Photo-induced formation of dissolved gaseous mercury in coastal and offshore seawater of the Mediterranean basin

The first measurements on the daily trend of dissolved gaseous mercury (DGM) concentration determined in coastal and offshore waters of the Mediterranean basin are reported. Marked daily behaviour tracking solar radiation has been observed at the coastal sampling station with DGM values ranging from 11.0 to 38.9 pg/l. Contrary to these observations the DGM values in offshore water samples (11.9-20.0 pg/l) were independent of the sampling time, thus identifying the absence of higher levels during the hours of maximum insolation. The availability of Hg2+ substrate necessary for the photo-reaction processes of DGM formation has been evaluated by measuring the reactive mercury concentration. In offshore waters the lower DGM concentrations are attributable to the substrate as a limiting factor. The highest concentration of DOC measured in coastal seawater with respect to the offshore one could moreover enhance the reaction rates of DGM production through the formation of inorganic mercury complexes and weaker organic associations.     

Fecal indicator bacteria and Salmonella in ponds managed as bird habitat, San Francisco Bay, California, USA

Throughout the world, coastal resource managers are encouraging the restoration of previously modified coastal habitats back into wetlands and managed ponds for their ecosystem value. Because many coastal wetlands are adjacent to urban centers and waters used for human recreation, it is important to understand how wildlife can affect water quality. We measured fecal indicator bacteria (FIB) concentrations, presence/absence of Salmonella, bird abundance, and physico-chemical parameters in two coastal, managed ponds and adjacent sloughs for 4 weeks during the summer and winter in 2006. We characterized the microbial water quality in these waters relative to state water-quality standards and examined the relationship between FIB, bird abundance, and physico-chemical parameters. A box model approach was utilized to determine the net source or sink of FIB in the ponds during the study periods. FIB concentrations often exceeded state standards, particularly in the summer, and microbial water quality in the sloughs was generally lower than in ponds during both seasons. Specifically, the inflow of water from the sloughs to the ponds during the summer, more so than waterfowl use, appeared to increase the FIB concentrations in the ponds. The box model results suggested that the ponds served as net wetland sources and sinks for FIB, and high bird abundances in the winter likely contributed to net winter source terms for two of the three FIB in both ponds. Eight serovars of the human pathogen Salmonella were isolated from slough and pond waters, although the source of the pathogen to these wetlands was not identified. Thus, it appeared that factors other than bird abundance were most important in modulating FIB concentrations in these ponds.     

Water quality in Scotland: the view of the regulator

Water quality in Scotland has progressively improved over the past 50 years as the environmental damage, which resulted from the industrial revolution, has been addressed. This paper provides an overview of current water quality in rivers, lochs, estuaries and coastal waters and describes the limited information available on groundwater. The main factors affecting water quality are reviewed, with sewage, diffuse agricultural pollution, acidification and urban drainage identified as the most important. Trends in pollution pressure and levels of investment in pollution control have been used to predict the condition of Scotland's surface water over the next 10 years. Major improvements are expected. However, progress will be slowed by the increased relative importance of diffuse sources of pollution, which are less amenable to legislative controls. Future changes in environmental monitoring are also expected to move the emphasis away from point source pollution. The current freshwater classification schemes are based upon a relatively narrow measure of water quality and are expected to expand to include a wider range of ecological parameters. This will result in an increase in the waters defined as impacted as the effects of other environmental pressures are taken into account. Finally the implications of these changes for the future management of the aquatic environment are assessed.     

Extent of sewage pollution in coastal environment of Mumbai,India: an object‐based image analysis

The coastal water quality of Mumbai is deteriorating by receiving partially treated effluent from wastewater treatment facilities, sewage discharges from ocean outfalls and discharges from point and non‐point sources in the creek and coast. A novel approach of object‐based image analysis has been used in this research study to assess the extent of sewage pollution in the coastal environment of Mumbai. For this, Indian Remote Sensing P6 Linear Imaging Self Scanning IV image was used for multiresolution segmentation and rule‐based image classification as per normalised difference water index and normalised difference turbidity index. Water quality regions as per classification were strongly correlated with observed water quality parameters. Based on classified regions and water quality parameters, extent of sewage pollution in the coast was ranked from high to least polluted. The approach developed in this methodology should be tested in similarly polluted waters to ascertain its adaptability for assessing the spatial extent of sewage pollution.     

Modelling the fate of faecal indicators in a coastal basin

The paper describes a modelling study of near-shore coastal waters, undertaken to assess the impact of various bacterial input loads on the receiving waters in a coastal basin in the UK. Total and faecal coliforms, used as the indicators for bathing water quality under the European Union (EU) Bathing Water Directive, were numerically modelled using a 2D depth integrated hydro-environmental model. Details are given of the governing equations and solution methods used in the numerical model, together with a discussion of the recent development in faecal bacterial indicator modelling. Details are also given of a field data collection exercise, which involved initially collecting existing information on effluent input loads and followed by an intensive field survey. Using the water quality model, the mortality rate of the pathogen bacteria was investigated. Three methods were used to represent the relationship between the decay rate and the level of solar radiation including: a constant decay rate, day- and night-time decay rates and a solar radiation related time varying decay rate. Relatively close agreement between model predicted and measured total and faecal coliform concentration distributions were obtained for different day- and night-time decay rates and time varying decay rates. No significant differences were found in the optimum decay rates for total and faecal coliform levels. Finally, the impact of the individual inputs on the bathing water quality of the basin was also statistically and numerically investigated. Results showed that the River Irvine was the most significant input during high river flows, and that under these conditions the bathing waters were likely to fail to comply with the European Union Bathing Water Directive. For base river flow conditions the Meadowhead effluent input was found to be critical for both total and faecal coliform level predictions.     

Decay of intestinal enterococci concentrations in high-energy estuarine and coastal waters: towards real-time T90 values for modelling faecal indicators in recreational waters

Intestinal enterococci are the principal 'health-evidence-based' parameter recommended by WHO for the assessment of marine recreational water compliance. Understanding the survival characteristics of these organisms in nearshore waters is central to public health protection using robust modelling to effect real-time prediction of water quality at recreation sites as recently suggested by WHO and the Commission of the European Communities Previous models have more often focused on the coliform parameters and assumed two static day-time and night-time T90 values to characterise the decay process. The principal driver for enterococci survival is the received dose of irradiance from sunlight. In the water column, transmission of irradiance is determined by turbidity produced by suspended material. This paper reports the results of irradiated microcosm experiments using simulated sunlight to investigate the decay of intestinal enterococci in relatively turbid estuarine and coastal waters collected from the Severn Estuary and Bristol Channel, UK. High-turbidity estuarine waters produced a T90 value of 39.5 h. Low-turbidity coastal waters produced a much shorter T90 value of 6.6 h. In experiments receiving no irradiation, high-turbidity estuarine waters also produced a longer T90 of 65.1 h compared with corresponding low-turbidity coastal waters, T90 24.8 h. Irradiated T90 values were correlated with salinity, turbidity and suspended solids (r>0.8, p<0.001). The results suggest that enterococci decay in irradiated experiments with turbidity >200 NTU is similar to decay observed under dark conditions. Most significantly, these results suggest that modelling turbidity and or suspended solids offers a potential means of predicting T90 values in 'real-time' for discrete cells of a hydrodynamic model.     

Population growth away from the coastal zone: Thirty years of land use change and nutrient export in the Altamaha River, GA

We used more than thirty years of water quality monitoring data collected by the United States Geological Survey at several stations in the Altamaha River and its tributaries to examine the relationship between population density, agricultural land use, and nutrient export from the watershed. Population densities in the Altamaha River watershed increased during the study period, most notably in the upper watershed near metropolitan Atlanta, while agricultural land use declined throughout the watershed. NO_x, TN and P in rivers were related to human population densities, while OC and NH₄⁺ concentrations in rivers were apparently related to agricultural land use. A general pattern of increasing NO_x and TN and decreasing NH₄⁺, P and OC over time throughout the watershed reflected changing population and land use. The overall average load from the Altamaha River to the coastal zone during the study period was 1.1, 5.6, 16.9, 0.9 and 262 kmol km^− 2 yr^− 1, delivering 40, 197, 596, 30, and 9213 · 10⁶ mol yr^− 1 of NH₄⁺, NO_x, TN, P and OC, respectively, to the coastal zone. The nutrient export patterns suggest that N and P loading to rivers in the Altamaha River watershed was greatest in the upper watershed where high population densities were found, and in-stream processing, dilution, and only moderate inputs during transit through the lower watershed resulted in relatively low export from the watershed to coastal waters.     

A Method to Simulate the Impact of Acid Mine Drainage on River Systems

Abandoned mines create pollution problems in rivers as minewater levels rise and discharges of metal-rich acidic waters occur. Mines adjacent to rivers can cause serious pollution problems, reducing fish stocks and preventing restocking. A computer model has been used to simulate the impact of these discharges and to devise an optimal treatment strategy to meet river quality objectives. The use of this model, through application to two case studies, is described.     

Multistep approach to identification of limiting nutrients in Northern Adriatic eutrophied coastal waters

The problem of the identification of the primary limiting nutrient in eutrophied coastal waters of the Northern Adriatic was tackled by a multistep approach, with emphasis on the measurement of physiological indicators of nutrient deficiency. Laboratory experiments were carried out in advance to select the most significant indicators of specific nutrient deficiency and to verify their sensitivity and field applicability. The physiological parameters examined were: assimilation coefficient, ¹⁴C-dark uptake to photosynthetic ¹⁴C-uptake ratio, ammonium ion enhancement ratio, chlorophyll content per unit of algal biomass, alkaline phosphatase activity. Ammonium ion enhancement ratio and alkaline phosphatase were found to be the most significant indicators of nitrogen and phosphorus deficiency respectively and were used for studies of the coastal waters. The field results indicated that the phytoplankton populations were phosphorus limited. Nitrogen deficiency was never found during the whole sampling period.     

Application of the Kohonen neural network in coastal water management: methodological development for the assessment and prediction of water quality.

Kohonen neural network (KNN) was applied to nutrient data (ammonia, nitrite, nitrate and phosphate) taken from coastal waters in a Spanish tourist area. The activation maps obtained were not sufficient to evaluate and predict the trophic status of coastal waters. To achieve this aim, a new methodology is proposed which uses as its starting point the activation maps obtained from KNN. Firstly, to evaluate the trophic status of the coastal waters, it consists of the development of a quadrat system which enables a better classification than the traditional classification based simply on standardized data. The new classification allows clear differentiation of water quality within the mesotrophic band. Secondly, and in order to use the activation maps as predictive tools, the trophic classification, obtained from activation maps, was transposed onto new activation maps. To do this, the activation maps of the sampling points which defined each trophic group were superimposed. To avoid unnecessary complexity and to facilitate the process, this superimposition was undertaken only where the frequency exceeded 0.05. In this way, four frequency maps related to the trophic status of coastal waters (potentially eutrophic, high mesotrophic, low mesotrophic and oligotrophic) were obtained. There was no loss of relevant information in the new maps thus obtained. These frequency maps served as the basis for the successful prediction of the trophic status of random samples of coastal waters. This methodology, based on KNN, is proposed as a tool to aid the decision-making in coastal water quality management.     

Studies of the mixing of coastal waters in liverpool bay using dissolved silicate as a tracer

The essential prerequisites to be met by a natural tracer in coastal waters are stated and an assessment made of the suitability of dissolved silicate. The application of silicate as a tracer, in conjunction with salinity and temperature, is illustrated with reference to a four-component mixing model of Liverpool Bay during January 1975. The model provides evidence for an anticlockwise residual surface circulation of the coastal waters.     

The marine corrosion of structural steels in brackish and fresh waters

High-quality models are required to describe the corrosion of structural steels in marine, brackish and fresh waters and these models should, preferably, be based on a proper understanding of the corrosion processes involved. The models should then be used to interpret field data, rather than attempting to derive models empirically from field data. On this basis a multi-phase corrosion–time model has been proposed previously for mild and low alloy steels subject to immersion in ‘at-sea’ conditions. This model is reviewed and extended to brackish and fresh waters in this paper. The scientific principles show that salinity is not the critical issue for the corrosiveness of water. Instead, the critical parameters are the temperature, pH and calcium carbonate solubility when corrosion is governed by oxidation. For later corrosion, governed by anaerobic bacterial activity, the available nutrient level and rate of supply of nutrients control the observed rate of corrosion. The data available at the present time for estimating all the parameters of the new model are somewhat preliminary and new corrosion monitoring programmes will be required to augment the information and to fully characterize the corrosivity of coastal and harbour waters. However, indicative trends for the parameters, based on currently available data, are given and permit the construction of corrosion loss curves for practical applications.     

Environmental flow assessment for rivers feeding a coastal wetland complex in the Pacific coast of northwest Mexico

Hydrological variability is one of the main drivers for rivers structure, and functionality, making the environmental flow (EF) assessment a key element to understand some ecological processes depending on it. Therefore, we aimed to evaluate the EF regime for the main rivers feeding a coastal wetland complex in northwest Mexico, following the hydrologic methodology officially approved by the Mexican National Water Commission based on daily data series (1975–2014). A mean annual runoff around 11 556 Mm³ was estimated to feed the Marismas Nacionales (MN) wetlands system from the discharge of seven rivers. It is expected that the estimated flows, regarded as necessary for the MN system to function properly as a whole, will change because of regional hydraulic infrastructure plans, threatening the discharge of the San Pedro and Baluarte rivers by reducing the flow significantly with negative effects on the MN wetlands.     

Relationships between microbial water quality and environmental conditions in coastal recreational waters: the Fylde coast, UK.

This paper explores ways in which the analysis of microbial data from routine compliance monitoring, in combination with basic environmental data, can provide insight into the factors affecting faecal-indicator organism concentrations in coastal waters. In the case study presented, eight designated bathing waters on the Fylde coast are continuing to exhibit unreliable compliance with the Imperative standards for total coliform (TC) and faecal coliform (FC) concentrations specified in the EU Bathing Water Directive (76/160/EEC), despite significant reductions in geometric mean concentrations following recent major investment in the sewerage infrastructure. Faecal streptococci (FS) concentrations have remained high and have not been improved by the new sewerage schemes. The results suggest that, prior to the schemes, higher bacterial concentrations were strongly associated with rainfall; and sewage sources were important for TC and FC, but less important for FS, which may have been more strongly affected by diffuse catchment sources. In the post-schemes period, catchment sources appear to be of greater significance; rainfall remains as a significant, though less important, predictor; and tide height at time of sampling, together with variables such as sunshine and the proportion of onshore winds (which affect the survival and movement of bacteria that have already entered the coastal waters), assume greater significance. The approach used here provides a cost-effective management tool for the exploratory investigation of any monitoring point that is failing to meet recreational water quality standards.     

Detection of DNA damage in haemocytes of Mytilus galloprovincialis in the coastal ecosystems of Kastela and Trogir bays, Croatia

Coastal waters are burdened with different contaminants of anthropogenic origin due to intensive urbanisation and economical development. Bays, semi-enclosed areas with limited water renewal ability, are particularly endangered by contaminant inputs. Kastela Bay (Dalmatia, Eastern Adriatic) has earlier been identified as an area loaded with diffuse sources of pollution, including genotoxic agents. However, there is lack of data on the effects of these contaminants on the local marine fauna. The aim of this study was to assess genotoxic impacts in Kastela Bay and the neighbouring Trogir Bay using the micronucleus test and Comet assay with mussel (Mytilus galloprovincialis) haemocytes. Native and caged mussels were included in the studies. Our results confirmed that mussels in Kastela and Trogir Bays are affected by genotoxic contaminants. In addition to mussels from the most known polluted site (Vranjic), there was evidence for genotoxic effects in mussels collected at other locations. The response in the micronucleus test and the Comet assay differed somewhat between sites, the latter apparently being more sensitive, but the two methods complement each other and it is therefore desirable to use them both in monitoring the impacts of genotoxic pollution in coastal waters.     

A mechanistic model of runoff-associated fecal coliform fate and transport through a coastal lagoon

Fecal coliform (FC) contamination in coastal waters is an ongoing public health problem worldwide. Coastal wetlands and lagoons are typically expected to protect coastal waters by attenuating watershed pollutants including FC bacteria. However, new evidence suggests that coastal lagoons or marshes can also be a source of high indicator organism concentrations in coastal waters. We asked for a Mediterranean-type climate, what is the fate of runoff-associated FC through a coastal lagoon? To address this question, we developed a mass balance-based, mechanistic model of FC concentration through a coastal lagoon and simulated, for summer and winter conditions, FC within the lagoon water column, lagoon sediments, and in the ocean water just downstream of the lagoon mouth. Our model accounts for advective flow and dispersion, decay and sedimentation and resuspension of FC-laden sediments during high flow, erosional conditions. Under low flow conditions that occur in the summer, net FC decay and FC storage in lagoon sediments are predicted. Under high flow conditions that occur in the winter, FC-laden sediments are predicted to erode, resuspend and flow out of the lagoon where they elevate FC concentrations in the coastal ocean. For both seasonal conditions, the predicted water column FC concentrations were within an order of magnitude of field measurements for a reference site in southern California. Our results suggest that there are seasonally varying roles for coastal lagoons in mediating FC contamination to coastal waters.     

Tracer applications of ultra-violet absorption measurements in coastal waters

Data on the ultra-violet adsorption characteristics of various natural fresh and marine waters are presented. Differences in both the magnitude and shape of spectra from river waters are considered and from them four absorption indices are developed as being of potential tracer value to mixing studies in coastal waters. In this context the indices are assessed with reference to ultra-violet absorption and salinity measurements collected during two winter cruises off the west coast of Great Britain.     

Temporal study of Helicobacter pylori presence in coastal freshwater, estuary and marine waters

Helicobacter pylori, a gastric pathogen, is believed to be transmitted via the fecal-oral route as well as the oral-oral route. Its presence and viability in environmental waters is not well characterized. The goals of this study were to test H. pylori presence via molecular methods in freshwater, estuarine and beach sites in Delaware over both short and long time scales and to establish whether fecal indicator bacteria, including total Enterococcus and human-specific Bacteroidetes species, are predictive of the pathogen in these waters. The presence of Helicobacter pylori was initially tested by PCR with newly designed 23S rRNA gene primers against Helicobacter spp. and confirmed by sequencing. Two coastal beach sites were repeatedly positive in 2007. Clone library analysis indicated the persistence of one operational taxonomic unit (OTU) over time at one site. Detection of H. pylori was also determined by PCR assays from DNA and RNA for the 16S rRNA gene, as well as DNA for the ureA and cagA genes. Approximately 21% of the samples were positive for H. pylori 16S rRNA gene and 80% of those were also positive for H. pylori 16S rRNA, indicating that this potential pathogen is not only present in natural waters, but also probably viable. There was no correlation between the occurrence of H. pylori and fecal indicator bacteria, suggesting that standard water quality tests are ineffective in predicting the presence of this pathogen in natural waters. These results demonstrate the widespread presence of potentially viable H. pylori in coastal marine and estuarine waters. Additionally, the repeatedly positive samples indicate either a continual contamination source or persistence of H. pylori in marine waters.     

Significance of phosphorus in lakes and coastal water sediments and benthos

The dynamics of availability of sediment phosphorus to the overlying water depends on P concentration of interstitial water which in turn depends on the redox intensity and the affinity of the solid sediment phases for P. In lakes and coastal waters substantial fractions of P become irretrievably deposited into the sediments, but in lakes the seasonal sequence of P release to the water from the sediments—after spring and fall overturn, preceding periods of massive algal growth—and of P binding to the sediments—prevailing during the later parts of the stagnation period—tends to facilitate algal blooms in shallow waters. With increasing depth of the lake the net removal of P from the water by the sediments becomes preponderant and the quantity of P released from the sediments to the epilimnion becomes small relative to other fluxes.Diffusional transport of P through interstitial water has been determined experimentally for various sediments; these results are compared with observed transfer rates across the sediment water interface in lakes and coastal waters.There are essentially the following ways for P to be deposited: (1) Adsorption of P on clays; (2) burying of detrital P; (3) chemical precipitation of apatite; and (4) diagenetic replacement of calcite (e.g. skeletal carbonate) by substitution of carbonate by phosphate. Accumulation of P, regenerated from detritus as it occurs most extensively in shallow waters and under conditions of counter-current systems (estuaries), does not in itself lead to an increase in the relative apatite saturation because the regeneration of one P atom is accompanied by an increase in acidity caused by the formation of ca. 106 CO₂ molecules. In order to exceed the critical ion product, the excess of CO₂ must be lost or neutralized. Such conditions are encountered in areas of upwelling, where excess CO₂ is lost to the atmosphere and under reducing conditions where denitrification and SO₄²⁻ reduction consume hydrogen ions.A simplified steady state model will be used to depict that the dynamics of P transformations—especially the rate of regeneration of P from phytoplankton, benthos, detritus, and sediments and the rate of supply of soluble P to the algae—are more important in determining productivity than is the concentration of P or the P-reserve.     

Development of a nearshore weed‐screen. A nature coastal defence idea

Laminaria sp. are examined as the most promising kelp type for controlled macroalgae cultivation on a small‐scale in Belgian North Sea coastal waters. An appropriate housing, the so‐called “nearshore weed‐screen”, has been developed to contain the transplanted kelps. The case is argued for a closed rigid cage to offset detritus losses and other storm‐induced losses as opposed to more traditional open, viz. exposed, systems. Possible economic returns on the sold product — kelp for alginate and biogas — are pinpointed. A need for new uses is quoted to make the venture economically viable. The weed‐screen design is put forward as a means of reducing current beach maintenance expenditures, so generating a possible new source of income for the “thalassa‐farm”.