Stone Mountain is one of metro Atlanta’s most popular hiking spots. It also happens to be one of the 7 natural wonders of Georgia joining the ranks of; Amicalola Falls, Warm Springs, Okefenokee Swamp, Providence Canyon, Radium Springs and Tallulah Gorge. Stone Mountain was formed from an upwelling of magma, about the same time that the Blue Ridge Mountains were formed. Stone Mountain is a giant igneous monolith (meaning it is one continuous rock) that has a circumference of 5 miles at the base above ground but extends further underground. While it is very large it is not the largest piece of granite in the world, and some of the mountain is not composed entirely of granite as composition ranges from quartz monzonite to granite and granodiorite (according to the Georgia Geological Survey Bullet). It is unclear what the largest piece of granite in the world is; I’ve heard the same claim from the Polar Caves in New Hampshire and from a rock in Yellowstone.
There are many interesting species to observe at Stone Mountain as well. During the rainy season in the pools clam shrimp (Laevicaudata) and fairy shrimp (Anostraca) can be observed. Both of these are orders of small bivalves and crustaceans. The fairy shrimp is most commonly known as the sea monkey or brine shrimp. Clam shrimps are very similar but they have a protective shell around the shrimp. They are both able to enter a state called diapause, in this state the eggs basically dry out and remain that way until it rains again. The eggs can even survive being out in space! Centuries later the eggs are still able to hatch. The species are not mobile unless they are aided by wind, bird’s feet, or currents. Fairy shrimp can well found on every single continent, including Antarctica.
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.