Benzene has often been observed to be resistant to microbial degradation under anoxic conditions. A number of recent studies, however, have demonstrated that anaerobic benzene utilization can occur. This study extends the previous reports of anaerobic benzene degradation to sediments that varied with respect to contamination input, predominant redox condition, and salinity. In spite of differences in methodology, microbial degradation of benzene was noted in slurries constructed with sediments from various geographical locations and range from aquifer sands to fine-grained estuarine muds, under methanogenic, sulfate-reducing, and iron-reducing conditions. In aquifer sediments under methanogenic conditions, benzene loss was concomitant with methane production, and microbial utilization of [14C]benzene yielded 14CO2 and 14CH4. In slurries with estuarine and aquifer sediments under sulfate-reducing conditions, the loss of sulfate in amounts consistent with the stoichiometric degradation of benzene or the conversion of [14C]benzene to 14CO2 indicates that benzene was mineralized. Benzene loss also occurred in the presence of Fe(III) in sediments from freshwater environments. Microbial benzene utilization, however, was not observed under denitrifying conditions. These results indicate that the potential for the anaerobic degradation of benzene, which was once thought to be resistant to non-oxygenase attack, exists in a variety of aquatic sediments from widely distributed locations.

Large-scale experiments using a hydrocyclone, a self-cleaning 50 µm screen, and a UV unit were undertaken to evaluate the treatment efficiency of these commercially available units for preventing the transfer of unwanted species via ships' ballast water. The water flow through the treatment system was approximately 5.7 m 3 min -1. The effect of increased suspended solids on these processes was the focus of this research. During each experimental run, 760 l samples were obtained and passed through 35 µm plankton nets for zooplankton collection. Samples were also collected for phytoplankton, microbiological, ATP and protein analyses. After the initial samples were obtained, a second set of samples was held for 18 h to determine the effects of storage on the effectiveness of treatment processes. Screening the seawater at 50 µm removed most of the zooplankton and a small percentage of the microphytoplankton, but hydrocyclonic separation was not effective. Initially, UV treatment reduced the viable count of microorganisms to an undetectable level; however, bacterial regrowth was observed in the samples held for 18 h. Statistical evaluation showed that increased turbidity (5 to 90 nephelometer turbidity units; NTU) had no effect on the treatment regime, even on the UV unit. At the highest turbidity (90 NTU), the UV dose was lowered to approximately 35 mW s cm -2 ; however, this dose was still sufficient to inactivate microorganisms. Overall, it was observed that only the 50 µm screen was effective in the removal of organisms, especially potential invading organisms such as large zooplankton or invertebrate larvae.KEY WORDS: Ballast water treatment · Hydrocyclone · Self-cleaning screen · UV treatment · Plankton Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 258: [51][52][53][54][55][56][57][58][59][60][61][62][63] 2003 emerged due to range shifts of hosts, rather than introductions of new pathogens.Management practices to prevent the transport of unwanted species of ballast water discharges have been slow in evolving. International organizations such as the International Maritime Organization (IMO), through its Marine Environment Protection Committee (MEPC), are working to draft a legal instrument to control ballast water discharges. However, it does not appear that such an instrument will be approved by the IMO before the year 2005. In the meantime, individual port states have initiated their own ballast-water management plans in an attempt to protect their natural resources. The leader in this effort has been Australia, which has initiated ballast-water management scenarios since the early 1990s (AQIS 1994(AQIS , 1995.Most recommended and/or required ballast water management scenarios around the world involve the exchange or dilution of in-shore ballast waters with offshore open ocean waters. It is assumed that open ocean waters are greatly reduced with respect to biomass, or the organisms present pose little threat for invasion to in-shore communities. W...

Enrichment cultures from marine sediments mineralized benzene while using sulfate as the terminal electron acceptor. Parallel cultures using river marsh sediment displayed no activity. Mineralization was confirmed by release of 14CO2 from radiolabeled benzene. The dependence on sulfate reduction was demonstrated by stoichiometric balances and the use of specific inhibitors. This work supports recent observations that anaerobic benzene degradation takes place coupled to sulfate reduction.