Effects of Supraseasonal Drought on Karst Aquatic Communities of the Edwards Plateau

Supraseasonal droughts refer to an unpredictable period of below average precipitation occurring over multiple seasons and are predicted to become more frequent in central Texas under future climate scenarios. The purpose of this study was to opportunistically assess the effects of a supraseasonal drought (2022 – 2024) on aquatic habitats, mussel assemblage, and fish assemblage within headwater (N = 6 sites), mainstem (N = 10 sites), and tributary (N = 4 sites) reaches of the upper Guadalupe River. At the start of an exceptional drought in 2022 and through 2024, streamflow from spring outflows of karst aquifers were sufficient to provide flowing water habitats in the headwater reaches, upper mainstem, and one of the tributaries. Farther downstream in the mainstem, stream flows became subsurface and reemerged periodically to provide surface waters. All reaches, including the downstream reach with fragmented flows, supported mussels, including federally listed Cyclonaias necki and Lampsilis bergmanni. Likewise, all reaches supported spring-associated fishes and riverine fishes, including several imperiled species, with spring-associated fishes persisting in the headwater reaches between 2022 and 2024. Although exceptional and supraseasonal droughts are typically linked to substantial changes in aquatic communities in more humid regions, lack of detectable changes in aquatic habitats and fish assemblages within a semi-arid region (this study) were attributed to continuous flow of water from karst aquifers and to an aquatic community that has been filtered (e.g., retreating edge hypothesis) via a shift towards a semi-arid climate during Holocene warming.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Biology

Grantor

Texas State University

Year dc:date.issued

2025

Author dc:creator

• Wilroy, Ayden

Advisor dc:contributor.advisor

• Bonner, Timothy

Committee members dc:contributor.committeemember

• Dutton, Jessica
• Gabor, Caitlin

• supraseasonal drought
• fish
• mussels
• resistance
• headwaters

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10877/23063

OAI identifier oai:identifier

oai:digital.library.txst.edu:10877/23063