Wednesday, April 16, 2014

Stream food webs in an altered environment

The following is guest post by Briana Cairco, a freshman at Clemson University enrolled in Dr. Barrett's Creative Inquiry course focused on amphibian conservation.

My name is Briana Cairco, I’m a freshman wildlife and fisheries major and entomology minor at Clemson University in South Carolina. This semester I’ve have the wonderful opportunity to take a Creative Inquiry class studying the effects of exurbanization on salamanders in Appalachia. As you may or may not know, the Appalachian Mountains are home to more species of salamander than any other place on earth, so there is no better place to study salamanders than in our own backyard.

So, what is exurbanization? Exurbanization is basically urban sprawl, people like having the amenities of the city, but want to live in a more rural area. So, land outside of cities is developed to provide easy access to the city, and a more natural environment to live in. This process may be the best of both worlds for humans, but these exurban communities can decimate the ecosystem they’re in. These communities may not seem so bad at first glance, but when you consider the sedimentation from the construction, the runoff from fertilized lawns, the increased salinity from road salt, and so many other factors that impact the streams, the threat these communities pose to amphibians is very real. Our goal this semester is to sample streams with a varying exposure to these developments in order to determine the effects exurbanization has on the salamander population as a whole.

Within our group each person is conducting his or her own research on a related topic. I chose to research the relationships between species of macroinvertebrates and species of salamanders. I will be using the salamander data we get and collecting data on the variety of invertebrates and looking at any correlation between the two. Salamanders are the top predator in these streams that we are examining, so when their populations suffer it is safe to assume that the invertebrate community will change as well. Either they will increase because they aren't being hunted, or they will decrease because whatever is threatening the salamanders is threatening them too.

Certain species of both invertebrates and salamanders are more sensitive to environmental changes. When we look at the data between sites with different water quality readings it would be interesting to see if any of the species seem to be sensitive to particular variables. Between sites with similar water quality, results may show which invertebrate and salamander species have interdependent relationships. There are so many variables in these sites that it could be hard to say whether particular species have a special relationship, but it would be really interesting if for example, sites with caddis fly larvae as the predominant invertebrate also seemed to have the most black belly salamanders. Maybe this study could show if the salamanders have a favorite food, or it could just show which invertebrate and salamanders have similar habitat preferences.
The task is a little daunting since there are so many things out of our control, the invertebrate populations will be affected by the season, so I will have to take into account the breeding period for the species we find.  Also, the size of invertebrate is important a small stream could support thousands of tiny stonefly larvae, but obviously not as many hellgrammites. So instead of just comparing the numbers, I’ll need to compare changes in species abundance between sites.

I will be using this identification key from Auburn University to identify the invertebrates by order, then by their feeding group. There are four feeding groups; shredders, which rely on dead plant and animal material, scrapers/grazers, which eat living plant matter and algae, predators, which eat other invertebrates, and collectors/filterers, which filter fine material from the water.  Most stone fly larvae are shredders, except for families Perlidae, Chloroperlidae, and Perlodidae which are predatory, and have obvious physical differences. The mayfly larvae we will encounter will be collectors, except for family Heptageniidae which are scrapers, and are also easy to differentiate because they appear to have no head.  The caddis fly larvae are more difficult to differentiate so since the majority of species are scrapers, any caddis fly larvae will be classified as a scraper. The megalopterans (like hellgrammites) are predators; as are both dragonfly and damsel fly larvae. I think these feeding groups will be helpful in connecting stream quality and both salamander and invertebrate abundance.

I’m really excited to start sampling, and I haven’t seen any articles about the relationships between certain invertebrates and salamander species yet, so I have no idea what to expect.

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