Bacterial pollution in the coastal waters of the suburbs north and south of Tunis

The inshore waters of Northern and Southern suburbs of Tunis are chiefly polluted aroud urban cities. The pollution increases with temperature, men (touristes and bathers), the actions of wind and currentology.     

Bacterial pollution of the littoral waters of the northern suburbs of Tunis

The authors present in this paper a study of the bacterial pollution of inshore waters of northern suburbs of Tunis, on the basis of 180 sampled collected in 15 different stations, 15 monthly (one for each station). Three districts have been considered: Raouad-Gammarth, La Marsa-Carthage and La Goulette. This last district is mostly submitted to the bacterial pollution, caused by its neighbourhood of the lagoon of Tunis "reserve of pollution" and of the city of Tunis.     

Ecology of coliphages in southern California coastal waters

Aims: This study aims to investigate the ecology of coliphages, an important microbial pollution indicator. Specifically, our experiments address (i) the ability of environmental Escherichia coli (E. coli) to serve as hosts for coliphage replication, and (ii) the temporal and spatial distribution of coliphages in coastal waters. Methods and Results: Water samples from three locations in California’s Newport Bay watershed were tested for the presence of coliphages every 2 weeks for an entire year. A total of nine E. coli strains isolated from various sources served as hosts for coliphage detection. Coliphage occurrence was significantly different between freshwater, estuarine and coastal locations and correlated with water temperature, salinity and rainfall in the watershed. The coliphages isolated on the environmental hosts had a broad host‐range relative to the coliphages isolated on an E. coli strain from sewage and a US EPA recommended strain for coliphage detection. Conclusions: Coliphage occurrence was related to the temperature, rainfall and salinity within the bay. The adaptation to a broad host‐range may enable the proliferation of coliphages in the aquatic environment. Significance and Impact of the Study: Understanding the seasonal variation of phages is useful for establishing a background level of coliphage presence in coastal waters. The broad host‐range of coliphages isolated on the environmental E. coli host calls for investigation of coliphage replication in the aquatic environment.     

Bacterial pollution of the lagoon of Tunis

The authors present in this paper a study about the bacterian pollution of the lagoon of Tunis based on 120 samples collected in 10 different stations. This study points out that the lagoon is polluted (50.8% of the samples) mostly in autumn and in winter. The pollution is exogenous, chiefly caused by the rain spreading over polluted waters of wastes and of rivers, and also by the action of the winds and of the currents on the sediments hosting microbiological parameters of faecal pollution.     

Comparative approach to capture bacterial diversity of coastal waters

Despite the revolutionary advancements in DNA sequencing technology and cultivation techniques, few studies have been done to directly compare these methods. In this study, a 16S rRNA gene-based, integrative approach combining culture-independent techniques with culture-dependent methods was taken to investigate the bacterial community structure of coastal seawater collected from the Yellow Sea, Korea. For culture-independent studies, we used the latest model pyrosequencer, Roche/454 Genome Sequencer FLX Titanium. Pyrosequencing captured a total of 52 phyla including 27 candidate divisions from the water column, whereas the traditional cloning approach captured only 15 phyla including 2 candidate divisions. In addition, of 878 genera retrieved, 92.1 % of the sequences were unique to pyrosequencing. For culture-dependent analysis, plate culturing, plate washing, enrichment, and high-throughput culturing (HTC) methods were applied. Phylogenetic analysis showed that the plate-washing clones formed a cluster devoid of any previously cultured representatives within the family Rhodobacteraceae. One HTC isolate (SF293) fell into the OM182 clade, which was not recovered by other culturing methods described here. By directly comparing the sequences obtained from cultures with those from culture-independent work, we found that only 33% of the culture sequences were identical to those from clone libraries and pyrosequences. This study presents a detailed comparison of common molecular and cultivation techniques available in microbial ecology. As different methods yielded different coverage, we suggest choosing the approach after carefully examining the scientific questions being asked.     

The development of policy approaches for reducing nitro-gen pollution to coastal waters of the USA

Two-thirds of the coastal rivers and bays in the United States are degraded from nutrient pollution, and nitrogen inputs these waters continue to increase. The nitrogen comes from a variety of sources, including runoff from agricultural fields, concentrated animal feeding operations, atmospheric deposition from fossil fuel combustion, and sewage and septic wastes. Technical solutions for nitrogen pollution exist at reasonable cost. That most of these solutions have not yet been implemented to any significant extent across the United States suggests that new policy approaches are necessary. The best solution may involve a combination of voluntary and mandatory approaches, applying different approaches to different sources of nitrogen pollution. A watershed-based approach that relies heavily on voluntary mechanisms (such as crop-yield insurance to reduce over-fertilization) is likely to be the most effective for some sources of nitrogen (such as runoff from agricultural fields), while a uniform national regulatory approach may be better for others (such as NOx emissions from fossil fuel combustion). Implementation of management strategies should be carefully coupled to monitoring programs to assess the effectiveness of these strategies. While both nitrogen and phosphorus are important to control, the focus should be on nitrogen management, in part because nitrogen is more generally the causal agent of coastal eutrophication. Also, while nitrogen-control practices tend to also reduce phosphorus pollution, phosphorus-control practices often have little effect on nitrogen. Although current scientific and technical knowledge is sufficient to begin to make substantial progress toward solving coastal nitrogen pollution, progress will be made more quickly and more cost effectively with increased investment in appropriate scientific research.     

The development of policy approaches for reducing nitrogen pollution to coastal waters of the USA

Two-thirds of the coastal rivers and bays in the United States are degraded from nutrient pollution, and nitrogen inputs these waters continue to increase. The nitrogen comes from a variety of sources, including runoff from agricultural fields, concentrated animal feeding operations, atmospheric deposition from fossil fuel combustion, and sewage and septic wastes. Technical solutions for nitrogen pollution exist at reasonable cost. That most of these solutions have not yet been implemented to any significant extent across the United States suggests that new policy approaches are necessary. The best solution may involve a combination of voluntary and mandatory approaches, applying different approaches to different sources of nitrogen pollution. A watershed-based approach that relies heavily on voluntary mechanisms (such as crop-yield insurance to reduce over-fertilization) is likely to be the most effective for some sources of nitrogen (such as runoff from agricultural fields), while a uniform national regulatory approach may be better for others (such as NO_x emissions from fossil fuel combustion). Implementation of management strategies should be carefully coupled to monitoring programs to assess the effectiveness of these strategies. While both nitrogen and phosphorus are important to control, the focus should be on nitrogen management, in part because nitrogen is more generally the causal agent of coastal eutrophication. Also, while nitrogen-control practices tend to also reduce phosphorus pollution, phosphorus-control practices often have little effect on nitrogen. Although current scientific and technical knowledge is sufficient to begin to make substantial progress toward solving coastal nitrogen pollution, progress will be made more quickly and more cost effectively with increased investment in appropriate scientific research.     

The development of policy approaches for reducing nitrogen pollution to coastal waters of the USA

Two-thirds of the coastal rivers and bays in the United States are degraded from nutrient pollution, and nitrogen inputs these waters continue to increase. The nitrogen comes from a variety of sources, including runoff from agricultural fields, concentrated animal feeding operations, atmospheric deposition from fossil fuel combustion, and sewage and septic wastes.Technical solutions for nitrogen pollution exist at reasonable cost. That most of these solutions have not yet been implemented to any significant extent across the United States suggests that new policy approaches are necessary. The best solution may involve a combination of voluntary and mandatory approaches, applying different approaches to different sources of nitrogen poilution. A watershed-based approach that relies heavily on voluntary mechanisms (such as crop-yield insurance to reduce over-fertilization) is likely to be the most effective for some sources of nitrogen (such as runoff from agricultural fields), while a uniform national regulatory approach may be better for others (such as NOx emissions from fossil fuel combustion). Implementation of management strategies should be carefully coupled to monitoring programs to assess the effectiveness of these strategies. While both nitrogen and phosphorus are important to control, the focus should be on nitrogen management, in part because nitrogen is more generally the causal agent of coastal eutrophication. Also, while nitrogen-control practices tend to also reduce phosphorus pollution, phosphorus-control practices often have little effect on nitrogen.Although current scientific and technical knowledge is sufficient to begin to make substantial progress toward solving coastal nitrogen pollution, progress will be made more quickly and more cost effectively with increased investment in appropriate scientific research.     

Influence of UV-B radiation on bacterial activity in coastal waters

The impact of UV-B radiation (290–315 nm) on bacterialactivity and abundance in coastal water was studied in mesocosmexperiments in May 1994 and May 1995 at Kristineberg MarineResearch Station, Sweden. Mesocosms (6 m³) containing naturalpelagic communities were exposed either to ambient irradiation(AMB), ambient irradiation with enhanced UV-B (+UV) (0.7 W m^–24 h every day around noon), or ambient irradiation screenedfor UV-B (–UV). Bacterial activity in the mesocosms wasmeasured by means of thymidine incorporation in short-term testsduring incubations at ambient irradiation, at ambient irradiationwith enhanced UV-B, and at ambient irradiation screened forUV-B. In +UV mesocosms, bacterial activity was significantlystimulated when incubated at ambient radiation. The stimulatingeffect was suggested to be due to an increase in carbon or nutrientsupply through a photodegradation of recalcitrant dissolvedorganic material (DOM). Low attenuation coefficients for UV-Band PAR (400–700 nm) in the +UV mesocosms supported thishypothesis. The bacterial activity in +UV mesocosms, however,was inhibited when incubations were made at enhanced UV-B irradiation,implying that the bacteria had become more sensitive to UV-Bradiation. The increased sensitivity to UV-B exposure in bacterialassemblages that already had been exposed and stressed by UV-Bradiation is suggested to be due to an overburdening of theenergy-consuming DNA repair mechanism. The data suggest thatincreased UV-B radiation, which might occur with ozone depletion,may both stimulate and suppress bacterial activity in coastalwaters, implying that the net outcome of enhanced UV-B radiationcould be an unchanged bacterial activity.     

Distribution and biology of marine cladocerans in the coastal waters of southern China

Geographical and seasonal distributions of marine cladocerans in the coastal waters of southern China were studied. Penilia avirostris was the most common species, followed by Evadne tergestina and Podon schmackeri. P. avirostris and E. tergestina were most common during summer. P. schmackeri, found only in a small bay northeast of Hong Kong, showed no clear seasonal pattern of occurrence. P. avirostris and E. tergestina were found at temperatures ranging from 16–32°C and salinity ranging from 7.3–37.2. P. schmackeri was restricted to a temperature range of 17–29°C and a salinity range of 31.0–37.2. No significant relationships between marine cladoceran abundance and chlorophyll a concentration were found in samples taken from Tolo Harbour. Parthenogenetic brood size of P. avirostris and E. tergestina ranged from 1 to 14, while P. schmackeri was found to carry up to 19 embryos per brood. No geographical trend in fecundity patterns was observed. No correlation was found between body length and brood size. The occurrence of females with resting eggs was rare.     

Bacterial pollution of Messina coastal waters: a one year study

A year's monitoring of faecal pollution of marine coastal waters surrounding Messina was carried out in 1996/97. The distribution of faecal coliforms was evaluated in 15 stations located along the Sicilian coastline, sampled monthly in coincidence of the two opposing current phases ("montante" and "scendente" currents) which characterise the Straits of Messina. The data obtained provided a complete picture of hygienic-sanitary conditions of the area and highlighted the presence of heavily polluted sites in correspondence with river outflows. Higher bacterial counts were associated with lower salinity values and higher ammonia concentrations; over an annual study, they occurred during the coldest months, showing the negative impact of continental water inputs on the bacteriological quality of coastal waters.     

Mixotrophic haptophytes are key bacterial grazers in oligotrophic coastal waters

Grazing rate estimates indicate that approximately half of the bacterivory in oligotrophic oceans is due to mixotrophic flagellates (MFs). However, most estimations have considered algae as a single group. Here we aimed at opening the black-box of the phytoflagellates (PFs) <20 μm. Haptophytes, chlorophytes, cryptophytes and pigmented dinoflagellates were identified using fluorescent in situ hybridization or by standard 4′,6-diamidino-2-phenylindole staining. Their fluctuations in abundance, cell size, biomass and bacterivory rates were measured through an annual cycle in an oligotrophic coastal system. On average, we were able to assign to these groups: 37% of the total pico-PFs and 65% of the nano-PFs composition. Chlorophytes were mostly picoplanktonic and they never ingested fluorescently labeled bacteria. About 50% of the PF <20 μm biomass was represented by mixotrophic algae. Pigmented dinoflagellates were the least abundant group with little impact on bacterioplankton. Cryptophytes were quantitatively important during the coldest periods and explained about 4% of total bacterivory. Haptophytes were the most important mixotrophic group: (i) they were mostly represented by cells 3–5 μm in size present year-round; (ii) cell-specific grazing rates were comparable to those of other bacterivorous non-photosynthetic organisms, regardless of the in situ nutrient availability conditions; (iii) these organisms could acquire a significant portion of their carbon by ingesting bacteria; and (iv) haptophytes explained on average 40% of the bacterivory exerted by MFs and were responsible for 9–27% of total bacterivory at this site. Our results, when considered alongside the widespread distribution of haptophytes in the ocean, indicate that they have a key role as bacterivores in marine ecosystems.     

Nitrogen metabolism by heterotrophic bacterial assemblages in Antarctic coastal waters

Field studies to examine the in situ assimilation and production of ammonium (NH₄ ⁺) by bacterial assemblages were conducted in the northern Gerlache Strait region of the Antarctic Peninsula. Short term incubations of surface waters containing ¹⁵N-NH₄ ⁺ as a tracer showed the bacterial population taking up 0.041–0.128 g-atoms Nl^–1d^–1, which was 8–25% of total NH₄ ⁺ uptake rates. The large bacterial uptake of NH₄ ⁺ occurred even at low bacterial abundance during a rich phytoplankton bloom. Estimates of bacterial production using ³H-leucine and -adenine were l.0gCl^–1 d^–1 before the bloom and 16.2 g Cl^–1 d^–1 at the bloom peak. After converting bacterial carbon production to an estimate of nitrogen demand, NH₄ ⁺ was found to supply 35–60% of bacterial nitrogen requirements. Bacterial nitrogen demand was also supported by dissolved organic nitrogen, generally in the form of amino acids. It was estimated, however, that 20–50% of the total amino acids taken up were mineralized to NH₄ ⁺. Bacterial production of NH₄ ⁺ was occurring simultaneously to its uptake and contributed 27–55% of total regenerated NH₄ ⁺ in surface waters. Using a variety of ¹⁵N-labelled amino acids it was found that the bacteria metabolized each amino acid differently. With their large mineralization of amino acids and their relatively low sinking rates, bacteria appear to be responsible for a large portion of organic matter recycling in the upper surface waters of the coastal Antarctic ecosystem.     

Kinetic modulation of bacterial hydrolases by microbial community structure in coastal waters

In this study, we hypothesized that shifts in the kinetic parameters of extracellular hydrolytic enzymes may occur as a consequence of seasonal environmental disturbances and would reflect the level of adaptation of the bacterial community to the organic matter of the ecosystem. We measured the activities of enzymes that play a key role in the bacterial growth (leucine aminopeptidase, β- and α-glucosidases) in surface coastal waters of the Eastern Cantabrian Sea and determined their kinetic parameters by computing kinetic models of distinct complexity. Our results revealed the existence of two clearly distinct enzymatic systems operating at different substrate concentrations: a high-affinity system prevailing at low substrate concentrations and a low-affinity system characteristic of high substrate concentrations. These findings could be the result of distinct functional bacterial assemblages growing concurrently under sharp gradients of high-molecular-weight compounds. We constructed an ecological network based on contemporaneous and time-delayed correlations to explore the associations between the kinetic parameters and the environmental variables. The analysis revealed that the recurring phytoplankton blooms registered throughout the seasonal cycle trigger the wax and wane of those members of the bacterial community able to synthesize and secrete specific enzymes.     

Monitoring of fecal pollution in coastal waters by use of rapid enzymatic techniques.

Enzyme assays for 4-methylumbelliferyl-beta-D-galactopyranosidase and 4-methylumbelliferyl-beta-D-glucuronidase activities were used for rapid detection (25 min) of fecal water pollution and to determine the impact of sewage discharge in coastal waters. Two coastal areas were investigated: (i) an estuary characterized by a high degree of contamination downstream of a discharge from a sewage treatment plant and a low degree of water renewal and (ii) a fjord with a low degree of pollution and a high degree of water renewal. Statistical analysis showed that a global correlation curve could be used to estimate concentrations of culturable fecal coliform bacteria in the two coastal areas, although environmental factors important for cell physiology (e.g., salinity) varied at different sampling locations. The sensitivity limit for detection of 4-methylumbelliferyl-beta-D-glucuronidase activity corresponded to bacterial concentrations on the order of 10 to 100 CFU/100 ml. The 4-methylumbelliferyl-beta-D-galactopyranosidase assay was less sensitive because of a higher rate of substrate autohydrolysis. The detection limit corresponded to bacterial concentrations on the order of 100 to 1,000 fecal coliforms per 100 ml.     

Ecological classification of macroalgae and angiosperm communities of inner coastal waters in the southern Baltic Sea

A classification system of macroalgae and angiosperms for the inner coastal waters of the Baltic coast of Mecklenburg-Vorpommern (Germany) was developed according to the guidelines of the European Water Framework Directive. These guidelines ask for a five-step classification scheme (high, good, moderate, poor, bad) of the ecological state based on submerged macrophytes.The approach is based on the comparison of the occurrence and distribution of plant communities in 1999–2003 with historical data of submerged macrophytes and their community structure. Due to the lack of appropriate data, historical depth distribution limits of plant communities were calculated based on modelled historical underwater light climate.Despite the fact of very heterogeneous salinities (0.5–20.0 practical salinity units, psu) and substrate types (silty–sandy) in the study area, two general main criteria were identified as appropriate indicators of eutrophic degradation of the inner coastal waters: (1) the lower distribution depth of plant communities and (2) the loss of charophyte-dominated plant communities. Based on these two criteria, a five-step classification scheme is proposed for the characterisation of the ecological state. The depth limit boundaries between the ecological classes were calculated by 5, 25, 50 and 75% reduction of the water transparency. Based on this calculation, the ecological status is described by the gradual upward shift of the vegetation depth limit. Complementary to the decrease of depth limits the loss of charophyte-dominated plant communities characterises the border between moderate and poor ecological conditions.     

Length-weight relationships of Ponto-Caspian gammarids that have overcome the salinity barrier of the southern Baltic Sea coastal waters

Gammarids from the Caspian complex have invaded many European waters along the rivers and canals of the inland migration corridors. The species examined in this work are well known as invaders of European freshwater environments, so the colonization of brackish habitats is a phenomenon inviting more detailed investigation. The aim of this study was to determine the condition of the Ponto-Caspian gammarids Pontogammarus robustoides (G.O. Sars, 1894), Obesogammarus crassus (G.O. Sars, 1894), Dikerogammarus haemobaphes (Eichwald, 1841) and Dikerogammarus villosus (Sowinsky, 1894) as expressed by the relationship between total length and the wet weight of specimens in the brackish waters of the Gulf of Gdansk (Poland). The relationships can be regarded as responses to a newly expanded habitat after they overcome the salinity barrier of the southern Baltic Sea coastal waters. All these Ponto-Caspian gammarids demonstrated an increase in weight with increasing total length: P. robustoides (b = 2.852), O. crassus (b = 3.3477), D. haemobaphes (b = 3.7855) and D. villosus (b = 2.6917). The results are an indicator of the relatively good condition of the organisms and indicate that the brackish environment of the Gulf of Gdansk affords them excellent possibilities for growth.     

Diurnal variation of cell proliferation in three bacterial taxa from coastal North Sea waters

Pulse-labeling with bromodeoxyuridine (BrdU) in combination with fluorescence in situ hybridization was applied to quantify the percentage of proliferating cells in coastal North Sea waters. In order to assess diurnal variability, we sampled eight or nine times, respectively, within 3 consecutive days at two seasons. Bacteria affiliated with the Roseobacter, SAR86, and NOR5 lineages constituted on average 19% +/- 3%, 8% +/- 2%, and 6% +/- 1% of all cells in May 2002 and 17% +/- 3%, 10% +/- 2%, and 11% +/- 3% in August. The relative abundances of the three populations either remained stable, or they changed very gradually during the observation periods. On average, 38 and 39% of all Bacteria exhibited DNA de novo synthesis in May and August, respectively. The fractions of proliferating cells in bacteria of the SAR86 (May, 59%; August, 72%) and the Roseobacter (48 and 53%) lineages were significantly above the community average. A substantial cell proliferation of population NOR5 (34%) was only encountered in August, concomitant with a dinoflagellate bloom. Significant short-term fluctuations of DNA-synthesizing cells were observed in Roseobacter during May and in NOR5 during August, hinting at a pronounced (temporal or spatial) mesoscale patchiness of growth rates in these populations. Since the BrdU proliferation assay is susceptible to misinterpretation, we also modeled the expected number of labeled cells at increasing BrdU incubation times in a slowly growing bacterial population. We suggest that the absence of visible DNA synthesis in marine bacterioplankton cells after DNA pulse-labeling must not be interpreted as an indication of cell "inactivity."