Detritivore sea cucumbers appear to have been abundant on historic tropical reefs, but (1) have been heavily exploited since at least the mid-1800s, (2) often show minimal recovery post-harvest, and (3) are relatively depleted from modern marine communities. Because they were more abundant, fed on bacteria, microalgae, and other organics, and processed tremendous masses of sediments, removing these detritivores from tropical seas may have suppressed removal of sedimentary pathogens, and impacted co-occurring species in ways that are not documented. We conducted enclosure and exclosure experiments of the sea cucumber Holothuria atra in a back reef lagoon in Moorea, French Polynesia and found that excluding this sea cucumber increased a measure of sediment surface pigmentation by about 10 9 but also decreased the potency of extracts from a co-occurring coral (Acropora cytherea) against the heat-activated coral pathogen Vibrio coralliilyticus by a significant 52%. This suggests that the large-scale removal of detritovores from shallow tropical seas may make some co-occurring foundation species more susceptible to pathogens during periods of elevated temperatures or other stresses.