Effects of tributyltin, linear alkylbenzenesulfonates, and nutrients (nitrogen and phosphorus) on nucleoid‐containing bacteria

Abstract

AbstractEffects of tributyltin (TBT) and linear alkylbenzenesulfonate (LAS) on the number of nucleoid‐containing bacteria (NCB) were examined in 15 marine enclosures situated in Knebel Vig, Denmark. Nucleoid‐containing bacteria were enumerated using a newly revised methodological approach including glutaraldehyde fixed 4′,6′ diamidino‐2‐phenylindole (DAPI) preparations rinsed with 2‐propanol. Additions of TBT (0.0025–9.7 nM) reduced the number of NCB up to 62%, whereas additions of LAS (15 μM) increased the numbers. Total counts were not affected by the two toxicants. Values of no‐observed‐effect concentration, lowest‐observed‐effect concentration, and concentration at 30% effectiveness for TBT on NCB were 0.020, 0.16, and 0.0036 nM, respectively. These values are much lower than those previously reported by other techniques and are similar to or lower than TBT concentrations measured in harbors and coastal sea regions, suggesting that natural bacterial assemblages in many marine environments are toxified by TBT. Additions of nutrients stimulated both total counts (twofold) and NCB (fourfold), whereas addition of LAS + nutrients stimulated only NCB. Results from two diel studies demonstrated that NCB varied more on a diel scale than did total counts. Nevertheless, the effects of the two toxicants on NCB were significantly higher than the measured diel changes, suggesting that NCB can be used as a sensitive parameter to test effects of toxicants on pelagic ecosystems.