摘要:

The results of exposure of 304 stainless steel and grade 2 titanium to Tuticorin harbour waters are presented. With coupons immersed under low‐light conditions, microfouling caused the polarisation of free corrosion potentials to nobler values (ennoblement) during the early stages and toward more active values after about 10 d. Under natural conditions, on the other hand, the ennoblement of corrosion potentials occurred more consistently in the presence of sunlight. This effect was particularly marked during the first 10 to 12 d but became much reduced upon further exposure. Potential excursion data are complemented by test results on biofilm succession and characterization. It is suggested that the ennoblement process may not be an effect of low pH, but rather linked to neutral biofilm conditions.

ISSN:0892-7014    

DOI:10.1080/08927019309386258

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The effect of alternating oxic and anoxic conditions (12 h oxic‐12 h anoxie) on sulfate reducing activity, iron‐sulfur chemistry and the corrosion of mild steel, has been studied in biofilm reactors.

ISSN:0892-7014    

DOI:10.1080/08927019309386259

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A diverse bacterial community, dominated by Gram negative populations, was found associated with biofilms of the fouling diatom,Amphora coffeaeformis. In the characterization of some members of this culturable bacterial community, emphasis was placed upon their ability to enhance growth of the diatom in elevated Cu2+concentrations. Some selected bacterial consorts, particularly those belonging to the generaPseudomonasandRhodococcus, enabledA. coffeaeformisto grow in artificial sea water medium containing normally inhibitory Cu2+concentrations, demonstrating their ability to establish functional interactions with the diatom leading to enhanced copper tolerance. Owing to the specific nature of the beneficial effect (only produced by certain consorts and under copper stress), the establishment of such interactions could be regarded as a mechanism of copper resistanceof A. coffeaeformis.

ISSN:0892-7014    

DOI:10.1080/08927019309386260

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Observations of the behaviour of the common cockle,Cerastoderma edule(L.), exposed to various concentrations of industrial Chloros (sodium hypochlorite; NaOCl) in the laboratory for 24 h, were made prior to, during and after exposure. Five days after removal of Chloros no abnormal behavioural responses were observed at concentrations below 15 ppm. Between 15–25 ppm NaOCl behavioural changes were observed; cockles showed foot protrusions, shell value gaping and suffered low mortalities, whereas at concentrations above 25 ppm NaOCl there was 100% mortality. Cockles, like many species of bivalve, contain within their shells a complete record of the environmental conditions to which they have been exposed throughout their life. The record takes the form of tidal microgrowth bands which are laid down in the shell structure. Marked cockles grown for 14 d in a simulated laboratory tidal regime of 9 h immersion : 3 h emersion were exposed to Chloros for 9 h (1 simulated high tide). One group was then allowed to grow for a further 7.5 d and another group for 22.5 d. Acetate peel replicas of the sectioned shells showed that all cockles subjected to Chloros produced a cleft in the shell as a result of shell valve closure and withdrawal of the mantle edge during exposure. Post‐Chloros shell growth was disrupted with the deposition of deformed growth increments; normal incremental growth only resuming after several days. Control cockles showed none of these features. Shell valve movements of cockles prior to, during and after exposure to Chloros were recorded. Before exposure to Chloros a regular pattern of shell valve opening and closing was observed, corresponding to high and low tides respectively. During an 8 h exposure to Chloros immediate shell valve closure occurred with subsequent erratic shell valve activity. Upon immersion in fresh sea water the normal pattern of activity was immediately resumed, although the amplitude of shell gape was reduced.

ISSN:0892-7014    

DOI:10.1080/08927019309386261

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Adsorption of a “conditioning”; film precedes the development of communities typically dominated by diatom slimes, filamentous algae or invertebrates. The type and extent of fouling is often specific to a particular location, being influenced by water chemistry, eutrophication and whether any local control measures are employed. The zebra mussel,Dreissena polymorpha, and its rapid spread in North America, makes it probably the most economically important fouling organism in freshwaters at the present time. The types of fouling control measures in current use and future developments are discussed.

ISSN:0892-7014    

DOI:10.1080/08927019309386262

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A marine bacterium D2 (CCUG 26757) isolated from a tunicateCiona intestinalisspecimen produced a low molecular weight component which inhibits barnacle and tunicate larvae and prevents their settlement on solid surfaces (Holmströmet al., 1992). In order to perform chemical and structural analyses of the component independent of season, a bioassay, complementary to tests with invertebrate larvae was developed. This bioassay is based on tissue cell culture techniques and growth of the AGS cell line. It was previously shown that the toxic component is a stationary phase released product, which is heat stable and less than 500 Dalton in size (Holmströmet al., 1992). Furthermore, it is not a peptide or a protein and metaperiodate treatment increases its toxicity to larvae indicating that it binds to or contains carbohydrate moieties. In this study, these results were confirmed by using the anchorage dependent human gastric adenocarcinoma (AGS) cell line as a bioassay. Fractionation of the D2 supernatant on a Sephadex G‐200 column and addition of different size fractions to the AGS tissue culture cells, showed that both a low and a high molecular weight fraction inhibited cell growth. Exposure ofBalanus amphitriteandC. intestinalislarvae to the same fractions, showed that the low molecular weight fraction that inhibited growth of the cells corresponds to the component that inhibited larvae of both organisms. The high molecular weight fraction was found to inhibit larvae ofB. amphitrite.

ISSN:0892-7014    

DOI:10.1080/08927019309386263

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The spatial variability for most measurable parameters contained within biofilms is very large. Therefore a procedure for determining statistically representative regions of analysis is desirable. Scanning confocal laser microscopy, a computer‐controlled xy stage, and fluorescence exclusion staining were used to obtain a series of optical thin sections of biofilms formed by motile (mot+) and nonmotile (mot−)Pseudomonas fluorescenson the surfaces of glass flow cells. Based on a representative elementary area (REA) analysis procedure, the images were used to construct montages large enough to encompass the range of variation in biofilm cell area. The minimum area of analysis required to be representative varied with depth in the biofilm and between the strains used. Biofilms consisting of mot−P. fluorescenswere variable. Thus, large area (REA ≥ × 105‐μm−) were required for statistically valid comparisons of cell distribution. REAs for the mot+biofilm reflected a more uniform distribution of cells at all depths (REA >6 x 104um"); however, significant differences between the mean cell areas at the 0, 8 and 16 μm sampling depths were still observed (range = 4.8 ± 3.1 to 15.1 ± 7.8 μm‐50 μm−2). Phenotypic heterogeneity was evident in mot−biofilms in the form of cell filaments, which were absent in the mot−biofilms. Filament formation in pseudomonads is a response to oxygen limitation, suggesting microscale variation of this parameter within the biofilm. The existence of microenvironments was further supported by the observation that the concentration of fluorescein molecules within cell masses in the mot−biofilm reached only 57% of the macroenvironment fluorescein concentration. In addition, topographical analyses showed that mot+biofilms were significantly deeper than mot”; biofilms (42 ± 19 μmvs19 ± 10 μm, respectively). This factor, in conjunction with an increase in the amount of cell material and associated polymers at all biofilm depths may have resulted in hindered diffusion of oxygen. These studies also confirm that cellular motility plays an important role during cell positioning and formation of biofilm microenvironments, which in turn may induce changes in cell morphology and metabolism. These observations may be relevant where predictive models have been based on unrepresentative biofilm regions or assumptions that the biofilm was isotropic.

ISSN:0892-7014    

DOI:10.1080/08927019309386264

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0892-7014    

DOI:10.1080/08927019309386257

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor