Iodineminho Study: Iodine Supplementation and Prevalence of Iodine Deficiency in Pregnant Women

CONTEXT

Iodine is necessary for the proper brain development. The prevalence of iodine deficiency in Portuguese pregnant women led the health authorities, in 2013, to recommend iodine supplementation for women in preconception, throughout pregnancy and during lactation.

OBJECTIVE

To assess the impact of iodine supplementation initiated in the preconception or the first trimester of pregnancy on the prevalence of iodine deficiency and maternal thyroid status.

METHODS

An observational prospective cohort study that follows thyroid function and iodine status of women recruited in preconception or in the first trimester of pregnancy.

RESULTS

The median urinary iodine concentration (UIC) was significantly higher among women taking iodine supplements (no-supplement group UIC=63µg/L; supplement group UIC =100µg/L, p = 0.002) but still below the levels recommended by the World Health Organization. Only 15% of pregnant women had adequate iodine status and 17% showed UIC < 50 µg/l. There was no influence of whether iodine supplementation started in preconception or in the 1st trimester of gestation (UIC preconception group: 112µg/L vs UIC pregnancy group: 91µg/L, p = 0.569). In the 1st trimester of pregnancy, total thyroxine levels were lower and free triiodothyronine levels were higher in non-supplemented women. Thyroglobulin levels were lower in women who started iodine supplementation in preconception compared to non-supplemented women and women who started iodine supplementation during gestation.

CONCLUSION

In the Minho region of Portugal, fertile women have insufficient iodine intake. Additional public health measures are needed since the current recommendations for iodine supplementation for pregnancy are unsatisfactory to achieve an adequate iodine status.

Iodine intake assessment in the staff of a Porto region university (Portugal): the iMC Salt trial

PURPOSE

Iodine deficiency disorder (IDD) is an ongoing worldwide recognized problem with over two billion individuals having insufficient iodine intake. School-aged children and pregnant women are often target groups for epidemiological studies, but there is a lack of knowledge on the general adult population. The aim of this study was to assess the iodine status among a Portuguese public university staff as a proxy for the adult working population.

METHODS

The population study covered 103 adults within the iMC Salt randomized clinical trial, aged 24-69 years. Urinary iodine concentration was measured spectrophotometrically using the Sandell-Kolthoff reaction. Iodine food intake was assessed using a 24-h dietary recall. The contribution of discretionary salt to the iodine daily intake was assessed through 24-h urinary sodium excretion (UIE) and potentiometric iodine determination of household salt.

RESULTS

The mean urine volume in 24 h was 1.5 L. The median daily iodine intake estimated from 24-h UIE was 113 µg/day, being lower among women (p < 0.05). Only 22% of participants showed iodine intake above the WHO-recommended cutoff (150 µg/day). The median daily iodine intake estimated from the 24-h dietary recall was 58 µg/day (51 and 68 µg/day in women and men, respectively). Dairy, including yoghurt and milk products, were the primary dietary iodine source (55%). Iodine intake estimated from 24-h UIE and 24-h dietary recall was moderately correlated (Spearman rank correlation coefficient r = 0.34, p < 0.05). The average iodine concentration in household salt was 14 mg I/kg, with 45% of the samples below the minimum threshold preconized by WHO (15 mg I/kg). The contribution of discretionary salt to the daily iodine intake was around 38%.

CONCLUSION

This study contributes new knowledge about iodine status in Portuguese working adults. The results revealed moderate iodine deficiency, particularly in women. Public health strategies and monitoring programs are needed to ensure iodine adequacy in all population groups.

River water analysis using a multiparametric approach: Portuguese river as a case study

The Ave River in northern Portugal has a history of riverbanks and water quality degradation. The river water quality was assessed by physicochemical, biological (macroinvertebrates) and microbiological (Enterococcus spp. and Escherichia coli) parameters in six locations (A-F, point A being the nearest to the source) throughout its course during a year. Epilithic biofilms were studied through polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE). Antimicrobial susceptibility testing helped with selecting isolates (n = 149 E. coli and n = 86 enterococci) for further genetic characterization. Pursuant to physicochemical and macroinvertebrates-based parameters, the river water was of reasonable quality according to European legislation (Directive 2000/60/EC). However, the microbiological analysis showed increased fecal contamination downstream from point C. At point D, four carbapenem-resistant E. coli isolates were recovered. Paradoxically, point D was classified as a point of 'Good Water Quality' according to macroinvertebrates results. Point F presented the highest contamination level and incidence of multidrug-resistant (MDR) isolates in the water column (13 MDR enterococci out of 39 and 33 MDR E. coli out of 97). Epilithic biofilms showed higher diversity in pristine points (A and B). Thus, biological and microbiological parameters used to assess the water quality led to divergent results; an outcome that reinforces the need for a holistic evaluation.

Can non-fortified marine salt cover human needs for iodine?

Iodine deficiency remains a worldwide problem with two billion individuals having insufficient iodine intake. Universal salt iodisation was declared by UNICEF and WHO as a safe, cost-effective, and sustainable way to tackle iodine deficiency. In Portugal, the few studies available unravel an iodine status below the WHO guidelines for pregnant women and school-aged children. In the present study, the iodine levels of household salt consumed in Portugal was assessed, for the first time. Non-iodised (median 14 ppm) and fortified (median 48 ppm) marine salt samples showed iodine levels lower than the minimum and above the maximum threshold recommended by non-mandatory Portuguese law and WHO recommendations, respectively. This study calls attention to the fact that marine salt per se, in spite of containing a natural high amount of iodine, requires further fortification in order to be used as an effective tool to deal with iodine insufficiency.

Endemic goiter and iodine deficiency status among Guinea-Bissau school-age children

BACKGROUND/OBJECTIVES

Iodine deficiency disorders are estimated to affect 25% of all school-age children around the world. Current policies concerning iodine deficiency disorders in many countries are not based on robust or recent national data. Our objective was to evaluate the current status of iodine nutrition in Guinea-Bissau (West Africa).

SUBJECT/METHODS

A cross-sectional survey including 299 school-age children, aged 6-14 years old, from four distinct regions of Guinea-Bissau across a coast-hinterland gradient (Bolama, Bissau, Cambaju-Bafatá, and Gabú) was performed. Several iodine deficiency disorders indicators were used: total goiter rate, median urinary iodine concentration (UIC) and regional iodine content in household salt and drinking water samples. Data on the total goiter rate were obtained by thyroid ultrasound.

RESULTS

Goiter was found in 73.5% (CI 95%, 68.5-78.2%) of the school-age children. We observed a median urinary iodine concentration of 110  mcg/l, with 7.3% of the studied population presenting urinary iodine concentration  < 50  mcg/l. Only 12.5% of the household salt samples revealed iodine content ≥  15  mg/kg. Median well water iodine concentration was 11.7  mcg/l.

CONCLUSIONS

Guinea-Bissau presents high rates of goiter in school-age children despite satisfactory median urinary iodine concentration population levels. Salt and drinking water iodine median content cannot explain these findings. Further studies following the progress in iodine deficiency status and the presence of potential goitrogens in diet of this vulnerable population are in needed.

Development of a robust, fast screening method for the potentiometric determination of iodide in urine and salt samples

In this work, a potentiometric flow injection method is described for the fast bi-parametric determination of iodide and iodate in urine and salt samples. The developed methodology aimed for iodine speciation with a potentially portable system (running on batteries). The iodate reduction to iodide was effectively attained in line within the same manifold. The iodide determination was accomplished in the dynamic range of 2.50×10^-6-1.00×10^-3M and the total iodine dynamic range, resulted from iodide plus iodate, was 3.50×10^-6-2.00×10^-3M. The calculated limits of detection were 1.39×10^-6M and 1.77×10^-6M for iodide and iodate, respectively. A determination rate of 21h^-1 for the bi-parametric iodide and iodate determination was obtained for sample injection. The urine samples (RSD <5.8% for iodide and RSD <7.0% for iodate) results were in agreement with those obtained by the classic Sandell-Kolthoff reaction colorimetric reference procedure (RD <7.0%) and standard samples from Centers for Disease Control and Prevention, Atlanta, USA (CDC) international inter-laboratory EQUIP program. The developed flow method was also successfully applied to the iodide and iodate determination in salt samples (RSD <3.1% for iodate and iodide), with comparable results to conventional procedures. No significant interferences were observed interference percentage <9% for both determinations.

Nutrient variability and its influence on nitrogen processes in a highly turbid tropical estuary (Bangpakong, Gulf of Thailand)

Estuarine ecosystems in SE Asia have been poorly studied when compared to other tropical environments. Important gaps exist particularly in the understanding of their biogeochemical function and contribution to global change. In this work we looked into N-turnover in the water column and sediments of the Bangpakong estuary (13°N). A seasonal sampling program was performed along the salinity gradient covering different stretches of the estuary (68km). Key physical and chemical characteristics were also monitored in order to unravel possible environmental controls. Results showed the occurrence of active denitrification in sediments (5.7-50.9nmol N-N2/(cm(3)·hr)), and water column (3.5-1044pmol N-N2/(cm(3)·hr)). No seasonal or spatial variability was detected for denitrification potential in sediment samples. However, in the water column, the denitrification activity peaked during the transition season in the downstream sites coinciding with high turbidity levels. Therefore, in that period of the year, the water column compartment may be an important contributor to nitrate reduction within the estuary. The rather low nitrification rates detected were not always measurable, probably due to the reduced oxygen content and high siltation. This study is one of the few dealing simultaneously with sediments and water column processes in a highly turbid tropical estuary. Therefore, it emerges as a valuable contribution for the understanding of the dynamics of the nitrogen cycle in tropical environments by exploring the role of estuarine N microbial activity in reducing the effects of increased nitrogen loads.

Detection and Quantification of Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus in Coastal Waters of Guinea-Bissau (West Africa)

V. cholerae, V. parahaemolyticus, and V. vulnificus are recognized human pathogens. Although several studies are available worldwide, both on environmental and clinical contexts, little is known about the ecology of these vibrios in African coastal waters. In this study, their co-occurrence and relationships to key environmental constraints in the coastal waters of Guinea-Bissau were examined using the most probable number-polymerase chain reaction (MPN-PCR) approach. All Vibrio species were universally detected showing higher concentrations by the end of the wet season. The abundance of V. cholerae (ISR 16S-23S rRNA) ranged 0-1.2 × 10(4) MPN/L, whereas V. parahaemolyticus (toxR) varied from 47.9 to 1.2 × 10(5) MPN/L. Although the presence of genotypes associated with virulence was found in environmental V. cholerae isolates, ctxA+ V. cholerae was detected, by MPN-PCR, only on two occasions. Enteropathogenic (tdh+ and trh+) V. parahaemolyticus were detected at concentrations up to 1.2 × 10(3) MPN/L. V. vulnificus (vvhA) was detected simultaneously in all surveyed sites only at the end of the wet season, with maximum concentrations of 1.2 × 10(5) MPN/L. Our results suggest that sea surface water temperature and salinity were the major environmental controls to all Vibrio species. This study represents the first detection and quantification of co-occurring Vibrio species in West African coastal waters, highlighting the potential health risk associated with the persistence of human pathogenic Vibrio species.

Salt marsh sediment characteristics as key regulators on the efficiency of hydrocarbons bioremediation by Juncus maritimus rhizospheric bacterial community

Mitigation of petroleum hydrocarbons was investigated during a 5-month greenhouse experiment, to assess the rhizoremediation (RR) potential in sediments with different characteristics colonized by Juncus maritimus, a salt marsh plant commonly found in temperate estuaries. Furthermore, the efficiency of two bioremediation treatments namely biostimulation (BS) by the addition of nutrients, and bioaugmentation (BA) by addition of indigenous microorganisms, was tested in combination with RR. The effect of the distinct treatments on hydrocarbon degradation, root biomass weight, and bacterial community structure was assessed. Our result showed higher potential for hydrocarbon degradation (evaluated by total petroleum hydrocarbon analysis) in coarse rhizosediments with low organic matter (OM), than rhizosediments with high OM, and small size particles. Moreover, the bacterial community structure was shaped according to the rhizosediment characteristics, highlighting the importance of specific microbe-particle associations to define the structure of rhizospheric bacterial communities, rather than external factors, such as hydrocarbon contamination or the applied treatments. The potential for hydrocarbon RR seems to depend on root system development and bacterial diversity, since biodegradation efficiencies were positively related with these two parameters. Treatments with higher root biomass, and concomitantly with higher bacterial diversity yielded higher hydrocarbon degradation. Moreover, BS and BA did not enhance hydrocarbons RR. In fact, it was observed that higher nutrient availability might interfere with root growth and negatively influence hydrocarbon degradation performance. Therefore, our results suggested that to conduct appropriate hydrocarbon bioremediation strategies, the effect of sediment characteristics on root growth/exploration should be taken into consideration, a feature not explored in previous studies. Furthermore, strategies aiming for the recovery of bacterial diversity after oil spills may improve the efficiency of hydrocarbon biodegradation in contaminated salt marsh sediments.

Iodine speciation in coastal and inland bathing waters and seaweeds extracts using a sequential injection standard addition flow-batch method

The present work describes the development of a sequential injection standard addition method for iodine speciation in bathing waters and seaweeds extracts without prior sample treatment. Iodine speciation was obtained by assessing the iodide and iodate content, the two inorganic forms of iodine in waters. For the determination of iodide, an iodide ion selective electrode (ISE) was used. The indirect determination of iodate was based on the spectrophotometric determination of nitrite (Griess reaction). For the iodate measurement, a mixing chamber was employed (flow batch approach) to explore the inherent efficient mixing, essential for the indirect determination of iodate. The application of the standard addition method enabled detection limits of 0.14 µM for iodide and 0.02 µM for iodate, together with the direct introduction of the target water samples, coastal and inland bathing waters. The results obtained were in agreement with those obtained by ICP-MS and a colorimetric reference procedure. Recovery tests also confirmed the accuracy of the developed method which was effectively applied to bathing waters and seaweed extracts.

Development of autochthonous microbial consortia for enhanced phytoremediation of salt-marsh sediments contaminated with cadmium

Microbial assisted phytoremediation is a promising, though yet poorly explored, new remediation technique. The aim of this study was to develop autochthonous microbial consortia resistant to cadmium that could enhance phytoremediation of salt-marsh sediments contaminated with this metal. The microbial consortia were selectively enriched from rhizosediments colonized by Juncus maritimus and Phragmites australis. The obtained consortia presented similar microbial abundance but a fairly different community structure, showing that the microbial community was a function of the sediment from which the consortia were enriched. The effect of the bioaugmentation with the developed consortia on cadmium uptake, and the microbial community structure associated to the different sediments were assessed using a microcosm experiment. Our results showed that the addition of the cadmium resistant microbial consortia increased J. maritimus metal phytostabilization capacity. On the other hand, in P. australis, microbial consortia amendment promoted metal phytoextraction. The addition of the consortia did not alter the bacterial structure present in the sediments at the end of the experiments. This study provides new evidences that the development of autochthonous microbial consortia for enhanced phytoremediation of salt-marsh sediments contaminated with cadmium might be a simple, efficient, and environmental friendly remediation procedure.

CAPSULE ABSTRACT

Development of autochthonous microbial consortia resistant to cadmium that enhanced phytoremediation by salt-marsh plants, without a long term effect on sediment bacterial diversity.

Diversity and dynamics of the Vibrio community in well water used for drinking in Guinea-Bissau (West Africa)

Bacteria of the genus Vibrio are ubiquitous in aquatic environments and can be found either in culturable or in a viable but nonculturable (VBNC) state. The genus comprises many pathogenic species accountable for water and food-borne diseases that prove to be fatal, especially in developing countries, as in Guinea-Bissau (West Africa), where cholera is endemic. In order to ascertain the abundance and structure of Vibrio spp. community in well waters that serve as the sole source of water for the population, quantitative polymerase chain reaction (qPCR), PCR-denaturant gradient gel electrophoresis (DGGE), and cloning approaches were used. Results suggest that Vibrio spp. were present throughout the year in acidic, freshwater wells with a seasonal community composition shift. Vibrio spp. abundance was in accordance with the abundance found in coastal environments. Sequences closely related to pathogenic Vibrio species were retrieved from well water revealing exposure of the population to such pathogens. pH, ammonium, and turbidity, regulated by the rain pattern, seem to be the variables that contributed mostly to the shaping and selection of the Vibrio spp. community. These results reinforce the evidence for water monitoring with culture-independent methods and the clear need to create/recover water infrastructures and a proper water resources management in West African countries with similar environmental conditions.

Water bags as a potential vehicle for transmitting disease in a West African capital, Bissau

BACKGROUND

Street vendors of chilled packaged water have an increasing role in meeting the drinking water demand of people on the move in developing nations. Hygienic conditions can be questionable, and water quality screening scarce or non-existent.

METHODS

In order to ascertain the quality of the packaged water sold by street vendors in Bissau, the capital of the Western African country Guinea-Bissau, water bags were screened in 2011 and during the 2012 cholera outbreak for key physical, chemical and microbiological parameters.

RESULTS

Water used to fill the hand-filled hand-tied bags originated from communal tap water and melted ice. All samples (n=36) were microbiologically contaminated, although levels showed a pronounced variability (e.g. 7-493 372 cfu 250 ml(-1) for Escherichia coli). In 2012, the fecal contamination levels increased (p<0.05), and Vibrio cholerae was detected in all water bags obtained from the neighborhood where the outbreak started.

CONCLUSION

Findings showed that all packaged water samples were unfit for human consumption and during the 2012 cholera outbreak represented a potential vehicle for the spread of the disease. The design of measures to decrease the risk associated to the consumption of highly contaminated chilled water is clearly required.

Prevalence of antibiotic resistance in bacteria isolated from drinking well water available in Guinea-Bissau (West Africa)

The dissemination of antibiotic-resistant bacteria and the spread of antibiotic resistance genes are a major public health concern worldwide, being even proposed as emerging contaminants. The aquatic environment is a recognized reservoir of antibiotic resistant bacteria, and antibiotic resistance genes have been recently detected in drinking water. In this study, the water quality and the prevalence of antibiotic resistance of heterotrophic culturable bacteria were characterized seasonally in wells that serve the population of Guinea-Bissau (West Africa) as the sole source of water for drinking and other domestic proposes. The results revealed that well water was unfit for human consumption independently of the season, owing to high acidity and heavy fecal contamination. Moreover, potentially pathogenic bacteria, which showed resistance to the most prescribed antibiotics in Guinea-Bissau, were isolated from well water, posing an additional health risk. Our results suggest that well water not only fosters the transmission of potential pathogenic bacteria, but also represents an important reservoir for the proliferation of antibiotic resistant bacteria, that can aggravate the potential to cause disease in a very vulnerable population that has no other alternative but to consume such water.

Analysis of the bacterial community composition in acidic well water used for drinking in Guinea-Bissau, West Africa

Potable water is a resource out of reach for millions worldwide, and the available water may be chemically and microbiologically compromised. This is particularly acute in Africa, where water-networks may be non-existent or restricted to a small fraction of the urban population, as in the case of Guinea-Bissau, West Africa. This study was carried out seasonally in Bolama (11°N), where unprotected hand-dug wells with acidic water are the sole source of water for the population. We inspected the free-living bacterial community dynamics by automated rRNA intergenic spacer analyses, quantitative polymerase chain reaction and cloning approaches. The results revealed a clear seasonal shift in bacterial assemblage composition and microbial abundance within the same sampling site. Temperature, pH and turbidity, together with the infiltration and percolation of surface water, which takes place in the wet season, seemed to be the driving factors in the shaping and selection of the bacterial community and deterioration of water quality. Analysis of 16S rDNA sequences revealed several potential pathogenic bacteria and uncultured bacteria associated with water and sediments, corroborating the importance of a culture-independent approach in drinking water monitoring.

Potential of phytoremediation for the removal of petroleum hydrocarbons in contaminated salt marsh sediments

Degradation of petroleum hydrocarbons in colonized and un-colonized sediments by salt marsh plants Juncus maritimus and Phragmites australis collected in a temperate estuary was investigated during a 5-month greenhouse experiment. The efficiency of two bioremediation treatments namely biostimulation (BS) by the addition of nutrients, and bioaugmentation (BA) by addition of indigenous microorganisms was tested in comparison with hydrocarbon natural attenuation in un-colonized and with rhizoremediation in colonized sediments. Hydrocarbon degrading microorganisms and root biomass were assessed as well as hydrocarbon degradation levels. During the study, hydrocarbon degradation in un-colonized sediments was negligible regardless of treatments. Rhizoremediation proved to be an effective strategy for hydrocarbon removal, yielding high rates in most experiments. However, BS treatments showed a negative effect on the J. maritimus potential for hydrocarbon degradation by decreasing the root system development that lead to lower degradation rates. Although both plants and their associated microorganisms presented a potential for rhizoremediation of petroleum hydrocarbons in contaminated salt marsh sediments, results highlighted that nutrient requirements may be distinct among plant species, which should be accounted for when designing cleanup strategies.

Bioremediation potential of microorganisms from a sandy beach affected by a major oil spill

The aim of this work was to evaluate the bioremediation potential of microorganisms from intertidal sediments of a sandy beach affected by a major oil spill 7 years before and subject to chronic petroleum contamination since then. For that, the response of microorganisms to a new oil contamination was assessed in terms of community structure, abundance, and capacity to degrade hydrocarbons. Experiments were carried out under laboratory-controlled conditions by mixing sediment with crude oil with three different nitrogen supplementations in 50 ml serum bottles under constant shake for 15 days. Autochthonous microorganisms were able to respond to the new oil contamination by increasing their abundance (quantified by DAPI) and changing the community structure (evaluated by DGGE). This response was particularly clear for some specific bacterial groups such as Pseudomonas, Actinomycetales, and Betaproteobacteria. These communities presented an important potential for hydrocarbon degradation (up to 85 % for TPHs and 70 % for total PAHs), being the biodegradation stimulated by addition of an appropriate amount of nitrogen.

Bacterial community response to petroleum contamination and nutrient addition in sediments from a temperate salt marsh

Microbial communities play an important role in the biodegradation of organic pollutants in sediments, including hydrocarbons. The aim of this study was to evaluate the response of temperate salt marsh microbial communities to petroleum contamination, in terms of community structure, abundance and capacity to degrade hydrocarbons. Sediments un-colonized and colonized (rhizosediments) by Juncus maritimus, Phragmites australis and Triglochin striata were collected in a temperate estuary (Lima, NW Portugal), spiked with petroleum under variable nutritional conditions, and incubated for 15 days. Results showed that plant speciation emerged as the major factor for shaping the rhizosphere community structure, overriding the petroleum influence. Moreover, when exposed to petroleum contamination, the distinct salt marsh microbial communities responded similarly with (i) increased abundance, (ii) changes in structure, and (iii) decreased diversity. Communities, particularly those associated to J. maritimus and P. australis roots displayed a potential to degrade petroleum hydrocarbons, with degradation percentages between 15% and 41%, depending on sediment type and nutritional conditions. In conclusion, distinct salt marsh microbial communities responded similarly to petroleum contamination, but presented different pace, nutritional requirements, and potential for its biodegradation, which should be taken into account when developing bioremediation strategies.

Potential of the microbial community present in an unimpacted beach sediment to remediate petroleum hydrocarbons

The potential of the microbial communities present in the intertidal zone of an unimpacted beach (a beach that did not suffer any significant oil spill) to degrade hydrocarbons was investigated. For that, laboratory-based microcosms (50-ml flasks) were set up with sandy beach sediment spiked with crude oil and incubated with local seawater for 15 days in the dark. Three bioremediation treatments were tested (biostimulation (BS), autochthonous bioaugmentation (AB), and combined treatment of biostimulation + bioaugmentation (BS + AB)) and the results were compared with natural attenuation (NA). Visual inspection showed clearly an oil solubility increase (confirmed by a higher hydrocarbons concentration in supernatant solutions) for all tested treatments when compared to NA. Significant degradation of the oil, shown by different profiles of petroleum hydrocarbons, was also observed for the different treatments particularly for BS + AB. Therefore, the microbial community of this unimpacted beach sediment could respond to an oil spill, degrading hydrocarbons. But to increase the natural attenuation pace, obtained results indicated that BS + AB is an appropriate approach for the bioremediation of beaches recently impacted by an oil spill. The autochthonous microbial cultures can be obtained "before" or "after" the contamination of the target site, being inoculated into the site right after it contamination.

The role of salinity in shaping dissolved inorganic nitrogen and N₂O dynamics in estuarine sediment-water interface

We investigated the influence of salinity on sediment inorganic nitrogen dynamics in three Portuguese estuaries (Cávado, Ave and Douro). Anaerobic slurry experiments were run at different salinity treatments (0, 10, and 25) and net changes in concentration of nitrate, nitrite, ammonium, and nitrous oxide were monitored. Salinity-induced NH₄⁺ sediment desorption was observed at all sites. No significant salinity driven changes in NO₃⁻ concentrations were observed, except for Ave estuarine sediments, where NO₃⁻ consumption increased 10 times as the salinity rose from 0 to 10. In the upper stretches of the three estuaries, N₂O production increased sharply as salinity rose. Although no stimulation of N₂O production was observed in higher salinity areas, the salinity-driven changes in N₂O production are of major concern given the greenhouse characteristics of the gas. The global trend of decreasing freshwater discharge, and therefore increase in salinity, to estuarine systems could thereby exacerbate N₂O production and global warming.

Influence of different salt marsh plants on hydrocarbon degrading microorganisms abundance throughout a phenological cycle

The influence of Juncus maritimus, Phragmites australis, and Triglochin striata on hydrocarbon degrading microorganisms (HD) in Lima River estuary (NW Portugal) was investigated through a year-long plant life cycle. Sediments un-colonized and colonized (rhizosediments) by those salt marsh plants were sampled for HD, total cell counts (TCC), and total petroleum hydrocarbons (TPHs) assessment. Generally, TCC seemed to be markedly thriving by the presence of roots, but without significant (p > 0.05) differences among rhizosediments. Nevertheless, plants seemed to have a distinct influence on HD abundance, particularly during the flowering season, with higher HD abundance in the rhizosediments of the fibrous roots plants (J. maritimus < P. australis < T. striata). Our data suggest that different plants have distinct influence on the dynamics of HD populations within its own rhizosphere, particularly during the flowering season, suggesting a period of higher rhizoremediation activity. Additionally, during the vegetative period, plants with fibrous and dense root system tend to retain hydrocarbons around their belowground tissues more efficiently than plants with adventitious root system. Overall results indicate that fibrous root plants have a higher potential to promote hydrocarbons degradation, and that seasonality should be taken into account when designing long-term rhizoremediation strategies in estuarine areas.

Methanethiol accumulation exacerbates release of N2 O during denitrification in estuarine sediments and bacterial cultures

Microbes play critical roles in the biogeochemical cycling of nitrogen and sulfur in aquatic environments. Here we investigated the interaction between the naturally occurring organic sulfur compound methanethiol (MeSH) and the final step of the denitrification pathway, the reduction of nitrous oxide (N2 O) to dinitrogen (N2 ) gas, in sediment slurries from the temperate Douro and Ave estuaries (NW Portugal) and in pure cultures of the marine bacterium Ruegeria pomeroyi. Sediment slurries and cell suspensions were amended with a range of concentrations of either MeSH (0-120 µM) or methionine (0-5 mM), a known precursor of MeSH. MeSH or methionine additions caused N2 O to accumulate and this accumulation was linearly related to MeSH concentrations in both coastal sediments (R(2)  = 0.7-0.9, P < 0.05) and R. pomeroyi cell suspensions (R(2)  = 0.9, P < 0.01). Our results suggest that MeSH inhibits the final step of denitrification resulting in N2 O accumulation.

Evaluation of the ecological status of an impaired watershed by using a multi-index approach

The objective of this study was to use an integrative approach to assess the ecological status of a small river impacted by multiple sources of disturbance. The River Febros (NW Portugal) is a small and highly impacted non-regulated river; approximately 44% of the watershed area is dedicated to agriculture, but there is also some urbanization. Environmental status was evaluated using a new multi-index approach, combining quality indices for water (Water Quality Index (WQI)), benthic macroinvertebrates (Iberian Biological Monitoring Working Party Index (IBMWP)), and human modification (Riparian Forest Quality Index (QBR)); Ecological Status River Mediterranean Index (ECOSTRIMED); River Habitat Survey (RHS)). Surveys were carried out between October 2002 and 2003, along four stretches of the main course of the river for physicochemical characteristics, as well as water microbiology and macroinvertebrates. Water quality was poor at all sites (WQI averaged 30.4%) and decreased downstream. The RHS (assessment of instream habitats and the river corridor) and the QBR quantification displayed the same trend. Macroinvertebrates diversity was permanently low with only the most tolerant insects taxa present; oligochaetes dominated. The ecological status of River Febros was well represented using the experimental assessment system, where a downstream decrease in condition was noticeable (in spite of a lower water quality upstream). Our results emphasize the importance of assessing several components of disturbed ecosystems in order to ascertain overall quality and the importance of promoting improvement of the riparian gallery as a buffer against multiple agents of disturbance.

Potential rates and environmental controls of denitrification and nitrous oxide production in a temperate urbanized estuary

Denitrification may play a major role in inorganic nitrogen removal from estuarine ecosystems, particularly in those subjected to increased nitrate and organic matter loads. The Douro estuary (NW Portugal) suffers from both problems: freshwater input of nitrate and organic load from untreated wastewater discharges. To assess how these factors might control sediment denitrification, a 12-month survey was designed. Denitrification potential and nitrous oxide (N(2)O) production were measured at different locations using the slurry acetylene blockage technique. Denitrification rate ranged from 0.4 to 38 nmol N g⁻¹ h⁻¹, increasing towards the river mouth following an urban pollution gradient. N(2)O production, a powerful greenhouse gas implicated on the destruction of the ozone layer, was significantly related with sediment organic matter and accounted for 0.5-47% of the N gases produced. Additional enrichment experiments were consistent with the results found in the environment, showing that sediments from the upper less urban stretch of the estuary, mostly sandy, respond positively to carbon and, inversely, in organic rich sediments from the lower estuary, the denitrification potential was limited by nitrate availability. The obtained results confirmed denitrification as an important process for the removal of nitrate in estuaries. The presence of wastewater discharges appears to stimulate nitrogen removal but also the production of N(2)O, a powerful greenhouse gas, exacerbating the N(2)O:N(2) ratio and thus should be controlled.

Ability of salt marsh plants for TBT remediation in sediments

INTRODUCTION

The capability of Halimione portulacoides, Spartina maritima, and Sarcocornia fruticosa (halophytes very commonly found in salt marshes from Mediterranean areas) for enhancing remediation of tributyltin (TBT) from estuarine sediments was investigated, using different experimental conditions.

METHODS

The influence of H. portulacoides on degradation of the butyltin compounds was assessed in two different ways: (1) a 9-month ex situ study carried out in a site of Sado River estuary, center of Portugal, which used polluted sediments collected at other nonvegetated site from the same estuary; and (2) a 12-month laboratorial study, using both plant and sediment collected at a relatively clean site of Cávado River estuary, north of Portugal, the sediment being doped with TBT, DBT, and MBT at the beginning of the experiment. The role of both S. fruticosa and S. maritima on TBT remediation in sediments was evaluated in situ, in salt marshes from Marim channel of Ria Formosa lagoon, south of Portugal, which has large areas colonized by each one of these two plants. For estimation of microbial abundance, total cell counts of sediment samples were enumerated by the DAPI direct count method. Butyltin analyses in sediment were performed using a method previously validated, which consisted of headspace solid-phase micro-extraction combined with gas chromatography-mass spectrometry after in situ ethylation (with tetraethylborate).

RESULTS

Sediments colonized both ex situ and at lab by H. portulacoides displayed TBT levels about 30% lower than those for nonvegetated sediments with identical initial composition, after 9-12 months of plant exposure. In addition, H. portulacoides showed to be able of stimulating bacterial growth in the plant rhizosphere, which probably included degraders of TBT. In the in situ study, which compared the levels of TBT, DBT, and MBT in nonvegetated sediment and in sediments colonized by either S. maritima or S. fruticosa from the same area, TBT and DBT were only detected in nonvegetated sediment, whereas MBT was quantified in most samples.

DISCUSSION

This work demonstrated that H. portulacoides has potentiality to be used for enhancing TBT remediation in sediments from salted areas. The results observed in situ for S. maritima or S. fruticosa suggested that these two salt marsh plants also favored TBT remediation.

CONCLUSION

Therefore, the application of halophytes in technologies for TBT remediation in sediments seems to be efficient both in situ and ex situ, cost effective, and nondestructive, despite the fact that they have been rarely used for this purpose so far.

Influence of surfactants on the Cu phytoremediation potential of a salt marsh plant

To assess the possible effect that surfactants commonly found in the aquatic environment may have on the remediation potential of the salt marsh plant Halimione portulacoides, a non-ionic (Triton X-100) and an anionic (sodium dodecyl sulfate, SDS) surfactants were used. Experiments were carried out in the laboratory, either in hydroponics (sediment elutriate) or in sediment soaked in elutriate, using sediment and water from an estuarine salt marsh (Cávado River, NW Portugal). Groups of H. portulacoides (grown in a greenhouse) were exposed for 6d to media with 0.16mM added Cu(II) in the absence and in the presence of each one of the two selected surfactants, at concentrations lower than the respective micellar critical concentration. Cu was determined in solutions, sediments and in different plant tissues before and after experiments. Plant photosynthetic efficiency did not indicate deletory effects of the exposure to the added pollutants. The non-ionic surfactant Triton X-100 and, to a lesser extent, the anionic surfactant SDS too, favored Cu accumulation in the plant roots but not Cu translocation, indicating that surfactants may favor Cu adsorption to the roots (phytostabilization). On the other hand, both surfactants favored Cu solubility from the sediment. Therefore, the presence of surfactants, which are frequently found in estuarine areas, as a result of urban and industrial effluent discharges, may condition metal distribution in those environments.

Influence of a salt marsh plant (Halimione portulacoides) on the concentrations and potential mobility of metals in sediments

Influence of Halimione portulacoides, commonly found in temperate salt marshes, on sediment metal contents, speciation and potential mobility in case of sediment re-suspension was evaluated. Both colonized and non-colonized sediments were studied for total Cd, Cu, Pb and Zn contents and metal fraction exchangeable to water collected in situ. Sediment elutriates, prepared with water collected from each site, were used to simulate a sediment re-suspension phenomenon. As the characteristics and degree of contamination of sediments may influence system behaviour, salt marshes of two Portuguese estuaries, Cavado (NW coast) and Sado (SW coast), were studied. Cu, Pb and Zn contents higher than ERL (quality guideline, effect range-low) were observed, indicating potential risks for living organisms. Strong Cu-complexing organic ligands, also determined in both water and elutriates, were higher in rhizosediment elutriates, at concentrations similar, or even higher, to those of Cu. Such ligands condition metals speciation in the water column and probably also metal bioavailability. From rhizosediment significant amounts of Cu and Zn were transferred to the aqueous phase, concentrations 2-8 times higher than concentrations present in water. In contrast, elutriates of non-colonized sediment removed metals from water, Cu and Zn levels in elutriates being 2-6 times lower than initial ones. Cd and Pb levels in water and elutriates were not measurable in most cases. Results clearly indicate that metals potential solubility in the rhizosphere of plants was markedly higher than that in the surrounding sediment. The obtained results indicated that H. portulacoides presence (and probably other salt marsh plants) may cause a marked increase in metals concentrations in dissolved phase (pore water or even water column if rhizosediment is re-suspended). As salt marsh plants may be abundant in temperate and subtropical estuaries and costal lagoons, this phenomenon should not be disregard in future studies towards the sustainable management of such environments.

Can PAHs influence Cu accumulation by salt marsh plants?

The presence of polycyclic aromatic hydrocarbons (PAHs) may change the mechanisms of metal uptake, thus influencing kinetics and extent of metal phytoextraction. Studies on the subject are scarce, particularly for salt marsh plants. The aim of this work was to investigate the effect of PAHs on the uptake of Cu by Halimione portulacoides, a plant commonly found in salt marshes. Experiments were carried out in the laboratory, either in hydroponics (sediment elutriate) or in sediment soaked in elutriate, which were prepared with sediment and water from a salt marsh of the Cavado river estuary (NW Portugal). Groups of H. portulacoides (grown in a greenhouse) were exposed to those media during six days. Cu2+ (as Cu(NO3)2), 10(2) and 10(4) microg l(-1), was added to the media as well as 1.6 microg l(-1) of the sixteen EPA priority PAHs (0.1 microg l(-1) of each PAHs). Cu was assayed in solutions, sediments and different plant tissues before and after experiments. After exposure, photosynthetic efficiency and levels of chlorophylls were also measured, indicating that plant stress indicators were identical in all plants independently of the media to which the plants were exposed. PAHs influenced both the soluble Cu fraction and Cu uptake by plants. The amounts of metal accumulated in both roots and stems were significantly higher when the 10(4) microg l(-1) of Cu enriched elutriate was amended with PAHs. Thus, results suggest that PAHs may modify Cu solubility, the Cu sorption by plants and/or the passive penetration of Cu into the root cells. Therefore, the combined effects of different types of pollutants should be taken in consideration when studying the remediation potential of plants, namely in terms of phytoextraction.

Composition and activity of beta-Proteobacteria ammonia-oxidizing communities associated with intertidal rocky biofilms and sediments of the Douro River estuary, Portugal

AIMS

To characterize the phylogenetic composition of ammonia-oxidizing bacteria (AOB) of the beta-subclass of the class Proteobacteria in intertidal sediment and rocky biofilms of the Douro estuary, and evaluate relationships with environmental variables and N-biogeochemistry.

METHODS AND RESULTS

Cluster analysis of denaturing gradient gel electrophoresis profiles showed differences in beta-Proteobacteria AOB assemblage composition between rocky biofilms and sediments. All sequences obtained from intertidal rocky biofilm sites exhibited phylogenetic affinity to Nitrosomonas sp. lineages, whereas a majority of the sequences from the sediment sites were most similar to marine Nitrosospira cluster 1. Hierarchical cluster analysis based on environmental variables identified two main groups of samples. The first contained samples from rocky biofilm sites characterized by high concentrations of NO2- and NH4+, and high organic matter and chlorophyll a content. The second group contained all of the sediment samples; these sites were characterized by lower values for the variables above. In addition, rocky biofilm sites exhibited higher nitrification rates.

CONCLUSIONS

Intersite differences in environmental and/or physical conditions led to the selection of different populations of beta-Proteobacteria AOB, supporting different magnitudes of N-cycling regimes.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study represents an important step in establishing the influence of environmental factors on the distribution of beta-Proteobacteria AOB with possible consequences for N-biogeochemistry.

Dynamics of nitrous oxide reductase genes (nosZ) in intertidal rocky biofilms and sediments of the Douro River estuary (Portugal), and their relation to N-biogeochemistry

In this study, temporal variability of nosZ genotypes was evaluated in two intertidal rocky biofilms and two intertidal sediment sites of the Douro River estuary, Portugal. The results were compared to rates of key N-cycle processes and environmental variables to examine possible links between denitrifier community dynamics and N biogeochemistry. Genetic heterogeneity of the nosZ gene was evaluated by terminal restriction fragment length polymorphism analysis (T-RFLP) and by sequencing cloned nosZ gene fragments. Phylogenetic analysis showed that the majority of the nosZ genes detected were most similar to nosZ genes from isolates affiliated with alpha-subclass of the class Proteobacteria. Results revealed low nosZ genotype richness, and hierarchical cluster analysis showed significant differences in the composition of denitrifier communities that inhabit different intertidal environments of the Douro River estuary. Monthly surveys of nosZ genotypes from sandy sediments showed that, while the same T-RFLP peaks were present in all samples, shifts in the relative peak areas of the different nosZ genotypes occurred. Canonical correspondence analysis, based on data from the monthly survey, revealed a strong relationship between the relative peak areas of some T-RFLP operational taxonomic units (OTUs) with denitrification rate and NO3- availability. Results suggest that denitrifiers with specific nosZ genotypes (OTUs) have competitive advantage over others when NO3- fluctuates in the system; these fluctuations reflect, in turn, variability in denitrification rates.

The quest for safe drinking water: an example from Guinea-Bissau (West Africa)

While humans require water for life, one-sixth of our species lives without access to safe water. In Africa, the situation is particularly acute because of global warming, the progression of the Sahara desert, civil unrest and poor governance, population growth, migration and poverty. In rural areas, the lack of adequate safe water and sanitary infrastructures leaves millions with doubtful water quality, increasing the harshness of daily life. In this paper, a pilot study was conducted during the wet season on Bolama Island (Guinea-Bissau, West Africa), a UNESCO Man and the Biosphere Reserve. Twenty-eight shallow wells, supplying water to most of the population, were sampled for microbiological, physical and chemical water quality characteristics. A ten-parameter water quality index (WQI) adapted to tropical conditions was applied to compare the different wells. About 79% of the wells showed moderate to heavy fecal contamination. From the surveyed parameters, it was found that chemical contamination was less important, although all samples were acidic, with the pH averaging 5.12+/-0.08. The WQI was 43+/-4% (0%-worst; 100%-best quality), showing that the water from the majority of wells was polluted but should be suitable for domestic use after appropriate treatment. At the onset of the wet season, diarrhea represented 11.5% of all medical cases, 92.5% of which were children aged <15. This paper suggests inexpensive steps to reduce the fecal contamination and control the pH in order to increase the potability of the well water and, concomitantly, to raise the living standards of the population in one of the poorest countries of the world.

A Water Quality Index applied to an international shared river basin: the case of the Douro River

A Water Quality Index (WQI) is a numeric expression used to evaluate the quality of a given water body and to be easily understood by managers. In this study, a modified nine-parameter Scottish WQI was used to assess the monthly water quality of the Douro River during a 10-year period (1992-2001), scaled from zero (lowest) to 100% (highest). The 98,000 km(2) of the Douro River international watershed is the largest in the Iberian Peninsula, split between upstream Spain (80%) and downstream Portugal (20%). Three locations were surveyed: at the Portuguese-Spanish border, 350 km from the river mouth; 180 km from the mouth, where the river becomes exclusively Portuguese; and 21 km from the mouth. The water received by Portugal from Spain showed the poorest quality (WQI 47.3 +/- 0.7%); quality increased steadily downstream, up to 61.7 +/- 0.7%. In general, the water quality at all three sites was medium to poor. Seasonally, water quality decreased from winter to summer, but no statistical relationship between quality and discharge rate could be established. Depending on the location, different parameters were responsible for the episodic decline of quality: high conductivity and low oxygen content in the uppermost reservoir, and fecal coliform contamination downstream. This study shows the need to enforce the existing international bilateral agreements and to implement the European Water Quality Directive in order to improve the water quantity and quality received by the downstream country of a shared watershed, especially because two million inhabitants use the water from the last river location as their only source of drinking water.

Spatial and seasonal variations of the macrobenthic community and metal contamination in the Douro estuary (Portugal)

The macrobenthic community structure and characteristics of sediments were studied in samples collected seasonally at five stations in the lower mesotidal Douro estuary, Portugal. Sediment characterisation included grain size distribution, total-recoverable metals (Al, Fe, Mn, Zn, Cu, Cr, Pb, Ni and Cd), acid-volatile sulphides (AVS) and simultaneously extracted metals (SEM) and total organic matter contents. Spatial variation surpassed temporal variation both in terms of environmental parameters and community structure. Clear anthropogenic contamination in terms of Zn, Cr, Cu and Pb, and a positive SEM-AVS, indicating the potential bioavailability of these metals, were detected on the north bank of the estuary. Multivariate analysis revealed that in addition to natural sediment characteristics, the anthropogenic metal contamination was influencing the macrobenthic community structure. In fact, greater concentrations of Zn, Cr, Cu and Pb were associated with lower number of species and/or diversity. Finally, the dry weight-normalised metal concentrations appeared as a more useful tool than the SEM-AVS model in predicting disturbance of the macrobenthic community in the studied area.

Effect of salinity and inorganic nitrogen concentrations on nitrification and denitrification rates in intertidal sediments and rocky biofilms of the Douro River estuary, Portugal

The regulatory effects of salinity and inorganic nitrogen compounds on nitrification and denitrification were studied in intertidal sandy sediments and rocky biofilms in the Douro River estuary, Portugal, over a 12-month period. Nitrification and denitrification rates were measured in slurries of field samples and enrichment experiments using the difluoromethane and the acetylene inhibition techniques, respectively. Salinity did not regulate denitrification in either environment, suggesting that halotolerant bacteria dominated the denitrifier communities. However, nitrification rates were stimulated when salinity increased from 0 to 15 practical salinity units. NO3- addition experiments revealed that NO3- availability stimulates denitrification rates in sandy sediments, but not in rocky biofilms; however, in rocky biofilms a positive and linear relationship was observed between denitrification rates and water column NO3- concentrations (r=0.92) during the monthly surveys. The N2O:N2 ratios increased rapidly when NO3- increased from 63 to 363 microM; however, results from monthly surveys showed that environmental parameters other than NO3- availability may be important in controlling the variation in N2O production via denitrification. Ammonium additions to sandy sediments stimulated nitrification rates by 35% for the 20 microM NH4+ addition, but NH4+ appeared to inhibit nitrification at high concentration addition (200 microM NH4+). In contrast, rocky biofilm nitrification was stimulated by 65% when 200 microM NH4+ was added.

Sediment quality in the Douro river estuary based on trace metal contents, macrobenthic community and elutriate sediment toxicity test (ESTT)

The aim of this study was to evaluate the sediment quality in the mesotidal Douro River estuarine environment, in order to identify areas where sediment contamination could cause ecosystem degradation. Samples were obtained in five locations and sediment characterised for grain size, total organic matter, total-recoverable metals (Al, Fe, Cu, Pb, Cr, Ni, Cd, Zn and Mn), as well as acid volatile sulfide (AVS) and simultaneously extracted metals (SEM). In situ effects were evaluated by examining the macrobenthic community structure. An elutriate sediment toxicity test (ESTT) was used to estimate the amount of metals and nutrients that could be exchanged with the water column through resuspension, and its positive or negative effects on the growth of the micro-alga Emiliania huxleyi in a 10 day test. Anthropogenic metal contamination was identified at the north bank of the Douro estuary, with deleterious effects on the macrobenthic community, namely decrease in number of species and diversity. This contamination could possibly also be toxic for water column organisms, in case of resuspension, as shown by the ESTT. Sediments from the salt marsh at the south bank showed an impoverished macrobenthic community and elutriate toxicity, which appeared to be due to anaerobic conditions. This study clearly shows the usefulness of the ESST approach to assess the biological effect of resuspension of estuarine sediments.

Microbiological water quality in urban coastal beaches: the influence of water dynamics and optimization of the sampling strategy

In the summer 2001, the microbiological water quality of two contiguous urban coastal beaches (Porto, Portugal) was surveyed for 18 consecutive days. The sampling strategy consisted in sampling surface water in early morning, noon and afternoon. A total of 184 samples were processed at Pastoras beach, a confined area between two jetties, and Ourigo Beach more open to the ocean. At the first beach site, all samples exceeded fecal contamination above guide values (GV) and 82.6% above mandatory values (MV) set out in the EU Bathing Water Directive; whereas at Pastoras Beach, the figures were 93.5% for GV and 26.1% for MV, showing a potential health risk. The periodicity of fecal indicators in raw sewage, the tidal status and wind conditions dramatically influenced the water quality. The quality decreased in the morning regardless of tide conditions, but improved subsequently during the day, particularly during high tide and under the influence of afternoon NW winds. These dynamics are incompatible with the fortnight routine sampling according to the recommendations of the EU Bathing Water Directive, and the strategy should be revised on a beach-to-beach basis, having in mind the profile for the coastal zone.

Comparison of the response of three microalgae species exposed to elutriates of estuarine sediments based on growth and chemical speciation

The elutriate sediment toxicity test (ESTT) provides a measure of the amount of a substance that is exchanged between the sediment and the aqueous phase during resuspension processes such as floods or dredging operations. This study used ESTT with two complementary aims: a comparison of the elutriates of two estuarine sediments (anaerobic muddy [A] and aerobic sandy [B]) in terms of toxicity and a comparison of the response of three different microalgae (Emiliania huxleyi (coccolithophore), Dunaliella minuta (green alga), and Phaeodactylum tricornutum (diatom)) to each elutriate in terms of growth, heavy metals uptake, and organic ligands release or uptake in order to find eventual differences of sensitivity. The interpretation of the results was based on chemical speciation in the culture media. Both elutriates, particularly A, were much richer than seawater (control medium) in some heavy metals and organic ligands able to bind strongly heavy metals. Elutriate A slightly inhibited P. tricornutum growth but stimulated growth of E. huxleyi and D. minuta. Elutriate B stimulated the growth of the three algal species. Therefore, the diatom behaved differently from both the coccolithophore and the green alga. Strong complexation of trace metals by organic ligands could be the cause of absence of the metallic toxicity of the elutriates. Growth inhibition of P. tricornutum in elutriate A could be caused by ammonia-N and/or organic compounds. The concentration of the organic ligands decreased markedly (about 75%) in both elutriates after 10 d of incubation in contrast to the control culture, where their concentration increased about 50% because of exudation. This phenomenon was interpreted to result from ligand uptake by the algae, free or as metal complexes. This work demonstrated that beside the evaluation of toxicity of free heavy metals to alga species, the organic ligands must not be ignored. Depending on the amount of ligand present, the toxicity can be reduced (sequestration) or enhanced (better availability through uptake of metal-ligand complexes). Since the applied ESTT is a standard procedure (U.S. Environmental Protection Agency) for the evaluation of dredged material proposed for ocean disposal, it is necessary to discuss results obtained during toxicity tests with such elutriates in detail.

Survival of faecal indicator bacteria in tropical estuarine waters (Bangpakong River, Thailand)

AIMS

To investigate the survival of cultivable bacteria in the tropical Bangpakong estuary (Eastern Thailand) under different salinities and light conditions.

METHODS AND RESULTS

Dark and light microcosm experiments using membrane diffusion chambers were carried out under three different experimental conditions, namely (i) low salinity, (ii) progressive mixing with brackish water and (iii) fast mixing with high salinity water spiked with raw urban sewage. Faecal coliforms declined faster than faecal enterococci, as shown by survival T90 values ranging from 82.2 +/- 4.2 to 14.5 +/- 0.8 h and 97.5 +/- 0.4-20.6 +/- 1.2 h, respectively. The survival of freshwater heterotrophic bacteria was higher but variable (121.2 +/- 5.0-30.1 +/- 14.3 h), whereas that of heterotrophic marine bacteria was rather stable (81.5 +/- 4.2-44.6 +/- 2.5 h).

CONCLUSIONS

Overall survival was higher in low salinities. Light had a further deleterious effect, since it accelerated the decay of faecal indicators, particularly in high salinities. Faecal enterococci had a higher resistance to environmental conditions compared with faecal coliforms.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is relevant to the understanding of the behaviour of different faecal indicator bacteria and the optimization of sewage treatment plants aimed at the reduction and/or elimination of faecal load discharged into estuarine waters submitted to salinity variations.

Macrobenthic community in the Douro estuary: relations with trace metals and natural sediment characteristics

The relationship between macrobenthic community structure and natural characteristics of sediment and trace metal contamination were studied in the lower Douro estuary (Portugal, NW, Iberian Peninsula), using an innovative threefold approach (SQG, Sediment Quality Guidelines), metal normalization to Fe, and macrobenthic community structure. This study allowed detection of a clear signature of anthropogenic contamination, in terms of Zn, Cu, Pb, and Cr in the north bank of the estuary, which experiences high urban pressure. Using the SQG approach, metal concentrations above ERM (effects range-median) were observed only at one sampling station, but several stations had levels above ERL (effects range-low). The macrobenthic community had a low diversity, with only 19 species found in the entire estuarine area, dominated by opportunistic species. The granulometric distribution of the sediments (estimated from the combination of organic matter, Fe and Al) seemed to be the major structuring factor for the communities, establishing the natural macrobenthic distribution pattern. The metals (Zn, Cu, Pb, and Cr) seemed to act as a disturbing factor over the natural distribution, with deleterious consequences for the macrobenthic communities.

Water quality and uses of the Bangpakong River (eastern Thailand)

The Bangpakong River is the most important watershed in the Eastern part of Thailand. Water quality parameters were sampled from June 1998 through May 1999 at 11 sites along a 227 km gradient, covering the wet season (June-November) and the dry season (December-May). Surface water was collected at three different stations per site (close to the banks and in the middle of the river), and analyzed for temperature, dissolved oxygen, turbidity, suspended solids, pH. ammonia, fecal coliforms, biochemical oxygen demand and chemical oxygen demand as well as conductivity, phosphate, and heavy metals. The Scottish water quality index (WQI) was adaptated to the tropical environment. The averaged WQI was low (41%) and quality declined significantly during the dry season (ANOVA, p<0.001). Although the quality rose somewhat at middle sites, only 27% of the WQI values during wet season and 2.5% during dry season were higher than 50%, denoting poor environmental quality. Within each season, the main sources of variability were the differences between sites along the gradient (48% during the wet season, 63% during the dry season), whereas monthly variability represented less than 20% of the variability. The seasonal results show that the river is suitable only for tolerant fish and wildlife species and is of doubtful use for potable water supply during the dry season. As quality improves during the wet period, water can be used for the production of potable water, but only with advanced treatment, and for indirect and noncontact recreational activities. In the middle stretches of the river, higher water quality permits multiple uses at moderate cost.

Crenarchaeota and Euryarchaeota in temperate estuarine sediments

AIMS

Application of molecular techniques to ecological studies has unveiled a wide diversity of micro-organisms in natural communities, previously unknown to microbial ecologists. New lineages of Archaea were retrieved from several non-extreme environments, showing that these micro-organisms are present in a large variety of ecosystems. The aim was therefore to assess the presence and diversity of Archaea in the sediments of the river Douro estuary (Portugal), relating the results obtained to ecological data.

METHODS AND RESULTS

Total DNA was extracted from sediment samples obtained from an estuary deprived of vegetation, amplified by PCR and the resulting DNA fragments cloned. The archaeal origin of the cloned inserts was checked by Southern blot, dot blot or colony blot hybridization. Recombinant plasmids were further analysed by restriction with AvaII and selected for sequencing. Phylogenetic analyses of 14 sequences revealed the presence of members of the domain Archaea. Most of the sequences could be assigned to the kingdom Crenarchaeota.

CONCLUSION

Most of these sequences were closely related to those obtained from non-extreme Crenarchaeota members previously retrieved from diverse ecosystems, such as freshwater and marine environments.

SIGNIFICANCE AND IMPACT OF THE STUDY

The presence of archaeal 16S rDNA sequences in temperate estuarine sediments emerges as a valuable contribution to the understanding of the complexity of the ecosystem.

Isolation and characterization of two new methanesulfonic acid-degrading bacterial isolates from a Portuguese soil sample

Two novel bacterial strains that can utilize methanesulfonic acid as a source of carbon and energy were isolated from a soil sample collected in northern Portugal. Morphological, physiological, biochemical and molecular biological characterization of the two isolates indicate that strain P1 is a pink-pigmented facultative methylotroph belonging to the genus Methylobacterium, while strain P2 is a restricted methylotroph belonging to the genus Hyphomicrobium. Both strains are strictly aerobic, degrade methanesulfonate, and release small quantities of sulfite into the medium. Growth on methanesulfonate induces a specific polypeptide profile in each strain. This, together with the positive hybridization to a DNA probe that carries the msm genes of Methylosulfonomonas methylovora strain M2, strongly endorses the contention that a methanesulfonic acid monooxygenase related to that found in the previously known methanesulfonate-utilizing bacteria is present in strains P1 and P2. The isolation of bacteria containing conserved msm genes from diverse environments and geographical locations supports the hypothesis that a common enzyme may be globally responsible for the oxidation of methanesulfonate by natural methylotrophic communities.