Host-pathogen relationships are an important subset of interspecies interactions that are capable of influencing population dynamics, community structure, and biogeochemical cycles. Relationships between hosts and pathogens are expected to shift in response to global climate change. Atmospheric and oceanic warming is already affecting many ecosystems, perhaps most markedly those in marine environments. Case studies illustrate some impacts ocean warming is having on marine host-pathogen dynamics, including: (1) increased host stress, (2) increased pathogen virulence, (3) pathogen range expansion, and (4) host range changes. Output from global climate models was used to calculate the number of additional months each year that various coastal regions around the globe may reach temperatures above a given threshold 50 and 100 years from now; for the Arctic region, we characterize changes in sea ice cover. Complex interactions between multiple ocean conditions that could also affect host-pathogen relationships, such as rising sea surface temperature, anoxia, ocean acidification, and stratification, should also be investigated.
