Future vulnerability of Modiolus modiolus reefs to climate change : from mechanisms to management

Abstract

This project was developed to address management needs for Modiolus modiolus reefs across the UK under the context of climate change. Investigations focused on reef populations at the southern limit of the range and northward over a latitudinal gradient including sites in Wales and the Isle of Man, off the coast of mainland Scotland and around Orkney and Shetland Islands. To improve understanding of species- and population-level vulnerabilities to warming and hypoxia, three key influences were studied: (1) environmental exposure, via collation of data on historical and future site conditions; (2) adaptive capacity, via determination of population genetic structure and connectivity; and (3) acclimatory ability, via investigation of oxidative stress response and energetic demands under climate change conditions. Results suggest that M. modiolus is vulnerable to future warming and hypoxia. However, vulnerability varies according to site conditions, stressor type, and exposure duration, and factors like feed availability and demographics may influence response. Consequently, it is concluded that populations face considerably different levels of climate change threat. Additionally, given moderate to high levels of connectivity between populations, adaptive capacity is likely to be low. Results are discussed collectively and implications for management, including contribution of evidence to management tools, are considered.