Understanding drivers of present and future water temperature patterns in a thermally vulnerable coastal lagoon

Abstract

Basin Head Harbour is a small coastal lagoon off the shore of Prince Edward Island, Canada, that is becoming increasingly warm in the summer to the detriment of the local biota. This study characterised sources of cold groundwater delivered to the lagoon and examined their influence on lagoon summertime water temperature. Field investigations used diverse instruments and drone-assisted thermal infrared imaging. Additionally, this study assessed the sensitivity of these cold-water inputs to future climate using a numerical model. Groundwater discharges generated localised cold-water refuges within the lagoon. Field investigations and a 1D subsurface model indicated that groundwater delivered to Basin Head Harbour will likely warm in response to future air temperature increases. Results suggested that the annual average temperature of shallow groundwater may warm more than 2℃ by the year 2100. Study findings are useful for the management of this critical Marine Protected Area and other coastal lagoon ecosystems.