Accumulation and fate of tributyltin species in microbial biofilms

Abstract

Microbial biofilms, composed of microorganisms originally obtained from estuarine harbor-exposed commercial organotin-painted panels, accumulated tributyltin (TBT) spiked into estuarine water.Both algal or bacterial-dominated biofilms were grown by varying nutrient conditions and were found to accumulate TBT in excess of 300 ng/mg biomass (dry weight basis) from estuarine water solutions containing 50 ^g/L TBT, corresponding to bioconcentration factors of over 7000. No degradation of TBT to dibutyltin (DBT) species was detected, either in the biofilm material or in the surrounding solution. Thus, the microbial biofilms concentrated but did not degrade TBT. These results suggest that microbial films on TBT-painted structures in marine environments concentrate TBT at materials surfaces, thereby acting as "capacitors". Such effects might make practical the use of p paints with extremely low TBT release rates delivering antifouling service with reduced environmental hazard.

Presence and effects of marine microbial biofilms on biocide-based antifouling paints

“…TBT þ release rate studies. The diffusion resistance/ trapping ability of biofilms was also confirmed by Blair et al (1988) and Schatzberg (1996) who reported a high degree of accumulation of TBT species within the biofilm matrix (bioconcentration factors 47000). As a direct consequence of this accumulation, a reduction in the release rate of the TBT moieties is expected (as observed by Mihm & Loeb, 1988) although, again, the shift from a bacterial to an algal biofilm led to contradictory results (see Figure 5).…”

“…copper and TBT-based compounds) is rapidly covered by a microbial biofilm (Saroyan, 1969;Bishop et al 1974;Loeb, 1980;Dempsey, 1981a;1981b;Jackson & Jones, 1988;Blair et al 1988;Mihm & Loeb, 1988;Heath et al 1993;Schatzberg, 1996;White et al 34 D. M. Yebra et al 1996;1999;Tang & Cooney, 1998;Woods et al 1988;Cooney & Tang, 1999;Valkirs et al 2003). Some examples of fouling sequences on AF paints are given by Jackson and Jones (1988).…”

Tin

“…Based on these data, it is estimated that TBTs are absorbed or bioconcentrated by bacteria (Blair et al 1988), phytoplankton (Laughlin et al 1986), mollusks (Waldock et al 1983), crustacean species (Evans et al 1984), and fish (Short andThrower 1986, Davies et al 1987). The few data currently available on the bioconcentration of tin and derived products is exclusively devoted to TBT; this reflects the widespread use of TBT as a biocide in marine antifoulants on the one hand, and the recent development of butyltin-specific analytical techniques on the other hand.…”