Dust Storms and The Dispersal of Aquatic Invertebrates in The Chihuahuan Desert Ecoregion
The Chihuahuan Desert surrounding El Paso, Texas is one of the most intense sources of dust in the Western Hemisphere. Within this vast desert are ephemeral wetlands with micrometazoan propagules contained within their sediment egg banks. Dispersal of aquatic microinvertebrates between habitats is vital for the success of their populations. Passive dispersal of the propagules provides an escape mechanism from unfavorable conditions. Upon desiccation of these habitats, windstorms can potentially transport propagules mixed within entrained sediments across regional scales. To study this process, I collected falling sediment from 91 windstorms, with 59 samples collected at the University of Texas at El Paso (UTEP) rehydrated to determine whether viable micrometazoans were transported in windblown sediment. An adjacent air quality station provided particulate matter and weather data. My results indicate that propagules of rotifers (monogononts & bdelloids), ciliates, gastrotrichs, tardigrades, nematodes, ostracods, and branchiopods were transported in these windstorms. In addition, samples collected at UTEP were analyzed to determine deposition rates, physical, and chemical composition of sediment from 68 events from 2011-2016. Annual deposition rates ranged from 85 to 164 g/m2/yr and averaged 111 g/m2/yr for the entire study, one of the highest documented dust/sand deposition rates in the Western Hemisphere. The collected material from all events was predominantly sand; thus, the events are sandstorms. Mineralogy of the sediment consisted largely of quartz along with plagioclase, calcite, alkali feldspars, gypsum, and micas. Major element composition was dominated by Si, with minor amounts of Al, Ca, Fe, Na, K, Mg, P and Ti. Maximum hourly PM10 concentration at the air quality monitoring station was 4,739 µg/m3, while maximum hourly PM2.5 was 414 µg/m3. The average PM2.5/10 ratio in wind-deposited material was 0.37 ± 0.05 for the 5-year collection period. Statistical analyses indicated a positive relationship between taxa transported and PM10 concentration (particles with aerodynamic diameters < 10 µm) and dust storm duration. Wind tunnel studies were also conducted to test entrainment of diapausing stages of several micrometazoans into the air by saltation bombardment. Results of those experiments demonstrated that resting stages of many microinvertebrates were detached from the soil, blown through the tunnel, and remained viable under controlled conditions realistically simulating wind erosion and anemochory, up to regional distances. Overall, this study used a multidisciplinary approach to demonstrate aquatic microinvertebrate dispersal by wind and document the physical and chemical characteristics of dust and sandstorms in the Chihuahuan Desert.
Rivas, Jose A., "Dust Storms and The Dispersal of Aquatic Invertebrates in The Chihuahuan Desert Ecoregion" (2019). ETD Collection for University of Texas, El Paso. AAI27667795.