As sea sludge has the potential to cause eutrophication and red tide resulting in the death of shellfish and offensive odors, an effective method to treat it is needed. It was found that adding soil taken from a mangrove swamp to sea sludge promoted an initial fermentation of the sludge constituents. The result suggested that certain microorganisms that were thought to inhabit the subtropical mangrove soil had the potential to play a significant role in the fermentation and that the use of the microorganisms in the mangrove soil might be useful for composting sea sludge.