Abstract
We attempt to identify the mechanism by which nitrogen enrichment increases the prevalence of aspergillosis, a disease caused by the terrestrial fungus Aspergillus sydowii , which infects sea fan corals ( Gorgonia ventalina ) throughout the Caribbean, by looking at the metabolic capabilities of the pathogen to (1) determine whether A. sydowii can catabolize sea fan‐derived nitrogen, (2) ascertain fungal preference for different nitrogen sources, and (3) determine whether fungi isolated from diseased sea fans preferentially assimilate sea fan‐derived nitrogen. Stable nitrogen isotope experiments demonstrated that A. sydowii is capable of assimilating and prefers sea fan‐ derived nitrogen (72% of available nitrogen) to nitrate and more readily assimilates nitrogen from coral tissue than gorgonin skeleton. Variation in the proportion of sea fan‐derived nitrogen assimilated by different fungal isolates was significant, with those from diseased sea fans showing greater nitrogen assimilation of sea fan tissue.