User:Mlatimore/sandbox

Macroinvertebrates in Riffles
Litter patches are a collection of leaves, coarse particulate organic matter, and small woody stems that can be found throughout riffles. In riffles, these patches form at a velocity between 13 and 89 cm s^-1, which allows for certain types of litter to be more abundant in riffles because they can stand up to the flow. Leaf litter is most commonly found in riffles, and thus influenced the type of macroinvertebrate functional group is found in riffles, like stoneflies being the dominant shredder species found in riffles. Other macroinvertebrates found in riffles are mayflies (Ephemeroptera), but not flies (Diptera). Midges (Chironomidae) and aquatic worms are also located in riffles.

Riffles also create a safe habitat for macroinvertebrates because of the varying depth, velocity, and substrate type found in the riffle. Densities of macroinvertebrates vary riffle to riffle because of seasonality or the habitat surrounding the riffle, but macroinvertebrate makeup is fairly consistent. While it can only be assumed that riffles can host a higher level of densities because of higher dissolved oxygen levels, there is a proven positive association between phosphate levels and macroinvertebrates in riffles, indicating that phosphate is an important nutrient for them. Seasonality is important for macroinvertebrate densities, and is characterized by temperature, like summer and winter, or it can be characterized by wetness, like wet and dry seasons. Macroinvertebrates are found in lower abundance during the rainy or wet season due to the high, constant amount of water into the riffle changing the system’s temperature, water velocity, and the aquatic community structure. Also, food and shelter and low flow rates during the dry season make it a more habitable time for higher densities of macroinvertebrates.