A statistical–dynamical method for predicting estuary morphology

A statistical–dynamical model for estuary morphodynamics is presented and demonstrated with a case study on the Humber Estuary, UK. The model presented here is hybrid in nature where simplified process dynamics are combined with a data-driven approach. The modelling methodology uses an inverse technique to construct an unknown source function in the model-governing equation, using historic measurements of estuary bathymetry. Spatial and temporal variability of the source function was established using empirical orthogonal eigenfunction analysis. Predictions of estuary morphology are obtained by extrapolating the temporal coefficients of the EOFs, in order to construct a predicted source function which is then used in the hybrid morphodynamic equation to obtain the predicted estuary morphology. The model was applied to predict the morphological evolution of the Humber Estuary over a period of a decade. Predicted results were compared with measured bathymetry data. The results reveal that the model captured the decadal scale morphodynamic response of the estuary with a good qualitative accuracy, despite the simplified approach used in the model. The accuracy of model predictions can be greatly improved if high-frequency bathymetry data are available.     

Sediment organic matter source estimation and ecological classification in the semi-enclosed Batan Bay Estuary,Philippines

The large organic matter flow in tropical coastal areas is recognized as an important process in the global carbon(C)cycle.However,the nature of organic matter flow in semi-enclosed tropical estuaries remains unclear due to the various environmental processes(tidal change,river flow,waves from the sea,and internal circulation)and organic matter sources therein.Thus,sediment organic matter(SOM)sources,and their distribution pattern,are key to understanding ecosystem material flow.Our research in the Batan Bay Estuary,Philippines,a semi-enclosed estuary under large mangrove deforestation,was conducted to determine ecosystem properties through analysis of C and nitrogen stable isotope ratios and environmental factors.First,we determined that mangrove litter,microphytobenthos,and phytoplankton are the main SOM sources in the Batan Bay Estuary.Second,the estuary was classified into three ecological zones(the Bay zone,Back-barrier zone,and River zone).In addition,we estimated SOM source ratios using the Stable Isotope Analysis in R package and determined different organic matter sources in different zone.The high ratios of mangrove litter as SOM indicate that a large amount of terrestrial plant organic matter remains despite the heavy mangrove deforestation that has occurred since the 1980s,and that the Back-barrier zone consists of a different type of ecosystem that promotes accumulation of C from mangrove litter and microphytobenthos.     

Inhibition of estuarine bacteria by metal refinery effluent

Water samples from the Humber Estuary adjacent to a discharge of metal refinery effluent were found to have high dissolved metal concentrations and low pH. Bacterial activities and concentrations of viable bacteria were low, indicating inhibition of bacteria and reduction in self-purification. Toxicity tests demonstrated that acid conditions and copper and arsenic amongst metals probably contributed to bacterial inhibition.     

Effects of varying estuarine conditions on the sorption of phenanthrene to sediment particles of Yangtze Estuary

The sorption of phenanthrene on the Yangtze Estuary sediment was studied under varying conditions of particle size, sediment organic contents, salinity, and dissolved organic matter (DOM) concentrations. Small sediment particles showed higher trapping capacity for phenanthrene due to the higher organic contents associated. The organic carbon-based partition coefficient of phenanthrene to the Yangtze Estuary sediment was obtained as 7120 L/kg, lower than the values for other soils or sediments reported in previous studies. The magnitude and direction of the salt effect were complicated by the specific DOM studied. The sediment sorption capacity was greatly increased in saline water in the absence of DOM but decreased in the presence of DOM. Given the conditions in the Yangtze Estuary, the equilibrium sorption of phenanthrene would be decreased with increasing salinity. Overall, the nature and content of both sediment-bound and dissolved organic matter dominate the sorption of hydrophobic organic contaminants in the estuary.     

Chemical characterization of porewaters in an intertidal mudflat of the Seine estuary: relationship to erosion-deposition cycles

A seasonal field study was carried out in the Seine estuary to determine the chemistry of sediment porewaters using the 'peeper' technique and changes in the elevation of the mudflats using the 'Altus' technique. This approach allowed us to evaluate the release of nutrients and to link these releases to the sediment hydrodynamics. Our results show that nutrient and organic matter cycling in a Seine estuary mudflat exhibits a seasonal behaviour, which is mainly influenced by variations in hydrodynamics. Sediments, rich organic matter, were input during floods and they were mineralized during summer and autumn, releasing nutrients and dissolved organic carbon into the sediment porewaters. The nutrient release, including ammonium, is mainly linked to the mineralization of organic matter, while the release of phosphate is delayed. The delay could be the result of phosphate association with organic matter and/or its co-precipitation with calcium and iron.     

Die EG‐Wasserrahmenrichtlinie: Ausweisung und Bewertung künstlicher und erheblich veränderter Gewässer

Designation and Assessment of Artificial and Heavily Modified Water Bodies under the EC Water Framework Directive The EC Water Framework Directive allows the Member States to designate artificial and heavily modified water bodies under specific conditions. For those water bodies the ecological assessment and the resulting programmes of measures will be based on the “maximum ecological potential” as reference conditions and not on the “high ecological status”, which has to be used for natural water bodies. Such designation is possible only, if the hydromorphology of the water bodies concerned has been substantially changed in character to maintain specified uses. The criteria for the designation are fulfilled, if restoration measures needed to meet the high ecological status would have significant adverse effects on the uses and if no other better environmental options would exist to maintain the specified uses. In late 1999 the EC‐Working Group on Heavily Modified Water Bodies (HMWB) has been established to develop criteria for the designation of artificial and heavily modified water bodies as well as for the determination of the maximum ecological potential. The working group has produced the guidance document “Identification and Designation of Artificial and Heavily Modified Water Bodies” in November 2002, which has been agreed by the European Water Directors on 21 November 2002 in Copenhagen. The guidance document is focusing on two time borders, the provisional identification of heavily modified water bodies until 2004 and the legally binding designation as artificial and heavily modified in the first river basin management plan in 2009 at the latest. The guidance document considered the main findings of 34 case studies for rivers, lakes, transitional and coastal waters carried out in 11 European countries. The results of the case studies as well as a summarizing synthesis were used as a fundamental basis to produce the guidance document. The practical examples given by the case studies were compiled as a toolbox which supplements the guidance for the purpose of its better application.     

Modeling the effect of artificial flow and sediment flux on the environment and plankton of an estuary

Estuarine environments are influenced by both river flows and oceanic tidal movement of water, sediment, and nutrients, often forming ecosystems that are rich in resources and biodiversity. The Yellow River once carried the world’s largest sediment load, but artificial structures have transformed its hydrodynamic processes. An annual Water-Sediment Regulation Scheme(WSRS) was introduced to flush accumulated sediment from the Xiaolangdi Reservoir, which provides flood control and water storage.Ho...     

Study on nutrient distribution and interaction with sediments in a macro-tidal estuary

An integrated hydro-environmental model has been developed for predicting the distribution of nutrients in estuarine and coastal waters. This paper also reports on an application of the model to the Loughor Estuary in the UK, which has a high tidal range. The horizontal two-dimensional model considers the hydrodynamic, sediment transport, dissolved oxygen and nutrient cycling processes. In particular, the effect of sediment suspension and deposition on the nutrient distribution in the water column has been included in the model. A TVD-MacCormack scheme has been adopted to numerically solve the coupled partial differential equations. Field surveys and laboratory experiments in connection with the Loughor Estuary were conducted to obtain measured data for model calibration and verification. It was found that the linear isotherm model gave a good approximation of the adsorption/desorption processes over the range of nitrogen and phosphorus concentrations measured in the natural estuary. Through experiments on the collected soil samples, the salinity-dependent partition ratios between the adsorbed and dissolved nutrients were determined. The results of the established model showed good agreement with the measured data. Finally, the model was used to examine the implications of changing the sewage effluent discharge scheme on the nutrient distributions in the estuary.     

Distribution and characteristics of suspended particulate matter in a heavily eutrophic estuary, Tokyo Bay, Japan

Bulk suspended particulate matter (SPM), chlorophyll a (Chl a), ignition loss, particulate organic carbon (POC), organic nitrogen, inorganic phosphorus (PIP), and organic phosphorus were investigated in the heavily eutrophic Arakawa River estuary, Japan. Chl a was high (approximately 35 microg l(-1)) in summer and low (approximately 6.7 microg l(-1)) in winter and autumn. POC from living phytoplankton accounted for approximately 34% and approximately 70% of total POC during low- and high-biomass seasons, respectively. During the low-biomass season, detrital POC distribution was conservative, and less reactive, land-derived materials mainly composed particulate organic materials (POM), but complex mixing of land-derived POM and autochthonous planktonic detritus caused nonconservative detrital POC behavior during the high-biomass season. PIP concentration in SPM decreased with increasing salinity, likely by desorption of soluble orthophosphate (ortho-P). The ortho-P released from SPM, 56% of the ortho-P input from the Arakawa River to the bay, was a significant potential source of biologically available phosphorus causing eutrophication of coastal environments.     

Transfer of organic contaminants to the Baltic in the Odra Estuary

This paper describes the transfer of organic contaminants to the sea, using PAHs (12 compounds) and PCBs (11 congeners) as examples, through a eutrophicated coastal lagoon (Szczecin Lagoon, on the Polish-German border). The transfer of contaminants study was based on their concentration in recent sediments (0-10 cm), in relation to different environmental conditions such as temperature, salinity, turbidity, oxygen and nutrients in water, hydrological conditions, organic carbon and biomarkers (pigments and their derivatives) in sediments. Results include the data obtained between 1994 and 2000, also those on before and afterwards the great flood in July 1997, at different stations in the Lagoon and the adjacent Pomeranian Bay. The results indicated that the eutrophic estuary of the shape of lagoon acts as an effective trap for the hydrophobic organic pollutants. The abundance and taxonomy of plankton as well as detritus derived from it play an important role in bonding the studied compounds. The salinity gradient in the lagoon has a significant influence upon deposition of the pollutants from the water column to the sediments and the residence time of the compounds there depends strongly on oxic-anoxic status of the sediments and the strength of interaction with sediments resulting from polarity, the type and stability of associates formed, as well as on hydrological conditions. We conclude that eutrophication in this area prevents pollution of the sea to some extent.     

Terrestrial discharge into the Great Barrier Reef Lagoon: nutrient behavior in coastal waters

Pollution of coastal regions of the Great Barrier Reef World Heritage Area (GBRWHA) is dominated by river discharge associated with agricultural development of the adjacent catchments. Runoff of sediment, nutrients and pesticides has sharply increased since European settlement. Since 1991 plumes from river discharge entering the GBRWHA have been mapped by aerial mapping of plume edges and concentrations of contaminants in plumes measured. Plume dispersion is governed primarily by wind speed and direction. Most plumes spread in a band up to 50 km from the coast. Particulate material discharged in the plumes is trapped within 10 km of the coast. Dissolved nutrients disperse much further and elevated nutrient concentrations are measurable at distances of hundreds of kilometres from river mouths. This differential transport of particulate versus dissolved nutrients is important for the potential effects of these materials and management of their generation on the Great Barrier Reef catchment.     

Spatial distribution and source apportionment of PAHs in surficial sediments of the Yangtze Estuary, China

Spatial distribution and source apportionment of polycyclic aromatic hydrocarbons (PAHs) in the surface sediments of the Yangtze Estuary, especially the North Branch, have been fully investigated. PAH concentrations increased with the descending distance from the inner estuary to the adjacent sea, and varied significantly in various estuarine regions. Water currents (e.g., river runoff and ocean current) greatly affected the distribution pattern. In addition, ambient sewage and traffic also contributed to the PAH pollution in the estuary. In the adjacent sea, PAH values along the -20m isobath were higher than those along the -10m isobath due to the "marginal filter" phenomenon formed by different water currents. In most sites, PAHs had poor correlations with sediment size, but had positive correlations with total organic carbon. Based on the qualitative and quantitative analysis results, PAH sources were proved to be mainly from a mixture of petroleum combustion, biomass, and coal combustion.     

Organic carbon deliveries and their flow related dynamics in the Fitzroy estuary

The Fitzroy estuary (Queensland, Australia) receives large, but highly episodic, river flows from a catchment (144,000 km(2)) which has undergone major land clearing. Large quantities of suspended sediments, and particulate and dissolved organic carbon are delivered. At peak flows, delta(13)C (-21.7+/-0.8 per thousand) and C/N (14.8+/-1.3) of the suspended solids indicate that the particulate organic material entering the estuary is principally soil organic carbon. At the lower beginning flows the particulate organic matter comes from in-stream producers (delta(13)C=-26 per thousand). The DOC load is about 10 times the POC load. Using the inverse method, budgets for POC and DOC were constructed for high and low flows. Under high flows, only a small portion of the POC and DOC load is lost in the estuary. Under dry season (low flow) conditions the estuary is a sink for DOC, but remains a source of POC to the coastal waters.     

The use of environmental integrative indicators to assess seabed disturbance in estuaries and coasts: Application to the Humber Estuary, UK

The coastal zone is subject to many and varied changes resulting from human activities and natural processes. Existing or emerging agreements and legislation acknowledge the relevance of indicators for monitoring these. In the UK, following a series of recent workshops, potential indicators of nearshore disturbance have been identified and grouped into three broad indices: 'Coastline Morphological Change', 'Resource Use Change' and 'Environmental Quality and its Perception'. The present study developed these indicators further and tested their use by applying them to 18 sections in the Humber Estuary, Eastern England. The results obtained reflect the current knowledge of the state of the Humber environment and show the potential of integrative indicators but indicate that further studies are required to assess the relative importance of the indicators and their value in reflecting the ability of the ecosystems to sustain natural habitats and populations at a good conservation status.     

Seasonal and spatial distribution of the microbenthic communities of the Rio de la Plata estuary (Argentina) and possible environmental controls

The relationship between microbenthic communities, the habitat characteristics, and physical and chemical gradients was studied in the Rio de la Plata estuary. Five replicates of the surface layer were collected seasonally, in 10 sampling sites influenced by different land uses. The distribution of microbenthic communities was governed by two gradients, the first one determined by anthropic factors, related to pollution, and the second one to conductivity and turbidity. The higher densities of producers were observed in sites characterized by fine sediments. During winter, spring, and summer cyanophytes were abundant, while in autumn the diatoms, particularly birraphideans, dominated. The ciliates were the most abundant group among consumers, particularly in winter, and their spatial distribution was influenced by the turbidity. The whole study area has an eutrophic condition. Turbidity and the enrichment with nutrients and organic matter explained 50% of the variability in the species’ distribution.     

The common agricultural policy and the general environmental policies concerned with agriculture in the European Community and their implications for fertilizer consumption

This paper traces the major developments in the European Common Agricultural Policy (CAP) and related environmental policy and examines their impact on the use of crop nutrients. The objectives of the CAP were set out in the Treaty of Rome in 1957 and have not been explicitly revised. The Community has, however, progressed from being a significant importer to a major exporter of food. Various changes in the policy measures/reforms, have been implemented, each to control the continuing increase in farm output. The latest of these in May 1992 reduced commodity prices towards world market levels, introduced 15% set aise for arable land, as well as agreeing a number of agri-environmental measures. Further changes are anticipated following the Uruguay Round of the General Agreement on Tariffs and Trade (GATT) and as new trade agreements are reached with the countries of the former Eastern Bloc. Inevitably, existing farm systems will be subject to careful reappraisal. The Community's environmental objectives were added to the Treaty in 1987 with the passing of the European Single Act. The interaction between agriculture and the environment has been a prominent concern. The Directive 91/676, which seeks to protect water against pollution caused by nitrate from agricultural sources, is the first Directive to have a major direct impact on farm practive. The Fifth Environmental Action Plan for 1993–2000 ‘Towards Sustainability’ selects agriculture as one of five industries for specific attention. The plan seeks an extensification of agriculture and a reduction in the use of chemicals. Changes in the amount of plant nutrients from both farmyard manure and mineral fertilizers used in agriculture are quantified. Methods of determining the efficiency with which they are utilized are assessed. New advisory techniques which will improve the efficiency of nutrient use on the farm are considered, as are the implications for the future demand for nutrients from mineral fertilizers. This paper is the view of the European Fertilizer Manufacturers Association.     

The use of monitoring data for identifying factors influencing phytoplankton bloom dynamics in the eutrophic Taw Estuary, SW England

Using the Taw Estuary as an example, data routinely collected by the Environment Agency for England and Wales over the period 1990-2004 were interrogated to identify the drivers of excessive algal growth. The estuary was highly productive with chlorophyll concentrations regularly exceeding 100 μg L⁻¹, mostly during periods of low freshwater input from the River Taw when estuarine water residence times were longest. However, algal growth in mid estuary was often inhibited by ammonia inputs from the adjacent sewage treatment works. The reported approach demonstrates the value of applying conventional statistical analyses in a structured way to existing monitoring data and is recommended as a useful tool for the rapid assessment of eutrophication. However, future estuarine monitoring should include the collection of dissolved organic nutrient data and targeted high temporal resolution data because the drivers of eutrophication are complex and often very specific to a particular estuary.     

Predicting the effects of sediment based internal nutrient loads on eutrophication in Kücükcekmece Lagoon for rehabilitation planning

In deep stratified coastal lagoons, hypoxic waters that result from phytoplankton decomposition in the stratified bottom waters are often associated with eutrophication. Decomposing biomass reaches the bottom sediments and enriches them with nutrients and organic matter. Nutrients trapped in sediments are released with time and promote excessive phytoplankton growth in the surface water. Because eutrophication in lentic ecosystems progresses in a self-fuelling cycle, outflow is the only available process for exporting excess nutrients to recover from eutrophication. Thus, rehabilitation of eutrophic coastal lagoons that have limited seawater interactions is a long term process. The importance of nutrient release from sediments on eutrophication and the delay effect of internal nutrient loading on the rehabilitation of a eutrophic coastal lagoon with limited seawater exchange were analysed in this study.An ecological model that couples the water column and the sediment diagenesis processes, was developed for water quality management purposes. Our findings indicate that the recovery of the Lagoon from eutrophication will be taken decades even in the absence of external nutrient loading. Therefore, we suggest applying rehabilitation strategies that control the nutrient fluxes from sediments for a faster recovery from heavily eutrophic conditions. Land-based nutrient sources must also be controlled because they feed water column and the bottom sediments with nutrients.     

Morphology and modern sedimentary deposits of the macrotidal Marapanim Estuary (Amazon,Brazil)

The northern Brazilian coast, east of the Amazon River is characterized by several macrotidal estuarine systems that harbor large mangrove areas with approximately 7600 km². The Marapanim Estuary is influenced by macrotidal regime with moderate waves influence. Morphologic units were investigated by using remote sensing images (i.e., Landsat-7 ETM+, RADARSAT- 1 Wide and SRTM) integrated with bathymetric data. The modern sedimentary deposits were analyzed from 67 cores collected by Vibracore and Rammkersonde systems. Analysis of morphology and surface sedimentary deposits of the Marapanim River reveal they are strongly influenced by the interaction of tidal, wave and fluvial currents. Based on these processes it was possible to recognize three distinct longitudinal facies zonation that revels the geological filling of a macrotidal estuary. The estuary mouth contain fine to medium marine sands strongly influenced by waves and tides, responsible for macrotidal sandy beaches and estuarine channel development, which are characterized by wave-ripple bedding and longitudinal cross-bedding sands. The estuary funnel is mainly influenced by tides that form wide tidal mudflats, colonized by mangroves, along the estuarine margin, with parallel laminations, lenticular bedding, root fragments and organic matter lenses. The upstream estuary contains coarse sand to gravel of fluvial origin. Massive mud with organic matter lenses, marks and roots fragments occur in the floodplain accumulates during seasonal flooding providing a slowly aggrading in the alluvial plain. This morphologic and depositional pattern show easily a tripartite zonation of a macrotidal estuary, that are in the final stage of filling.     

Anthropogenic influence on the organic fraction of sediments in two contrasting estuaries: a biochemical approach

Abundance and biochemical composition of organic materials in sediments of the estuaries of Mundaka and Bilbao (SE Bay of Biscay) were analysed to assess the effect of organic wastes released to these systems. Organic and labile contents were higher in the sediments of Bilbao, denoting organic enrichment with poorly decomposed materials by human dumping. Spatially, organic matter distribution skewed seaward in Bilbao and upward in Mundaka, in agreement with the location of major point sources of sewage. Labile material, proteins and protein:carbohydrate ratio showed upward increases in both estuaries, attributed to the oxygen restrictive conditions to decompose organic materials. Vertical distribution of organic components into sediments reflected the history of human activities. In Bilbao, the significant reduction of organic and labile compounds, and the decrease of protein:carbohydrate values in top layers seem a result of recent remedial actions to reduce urban sewage inputs and improve environmental conditions. Higher contributions of proteins and lipids were associated with anthropogenic materials, and higher contributions of carbohydrates with autochthonous materials. High protein:carbohydrate values indicate poorly decomposed materials of human origin. The close relationship of carbohydrates with chloropigments in Mundaka suggests that phytobenthic populations and derived detritus contributed to a greater extent to the organic fraction in this estuary.