INVESTIGATION OF GROUNDWATER-DERIVED THERMAL BUFFERING IN SHALLOW COASTAL HABITATS IN THE CONTEXT OF CLIMATE CHANGE

Basin Head Harbour (BHH), a Marine Protected Area in eastern Prince Edward Island, is the sole ecosystem inhabited by giant Irish moss (Chondrus crispus). Past and present anthropogenic stressors on this coastal system have driven this cold-water macroalgae towards near extinction. Elevated summertime water temperatures are partially responsible for the decline in survivable habitat, and this thermal stress is expected to increase in response to climate change. Despite the well-documented role of temperature in affecting biochemical processes in aquatic systems, few studies have characterized the complex patterns and drivers of water temperature in shallow coastal settings. A primary focus of this work is to explore the flowpath depth, volumetric contribution, and thermal sensitivity of groundwater discharged to the system. Hydrological and water quality monitoring, processed-based numerical modelling, and forefront thermal assessment technologies were used to expand our understanding of the thermal processes and dynamics of the study site. Summertime aerial thermal infrared surveys revealed focused near-shore spring discharges that are ubiquitously distributed throughout BHH. These springs maintain thermal refugia over tidal cycles; springs discharge at ~7.5℃ into shallow lagoon waters with average temperatures of ~23℃, supporting survivable temperatures for giant Irish moss. Numerical modelling is currently underway to identify the groundwater depth supplying springs and its sensitivity to future climate change. A reduction in the thermal buffering capacity of groundwater to BHH, paired with increasing ocean temperatures, may deleteriously impact giant Irish moss and other cold-water species. Assessing these compounding stressors is critical to informing federal and provincial resource conservation and management initiatives across the province, including the continued preservation of giant Irish moss. A secondary objective of this work is to evaluate the challenges and opportunities of applying various thermal measurement techniques in dynamic coastal environments. This presentation will discuss the innovative methods and preliminary findings of this work.