Response of aquatic microinvertebrates within isolated tallgrass prairie stream pools to experimental drying

Abstract

Intermittent streams experience varying drying and rewetting cycles that influence the organisms that are able utilize these systems. These disturbance regimes are expected to be greatly impacted by climate change and other anthropogenic impacts. Aquatic microinvertebrates have unique abilities to resist dying in dormant states that allow for emergence once rehydrated and can aid in the re-establishment of aquatic food webs after drying disturbance. To explore the response of microinverterabtes to drying, an experimental microcosm study was conducted to test the hypotheses: (1) aquatic microinvertebrate abundance will be lower after drying compared to those that remain filled, and (2) aquatic microinvertebrate abundance will be lower after a longer drying duration when compared to a shorter drying duration. Specifically, different microinvertebrate groups with differing resistant traits and strategies to survive drying will be assessed. Ten isolated intermittent stream pools were sampled from Youngmeyer Ranch, Elk County, Kansas in August of 2020. Three microcosms per pool were collected and randomly assigned one of three treatments (control, two-week drying period, or four-week drying period). Microcosms were then sampled three times a week with individual microinvertebrates identified and counted. We found support for our hypotheses and observed the potential for most taxa groups included to emerge after drying. Our findings indicate a dynamic response to drying durations. With increased awareness of the potential impacts to this endangered ecosystem, understanding how aquatic organisms cope with changes in disturbance regimes is critical to their protection.