Algae contribute nearly half of Earth’s primary production, forming the basis of most aquatic food webs. Their interactions with parasites are increasingly recognized as pivotal to microbial pelagic dynamics. In temperate and cold coastal zones, macroalgae also act as ecosystem engineers, providing habitat for fish and other fauna. Recently, the cultivation of aquatic organisms, and among them algae, has surged, driven by rising demand for food, animal feed, hydrocolloids, and other commodities. Global production tripled from 2000 to 2020, a boom that reflects humanity’s growing use of, and reliance on the oceans, especially in developing countries. On land, plant and animal domestication have shaped human societies and ecosystems since the Neolithic, with agricultural health linked to societal and ecological stability, a concept encapsulated by the One Health framework. In aquatic environments, especially marine coastal ecosystems, the rapid expansion of aquaculture mirrors a comparable mutation, which occurs far faster than historic agricultural spread, and is compounded by additional anthropic pressures, such as climate change. In this talk, I will cover recent work undertaken in my group to tackle these challenges, in particular the molecular and physiological characterisation of ecologically and environmentally relevant algal pathogens, the roles of programmed cell death and autophagy in brown algal immunity, and the domestication of alga microbiota and their potential use for biocontrol. I will conclude by illustrating how this work can underpin novel governance, as algae mostly fall outside the scope of extant regulations that govern plant and animal trade, biosecurity, or intellectual property.