, that's the end of my story for tonight.  Looks like I'm off to write that panel proposal!