The interstitial waters of some anaerobic carbonate mud from Harrington Sound, Bermuda, have been analyzed for several organic and inorganic chemical species. The pore-water chemistry is controlled by production of these species because of the action of anaerobic bacteria on organic matter in the sediment.

Interstitial waters from a series of shallow cores (approximately 1 m) were analyzed for the following aqueous species: pH, HCO< inf/3/^-, SO₄⁼, NH₄⁺, HS^-, CH₄, N₂, Ca⁺², Mg⁺², and SiO₂. The insoluble organic matter was analyzed for organic C and N. Some observed concentration ranges are NH₄⁺:O to 1 meq/l; HS^-:O to 1 meq/l; HCO₃^-:2.7 to 8.0 meq/l. The decrease in SO₄⁼ concentration varies from 0 to 2 meq/l. The abundance of all the dissolved organic species consistently increases with depth, with concurrent decreases in pH, SO₄⁼, Ca⁺², and Mg⁺². The C:N ratio in the metabolized organic matter is approximately 8. The ratio of CO₂/H₂S introduced into the pore waters is 5. This cannot be explained solely by the action of sulfate-reducing bacteria.

The data are consistent with a theoretical model of organic decay in a closed chemical system, in which the components of the aqueous phase maintain near-equilibrium with the minerals present.

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