The threat of coastal hypoxia in eastern Canadian waters - new opportunities for its mitigation and the potential of Bedford Basin (Nova Scotia) for required pilot study and demonstration

Ocean deoxygenation and expansion and intensification of hypoxia is a growing threat to marine biodiversity worldwide, especially in coastal waters. The causes include eutrophication due to excess input of nutrients. However, increasingly, warming and especially circulation- and mixing-related changes to oxygen supply connected with climate change are driving oxygen concentrations downwards. This is now a major problem on the Canadian east coast with growing hypoxic zones in the Lower St. Lawrence Estuary, as well as threats to shelf waters of Nova Scotia and coastal basins, including Bedford Basin. Current measures to protect marine biodiversity (e.g. marine protected areas) are ineffectual in addressing this threat. However, the sudden emergence of a green hydrogen industry offers a possible solution. Here we highlight the threat to eastern Canadian ecosystems, including commercial fish stocks, from hypoxia as well as the underlying causes and the potential for a solution. In the case of the Gulf of St. Lawrence, planned construction of a hydrogen plant near Stephenville, NL, holds potential to mitigate the growing threat through use of the oxygen by-product of hydrogen generation. Based on measurements and tracer studies, the location and magnitude of production appear to be “just right” to compensate for current oxygen losses. This mitigation approach (direct oxygen injection) has rarely been considered for marine environments to-date and involves magnitudes and timescales of oxygen transport and response that have not been attempted before. Nevertheless, it seems essential and urgent for ocean scientists, engineers and policymakers to work together to address this threat and explore its potential solution. A coordinated research effort into direct oxygen injection, involving broad multidisciplinary expertise should be established immediately. Field scale pilot studies in well-characterized, accessible locations appear to be the next key step required, as well as planning for larger scale deployment. There are several reasons why Bedford Basin, Nova Scotia is an ideal location for pilot studies and demonstrations. The questions that need to be addressed, the suitability of Bedford Basin, pilot study design and practicality issues are presented and discussed.