Sampling James River Rockpool system in Belle Isle

My summer research is focused on how genetic difference can affect species competition strength. My experimental organisms are zooplankton. The first step of the preparation work is to get genetic different zooplankton from James river rockpool system located in Belle Isle. The ideal focal species for my competition experiment is Daphnia pulex, which is a well studied species with all of its genome sequenced, and one other zooplankton species with relative large body size. Finding them is the tricky part. No one has looked into the zooplankton in Belle Isle rockpool system before. My professor and I had no idea what species we can find there. We were hoping to find Daphnia pulex and to choose the second focal species base on what we can find.

The advantage of study rockpool system is that each single pool have its own characteristic. Different pool environment means different zooplankton species composition. This means that while normal daphnia people have to drive around to find few different lakes, we can find hundreds of pools with diverse zooplankton communities in walking distance. We thought it’s promising and not to hard to find what we were looking for in such a diverse system. However, we soon discovered our worst enemy. The Rain. When there is too much rain, James River will be flooded. Then, the river flushes into the rock pools, and set the zooplankton communities back to zero. The frequent flood made us realized that coevolution between species could be hard to find under this system, this means that our original experimental design targeting coevolution is unlikely to work. With this tiny frustration, we soon realized that we can turn the set back into our advantage in studying community assembly. Every time the river floods, some communities will have to reassemble. A new sampling survey of the system  was added into our zooplankton hunt.

We went to Belle Isle a week after James river was flooded in June. Thirty four pools scattering in different area of Belle Isle  were randomly sampled. We went through all the samples under microscopes to look for alive target species. Then, I fixed the zooplankton with absolute ethanol, so I can go back and identify all the zooplankton species in each sampled pool. Unfortunately, we didn’t find much the first time.

After four daphnia hunting trips and almost a month of identifying zooplankton species, we finally found Dpahnia pulex and its future competitor in my experiment, Simocephalus vetulus. Now we have over a hundred beakers full of zooplankton swimming and enjoying their life in the lab. Our next step is to genotype D. pulex and S. vetulus to select 3 genetically different clones for each species for my later common garden and competition experiment.

 

Zeyi Han

Comments

  1. John Li says:

    What an interesting study. I like how you were able to turn the obstacle of flooding in the river towards a different focus, of community assembly. Was there any specific reasoning in choosing S. vetulus as the second species of focus? Regardless , good luck to the rest of your experiment!

  2. egeichenberger says:

    I can imagine that with all the rain lately the James must be running high or flooding pretty frequently! That’s too bad! How have you dealt with identifying daphnia (and other zooplankton) to species level? From what I remember from Aquatic Ecology, it’s very difficult to do and occasionally requires the use of genetic analysis. Additionally, do you expect to find high relatedness in the daphnia pulex you collected? Is there a chance that they could all be the same genotype?

  3. Yes. I have identified daphnia to species. So far we have seen D. pulex and D. ambiguia. We used a image key for zooplankton from Center of fresh water biology of University of New Hampshire. The daphnia don’t have cryptic species, as far as I know, so we don’t have to use genetic analysis for them. Unfortunately copepode have a lot of cryptic species, so we only identify them to order. From the genotype information we got so far. There are different clones in the area. The situation that they all have same genotype is also possible. The hybrid between D. pulex and D. pulicaria can be obligate asexual, which mean they don’t go through sexual reproduction. They can produce viable resting egg without the presence of male.

  4. Thanks! There are few reason we chose Simo as the second species. Simocephalus and daphnia are both in the Daphniidae family, so they have more competition going on compare to other less related species. There are two other genera in Daphniidae family, but they are either smaller (harder to work with and can be harder to keep alive) or too rare to find enough clones. D.pulex is really cute and personally I like them to win the competition, but I have no idea which species will win.

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