Nitrous oxide production by marine sponges

Many marine invertebrates emit the potent greenhouse gas nitrous oxide (N₂O), yet sponges remain uninvestigated. In this study, we provide the first direct measurements of N₂O production rates for ten sponge species collected off the coast of Sydney, Australia. Production rates varied by up to two orders of magnitude between species, with certain sponge species exhibiting some of the highest rates measured for any marine invertebrate to date. Gross morphological traits or microbial abundances could not explain the rate variation between species. Combining aquarium-measured N₂O production rates with field abundance surveys revealed that temperate sponge gardens can generate N₂O at levels comparable to or even exceeding those of marine sediments, seagrass meadows, and salt marshes. These findings indicate that sponges can have an important role in oceanic N₂O emissions, warranting further investigation to quantify their contribution to coastal greenhouse gas budgets.