Ecohydrogeology of Owens Valley, California Spring Systems: Relationships between Geochemistry, Benthic Macroinvertebrates, and Microbial Communities
AdvisorSada, Donald W.
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Integrating hydrogeology and aquatic ecology has intrigued ecologists and hydrologists. The challenges and importance of integrating these disciplines in groundwater-dependent ecosystems (e.g., springs) have been recognized and studied in mesic regions where these systems are at the headwater of streams. Although ecologists and hydrogeologists have studied aridland springs in terms of taxonomic data, habitat classifications, landscape placement, and sampling techniques, the current state of the science (i.e., integration of hydrogeological parameters and spring ecology) is still in its early stages.This dissertation provides insight into the association between hydrochemistry, invertebrate ecology, and microbial ecology in aridland springs in the southwestern Great Basin. Water chemistry, benthic macroinvertebrates (BMI), and benthic microbial samples were collected from undisturbed rheocrene (flowing into a channel) springs emerging along the Sierra Nevada Frontal Fault Zone in Owens Valley, California. We also sampled one regional spring on the eastern side of Owens Valley. Samples were collected during the summers of 2016 and 2017. First, we examined the temporal variability of benthic macroinvertebrate (BMI) communities before and after 17-years of hydrologic disturbances (frequent droughts and scouring floods) in 2000 and 2017 (Chapter 2). The results showed that persistent desert springs act as refugial aquatic habitats and protect the benthic communities, especially crenobiontics (obligatory spring dependent), during frequent drought and flood in arid regions. These findings motivated us to study the potential factors in shaping these stable communities. To do so, we compared the spatial distribution of BMI communities with the environmental characteristics of spring waters (Chapter 3). The results revealed that the geochemical fingerprint of spring water has a prominent role in shaping the structure of BMI communities in undisturbed aridland springs. Finally, we compared the ecological patterns of BMI and microbial communities found in these springs. Multivariate statistical and co-occurrence analyses were applied to both BMI and microbial communities to understand the relationship between these biological organizations (Chapter 4). The results indicated a relatively similar ordination pattern among BMI and microbial communities. We also highlighted the hydrochemistry as the primary driver of characterizing both microbial and BMI communities.