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

Abstract

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.

Long-term effects of tri-n-butyl-tin on the function of a marine sediment system

“…We thus had a situation where a concentration increment of 0.2 to 2 pm01 TBT g-' dry sediment caused a disturbance even though the sediment already contained 83 pm01 TBT g-' dry sediment. This is, however, in line with results from short-term incubations, where effects of TBT were seen at even lower additions (0.25 fmol TBT g-' dry sediment) to sediment from the same site (Dahllof et al 1999). We have no final explanation for the effect of such low additions, but it seems reasonable to assume that bioavailablity of TBT could be of importance.…”

“…Since we did not wish to further manipulate the sediment or the sediment community during the experiment, non-destructive sampling was a prerequisite. Fluxes of nutrients have already been used to detect effects of TBT on the microbial part of the sediment community in short-term experiments using sieved sediment in small-scale incubations (Dahllof et al 1999). When using fluxes as effect indicators, 3 major complications must be taken into account, namely coupled reactions (Levin 1989), functional redundancy (Pratt & Cairns 1996), and interactions between micro-organisms and fauna (Aller 1982, Santschi et al 1990).…”

Effects of zinc pyrithione and copper pyrithione on microbial community function and structure in sediments

“…For the nitrifying bacteria to compensate for decreased intracellular ATP levels caused by the actions of the pyrithiones, a decoupling and an increase of the nitrification occur, but little or no ATP is produced. An increase in nitrification was also found following TBT addition to sediment, resulting in an increased nitrate flux and a decreased ammonium flux [29]. It could be expected that the nitrate flux would decrease over time, because it would be detrimental for the bacteria if little or no ATP were gained during nitrification.…”

“…For further information on the open plug‐flux method, see Dahllof et al [29]. Reference controls with DMSO and sea‐water were prepared in the same manner.…”

Recovery of microbially mediated processes in soil augmented with a pentachlorophenol‐mineralizing bacterium

“…As with microbial respiration, ammonification is one process that is carried out by many microorganisms and has been found to be suppressed [18] or unaffected [18–20] following contaminant exposure. Nitrification, however, appears to be consistently sensitive to disturbance [8,11,18–23]. Nitrification is an essential microbially mediated process that is carried out by few groups of microorganisms.…”