Soil Salinity Drives Bacterial and Insect Richness Patterns in Delaware Bays

• Wendy Santana-Medina, Applied Molecular Biology & Biotechnology, University of Delaware

• Daniel McDevit, Associate in Arts Program, University of Delaware

Recent studies have shown that salinity levels are rising in portions of the Delaware Bay – a process known as saltwater intrusion. As the saltwater front pushes further into freshwater areas, coastal ecosystems are impacted by the rising salinity levels. This research project aims to determine whether we can develop a protocol to use soil eDNA to measure the effects of salinity on coastal ecosystems. eDNA has been used more frequently in recent years to study the biodiversity of species. The most popular and easiest method is through water-based samples. Soil eDNA, however, is not as commonly studied, and to date only a few studies have specifically used soil eDNA. In this study, we developed a novel method for the extraction of soil eDNA and used it to explore how salinity impacted biodiversity of soil bacteria and insects in Delaware. We collected soil samples from six Delaware locations (across two counties: New Castle and Sussex). To isolate and purify the eDNA, we trialed four different approaches on each sample. Gene regions (16S – bacteria and COI – insects) used to determine the taxonomic identity of the eDNA were amplified using PCR and sequenced using next-generation Nanopore Sequencing. The data was analyzed using bioinformatics systems and cleaned up with coding pipelines connected to a biological database. The results gave a narrowed-down salinity versus eDNA gradient with total sequence read count abundance. The data revealed that bacterial and insect richness decreased as salinity increased. Since our methodology proved to be efficient, we can use this new protocol to sample new locations and correct bias if necessary. Some future work would be to test new collections for more salinities to confirm the trend. Additionally, this method can be used to monitor the impact of saltwater intrusion through yearly sampling at the same sites.