Inter-annual variability in marine coastal Antarctic bacterioplankton

The dynamics of Antarctic coastal marine bacterioplankton has been studied over a 2-year period. Two field stations were sampled between one and three times a week in 1989 and 1991 in the “Terre Adélie” area. The survey included physicochemical (temperature and particulate organic matter) and bacteriological (total and heterotrophic counts, cell volume and frequency of dividing cells estimation) measurements. The results suggest that a strong interannual variability affects the total bacterial abundance, the mean cell volume, the percentage of free living cells and, to a lesser extent. the culturable saprophytic bacterial communities. The observed variability could be partly explained by a large deficit of solar irradiance during the 2nd year of study that may have affected sea ice and seawater primary production.     

Effect of dispersed oil on heterotrophic bacterial communities in cold marine waters

Mesocosm studies were conducted to evaluate the effect of dispersed oil on total and heterotrophic bacterial communities of under-ice seawater from the St. Lawrence Estuary. A regular survey of bacterial changes in the oil-contaminated seawater was performed during a two week period. The bacterial community structure was investigated by carrying out 27 morphological and biochemical tests on 168 isolated strains. The results show a detectable but transient response of the bacterial community to crude oil addition. While total bacterial counts were approximately constant during the experiment, dispersed oil induced an increase in heterotrophic bacterial microflora (from 10⁴ to 10⁵ bacteria ml^-1 after two weeks of contamination). The dispersed oil appeared to have an inhibitory effect on some components of the bacterial community. A decrease of most probable number values was observed just after addition of crude oil in the most polluted tanks and one day later in the less polluted tank. However, except for the most polluted tank, this adverse effect disappeared rapidly. While the dispersed oil induced a total disappearance of some components of the bacterial community in the most polluted tank, the structure of the bacterial community in the less polluted tank appeared relatively unchanged after 14 days of contamination.Offprint requests to: Daniel Delille     

Effects of nutrient and temperature on degradation of petroleum hydrocarbons in sub-Antarctic coastal seawater

In an attempt to evaluate the potential of petroleum bioremediation at high latitudes environments, microcosm studies using Antarctic coastal seawater contaminated with diesel or crude oil were conducted in Kerguelen Archipelago (49°22′S, 70°12′E). Microcosms were incubated at three different temperatures (4, 10 and 20°C). During experiments, changes observed in microbial assemblages (total direct count, heterotrophic cultivable microorganisms and hydrocarbon-degrading microorganisms) were generally similar for all incubation temperatures, but chemical data showed only some slight changes in biodegradation indices [Σ(C12–C20)/Σ(C21–C32) and C17/pristane]. The complete data set provided strong evidence of the presence of indigenous hydrocarbon-degrading bacteria in Antarctic seawater and their high potential for hydrocarbon bioremediation. The rate of oil degradation could be increased by the addition of a commercial fertilizer, but water temperature had little effects on biodegradation efficiency which is in conflict with the typical temperature-related assumption predicting 50% rate reduction when temperature is reduced by 10°C. Global warming of Antarctic seawater should not increase significantly the rate of oil biodegradation in these remote regions.     

Natural attenuation of diesel-oil contamination in a subantarctic soil (Crozet Island)

An accidental contamination occurred in subantarctic Crozet Island between July and November 1997 near the "Alfred Faure" scientific station (51°51'E-46°25'S). More than 20,000 l of diesel fuel was spilled in the soil in the vicinity of the power station. In order to evaluate the efficiency of the expected bioattenuation process, the contaminated area was sampled in December 1999 for bacterial and chemical analysis. All samples were analysed for total bacteria, heterotrophic viable assemblages and hydrocarbon-utilising microflora. The results of this first analytical survey clearly show a significant response of subantarctic microbial soil communities to the hydrocarbon contamination. Significant increases of total, heterotrophic and hydrocarbon-utilising micro-organisms occurred in the more contaminated zone (from less than 5᎒⁴ MPN g^-1 wet soil to more than 10⁸ MPN g^-1 wet soil for hydrocarbon-degrading micro-organisms). The very high numbers of hydrocarbon-degrading micro-organisms present in the more contaminated zone are clearly linked to early bioattenuation activities. Chemical results provided some clear indications that spilled fuel was still well preserved from chemical and biological weathering 1 year after the spill, as light aliphatics and aromatics were present in all oiled samples and little differences were usually observed between samples.     

Effects of Spilled Oil on Bacterial Communities of Mediterranean Coastal Anoxic Sediments Chronically Subjected to Oil Hydrocarbon Contamination

The effects of spilled oil on sedimentary bacterial communities were examined in situ at 20 m water depth in a Mediterranean coastal area. Sediment collected at an experimental site chronically subjected to hydrocarbon inputs was reworked into PVC cores with or without a massive addition of crude Arabian light oil (∼20 g kg⁻¹ dry weight). Cores were reinserted into the sediment and incubated in situ at the sampling site (20 m water depth) for 135 and 503 days. The massive oil contamination induced significant shifts in the structure of the indigenous bacterial communities as shown by ribosomal intergenic spacer analysis (RISA). The vertical heterogeneity of the bacterial communities within the sediment was more pronounced in the oiled sediments particularly after 503 days of incubation. Response to oil of the deeper depth communities (8–10 cm) was slower than that of superficial depth communities (0–1 and 2–4 cm). Analysis of the oil composition by gas chromatography revealed a typical microbial alteration of n-alkanes during the experiment. Predominant RISA bands in oiled sediments were affiliated to hydrocarbonoclastic bacteria sequences. In particular, a 395-bp RISA band, which was the dominant band in all the oiled sediments for both incubation times, was closely related to hydrocarbonoclastic sulfate-reducing bacteria (SRB). These bacteria may have contributed to the main fingerprint changes and to the observed biodegradation of n-alkanes. This study provides useful information on bacterial dynamics in anoxic contaminated infralittoral sediments and highlights the need to assess more precisely the contribution of SRB to bioremediation in oil anoxic contaminated areas.     

Molecular diversity analysis and bacterial population dynamics of an adapted seawater microbiota during the degradation of Tunisian zarzatine oil

The indigenous microbiota of polluted coastal seawater in Tunisia was enriched by increasing the concentration of zarzatine crude oil. The resulting adapted microbiota was incubated with zarzatine crude oil as the only carbon and energy source. Crude oil biodegradation capacity and bacterial population dynamics of the microbiota were evaluated every week for 28 days (day 7, day 14, day 21, and day 28). Results show that the percentage of petroleum degradation was 23.9, 32.1, 65.3, and 77.8%, respectively. At day 28, non-aromatic and aromatic hydrocarbon degradation rates reached 92.6 and 68.7%, respectively. Bacterial composition of the adapted microflora was analysed by 16S rRNA gene cloning and sequencing, using total genomic DNA extracted from the adapted microflora at days 0, 7, 14, 21, and 28. Five clone libraries were constructed and a total of 430 sequences were generated and grouped into OTUs using the ARB software package. Phylogenetic analysis of the adapted microbiota shows the presence of four phylogenetic groups: Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes. Diversity indices show a clear decrease in bacterial diversity of the adapted microflora according to the incubation time. The Proteobacteria are the most predominant (>80%) at day 7, day 14 and day 21 but not at day 28 for which the microbiota was reduced to only one OTU affiliated with the genus Kocuria of the Actinobacteria. This study shows that the degradation of zarzatine crude oil components depends on the activity of a specialized and dynamic seawater consortium composed of different phylogenetic taxa depending on the substrate complexity.     

Annual changes of microalgae biomass in Antarctic sea ice contaminated by crude oil and diesel fuel

The influence of diesel fuel and “Arabian light” crude oil contamination were investigated on the land fast ice located in the continental shelf of Terre Adélie, Antarctica, during the austral winter 1993. Autotrophic biomass exhibited a clear seasonal pattern. In uncontaminated sea ice, chlorophyll a concentration showed two maxima, one in April (50 mg m⁻³) during sea-ice formation, and the second one in spring just before the ice thaw (20 mg m⁻³). The crude oil and diesel fuel contamination induced a negative effect on ice-microalgae biomass, which remained at a weak level throughout the ice-covered period. However, the inhibitory effect of diesel contamination was immediate while the crude oil effect occurred after the autumn phytoplankton bloom. Addition of fertilizer (Inipol EAP-22) to diesel and crude oil had a clear favourable effect on ice-microalgae. Chlorophyll a biomass exhibited the same seasonal pattern in fertilized and uncontaminated areas. Accepted: 10 November 1998     

Biodegradation of Petroleum Hydrocarbons in Seawater at Low Temperatures (0–5 °C) and Bacterial Communities Associated with Degradation

In this study biodegradation of hydrocarbons in thin oil films was investigated in seawater at low temperatures, 0 and 5 °C. Heterotrophic (HM) or oil-degrading (ODM) microorganisms enriched at the two temperatures showed 16S rRNA sequence similarities to several bacteria of Arctic or Antarctic origin. Biodegradation experiments were conducted with a crude mineral oil immobilized as thin films on hydrophobic Fluortex adsorbents in nutrient-enriched or sterile seawater. Chemical and respirometric analysis of hydrocarbon depletion showed that naphthalene and other small aromatic hydrocarbons (HCs) were primarily biodegraded after dissolution to the water phase, while biodegradation of larger polyaromatic hydrocarbons (PAH) and C₁₀–C₃₆ n-alkanes, including n-hexadecane, was associated primarily with the oil films. Biodegradation of PAH and n-alkanes was significant at both 0 and 5°C, but was decreased for several compounds at the lower temperature. n-Hexadecane biodegradation at the two temperatures was comparable at the end of the experiments, but was delayed at 0°C. Investigations of bacterial communities in seawater and on adsorbents by PCR amplification of 16S rRNA gene fragments and DGGE analysis indicated that predominant bacteria in the seawater gradually adhered to the oil-coated adsorbents during biodegradation at both temperatures. Sequence analysis of most DGGE bands aligned to members of the phyla Proteobacteria (Gammaproteobacteria) or Bacteroidetes. Most sequences from experiments at 0°C revealed affiliations to members of Arctic or Antarctic consortia, while no such homology was detected for sequences from degradation experiment run at 5°C. In conclusion, marine microbial communities from cold seawater have potentials for oil film HC degradation at temperatures ≤5°C, and psychrotrophic or psychrophilic bacteria may play an important role during oil HC biodegradation in seawater close to freezing point.     

Nutrient Amendments of Inorganic Fertiliser and Oil Palm Empty Fruit Bunch and Their Influence on Bacterial Species Dominance and Degradation of the Associated Crude Oil Constituents

The effects of inorganic commercial fertiliser (N:P:K = 8:8:1) and oil palm empty fruit bunch (EFB) as nutrient amendments for crude oil degradation and microbial population shift by a microbial consortium [Pseudomonas sp. (UKMP-14T), Acinetobacter sp. (UKMP-12T), Trichoderma sp. (TriUKMP-1M and TriUKMP-2M)] were assessed. The bacterial populations present during crude oil degradation were analysed by spread plate method and 16S rRNA sequences, whereas the presence of fungi was assessed by growth on potato dextrose agar. Crude oil degradation analysed using gas chromatography-flame ionisation detection showed total petroleum hydrocarbon reduced between 70 and 100%, depending on the type of amendments compared to control (≈55%) after 30 days of incubation. Nutrient amendments using NPK fertiliser or EFB were found to influence the domination of different bacterial species, which in turn preferentially utilised different hydrocarbons. This study suggested different nutrient amendments could be used to preferentially select bacteria to degrade different components of crude oil, particularly pertaining to the recalcitrant phytane. This information is very useful for application of in situ bioremediation of soil hydrocarbon contamination.     

Community structures of heterotrophic bacteria of copepod fecal pellets

The total and heterotrophic bacterial microflora of gut andfecal pellets of the copepod Temora stylifera was studied inthe coastal zone of the northwestern Mediterranean basin. Digestivetracts and feces were always found to contain bacteria. Withmean values close to 10¹¹ cells ml^–1and 10¹⁰ colony-formingunits (CFU) ml^–1, both total and heterotrophic communitiesfound in fecal pellets largely exceeded the corresponding bacterialmicroflora observed in surrounding seawater (10⁵ cells ml¹ and10³ CFU ml^–). In the same way, the frequency of dividingcells and mean cell volumes increased, respectively, from 3%and 0.12µm³ in seawater to >6% and 0.24 µm³ infecal pellets. The bacterial community structure was investigatedby carrying out 29 morphological and biochemical tests on 147isolated strains. Although Pseudomonas was always the most frequentlyencountered genus, the bacterial communities found in copepodfecal pellets clearly differ from those inhabiting seawater.Vibrio species, which were not detected in seawater microflora,were always present in fecal pellet communities. The close correspondenceobserved between the potential metabolic characteristics ofthe fecal bacterial communities isolated from a subantarcticdeposit feeder (Mytilus edulis) and from zooplankton in thisMediterranean study suggests that the fecal community differentiationis an even more general feature.     

Short-term variations of bacterioplankton in Antarctic zone: Terre Adelie area

Previous studies on Antarctic seawater have demonstrated the presence of significant numbers of bacteria, but their in situ activity has not been demonstrated. In order to demonstrate this hypothetical activity, a scheduled survey was conducted from January to February 1986 in a coastal area of Adelie Land. Seawater samples were collected in a selected station every day or every hour during a 17 hour period. Bacterial communities in each sample were studied by measuring direct and viable counts, frequency of dividing cells estimation, taxonomic analysis, and heterotrophic potential. Complementary studies used batch cultures with artificial nutrient supplements. The results clearly suggest a strong potential activity of the natural Antarctic bacterial microflora.     

Seasonal changes of Antarctic marine bacterioplankton and sea ice bacterial assemblages

The distributions of bacterial populations in sea ice and underlying seawater were investigated on the continental shelf of the “Terre Adélie” area. A reference station was sampled weekly from January 1991 to January 1992. In winter, the survey included a minimum of six sampling layers: surface and bottom ice, brine, seawater from the interface, and at 0.5 and 2 m depth. In seawater, the total bacterial abundance ranged from 0.5 × 10⁵ cells ml⁻¹ in July to 6.0 × 10⁵ cells ml⁻¹ after ice break. Values reaching 2.5 × 10⁶ cells ml⁻¹ were recorded in the overlying ice cover. Mean cell volumes were twice as high in brine as in seawater. The saprophytic bacterial abundance ranged from 5.0 × 10⁴ CFU (colony-forming units) ml⁻¹ in some winter interface samples to less than 1.0 × 10³ CFU ml⁻¹ in most of the summer seawater samples. In sea ice a clear decreasing gradient for most of the studied bacterial parameters from the surface layers towards the bottom layer was found. The ice cover had a discernible impact on underlying seawater, but its influence was restricted to a limited interface layer.     

Chaetoceros resting spores in the Gerlache Strait, Antarctic Peninsula

The formation of resting spores in diatoms is a common phenomenon in neritic environments. Here we report on resting spores of the genus Chaetoceros associated with a layer of increased chlorophyll fluorescence, at a depth of more than 200 m, north of Brabant Island and in Wilhelmina Bay, southeast coast of the Gerlache Strait (64°41.0′S, 62°0.5′W). Six species of Chaetoceros were identified by the morphology and size of the resting spores. Given that Chaetoceros spp., both in vegetative cells and as resting spores, are commonly found in Antarctic coastal surface waters, their location at depth could represent the pelagic “waiting” or “seeding” populations mentioned for other environments. Received: 25 November 1996 / Accepted: 16 November 1997     

Microheological properties of different erythrocyte populations in persons with elevated arterial pressure and in physically active persons

Microrheological properties (aggregation and deformability) of erythrocytes separated by centrifugation at 30000×g density gradient into “young” and “old” (the upper and lower fractions, respectively) were studied. The erythrocytes were taken from physically active persons (PAP) and from those with elevated arterial pressure (EAP). A significant difference in microrheological properties of the “young” and “old” erythrocytes was found. The aggregation degree of “old” cells was nearly twice that of “young” cells. The deformability of the erythrocyte subpopulations was significantly different, though the difference was not so pronounced as in the case of aggregation. The aggregation of “young” and “old” erythrocytes in the PAP group was the least (28% lower than in the control). Note, that “old” erythrocytes in the PAP group had better microrheological properties than in the other groups. All erythrocyte populations in the EAP group were characterized by higher aggregation, decreased deformability, and decreased capacity for oxygen transport.     

Elevated cadmium accumulation in marine organisms from Terra Nova Bay (Antarctica)

 As a contribution towards identification of the principal environmental factors involved in cadmium accumulation in Antarctic marine organisms and the establishment of a baseline near the Italian Antarctic Station “Baia Terra Nova”, surface sediments, plankton and benthic organisms were studied in coastal waters of Terra Nova Bay (Ross Sea). The cadmium content of sediments was similar to that regarded as background in most marine coastal areas, whereas in surface water, phyto- and zooplankton it was similar to values measured in areas of enhanced upwelling. Algal and animal taxa dominating benthic associations had a higher cadmium content than related species from other seas. Very high concentrations of the metal were found in sponges (10–80 μg/g dw) and in the digestive gland of molluscs (up to 345 μg/g in Neobuccinum eatoni). The rapid regeneration of cadmium and its natural occurrence and bioavailability in highly productive coastal waters seem to be responsible for cadmium accumulation in the tissues of marine organisms near the “Baia Terra Nova” station. Received: 6 June 1995/Accepted: 23 November 1995     

Bacterial Diversity in Three Different Antarctic Cold Desert Mineral Soils

A bacterial phylogenetic survey of three environmentally distinct Antarctic Dry Valley soil biotopes showed a high proportion of so-called “uncultured” phylotypes, with a relatively low diversity of identifiable phylotypes. Cyanobacterial phylotypic signals were restricted to the high-altitude sample, whereas many of the identifiable phylotypes, such as the members of the Actinobacteria, were found at all sample sites. Although the presence of Cyanobacteria and Actinobacteria is consistent with previous culture-dependent studies of microbial diversity in Antarctic Dry Valley mineral soils, many phylotypes identified by 16S rDNA analysis were of groups that have not hitherto been cultured from Antarctic soils. The general belief that such “extreme” environments harbor a relatively low species diversity was supported by the calculation of diversity indices. The detection of a substantial number of uncultured bacterial phylotypes showing low BLAST identities (<95%) suggests that Antarctic Dry Valley mineral soils harbor a pool of novel psychrotrophic taxa.     

Diversity of the cyanobacterial microflora of the northern part of James Ross Island,NW Weddell Sea,Antarctica

The diversity and ecological distribution of cyanobacteria in the northern, deglaciated part of James Ross Island were studied during the Antarctic summer season 2005–2006. Seventy-five cyanobacterial morphotypes were observed in various habitats of this area. The identified cyanobacterial taxa belong to the characteristic and dominant types of coastal Antarctica, and majority of them appeared connected to special habitats and formed distinct populations and ecologically delimited communities. The results are compared and discussed with respect to phenotypically characterised cyanobacterial microflora of maritime Antarctica and to recent molecular analyses of cyanobacterial strains from different Antarctic regions. The existence of a specificity and characteristic composition of Antarctic cyanobacterial communities was demonstrated.     

Microbial Activity and Community Composition during Bioremediation of Diesel-Oil-Contaminated Soil: Effects of Hydrocarbon Concentration,Fertilizers, and Incubation Time

We investigated the influence of three factors—diesel oil concentration [2500, 5000, 10,000, 20,000 mg total petroleum hydrocarbons (TPH) kg⁻¹ soil], biostimulation (unfertilized, inorganic fertilization with NPK nutrients, or oleophilic fertilization with Inipol EAP22), and incubation time—on hydrocarbon removal, enzyme activity (lipase), and microbial community structure [phospholipid fatty acids (PLFA)] in a laboratory soil bioremediation treatment. Fertilization enhanced TPH removal and lipase activity significantly (P ≤ 0.001). The higher the initial contamination, the more marked was the effect of fertilization. Differences between the two fertilizers were not significant (P > 0.05). Microbial communities, as assessed by PLFA patterns, were primarily influenced by the TPH content, followed by fertilization, and the interaction of these two factors, whereas incubation time was of minor importance. This was demonstrated by three-factorial analysis of variance and multidimensional scaling analysis. Low TPH content had no significant effect on soil microbial community, independent of the treatment. High TPH content generally resulted in increased PLFA concentrations, whereby a significant increase in microbial biomass with time was only observed with inorganic fertilization, whereas oleophilic fertilization (Inipol EAP22) tended to inhibit microbial activity and to reduce PLFA contents with time. Among bacteria, PLFA indicative of the Gram-negative population were significantly (P ≤ 0.05) increased in soil samples containing high amounts of diesel oil and fertilized with NPK after 21–38 days of incubation at 20°C. The Gram-positive population was not significantly influenced by TPH content or biostimulation treatment.     

Bacteria which attack petroleum hydrocarbons in a saline medium

Bacterial strains were isolated from California coastal areas which showed the ability to oxidize normal paraffins, iso-paraffins, and aromatic hydrocarbons in a synthetic seawater medium. The ability to utilize a particular hydrocarbon was established not only on the basis of visible bacterial growth but also through a chromatographic technique which was standardized and which could define the amount of each hydrocarbon consumed by the bacteria in a mixture. Some of the strains exhibited vigorous hydrocarbon oxidation when exposed to synthetic mixtures of hydrocarbons as well as crude oil. Under conditions of aeration and agitation, mixed cultures could destroy approximately 50% of a South Louisiana crude oil in a period of 48 hr.