Introduction Section 1: What Makes a Disease Problematic? Chapter 1 When is a Parasite a Problem? Chapter 2 Investigating Marine Mass Mortality Using Rapid Nucleic Acid Sequencing and Artificial Intelligence: Going Back to Basics Chapter 3 The Use of Sentinel Studies for Assessing Disease Transmission in Marine Systems Section 2: Empirical Examples of Diseases - Iconic Hosts Chapter 4 Adapting the Disease Triad to a Spectrum for Coral Disease: Highlighting Variation in Coral Disease Chapter 5 Algal Diseases and their Intricate Relationship with Evolutionary Ecology Chapter 6 The Impact of Hematodinium perezi on American Blue Crabs Section 3: Large Scale Studies of Diseases Chapter 7 Patterns and Processes in Marine Parasite Biogeography and Macroecology Chapter 8 Community Patterns in Trophically-transmitted Helminth Parasites of Marine Fish Assemblages in Southern Coastal Chile Chapter 9 Introduced Marine Parasites: A Latitudinal Perspective Chapter 10 What is "Normal"? Defining Baseline States of Infection for Ecosystems Section 4: Factors that Interact, Exacerbate and Covary with Disease Chapter 11 Effects of Natural and Anthropogenic Environmental Stressors on Host-parasite Interactions in Marine Ecosystems Chapter 12 How Predators Affect Marine Parasites and Diseases Chapter 13 Temperature Effects on Marine Diseases Chapter 14 From Microbes to Meadows: How Community-interactions Drive Eelgrass Wasting Disease Across Scales Section 5: Genetic/Evolutionary Aspects Chapter 15 Heritability of Host Responses to Parasites in Marine and Estuarine Communities Chapter 16 From Sediment to Shells: The Evolution of Parasitism in the Polydora-complex (Polychaeta: Spionidae) Chapter 17 Aquaculture and the Eco-Evolutionary Dynamics of Marine Disease Chapter 18 Dispersal and the Evolutionary Landscape of Marine Parasitism Conclusion.