Environmental and anthropogenic stressors may influence the prevalence of disease-like phenotypes in an intertidal kelp

The effects of climate change and human pollution on ecosystems worldwide are becoming increasingly apparent and are expected to increase disease susceptibility, which could have devastating impacts when keystone species are affected. Habitat-forming kelps are vital ecosystem engineers in marine ecosystems. In the Southern Hemisphere, bull kelps (Durvillaea) shape shallow marine ecosystems, providing habitat, food and shelter for numerous marine organisms. Despite their ecological importance, little is known about kelp diseases and their drivers. Here, we survey various blemishes, potentially indicative of disease, in New Zealand Durvillaea poha populations. Generalized linear mixed modelling was used to explore which environmental and anthropogenic factors might affect blemish prevalence. Our analysis indicated that blemish prevalence may be influenced by combinations of external factors, such as the distance to sewage and river outlets and predominant land use. Our study lays the groundwork for mapping blemishes and their drivers in large, brown macroalgae, an essential step in exploring kelp diseases, improving predictions and protection of marine ecosystems.