Impact of Asian Clams (Corbicula fluminea) on on Unionidae, or the family of pearly freshwater mussels


Corbicula fluminea is a species of freshwater clam that is native to eastern Asia and has become an extraordinarily successful invader of freshwater ecosystems and is found on every continent except for Antarctica (Leff et al., 1990; Hornbach, 1992; Karatayev et al., 2007; Lucy & Graczyk, 2008; Sousa et al., 2008a; Crespo et al., 2015). It is widely theorized they were introduced as a food source on the west coast of the United States and were first discovered in the country in 1938 (Sinclair & Isom, 1963; Counts, 1981). Impressivly, C. fluminea have the highest secondary production values ever measured for a species colonizing a freshwater ecosystem and the highest record net productivity for any bivalve (McMahon, 2002; Sousa et al., 2008b). While there are multiple species of Corbicula that are invading aquatic systems, the most common species is C. fluminea (Renard et al., 2000; Siripattrawan et al., 2000). There are several factors that have led to successful invasions of C. fluminea including high fecundity, functional hermaphroditism, self-fertilization, rapid sexual maturity, lack of a parasitic life stage, pedal feeding (that is feeding via the cilia on the foot) and filter feeding, and the ability to disperse across long distances (McMahon, 2002).

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Bentic Macroinvertebrates

Does the title of this post sound like Greek to you? Simply put, benthic macroinvertebrates are little tiny bugs that live in our waterways, but you are able to see them with your naked eye. They are often the larvae of insects that we are more familiar with like blackflies, mayflies, and more! While ponds and lakes do have some, there is a higher number of species found in running waterways. And they can actually tell you a lot about the water that they live in! Many agencies use them as a measure of water quality. In a nutshell, some species are more tolerant of pollution than others. So you collect insects for a certain amount of time, count how many are pollution tolerant, pollution sensitive and pollution intolerant, and then do some easy math! You can also calculate what is called an EPT index. This is based on how many mayflies (Ephemeroptera), stoneflies (Plecoptera), and caddisflies (Trichoptera). This is great if you have a stream running on your property and want to know more about its health.

Because there are so many species, typically macroinvertebrates are broken down into families or orders. A dichotomous key is very helpful in their identification. In West Virgina alone, there are 538 species that the state has identified! This level of identification is hard without breaking out a microscope. In high school, I volunteered with a stream team that was partnered with a local university. We would go out and collect the samples and analyze them. While the EPA does have an SOP for sampling macroinvertebrates most state agencies have their own SOP which can be found by simply googling XYZ State macroinvertebrate sampling. I’m basing the rest of this information on the Georgia EPD SOP. These SOPs are similar to the EPA’s SOP but are adapted to be more effective based on the eco-region. I will detail how to conduct surveys in a future post but for now, let’s look at the different groups of macroinvertebrates.

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