Microbial metabolism inferred from chemical and isotopic compositions of pore water around bananas discovered on the deep-sea floor in the Tenryu Submarine Canyon

Abstract

We describe in detail the pore water chemistry in the sediments below a white mat around a bunch of bananas at a water depth of 2,200 m in the Tenryu Submarine Canyon. We infer the metabolism of microbes in the sediments around the bananas based on the chemical and isotopic compositions of the pore water. On the basis of the relation between ammonia and total carbonate (ΣCO₂) concentrations in the pore water, we identified that an excess ΣCO₂ was distributed around the bananas that cannot be explained by the decomposition of organic matter derived from marine organisms, indicating that the bananas decomposed to generate the excess ΣCO₂. We conclude that the bananas built a local organic-rich environment, stimulating the activity of organotrophic bacteria.