Towards the end of last week, on the 15th of March, we officially ended the winter bug collection season. Occurring twice a year, in winter and summer, bug collection seasons are often unique or different in their own way, even though they include many, or most, of the same creeks. Summer of 2017, for example, was remarkably rainy. The prevalence of rain caused a lot of collections to be delayed or cancelled altogether, which can happen due to too much rain or too little.
A lack of rain during this winter’s bug collection period was noted by Candice when I asked her if anything was unique or different this time around. “There has not been anything particularly unique about this collection season. Some notable things are that we were in drought the first part of the collection season for most of the state and remain in drought for part of the state. Temperatures this collection season have also been overall colder than the several previous seasons.”
Drought conditions, even minor, can impact the density of bugs in a creek and the diversity of species. Severe drought, which can and often does cause creeks and smaller streams to dry up entirely, and do so for extended periods of time, will have even more severe impacts. According to the National Integrated Drought Information System, “Abnormal dryness or drought are currently affecting approximately 2,422,000 people in Oklahoma, which is about 65% of the state's population.” Check out their website for maps and charts that illustrate that point.
The Oklahoma Drought Monitor Map, which can be viewed through the Oklahoma Mesonet, indicates much of the state remains in drought conditions, ranging all the way from “abnormally dry” to “exceptional drought.” We observed this firsthand during bug collections, with a number of creeks having no collection due to lack of water.
I asked Kim the same question about this year’s collection season and she noted, “I have noticed WAY more algae in almost 100% of the creeks I have been to this winter for bug collections. My thoughts on why there would be more algae then usual or ever before include: it has been dry so no rain water to flush out the creek systems; the outrageously warm/sunny days we’ve had this winter really aids the algae to grow; population keeps increasing, as does development, so more yards getting fertilized.”
This is something I saw firsthand when I visited Spring Creek here in Oklahoma City. Having been to that creek many times, it’s located in Martin Nature Park, around the corner from my house, it was shocking to see so much dark green algae. It is probable that a major reason for the extreme increase is all of the homes in the residential areas surrounding the park. With the much warmer, spring-like weather lately, people have likely been working on their lawns, including spraying fertilizers and nutrient-rich chemicals. With some recent rain, those nutrients would have washed right into Spring Creek.
The nutrients in question are nitrogen and phosphorus, which are a natural and essential parts of the ecosystem in any creek or stream. Too much of these, though, is a problem. In fact, the Environmental Protection Agency states that, “Nutrient pollution is one of America's most widespread, costly and challenging environmental problems.” This is because too much of these nutrients causes algae to grow at an increased rate, to the point that it can severely degrade and/or take over the ecosystem and habitat of the stream. An overabundance of algae can make it difficult for aquatic organisms to find food or places to breed or hide from predators, and can clog their gills, making it difficult to breathe. Too much algae also severely depletes the water’s dissolved oxygen content which is required by all the stream’s aquatic organisms, occasionally leading to fish kills.
While Spring Creek had a lot of algae, it also had a lot of life, albeit very tiny. There were small mayflies, midge flies and black flies aplenty. Candice also noted that she saw many black flies in her creeks this collection season, saying, “Some years there are none and other years there are lots!” This was one of those years when there were lots of the small, bowling-pin-shaped critters attached to rocks and other surfaces in the flowing water of a creek. There are almost 2,000 species of black flies in the world, with over 250 present in North America. Once the black fly larvae, who require flowing water, typically with a good level of dissolved oxygen, attach to a smooth surface using silk-like threads and tiny hooks on their abdomen, they let the current bring them food which they filter and collect. Their filtering behavior makes food available for other organisms while they are also an important food source for larger creatures. They spend one to six months in the larval stage before spending about a week in the transitional pupal stage then emerge from the stream as a fully-formed adult fly.
Black flies are described as “fairly” or “somewhat” tolerant to pollution, depending on who you ask, and usually are found in very large number when present. During bug collections and picking, they can be more of a nuisance than anything else, but they are still an important member of the stream’s ecosystem and can tell us a lot about its health.