Environmental influences on particle size distribution of Dreissena polymorpha environmental DNA in a Texas reservoir

Environmental DNA (eDNA) analysis provides an effective biodiversity survey method based on the analysis of genetic material shed into the environment and collected in bulk environmental samples such as water or sediment. With the expansion of eDNA applications, it is becoming increasingly important to understand the ecology of eDNA (i.e., origin, transport, state, and fate of shed genetic material) to choose appropriate sampling protocols and for interpretation of results. For example, research of eDNA particle size distribution (PSD), which describes the abundance and range of sizes of eDNA-bearing particles in the environment, can guide filter size selection for optimal capture of target eDNA. Previous PSD research has mainly targeted fish and has tended to occur in controlled mesocosms. To expand PSD research to novel taxonomic diversity and more natural settings, I analyzed the PSD of invasive Dreissena polymorpha (zebra mussels) by taking four weekly samples at four locations in Canyon Lake, a central Texas reservoir. I sequentially filtered replicate water samples through 12, 8, 5, 3, 1, and 0.2 μm filters followed by an ethanol precipitation to partition total eDNA into size fractions, then I used a species-specific quantitative PCR (qPCR) assay to quantify D. polymorpha eDNA captured in each. D. polymorpha eDNA was most abundant within ≥12 and 0.2-1 μm filter size fractions, indicating a bimodal distribution dominated by relatively large and relatively small particles. Other size fractions contained little to no D. polymorpha eDNA. Based on these results, the sampling method that balances eDNA capture and efficiency for optimal detection of D. polymorpha includes using a 1 μm filter pore size. The PSD and average total quantity of D. polymorpha eDNA varied between sampling events and locations. Land cover, wind factors, and water chemistry did not clearly influence this variation. Instead, patterns of eDNA quantity suggest spatiotemporal variation may be due to biological processes of the species such as spawning activity. Nevertheless, the PSD and patterns observed enabled me to make inferences on the D. polymorpha eDNA ecology. This includes that the state was more often captured in small particles until the brief presence of large particles (i.e., likely gametes), the degradation of those larger particles occurred within a week, and eDNA was not transported by wind factors and was able to be captured in surface water samples. Based on observed spatiotemporal variations affecting eDNA capture, PSD and eDNA quantity patterns and additional environmental variable effects should be determined for target species to access best sample methods and make informed analysis interpretations.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Wildlife, Aquatic, and Wildlands Science and Management

Grantor

Texas Tech University

Year dc:date.issued

2023

Author dc:creator

• Plate, Kaitlin

Chair dc:contributor.committeechair

• Barnes, Mathew

Committee members dc:contributor.committeemember

• Portillo, Carlos
• Surles, James

• Environmental DNA
• eDNA Ecology
• Zebra Mussels
• Invasive Species
• eDNA Detection

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/2346/96384

OAI identifier oai:identifier

oai:ttu-ir.tdl.org:2346/96384