Review: Host-pathogen dynamics of seagrass diseases under future global change

Human-induced global change is expected to amplify the disease risk for marine biota. However, the role of disease in the rapid global decline of seagrass is largely unknown. Global change may enhance seagrass susceptibility to disease through enhanced physiological stress, while simultaneously promoting pathogen development. This review outlines the characteristics of disease-forming organisms and potential impacts of global change on three groups of known seagrass pathogens: labyrinthulids, oomycetes and Phytomyxea. We propose that hypersalinity, climate warming and eutrophication pose the greatest risk for increasing frequency of disease outbreaks in seagrasses by increasing seagrass stress and lowering seagrass resilience. In some instances, global change may also promote pathogen development. However, there is currently a paucity of information on these seagrass pathosystems. We emphasise the need to expand current research to better understand the seagrass-pathogen relationships, serving to inform predicative modelling and management of seagrass disease under future global change scenarios. Conceptual design for how seagrass resilience and disease occurrence may shift under future global change scenarios. We limited our environmental variables to those most likely to cause increased vulnerability to seagrass ecosystems in the near future (temperature, salinity, and nutrient and sediment run-off). However, there will be more environmental stresses, including multiple stressor scenarios, which could elicit variable responses across pathogen and host species. This conceptual design was made with images courtesy of the Integration and Application Network, University of Maryland Center for Environmental Science (ian.umces.edu/imagelibrary/). [Display omitted] •The role of disease in global seagrass declines is largely unknown.•Seagrass disease risk and impact may be amplified under global change.•We review 3 groups of known seagrass pathogens: labyrinthulids, oomycetes and Phytomyxea.•There is an urgent need to expand the field of seagrass disease research.•We provide perspectives for future studies on seagrass-pathogen dynamics.