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PubMed2001

Zooplankton assemblages and biomass during a 4-period survey in a northern Mediterranean coastal lagoon.

The authors proposed to examine zooplankton biomass at three stations inside (T and Z) and outside (M) a coastal lagoon of the north-western Mediterranean Sea. Station T represented the lagoon central area, and station Z was positioned in a shellfish farming sector, while the seaside station (M) served as a reference of marine environment. Analyses were designed to outline the net zooplankton assemblages (taxonomic structures and length distributions) in different environmental conditions, including the farming activity. A discriminant analysis of environmental variables determined that temperature, salinity and phytoplankton implied mainly in spatial pattern of the samples. An ordination of taxa biomasses showed two main factors which might contribute to the organisation of the zooplankton assemblages: the geographical position and the thermal period. The geographical position integrated the lagoon-sea water exchange under forcing parameters (habitat, tides and winds). The thermal period reflected both the populations development cycles and the environmental constraints (temperature, salinity, trophic resources). The resulting effects appeared in structured zooplankton assemblages in space and time. The number of 50 microns interval length classes and of taxa decreased from the seaside and the lagoon central area free of farming activity to the shallower farming zone. But the biomass-length distribution profiles did not closely follow such an expected opposition between opened and confined areas: more extended profiles were observed at station Z. Biomass dominant size classes concerned the range up to 300 microns. This size category appeared to collapse in terms of biomass from the seaside or central area of the lagoon towards the farming area, similarly to zooplankton global biomass fluctuations. Difference between biomass levels and between biomass structures suggested that net zooplankton partly acted as food competitors of macro-filtering organisms, and as preys for farming shellfish and associated epifauna. This impact mainly concerned microzooplankton populations.

Animals↗
PubMed2001

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.

Environmental Monitoring↗
PubMed2003

Natural variation of copper, zinc, cadmium and selenium concentrations in Bembicium nanum and their potential use as a biomonitor of trace metals.

Copper, zinc, cadmium and selenium were measured in the gastropod mollusc Bembicium nanum at two uncontaminated locations, Jervis Bay and Rosedale, NSW, to determine natural variability of metals associated with gender, mass, shore position and temporal variability. Trace metals were also measured in B. nanum at three industrialised locations to determine the accumulation of trace metals in contaminated environments.Copper, zinc, cadmium and selenium concentrations were not significantly different between male and female B. nanum. No significant relationships were found between zinc, cadmium and selenium concentrations and mass. There was a significant relationship between copper concentration and mass but only 19% of the variation was explained by mass. Generally inherent variability within samples had a greater influence than gender or variations in mass on trace metal concentrations. No trend was found in cadmium and selenium concentrations with variation in shoreline position. Copper and zinc concentrations increased further away from the low tide mark, with a decrease in metal concentrations at the furthest site from the water. Variability in metal concentrations is attributable to variations in food source, food availability and different immersion times.Copper, zinc, cadmium and selenium concentrations varied over a 12-month period. Copper, cadmium and selenium were taken up and lost over time, as metal body burden followed the same trend as metal concentrations. Zinc concentrations were influenced by mass. Copper and cadmium concentrations fluctuated throughout the 12-month period but with no clear seasonal trends. Selenium concentrations peaked in spring (October), with concentrations remaining uniform over the other months. These differences in mean concentrations between months were most likely due to inherent trace metal variability associated with differences in food availability and changes in metabolic rates associated with changes in temperature during the study period. Measurement of trace metals in B. nanum at contaminated sites showed that B. nanum accumulates metals in response to contamination.B. nanum meets most of the requirements to be a biomonitor of trace metal contamination as they are abundant, sedentary, easy to identify, provide sufficient tissue for analysis, tolerate high concentrations of pollutants and they accumulate trace metals in response to contamination. However, as trace metal concentration can vary with mass, shoreline position and temporally, care must be taken to collect individual organisms with similar mass from similar shoreline positions and times.

Animals↗
PubMed2004

Cleaning oiled shores: laboratory experiments testing the potential use of vegetable oil biodiesels.

A series of laboratory experiments were carried out to test the potential of vegetable oil biodiesel for the cleaning of oiled shorelines. In batch experiments, biodiesel was shown to have a considerable capacity to dissolve crude oil, which appears to be dependent on the type of biodiesel used. Pure vegetable oil biodiesels (rapeseed and soybean) were significantly more effective in the cleanup of oiled sands (up to 96%) than recycled waste cooking oil biodiesel (70%). In microcosm and mesocosm experiments, oiled sediments were sprayed with biodiesel and subjected to simulated tides. Microcosm experiments revealed that, of those tested, the highest ratio of biodiesel to crude oil, had the highest effectiveness for cleaning fine sands, with ratios of 2:1 (biodiesel:crude oil) giving the best results. In the mesocosm experiments a ratio 1:1 of soybean biodiesel to crude oil removed 80% of the oil in cobbles and fine sands, 50% in coarse sand and 30% in gravel. Most of the oil was removed with the surface water, with only a small amount being flushed through the sediments. Particle size and pore size were important determinants in the cleanup and mobility of crude oil in the sediments in these static systems. It is expected that the biodiesel effectiveness should improve in the natural environment particularly in exposed beaches with strong wave action. However, more laboratory and field trials are required to confirm the operational use of biodiesel as a shoreline cleaner.

Environmental Pollution↗
PubMed2000

Oxygen deficit determinations for a major river in eastern Hong Kong, China.

Determination of oxygen deficit in the Hong Kong Shing-Mun River was based on the oxygen uptake by water, algal respiration and river sediment and the oxygen supplied to the river by surface reaeration and algal photosynthesis. A systematic study was conducted to examine the effect of water temperature, flow velocity and water depth on both the oxygen demands and the oxygen supplies. The oxygen budget of a water column in a selected section of the river was modeled. The results of the oxygen budget analysis showed that when water temperature was around 10 degrees C (the lowest temperature in the river), no deficit was observed. When water temperature was 10 degrees C to 20 degrees C, a small oxygen deficit appeared, especially in the deeper water. At the highest water temperature (30 degrees C), the oxygen deficit was maximal, -6.84 g O2/m2/day, in the night-time during the Spring tide period.

Environmental Monitoring↗
PubMed2000

Concentrations of suspended particulate organic carbon in the tidal Yorkshire Ouse River and Humber Estuary.

Data are presented for particulate organic carbon (POC) and particulate nitrogen (PN) concentrations in the Humber Estuary and tidal River Ouse Estuary. The POC data were derived from approximately monthly surveys and are consistent with data reported for suspended particulate matter (SPM) in the non-tidal River Ouse (the freshwater river) and with SPM, or bed sediments, in estuarine ecosystems such as the Mississippi, Delaware, San Francisco Bay, Tolo Harbour, the Vellar Estuary and Cochin Backwater, as well as the Loire, Gironde, Ems and Tamar Estuaries. Relative to the dry weight of SPM, the Humber-averaged organic carbon and nitrogen percentages during the year February 1995-March 1996 were 2.6 +/- 0.6% (mean and S.D.) and 0.21 +/- 0.04%, respectively. The ratio of Humber-averaged POC to Humber-averaged PN was 13 +/- 3. Higher POC levels were observed near the Humber's mouth and in the adjacent coastal zone during 'bloom' conditions, and in the upper estuarine reaches during large, winter and springtime freshwater inflows. At these times of high runoff, the POC content of SPM increased progressively up-estuary from the coastal zone to the tidal River Ouse. When inflows became very low, during late spring to early autumn of 1995, both the freshwater-saltwater interface (FSI) and the strengthening turbidity maximum (TM) moved further up-estuary and the POC content of SPM in the upper reaches of the Ouse became lower compared with that immediately down-estuary. This led to a poorly defined POC maximum near the confluence of the Humber, Ouse and Trent, before POC eventually decreased again towards the coastal zone. The lower POC contents in the upper estuarine reaches of the tidal Ouse may have been partly due to POC respiration by heterotrophic bacteria attached to SPM within the TM, consistent with the severe oxygen depletion observed there during high turbidity, summertime spring tides.

Carbon↗
PubMed2000

Seasonal variability of salinity, temperature, turbidity and suspended chlorophyll in the Tweed Estuary.

Results are presented from a campaign of measurements that were undertaken to examine seasonal variability in physical and chemical fluxes and processes within the Tweed Estuary during the period September 1996-August 1997. The study utilised monthly surveys, each of approximately 1 week duration. This article interprets a subset of the salinity, temperature, turbidity [suspended particulate matter (SPM) levels] and chlorophyll a data. Measurements discussed here were obtained throughout the estuary during high-speed transects that covered the region between the tidal river and the coastal zone. Longitudinal distributions of surface salinity depended strongly on freshwater runoff. During high runoff the surface salinity was low and the freshwater-saltwater interface (FSI) was located close to the mouth. The reverse was true at times of low runoff. Salinity stratification was generally strong. During the surveys, river runoff temperatures ranged from approximately 2 to 18 degrees C and coastal waters (approximately 33 salinity) from approximately 6 to 15 degrees C. Turbidity was low throughout the campaign (SPM < 30 mg l(-1)). Because of rapid flushing times (one or two tides), turbidity tended to mix conservatively between river and coastal waters. Higher coastal turbidity was associated with stronger wind events, and higher fluvial turbidity with spate events. Suspended chlorophyll a levels were usually low throughout the estuary (typically < 2 microg l(-1)) and showed large spatial variability. Because of the rapid flushing of the estuary, it is hypothesised that it was not possible for several algal cell divisions to occur before algae were flushed to the coastal zone. A 'bloom' occurred during the May 1997 survey, when chlorophyll a levels reached 14 microg l(-1). Higher chlorophyll a concentrations at that time occurred at very low salinities, indicating that these waters and algae were largely fluvially derived, and may have resulted from increasing springtime solar irradiation.

Chlorophyll↗
PubMed2001

Sediment dynamics in Rangoon river, Myanmar.

The behavior of fine-grained sediment in Rangoon River depends on seasonal variations in freshwater discharge and tidal amplitudes that range from 2 to 5 m. During the monsoon, freshwater with sediment concentrations of 1 g/l, or less, causes unidirectional, seaward flow. In the dry season, salinities reach 20% and sediment concentrations rise to 6 g/l. The saline intrusion advects large quantities of sediment landward from seaward sources. Near-surface sediment concentrations are very low during neap tides, while a layer of 'fluid mud' rests on the bottom. Current speeds greater than 0.2 m/s are needed to entrain sediment into the upper layer. Layered suspensions occur most commonly during decelerating phases of tidal flow and are dispersed by rapidly accelerating flow. When current speeds exceed 0.6 m/s, no 'fluid mud' forms, and sediment concentrations as great as 6-8 g/l extend through the water column.

Journal Article↗
PubMed2003

Measuring sediment exchange rates on an intertidal bank at Blacktoft, Humber Estuary, UK.

Results from a suite of Photo Electronic Erosion Pins (PEEPs) and manual pins installed on an intertidal bank at Blacktoft, near the confluence of the Rivers Trent and (Yorkshire) Ouse, UK are presented for summer 1997 (1 May-28 September). These reveal a pattern of erosion and deposition, which can be related to variations in tidal range, freshwater flow and wind speed over the period. During spring tides, greater resuspension of bed sediment leads to a greater availability of sediment in the water column for deposition on the bank. High wind speeds cause greater erosion of material from the bank due to wind-induced wave action. These processes of sediment exchange are also modified by the effects of biological activity on the sediment and of consolidation. It was demonstrated that the mean daily change in elevation of the upper part of the bank at Blacktoft was approximately 11 mm, which is two-three-fold less than the equivalent figure measured by a similar method at Burringham on the River Trent. It is thought that this difference is due to the effects of a greater concentration of suspended sediment settling onto the banks at Burringham, which are also subject to greater erosion due to their steeper slope. Results from a longer and more widespread survey of eight other intertidal banks in the Trent-Ouse Estuary system suggest that deposition and erosion occur in phase on all intertidal banks within the study area. Intertidal banks towards the upstream end of the system show much less variation in bank level than those further downstream.

Journal Article↗
PubMed2003

Dissolved nutrients in the Tweed Estuary, UK: inputs, distributions and effects of residence time.

Results are presented from a campaign in which dissolved inorganic nutrients were measured in the Tweed Estuary, UK. The data utilised here were derived from surveys undertaken on a monthly basis from January to August 1997. There was consistency between the nutrient concentrations observed in the freshwater reaches of the tidal estuary and earlier measurements made several km upstream, in the freshwater river. Typically, nitrate was of the order of 100 microM and silicate approximately half this, whereas phosphate and nitrite were typically approximately 1 microM. Seasonal fluctuations in freshwater nitrate and silicate were very large, with concentrations exceeding (respectively) 300 and 100 microM in winter and less than 30 and 10 microM in summer. The estuarine nutrients surveyed followed this general seasonal pattern. A simple box model was used to investigate the temporal behaviour of a hypothetical estuarine nutrient. The model demonstrated that large deviations from the 'broad-brush' seasonal pattern for nitrate and silicate could be expected to occur within the estuary as a result of runoff and residence-time variations. The model also demonstrated that mid-estuarine peaks observed in the longitudinal distributions of phosphate could only have arisen as a result of non-freshwater, wastewater phosphate inputs to the estuary. Without this mid-estuarine input, rapid flushing rates would have ensured that transients due to changing freshwater phosphate concentrations, runoff and tides (via the residence time) would have had relatively little impact on the classic, linear 'conservative' mixing diagram for the estuary. Conservative mixing was largely applicable to the other nutrients.

Journal Article↗
PubMed2003

Modelling intertidal sediment transport for nutrient change and climate change scenarios.

A model of intertidal sediment transport, including effects of bioturbation and biostabilisation, was applied to two transects on the east coast of England: Leverton (within the Wash) and Skeffling (in the Humber Estuary). The physical and biological parameters were chosen to represent four 1-year scenarios: a baseline year (1995), the same year but with estuarine nitrate inputs reduced by 50% and by 16%, and a year with climate change effects estimated for 2050. The changes in nitrate supply can potentially change microphytobenthos numbers within the surface sediment, which will then affect erodibility. The model results show a range of behaviour determined by bathymetry, external forcing and biotic state. When intertidal sediment transport is dominated by external sediment supply, the model produces highest deposition at the most offshore point, and there is greatest deposition in the winter and spring, when offshore sediment concentrations are highest. When intertidal processes dominate intertidal sediment transport, there is a peak of deposition at the high-shore level and erosion at mid-tide levels. The greatest deposition now occurs in winter and summer, when low chlorophyll levels mean that the sediment is most erodible. The Skeffling transect was dominated by intertidal processes for the baseline scenario and with a 16% reduction in nitrate. Under the climate change (warm winter) scenario, the Skeffling transect was dominated by external sediment supply. The scenario with 50% reduction in nitrate gave intermediate behaviour at Skeffling (intertidally driven during the winter and summer, and governed by offshore sediment supply during spring and autumn). The Leverton transect was dominated by offshore sediment supply for all the scenarios.

Chlorophyll↗
PubMed2003

Apparent homeostasis in the surface salinity of a turbid macrotidal estuary.

A simple, one-dimensional tide-ignoring model has been fitted to surface salinity measured at monthly intervals over 3 years on an extensive sampling grid in the Humber and tidal Ouse on the North Sea coast of the UK. With a constant and uniform axial dispersion, estimated at 296+/-7 m2 s(-1) (95% confidence limits), model deviations vary systematically in space and time. Postulating an influx of dispersive tendency with fresh water largely eliminates the systematic variation in space. Deviations from the simple model (observations-predictions) show a significant seasonal cycle, with minima in the summer and maxima in the winter, and decline significantly over the 3 years of the study. A model that incorporates a homeostatic tendency for the estuary to revert to a constant salinity profile, independent of river flow, appears to eliminate both the seasonal cycle and the trend. The half time of the homeostatic process is estimated to be between 76 and 97 days (95% confidence limits). It is concluded that sediment movement might be the basis of such a mechanism.

Journal Article↗
PubMed1999

Eutrophication process recorded in dinoflagellate cyst assemblages--a case of Yokohama Port, Tokyo Bay, Japan.

To investigate temporal changes of water quality, a role of dinoflagellate cysts preserved in surface sediments was examined in Yokohama Port in Tokyo Bay, Japan. Two cores were collected, and sedimentation rates and ages of both were dated as approximately 1900 years or slightly older on the basis of 210Pb and 137Cs concentrations. The temporal change in dinoflagellate cyst assemblages in the two cores reflects eutrophication in Yokohama Port in the 1960s. Abrupt increases in the cysts of Gyrodinium instriatum cysts strongly suggests that a red tide was caused by this species around 1985. Dinoflagellate cyst assemblages in surface sediments appear to be good biomarkers of changes in the water quality of enclosed seas.

Animals↗
PubMedDate not supplied

Mysids and trace metals: disruption of swimming as a behavioural indicator of environmental contamination.

Mysids are used frequently in standard laboratory studies of acute exposure to chemical contaminants. Their value for sub-lethal measures of biological response to predict the potential effects of environmental toxicants, however, has yet to be determined. In estuaries, mysids maintain their optimum position independent of the forces of river flow and tides; therefore, any disruption of swimming behaviour will have significant implications for their survival and position maintenance. In the present study, the effects of cadmium on the swimming behaviour of the hyperbenthic estuarine mysid Neomysis integer, which occupies the heads of European estuaries, are presented. Following 7 day exposure to cadmium, swimming behaviour (ability and orientation) was disrupted at 0.5 microgram Cd(aq)2+ l-1, a significantly lower cadmium concentration than that causing mortality (7 day LC50 of 2.58 micrograms Cd(aq)2+ l-1). The results of this investigation highlight the advantages of behavioural toxicity tests for predicting the influence of pollutants and support the use of mysids for estuarine monitoring.

Animals↗
PubMed2003

The influence of fish cage aquaculture on pelagic carbon flow and water chemistry in tidally dominated mangrove estuaries of peninsular Malaysia.

The impact of floating net cages culturing the seabass, Lates calcarifer, on planktonic processes and water chemistry in two heavily used mangrove estuaries in Malaysia was examined. Concentrations of dissolved inorganic and particulate nutrients were usually greater in cage vs. adjacent (approximately 100 m) non-cage waters, although most variability in water-column chemistry related to water depth and tides. There were few consistent differences in plankton abundance, production or respiration between cage and non-cage sites. Rates of primary production were low compared with rates of pelagic mineralization reflecting high suspended loads coupled with large inputs of organic matter from mangrove forests, fishing villages, fish cages, pig farms and other industries within the catchment. Our preliminary sampling did not reveal any large-scale eutrophication due to the cages. A crude estimate of the contribution of fish cage inputs to the estuaries shows that fish cages contribute only approximately 2% of C but greater percentages of N (32-36%) and P (83-99%) to these waters relative to phytoplankton and mangrove inputs. Isolating and detecting impacts of cage culture in such heavily used waterways--a situation typical of most mangrove estuaries in Southeast Asia--are constrained by a background of large, highly variable fluxes of organic material derived from extensive mangrove forests and other human activities.

Animals↗
PubMedDate not supplied

Observations of large-amplitude cross-shore internal bores near the shelf break, Santa Monica Bay, CA.

Two sets of moorings were deployed along a cross-shelf transect in central Santa Monica bay for four months in the winter of 1998-1999. Both sites had an array of instruments attached to tripods set on the seafloor to monitor currents over the entire water column, surface waves, near-bed temperature, water clarity and suspended sediment. A companion mooring had temperature sensors spaced approximately 10 m apart to measure temperature profiles between the surface and the seafloor. One array was deployed in 70 m of water at a site adjacent to the shelf break, just northwest of a major ocean outfall. The other was deployed on the mid shelf in 35 m of water approximately 6 km from the shelf break site. The subtidal currents in the region flowed parallel to the isobaths with fluctuating time scales around 10 days, a typical coastal-ocean pattern. However, during the falling phase of the barotropic spring tide, sets of large-amplitude, sheared cross-shore current pulses with a duration of 2-5 h were observed at the shelf break site. Currents in these pulses flowed exclusively offshore in a thin layer near the bed with amplitudes reaching 30-40 cm/s. Simultaneously, currents with amplitudes around 15-20 cm/s flowed exclusively onshore in the thicker layer between the offshore flow layer and the sea surface. The net offshore transport was about half the onshore transport. Near-surface isotherms were depressed 30-40 m. These pulses were likely internal bores generated by tidal currents. Bed stresses associated with these events exceeded 3 dynes/cm(2). These amplitudes are large enough to resuspend and transport not only fine-grained material, but also medium to coarse sands from the shelf toward the slope. Consequently, the seafloor over the shelf break was swept clear of fine sediments. The data suggest that the internal bores dissipate and are reduced in amplitude as they propagate across this relatively narrow shelf. There is evidence that they reach the 35 m site, but other coastal ocean processes obscure their distinctive characteristics.

California↗
PubMed2003

Health hazards due to pollution of waters along the coast of Visakhapatnam, east coast of India.

Environmental pollution that renders waters along the coastline and beaches unsatisfactory for use by the general public has become a global health problem. This study was conducted to examine the effects of pollution of beach waters and sediment at seven selected locations receiving land drainage along a 45-km stretch of the east coast near Visakhapatnam, India. Pathogenic bacteria were identified using standard methods of culturing on selective media. The Pollution Index (PI) was determined as the ratio of fecal coliform/fecal streptococci. Protozoan cysts and helminth ova were also identified by microscopic examination of water after appropriate staining. The results suggested that the beach waters in Visakhapatnam are hygienically poor. A high PI of the water in Lawson's Bay indicated that the water was unsuitable even for noncontact recreation (boating, etc.). Pathogen densities dissipated considerably from the source to the low tide mark. Sediments had significantly higher bacterial and protozoan populations but pathogen concentrations were low except in heavily used areas. The general distribution pattern suggests that the nature of the sediment has a significant role in the retention of bacteria, protozoan cysts, and soil-transmitted helminths.

Animals↗
PubMed2002

The historical development of human resources policies in the health sector of four Caribbean territories: imitated or created?

Health systems are labour intensive, dependent on a mix of professionals to provide health care in both public and private sectors. In this paper, we explore the historical development of human resources, focusing on doctors and nurses, in four Caribbean territories-the Bahamas, Martinique, Suriname and Trinidad and Tobago. All these territories have faced issues around the out-migration of doctors and nurses and tensions between public health, hospital services and private sector policies. Early policies to increase the number of nurses and doctors were costly, because they were implemented against a tide of increasing outward migration. Both push and pull factors were evident. Human resources policies focused on ways to counter pull factors-such as introducing regional medical training-but neglected push factors. These began to be addressed from the 1980s on, although tensions between public health, hospital services and private sector policies led to resistance and conflicts in attitudes to reform among health professionals. Policy responses were the product of many influences, and it is too simple to conclude they were either imported from abroad or internally generated. However, it is clear that in all four territories the medical profession played a dominant role in human resources policy development either directly or indirectly.

Bahamas↗