Lake Champlain is the sixth largest body of freshwater in the United States. Its nearly 600 miles of shoreline is bordered by Vermont to the east and New York to the west. The deepest and widest section of the lake is the home of Burlington Harbor and the University of Vermont's Rubenstein Ecosystem Science Laboratory.
Jason Stockwell, director of the lab, is doing research with UVM senior biology student Molly Morrissey on the vertical migration of Mysis shrimp, and has invited us to join them on a sampling trip.
Mysis shrimp is a glacial invertebrate inhibiting Lake Champlain since the end of the last glacial period -- over 10,000 years ago.
And in aquatic systems, both marine and freshwater, there is this phenomenon that is called Diel vertical migration, where a lot of the organisms will be down deep during the day and rise up in the evening, and feed at night, and then go back down during the day. And the thought is that they're going down deep to hide from visual predators, who can see them easier in the surface waters. So, they can feed on things up at the surface, but they can also feed on things down deep.
And so, the question is: Why are they undergoing this vertical migration? And so, the research we're doing is trying to get at these mechanisms of what's controlling that behavior.
On an unseasonably warm and cloudy mid-November afternoon, we board the Melosira, UVM's 45-foot research vessel.
Molly Morrissey's a fourth-year student, she's in biology, and she wanted to do research experience, get her hands wet. So, she's leading the charge on this effort.
And Bill Wurthell is my work-study student for this year, and he's been cleaning a lot of bottle, little bottles, but slowly we're getting him into more interesting things.
Also joining us is Professor Ellen Marsden, interim director of UVM's Wildlife and Fisheries Biology, and Chelsea Mitchell, UVM third-year biology student.
The Melosira leaves the dock at Burlington Harbor one and a half hours before sunset, with Captain Bill Lowell at the helm.
This is our electronic navigation program, and it feeds us information from our GPS. And we're going out into about 100 meters of water. And right now we're now navigating with the autopilot.
The work that we're doing is pilot work. We're trying to explore whether we can use enzymes, metabolic enzymes, in Mysis to serve as a proxy for their activity, for their migrations.
We were collecting animals down deep before sunset, when they're all done there, and collecting them up high, after sunset. And we're going to compare their enzymatic levels between those two time periods, and the hypothesis Molly is testing is: Are the enzyme levels in these Mysis that are up high after sunset greater than the enzyme levels that are down in the Mysis during the day when they're on the bottom?
The first Mysis sampling at the bottom of the lake is conducted 45 minutes before sunset.
We use something that's called the closing net. It basically has a trigger mechanism where you lower the net to the bottom, you start raising it, and you send a trigger down the wire, and it trips a mechanism which collapses the net on itself. And then you haul it up. And so, you're not sampling throughout the whole water column.
You see any?
Oh, there's one.
Oh, there's a few in here.
Oh, you got... 6.
You can see his legs moving.
So, the samples that we look at tonight, we're going to look at this certain protein called LEH, we're going to look at the content and compare it between the different types of Mysis that we're getting.
After the first sampling at the bottom of the lake with the closing net, we wait until just after sunset for the second sampling.
We wanted to catch the Mysis up high in the water column for that comparison, and so we use what's called the Tucker trawl, and it's basically a rectangular mouth opening with a fairly fine mesh net on it. And we just tow it along behind the boat at a certain depth, basically picking up Mysis like a trawl would a fish, and bring that aboard.
Now you're talking.
On board we pick through the sample, and we're looking at two different sizes of Mysis, big and small. We put them in a vial and put them on dry ice right away to quickly freeze them to lock in the enzymatic activities. And then we'll bring those into lab and do the enzyme analysis on that.
After two more Trucker trawl samplings at the surface, and one more closing-net sampling at the bottom of the lake, we return home to Burlington Harbor four hours after sunset.
So, did you enjoy that?
Yeah, it was great. Phenomenal.
One of the things I enjoy about science is teaching it to students in one-on-one situations, and seeing the excitement on their face, having them say, "This is the coolest thing I've ever done."
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