Abundance, transportation, and preservation of Mysis diluviana eDNA in freshwater ecosystems

Abstract

Environmental DNA (eDNA) has proven to be a valuable tool in detecting rare or invasive species, particularly within the Great Lakes and surrounding aquatic ecosystems. Recent work has shown that sedimentary eDNA (sedDNA) can reveal temporal changes in ecological community composition and can potentially be used to provide restoration guidelines for impacted ecosystems. However, uncertainties currently exist regarding the application of eDNA techniques in both sediment and aquatic freshwater ecosystems. For example, little is known regarding how diel movements affect the short-term persistence and transport of invertebrate eDNA within freshwater lakes and streams. In this study, I examined the effectiveness of both aqueous eDNA and lake sedDNA sensitivity to the presence of Mysis diluviana, a keystone macroinvertebrate species. Water and sediment samples were collected from five lakes at the IISD-Experimental Lakes area in Northwestern Ontario. Mysis sedDNA was extracted from sections of both freeze and gravity cores and tested using quantitative polymerase chain reactions (qPCR) to evaluate preservation and down-core presence. Day and night eDNA samples were analysed during the fall and compared across the epilimnion, metalimnion, and hypolimnion to assess the short-term persistence within a stratified lake. Water samples were collected between June until October of 2019 from a stream connecting two of the study lakes to examine the effect that seasonal variation within a stream may have on downstream sedDNA distribution. My results demonstrated that the occurrence of Mysis eDNA in dated sediment freeze cores closely matched known historical distributions. Further, the absence of significant day/night differences in Mysis eDNA between thermal layers in the fall indicates the persistence of eDNA in water over short time intervals. Similarly, high concentrations of Mysis eDNA in streams during fall compared to summer months provided further evidence for persistence as well as transport among lakes during certain time periods. My work demonstrates a valuable method to reconstruct past occupation histories and provide restoration guidelines of impacted ecosystems when applied to sediments by indicating candidate lakes for potential biological reestablishment, as well as indicates spatiotemporal factors that should be considered in the design of eDNA surveys.