Short-term effects of tri-n-butyl-tin on marine sediment samples using nutrient fluxes as effect indicators

Tri-n-b utyl-tin (TBT) was shown to affect fluxes of inorganic nutrients from incubated marine sediment samples at extremely low additions of TBTCl, 0.25 femtomol/g (fmol/g) dry sediment (∼80 fg/g). The sediment was incubated under both oxic and anoxic conditions in order to decouple processes in the nitrogen cycle. The fluxes of nitrate and ammonium were affected at an addition of 0.25 fmol TBT/g dry sediment in the oxic incubation. The nitrate flux was stimulated, probably due to stimulation of the autotrophic nitrifiers, causing the negative effect on the ammonium flux. This stimulation is consistent with one suggested mode of action of TBT, i.e., uncoupling of the proton gradient causing free electron flow without ATP production. All fluxes in the anoxic incubations were negatively affected, suggesting a reduced capability for mineralization of organic matter. Nitrate and ammonium fluxes in the anoxic incubations were affected at 2.5 and 8 fmol TBT/g dry sediment, respectively. The fluxes of phosphate and silicate in the anoxic incubation were affected at an addition of 0.25 fmol TBT/g dry sediment. The mode of action of TBT for the heterotrophic microorganisms in the anoxic case is likely to be direct inhibition of ATPase.