Harris, Rachel J.

Seagrasses are essential habitats for many species and provide critical ecosystem functions. Globally seagrasses are declining at an alarming rate. Locally, seagrass loss is concerning because of the magnitude of habitat loss as well as the uncertainty surrounding the mechanisms driving seagrass decline. We exposed two prevalent seagrasses in the IRL to the terrestrial herbicide Roundup QuikPROTM (active ingredient 73% glyphosate) and quantified seagrass response over 53 days in a closed tank system. Direct application of 112 mg glyphosate (15mL of 7.5 g/L) onto Halodule wrightii and Halophila johnsonii, simulating overspray during low tide, yielded persistent concentrations of 2.58 mg/L glyphosate after 13 days. Direct application had acute effects, but survivorship after 53 days was equivalent to Control tanks. Indirect application of 125 mg/L glyphosate, with persistent concentrations of 83.4 mg/L glyphosate after 13 days, resulted in complete H. johnsonii mortality and nearly complete mortality of H. wrightii. Despite high-water solubility, glyphosate poses a measurable threat to seagrasses which warrants further study.

Oyster reefs play vital roles in an estuary’s health by filtering the water and by serving as nurseries for many aquatic animals. The objective of this research was to investigate habitat use of smaller macroinvertebrates on restored oyster reefs. Small-scale (approx. 10 cm3) cage (bagged shell) and string (hanging shell) oyster cultch units were deployed on two restored oyster reefs in the Loxahatchee River Estuary for one year. Fauna inhabiting the units were monitored monthly, identified to the lowest practical taxonomic level, and categorized into functional groups based on feeding mode, living position, and mobility. Results showed similar abundance, richness, and diversity of functional groups in cage and string units. These findings suggest that even small-scale oyster reef restorations, such as individual ‘vertical oyster gardens’ (i.e. string units), add valuable habitat for smaller organisms. This research provides additional options for small-scale restoration efforts.