Community Resilience and Response to Salinity Gradients in Streams Flowing into Biscayne Bay, Florida

Contemporary shifts in global and local salinity dynamics are caused by various factors, including altered global hydrological cycles, poor water management practices, and salt pollution. For my Honor’s Thesis, I explored the effects that salinity has on communities of meiofauna in coastal streams. Meiofauna are small (45-1000 μm) aquatic invertebrates (microinvertebrates). They are taxonomically diverse and vital to the health and function of all aquatic ecosystems and their food webs. I hypothesized that more sensitive taxa will only be found within a narrow range of salinity, while others will tolerate and be found across a greater range. I quantified meiofauna biodiversity through DNA metabarcoding. First, I collected environmental samples at different points along multiple streams with salinity gradients and obtained the DNA ‘fingerprints’ (barcodes) unique to each species from all organisms present in each sample. I then analyzed the species richness, phylogenetic diversity, and community composition. The results indicate that salinity is a significant predictor of these biodiversity estimates. Also identified were taxa that are tolerant to a broad range of salinity and sensitive taxa found only within a narrow range and that are putative bioindicators of environmental changes. These findings contribute insight into how shifts in salinity are affecting similar meiofaunal communities around the world and into the development of evidence-based ecosystem management practices.