Academic literature on the topic 'Estuarine systems'

The typifi cation of estuaries and the division of estuary zones of the rivers of Primorsky Territory are considered. Based on the collected data on aquatic biota and the orography of water bodies, three main types of estuaries in Primorye were identifi ed – lowland rivers with an extended estuary zone (Razdolnaya, Tumannaya and Artemovka rivers), mountain rivers with an extended estuarine zone (Kievka, Avvakumovka, Partizanskaya, Milogradovka, Margaritovka and other rivers), mountain rivers with a short estuarine zone (Zerkalnaya, Sukhodol, Barabashevka, Narva, Ryazanovka and other rivers). Characteristics are given on the basis of which the boundaries of estuaries are distinguished. The defi nition of the estuary zone is given.

The rapid advance of remote sensing technology during the last few decades provides a new opportunity for measuring detectable estuarine spatial change. Although estuarine surface area and convergence are important hydraulic parameters often used to predict long-term estuarine evolution, the majority of automated analyses of channel plan view dynamics have been specifically written for riverine systems and have limited applicability to most of the estuaries in the world. This study presents MorphEst, a MATLAB-based collection of analysis tools that automatically measure estuarine planform geometry. MorphEst uses channel masks to extract estuarine length, convergence length, estuarine shape, and areal gain and loss of estuarine surface area due to natural or human factors. Comparisons indicated that MorphEst estimates closely matched with independent measurements of estuarine surface area (r = 0.99) and channel width (r = 0.92) of 39 estuaries along the South Korean coast. Overall, this toolbox will help to improve the ability to solve research questions commonly associated with estuarine evolution as it introduces a tool to automatically measure planform geometric features from remotely sensed imagery.

The northern coast of Brazil has more than 30 estuaries distributed along 650 km of coastline. These conditions favor the presence of relatively large fish communities in estuarine environments, but published information on the fish fauna in tidal creeks in northern Brazil is only available for some mangrove systems, and comparative studies between fish estuarine communities in different tidal creeks are less common. The choice of the study area was based on the fact that it has been poorly investigated with regard to estuarine fish fauna in comparison in mangrove tidal creeks using the same fishing gear. The objective of the present study was to compare the composition of the relative biomass of taxonomic, functional and ecological guilds of fish assemblages occurring in estuarine systems along the northern coast of Brazil. The study area of the present comparative analysis extended from the southeastern edge of the Marajoara Gulf to the western edge of the Maranhense Gulf. A comparative analysis among different estuarine systems was performed using data from other studies. The abundance of juveniles was greater in the Caeté, Curuçá and Cururuca estuaries than other estuaries. Cluster analysis separated the estuaries into two distinct groups and significant differences between these groups only exist in relation to geographical proximity. The present investigation indicates that the coastal region between the states of Pará and Maranhão is characterized by high dynamics and environmental heterogeneity, particularly with regard to changes in river discharge and tidal fluctuations. The present results underscore the importance of ecological information on ichthyofauna in tropical estuaries in order to include appropriate descriptors in conservation or restoration processes of marine communities and habitats.

Estuaries are especially vulnerable to the impacts of climate change because changes in climatic and hydrologic variables that influence freshwater and marine systems will also affect estuaries. We review potential impacts of climate change on Australian estuaries and their fish. Geographic differences are likely because southern Australian climates are predicted to become warmer and drier, whereas northern regions may see increased precipitation. Environmental factors, including salinity gradients, suspended sediment, dissolved oxygen and nutrient concentrations, will be influenced by changing freshwater input and other climate variables. Potential impacts will vary depending on the geomorphology of the estuary and the level of build-up of sand bars across estuarine entrances. Changes to estuarine fish assemblages will depend on associated changes to salinity and estuarine-mouth morphology. Marine migrants may be severely affected by closure of estuarine mouths, depending on whether species ‘must’ use estuarine habitat and the level of migratory v. resident individuals. Depending on how fish in coastal waters locate estuaries, there may be reduced cues associated with estuarine mouths, particularly in southern Australia, potentially influencing abundance. In summary, climate change is expected to have major consequences for Australian estuaries and associated fish, although the nature of impacts will show significant regional variation.

Abstract Estuaries are unique coastal ecosystems that sustain and provide essential ecological services for mankind. Estuarine ecosystems include a variety of habitats with their own sediment-fauna dynamics, all of them globally undergoing alteration or threatened by human activities. Mangrove forests, saltmarshes, tidal flats and other confined estuarine systems are under increasing stress due to human activities leading to habitat and species loss. Combined changes in estuarine hydromorphology and in climate pose severe threats to estuarine ecosystems on a global scale. The ReBentos network is the first integrated attempt in Brazil to monitor estuarine changes in the long term to detect and assess the effects of global warming. This paper is an initial effort of ReBentos to review current knowledge on benthic estuarine ecology in Brazil. We herein present and synthesize all published work on Brazilian estuaries that has focused on the description of benthic communities and related ecological processes. We then use current data on Brazilian estuaries and present recommendations for future studies to address climate change effects, suggesting trends for possible future research and stressing the need for long-term datasets and international partnerships.

Spatial variation in the structure of macrobenthic assemblages on intertidal flats is known to be related to different environmental variables. Most of the studies have observed that along the estuarine gradient, salinity is the most important variable driving the patterns of the macrobenthic assemblages. However, the great majority of studies have been done on single estuarine systems in temperate regions. We investigated the relationship between the macrobenthic assemblages in intertidal habitats and the environmental variables along three tropical estuaries. From lower to upper estuarine regions we sampled benthic macrofauna, salinity and sediments. The structure of the benthic assemblages was primarily related to salinity. There was a decrease in the number of taxa from the upper to the lower estuarine regions, indicating important deviation from Remane's model of estuarine diversity. There were important similarities of taxa abundance along different estuarine salinity gradients which can be properly tested in other tropical and temperate regions. We advocate that in order to adopt general and robust management practices it is essential to identify broad patterns and general rules governing estuarine systems.

Estuarine bank sediments have the potential to support the survival and growth of fecal indicator organisms, including Escherichia coli. However, survival of fecal pathogens in estuarine sediments is not well researched and therefore remains a significant knowledge gap regarding public health risks in estuaries. In this study, simultaneous survival of Escherichia coli and a fecal pathogen, Salmonella enterica serovar Typhimurium, was studied for 21 days in estuarine bank sediment microcosms. Observed growth patterns for both organisms were comparable under four simulated scenarios; for continuous-desiccation, extended-desiccation, periodic-inundation, and continuous-inundation systems, logarithmic decay coefficients were 1.54/day, 1.51/day, 0.14/day, and 0.20/day, respectively, for E. coli, and 1.72/day, 1.64/day, 0.21/day, and 0.24/day for S. Typhimurium. Re-wetting of continuous-desiccated systems resulted in potential re-growth, suggesting survival under moisture-limited conditions. Key findings from this study include: (i) Bank sediments can potentially support human pathogens (S. Typhimurium), (ii) inundation levels influence the survival of fecal bacteria in estuarine bank sediments, and (iii) comparable survival rates of S. Typhimurium and E. coli implies the latter could be a reliable fecal indicator in urban estuaries. The results from this study will help select suitable monitoring and management strategies for safer recreational activities in urban estuaries.

Estuaries are under increasing pressure owing to agricultural, urban and industrial developments in their catchments and their status as favoured sites for coastal development and recreation. Effective research on South Africa estuaries requires the synthesis of available scientific knowledge to efficiently address management concerns and so ensure the sustainable utilisation of estuaries. The approach of the Consortium for Estuarine Research and Management to these problems and the results of a co-ordinated research programme on decision support for the management and conservation of estuarine systems are described in this paper. While the importance and current status of South African estuaries are considered, attention is devoted primarily to the development of an integrated modelling approach to the freshwater requirements of estuaries. In particular, the application of a linked system of five models to a case study, the Great Brak Estuary is described and the role of prediction in promoting wise decision making for estuaries is treated.

Estuarine socio-ecological systems (SES) in the Western Indian Ocean (WIO) region face mounting pressures from overexploitation, habitat degradation, impacts of climate change and governance inadequacies. A regional assessment of seasonal-to-decadal change in SES of three estuaries (Bons Sinais in Mozambique, Ruvu in Tanzania and Tana in Kenya) was undertaken along 2000 km of tropical coastline (3°-18°S), using a systems-oriented approach and information collected during the Estuarize-WIO project (2016-2019). All three estuaries were open and tidal, but differed along gradients of geomorphology, annual precipitation, exposure to tropical storms, drought, sea level rise, and rural to urban development. Despite physical differences, similar marine species, mangrove assemblages, seasonality in fish-based farming systems and cultivated crops, and fishing methods were apparent across the region. Key differences were related to the scale of anthropogenic disturbance, discerned from land use / land cover (LULC) change analysis, which showed decadal increases in developed-, cultivated- and grasslands, at the expense of wetlands and forests, and seasonal transformation of wetlands to agriculture and grasslands. The three estuaries represented a gradient along urban-production-conservation dimensions, brought about by rural to urban transformation, and by freshwater and sediment diversion for economic development in upstream catchment areas. Household surveys indicated strongly seasonal livelihood strategies, with highest diversity in peri-urban settings, and reliance on different combinations of ecosystem goods and services in coastal and upstream rural settings. Estuarine fisheriesranged from unselective, low trophic-level fisheries using fine-mesh nets at the urbanized and most-disturbed Bons Sinais Estuary, to a more complex organized fishery at the least-disturbed Tana. At Ruvu, fisheries and agriculture production exit the system to distant markets. The systems-oriented approach demonstrated that human-induced processes affected WIO estuaries and dependent livelihoods more deeply than inherent physical differences. A key conclusion is that research, management and governance will benefit from regional cooperation, given the similarities of the systems and the different levels of disturbance.

For many decades, the role of estuaries as important nursery areas for fishes was accepted as fact by scientists and environmental managers. At the turn of the 21st century, a question mark was raised in relation to the reduced predation component of the nursery function, with some scientists contending that both large and small piscivorous fish species had access to the estuarine habitats that juvenile fishes in estuaries occupied. If true on a global scale, the nursery designation for these habitats would be compromised and the long-held paradigm that estuaries are important nursery areas for fishes would need to be revised. In this review, I examine the nature of fish nursery areas in estuarine littoral habitats from a mainly predation perspective and, based on a variety of ichthyofaunal and avifaunal studies, come to the conclusion that apart from a few selected estuarine systems, there is limited predation on juvenile fishes in these particular areas. This, coupled with the abundant suitable food resources for juvenile fish from different trophic categories, shelter from high-energy marine wave action and biological connectivity between a variety of submerged and emergent macrophyte communities, renders shallow estuarine littoral areas ideal nursery areas for the juveniles of mostly euryhaline marine fish species, the dominant component of estuarine ichthyofaunas globally. In addition, there are strong indications from the fossil record that these littoral estuarine nursery areas have been functioning since the Devonian, more than 350 million years ago.

Les estuaires sont constitués d'une vaste mosaïque d'habitats naturels et semi-naturels. L'objectif de cette thèse est d'étudier les végétations et les paysages végétaux des systèmes estuariens atlantique en France, en essayant de comprendre le fonctionnement et les schémas de distribution des différentes unités de végétation. La présente étude tente de mettre au point un modèle théorique commun de fonctionnement et de gradients écologiques, afin de compléter la classification et la connaissance écologique des estuaires, et une aide au suivi et à l’évaluation de l’utilisation des sols, des impacts humains, en développant un modèle spatio-temporel prédictif fondé sur la végétation réelle et potentielle, et en utilisant l'approche dynamico-caténale. Dans 8 estuaires sélectionnés, nous avons effectué des travaux sur le terrain pour une superficie totale de 98 318 ha, mettant en évidence 2 séries de végétation et 4 géopermaséries, correspondant à 131 associations végétales, 60 alliances, 43 ordres et 28 classes. Nous avons cartographié la végétation de trois estuaires représentatifs, ce qui représente une superficie totale de 74 433 ha. Un schéma synthétique des paysages végétaux estuariens est proposé, en intégrant les gradients géographiques et écologiques et les formes géomorphologiques
Estuaries generally include a wide mosaic of natural and semi-natural habitats. The objective of this thesis is to study the vegetation and Plant Landscape of French Atlantic estuarine Systems, trying to understand the functioning and the plant distribution patterns. The present study tries to carry out a theoretical common model of functioning and ecological gradients, in order to make a basis to improve their classification and ecological studies, and to Help the monitoring and assessment of land uses, land forms transformation and human impacts : developping a spatio-temporal predictive model based on actual and potential vegetation, using the dynamico-catenal approach.The study area corresponds to the Atlantic French estuaries. In 8 selected estuaries, we undertook fieldworks for a total of 98315 ha, highlighting 2 vegetation series and 4 geopermaseries, corresponding to 131 plant associations, 60 alliances, 43 ordos and 28 classes. We mapped the vegetation of three representative estuaries for a total of 74433 ha. A synthetic scheme of estuary vegetation landscape is proposed, integrating geographical and ecological gradients as well as geomorphologic forms

This thesis describes methodologies to detemiine organic and inorganic phosphorus in water and discusses biological, physical and chemical controls on the transformations of organic and inorganic phosphorus in laboratory microcosms of estuarine particle-water systems. Phosphorus is an important nutrient and the accurate determination of phosphorus species in natural waters is essential for understanding the biogeochemical cycling of the element. Chapter one reviews phosphorus impacts on water quality and relevant UK legislation, the sources, speclation and fractionation of phosphorus, the sediment/water phosphorus cycle and analytical methods for the determination of dissolved Inorganic phosphorus (DIP) and organic phosphorus (DOP) species In natural waters. Chapter two introduces the technique of segmented flow analysis and describes methods for the determination of inorganic phosphorus and total dissolved phosphorus after autoclaving. Segmented flow analysis is suitable for determining inorganic P and organic P species in freshwaters in the range of 1 - 300 pg P L"\ Calibrations were linear (R^ > 0.997) over the range 0.5 - 100 pg P L'^ with good precision (RSDs < 3 %). The LCD was 0.4 pg P L'^ for DIP and 3 pg P L'^ for DOP. The recoveries of 7 model organic phosphorus compounds (adenosine-5-triphosphate di-sodium salt (ATP), phytic acid (PTA), sodium tripolyphosphate (STP), methyltriphenylphosphonium bromide (MPT), p-nitrophenyl phosphate magnesium salt (p-NPP), p-D-glucose-6-phosphate monosodium salt (G-6-P) and cocartjoxylase (COCA)) were all > 90 %. Chapter three reports on bacterial uptake studies of phosphorus species in a plug-flow microcosm. Experiments using inert Duran and Siran beads as supports for bacterial bioflim development showed similar P uptake behaviour. Glucose-6-phosphate was almost fully utilised and converted to DIP after 3 days suggesting that labile organic phosphorus species could be a bioavailable source of P for bacteria. Phytic acid (a refractory P compound) released significant concentrations of DIP to the water column due to physical displacement. Chapter four describes phosphonjs transformations in a sediment-water flume due to turbulent resuspension events. The released DIP concentration had a strong linear relationship with shear stress in pure water and artiflcial seawater. However, no signtflcant relationship between DOP release and shear stress was observed. The sediment type and the water matrix significantly affected the magnitude of DIP and DOP release to the water column. Chapter flve extends the investigation of P exchange to constant resuspension events. The water matrix had a significant effect on the rate of DIP and DOP release from sediment and the sedimentAvaler equilibration time. Typically 6 - 12 % of total phosphorus in the sediment was released as DIP and DOP into the water column. When orthophosphate and phytic acid were added to both UHP and river water. SPM was able to buiffer theses additions. However, the SPM buffering capacity was much lower for G-6-P. The buffering capacity of the SPM for phytic acid was significant and permanent in UHP and biotic river water, whereas phytic acid was cycled in the abiotic experiments.

Doutoramento em Ciências do Mar
De um modo geral, os poluentes constituem uma ameaça para os ecossistemas aquáticos, originando grande preocupação nas entidades responsáveis pela gestão destas áreas. Por exemplo, o uso intensivo e continuado de poluentes em áreas agrícolas, perto de zonas húmidas costeiras, como o estuário do Mondego (Portugal), levou à execução de programas de monitorização, ao longo dos últimos 20 anos, para proteger e recuperar este sistema aquático. De acordo com informações recentes, obtidas junto de cooperativas agrícolas do vale do Mondego, Primextra® Gold TZ é o herbicida mais utilizado em campos de cultura de milho, sendo um dos 20 herbicidas mais vendidos em Portugal. Por outro lado, o cobre é largamente utilizado na formulação de pesticidas. A avaliação ecológica e de risco têm sido rotineiramente focadas na exposição individual de substâncias químicas, o que pode subestimar os riscos associados à ação tóxica de misturas. Assim, os potenciais efeitos sinergísticos, que podem levar a consequências mais graves e imprevisíveis para os ecossistemas estuarinos e marinhos, são subestimados. Apesar do recente aumento do número de estudos relacionados com a toxicidade de misturas de contaminantes orgânicos (grupo de pesticidas) e de contaminantes inorgânicos (grupo de metais), há ainda falta de informação científica sobre os efeitos destas misturas. A avaliação de risco ambiental normalmente tem como objetivo estudar os efeitos de contaminantes em endpoints, como a sobrevivência, o crescimento ou a reprodução, uma vez que a quantidade de biomassa disponível tem efeitos importantes sobre os níveis tróficos subsequentes e o funcionamento global do ecossistema. No entanto, um aspeto muitas vezes esquecido é a qualidade do alimento disponível, que tem implicações importantes na transferência de energia e de nutrientes ao longo da cadeia trófica. Portanto, para melhor compreender os efeitos das perturbações antrópicas, são necessários mais estudos sobre o efeito de mistura de substâncias orgânica-inorgânica na qualidade do alimento de espécies aquáticas não-alvo. Assim, este trabalho visa determinar os efeitos do herbicida Primextra® e do cobre, usados individualmente e em mistura, sobre a qualidade alimentar em sistemas estuarinos, considerando as respostas populacionais e bioquímicas nutricionais de organismos chave não-alvo: a diatomácea marinha (Thalassiosira weissflogii) e o copépode estuarino calanoide (Acartia tonsa). As diatomáceas como os copépodes são grupos dominantes na comunidade planctónica no estuário do Mondego, constituindo uma cadeia trófica simples: produtor primário –consumidor primário. Foram também usados náuplios de uma terceira espécie (Artemia franciscana) para determinar os efeitos tóxicos e bioquímicos individuais de ambos os poluentes e para comparar as suas respostas com as das outras duas espécies planctónicas Para isso foram desenvolvidos ensaios de toxicidade, envolvendo exposições a substâncias químicas individuais e a misturas equitóxicas, para obtenção e modelação de dados bioquímicos indicadores da qualidade alimentar: teor de ácidos gordos (FA), incluindo ácidos gordos essenciais, teor de proteína e teor de substâncias reativas de ácido tiobarbitúrico (TBARS). Esta escolha baseou-se no facto dos ácidos gordos serem uma das mais importantes moléculas transferidas através da cadeia trófica, em teias alimentares aquáticas, podendo ser usados como um bom indicador de stress. Os resultados mostraram que T. weissflogii foi a espécie mais sensível ao herbicida seguida por A. tonsa (CE50 = 0,008 mg / L e CE50 = 0,925 mg / L, respetivamente), enquanto o copépode foi a espécie mais sensível ao metal, seguido por T. weissflogii (CE50 = 0,234 mg / L e CE50 = 0,383 mg / L, respetivamente). A análise estatística dos efeitos da mistura metal-herbicida sustentou um efeito sinergístico significativo sobre a sobrevivência do copépode (relativamente ao modelo de ação independente), e um efeito significativamente antagonístico sobre o crescimento da diatomácea (relativamente ao modelo de adição de concentração). A composição em ácidos gordos das espécies zooplanctónicas respondeu com elevada sensibilidade aos dois tipos de exposição (individual e de mistura),tendo-se observado o efeito mais nocivo na concentração de ácidos gordos essenciais de A. tonsa após a exposição à mistura de metal-herbicida: o seu valor diminuiu significativamente (5 vezes) em comparação com o controlo. Os resultados dos modelos lineares generalizados, baseados na variação da composição bioquímica (total de FA, FA essenciais, teor de proteína e TBARS), para as substâncias individuais e para a mistura, revelaram que os efeitos desta foram não-aditivos, para o conteúdo de FA essenciais de ambas as espécies planctónicas. Já a qualidade alimentar de A. tonsa (consumidor primário) foi mais sensível aos stressors químicos comparativamente a T. weissflogii (produtor), quando as duas espécies foram expostas a níveis iguais de contaminação. O presente estudo sugere que a exposição simultânea a um metal e a um herbicida pode afetar negativamente a qualidade alimentar de espécies planctónicas, em diferentes níveis tróficos. Esse efeito pode, potencialmente, ser transferido para níveis tróficos superiores e causar alterações importantes no fluxo de energia através do sistema estuarino e, posteriormente, para a dieta humana.
Contaminants constitute a threat to aquatic communities and, thus to aquatic ecosystems. Pesticides are widely used to control pests and diseases in crop production. Among these agrochemicals, herbicides are commonly applied on crops to control adventive infestations. Thus, the intensive usage of pollutants in agriculture areas near ecological coastal wetlands led to the implementation of the Pesticide-Monitoring programs to recover aquatic systems, such as in the Mondego estuary, Portugal, since 1998. Nowadays, and according to the information from agricultural cooperatives of Mondego valley, the herbicide Primextra® Gold TZ is the herbicide most used in corn crops fields and is one of the 20 best-selling herbicides in Portugal, whereas copper is mainly used in pesticide`s formulation. Traditional effect and risk assessment have been routinely focused on exposures to single chemicals, which may underestimate the risks associated with toxic action of mixtures. Thus, the potential synergistic effects that may lead to more severe and unpredictable consequences for estuarine and marine ecosystems are ignored. Recently, there are an increasing number of studies dealing with toxicity of mixtures of either organic contaminants (group of pesticides) or inorganic contaminants (group of metals). However, studies with mixture experiments of metals and pesticides still remain scarce. Furthermore, environmental risk assessment typically aims to study the effects of contaminants on endpoints such as survival, growth or reproduction, since the available quantity of the biomass has important effects on the subsequent trophic levels and the overall ecosystem functioning. However, an often overlooked aspect of food availability is food quality, which has important implications on the energy and nutrient transfer through the food web. Further information about the effect of organic-inorganic mixture on the food quality of aquatic organisms, which are typical non-target species for these contaminants, is needed. This research aims to determine the effects of anthropogenic stressors on the food quality in estuarine systems by means of both, individual and mixture exposures, to the herbicide Primextra® and the metal copper, on the toxicity and nutritionally important biochemical parameters of key non-target organisms: a marine diatom (e.g. Thalassiosira weissflogii) and a estuarine calanoid copepod (e.g. Acartia tonsa) – both are dominant plankton groups in the Mondego estuary, constituting simple trophic food chain: primary producer – primary consumer. A third species, the brine shrimp Artemia franciscana (nauplii), was also added to the study to determine toxic and biochemical individual effects of both pollutants and to compare its response with the two other planktonic species. In this study a joint approach was applied, i.e. controlled laboratory experiments (toxicity tests and microcosm bioassays), involving single and equitoxic mixture exposures to chemical stressors combined with the further modelling of the obtained biochemical data: fatty acids (FA) content, including the essential FA, protein content and content of thiobarbituric acid reacting substances (TBARS) as important indicators of the food quality. Moreover, fatty acids are one of the most important molecules transferred across the plant-animal interface in aquatic food webs and can be used as good indicators of stress. The conducted lab incubations showed that T. weissflogii was the most sensitive species to the herbicide followed by A. tonsa (EC50 = 0.008 mg/L and EC50 = 0.925 mg/L, respectively), whereas the copepod was the most sensitive species to the metal in comparison to T. weissflogii (EC50 = 0.234 mg/L and EC50 = 0.383 mg/L, respectively). The statistical analysis of mixture effects revealed that the metal-herbicide mixture acted significantly synergistic on the copepod survival (relatively to the independent action model), while acted significantly antagonistic on the diatom growth (relatively to the concentration addition model). FA composition of zooplanktonic species responded with higher sensitivity to both, the individual and mixture exposures with the most harmful effect on the essential FA of A. tonsa after exposure to the metal-herbicide mixture: their amount significantly decreased (5 times) compared to the uncontaminated treatment. The results of the generalized linear models fitted to the experimentally observed responses of biochemical composition (total FA, essential FA, protein and TBARS contents) to the single substances and the mixture revealed that effects of the copper-Primextra® mixture were non-additive for the essential FA content of both planktonic species. They further showed that the food quality of the species from higher trophic level, i.e. primary consumer A. tonsa was more sensitive to the chemical stressors than for the primary producer T. weissflogii, when species were exposed to the equal levels of contamination. The study concludes that simultaneous exposure to metal and pesticide contaminants adversely affect the food quality of planktonic species at different trophic levels and this can potentially be transferred to higher trophic levels and cause important implications for the energy flow through the estuarine system and subsequently the human diet.
Verontreinigingen vormen een bedreiging voor in het water levende gemeenschappen en daarom ook voor aquatische ecosystemen. Pesticiden worden op grote schaal gebruikt om ziekten en plagen in de plantaardige productie te controleren. Onder deze landbouwchemicaliën, worden herbiciden vaak toegepast op gewassen om adventive besmettingen te controleren. Zo heeft het intensief gebruik van verontreinigende stoffen in landbouwgebieden in de buurt van ecologische wetlands geleid tot de uitvoering van Pesticide-Monitoring-programma's sinds 1998 om aquatische systemen, zoals in het Mondego estuarium (Portugal) te herstellen. Op basis van de huidige informatie uit agrarische coöperaties van de Mondego-vallei blijkt dat de herbicide Primextra® Gold TZ de meest gebruikte herbicide is in maïsvelden en dat het één van de 20 best verkopende herbiciden in Portugal is waarbij koper het voornaamste element van de samenstelling vormt. Traditionele effect- en risicobeoordeling zijn routinematig gericht op blootstelling aan enkele chemische stoffen, die de risico's van de toxische werking van mengsels kunnen onderschatten. Zo worden de potentiële synergetische effecten die kunnen leiden tot meer ernstige en onvoorspelbare gevolgen voor estuariene en mariene ecosystemen genegeerd. Recent zijn er een toenemend aantal studies gebeurd die toxiciteit van mengsels van ofwel organische verontreinigingen (groep pesticiden) of anorganische verontreinigingen (groep metalen) onderzoeken. Studies met mengselexperimenten van metalen en pesticiden zijn nog steeds schaars. Bovendien heeft milieurisicobeoordeling typisch tot doel om de effecten van contaminanten op eindpunten zoals overleving, groei of reproductie te bestuderen, omdat de beschikbare hoeveelheid biomassa belangrijke gevolgen heeft voor de hogere trofische niveaus en het algemeen functioneren van het ecosysteem. Echter, een vaak vergeten aspect van de voedselbeschikbaarheid is de kwaliteit van het voedsel, wat belangrijke gevolgen kan hebben voor de energie- en voedingsstoffenoverdracht in de voedselketen. Verdere informatie over het effect van de organische-anorganische mengsel op de voedselkwaliteit van het aquatische organismen, die vaak geen doelsoorten voor deze verontreinigingen zijn, is daarom noodzakelijk. Dit onderzoek heeft tot doel de effecten van antropogene stressoren op de voedselkwaliteit in estuariene systemen te bepalen door middel van blootstelling aan zowel individuele concentraties als mengsels van herbicide Primextra® en het metaal koper, op de toxiciteit en de nutritioneel relevante biochemische parameters van belangrijke non-target organismen: een mariene diatomee (bijv Thalassiosira weissflogii) en een estuariene calanoid copepod (bijv Acartia tonsa) - beide zijn één van de belangrijkste planktongroepen in de Mondego estuarium, die een eenvoudig trofische voedselketen voorstellen tussen primaire producent en primaire consument. Een derde soort, (de nauplii van) Artemia franciscana, werd ook toegevoegd aan de studie om de toxische en biochemische individuele effecten van beide polluenten te bepalen en om zijn respons te vergelijken met de twee andere planktonsoorten. In deze studie werd een gezamenlijke aanpak toegepast waanbij laboratoriumexperimenten (toxiciteitstesten en microcosmos bioassays), met blootstelling aan één of aan een equitoxische mengsel van chemische stressoren, werden gecombineerd met het verder modellering van de verkregen biochemische data: vetzuren, met bijzondere aandacht voor essentiële vetzuren, eiwitgehalte en de inhoud van thiobarbituurzuur reagerende stoffen (TBARS) als belangrijke indicatoren voor voedselkwaliteit. Daarenboven zijn vetzuren één van de belangrijkste moleculen overgedragen aan de plant-dier interface in aquatische voedselwebben en kunnen ze gebruikt worden als goede indicatoren van stress. De uitgevoerde labincubaties toonden dat T. weissflogii de meest gevoelige soort was voor de herbicide gevolgd door A. tonsa (EC50 = 0.008 mg / L en EC50 = 0.925 mg / L, respectievelijk), terwijl de copepoden het meest gevoelig waren voor het metaal tenopzichte van T. weissflogii (EC50 = 0.234 mg / L en EC50 = 0.383 mg / L respectievelijk). De statistische analyse van mengseleffecten bewees dat het metaal-herbicide mengsel significant synergistisch werkte op de overleving van de copepoden (ten opzichte van de onafhankelijke actiemodel), terwijl significante antagonistische effecten op de diatomeeëngroei optraden (ten opzichte van de concentratieadditiemodel). FA samenstelling van de zooplanktonische soorten reageerde met een hogere gevoeligheid op beide, individuele en mengsel, blootstellingen met de meest schadelijke gevolgen voor de essentiële vetzuren van A. tonsa na blootstelling aan het metaal-herbicide mengsel: de vetzuurconcentratie daalde aanzienlijk (tot 5 maal) ten opzichte van de onbesmette behandeling. De resultaten van de gegeneraliseerde lineaire modellen toegepast op de experimenteel waargenomen responsen van biochemische samenstelling (totale vetzuren, essentiële vetzuren, eiwit- en TBARS concentraties) tenopzichte van de afzonderlijke stoffen en van het mengsel toonden aan dat effecten van het koper-Primextra® mengsel niet additief waren voor de concentratie van de essentiële vetzuren van beide planktonische soorten. Verder bleek de voedselkwaliteit van de soort op het hoger trofisch niveau, namelijk de primaire consument A. tonsa, gevoeliger te zijn voor de chemische stressoren dan de primaire producent T. weissflogii, wanneer soorten werden blootgesteld aan gelijke verontreinigingsniveaus. De studie concludeert dat gelijktijdige blootstelling aan metalen en pesticiden verontreinigingen een negatieve invloed heeft op de voedselkwaliteit van planktonische soorten op verschillende trofische niveaus en dit kan mogelijk worden overgedragen naar hogere trofische niveaus met belangrijke gevolgen voor de energiestroom door het estuariene systeem en vervolgens ook voor het menselijke dieet.

The knowledge and understanding of sediment transport is essential for the development of effective management strategies for nutrient and sediment loading in estuarine systems. Estuarine suspended sediment (in high concentrations), has the ability to adversely impact upon surrounding ecosystems, such as the Great Barrier Reef, Australia. Due to a recent decline in water and sediment quality, it has recently been mandated that a number of tropical, coastal estuarine systems in Queensland, such as the Fitzroy River estuary, have their sediment loading reduced. In order to meet these requirements, a greater understanding of the sediment transport dynamics and driving processes (such as flocculation and settling velocity) needs to be achieved, and the accuracy of estimation improved. This research project was motivated by the need to improve the general accuracy of field measurements for estuarine suspended sediment transport and dynamics. Field-based measurements (especially settling velocity) are necessary for the parameterisation of sediment transport models. The difficulty in obtaining accurate, in situ data is well documented and is generally limited to methods that isolate a water sample from its natural environment, removing all influences of estuarine turbulence. Furthermore, the water samples are often extracted from points (Eulerian) where the history of the suspended particles is generally unknown. These sampling methods typically contain intrinsic errors as suspended sediment transport is essentially Lagrangian (i.e., flows with the net motion of flow-field) in nature. An investigation into different drogue systems conducted in parallel with a study into the tidal states of the Fitzroy River estuary led to the development of a novel Lagrangian drogue device, the LAD. Additionally, the water-tracking ability of the LAD was tested and found to accurately follow a parcel of estuarine water over a slack water period. Therefore the LAD was deployed in the Fitzroy River to assist in the further understanding of complex sediment transport processes such as flocculation and settling velocity in a natural estuarine flow field. The final device (the LAD - Lagrangian Acoustic Drogue) was developed, utilizing the principals of acoustic backscatter intensity-derived SSC measurements. The investigation of a series LAD deployments (during slack water) in the Fitzroy River estuary, revealed the dominant suspended sediment processes and also gave an insight into the prevailing flow-patterns. Results showed the presence of a settling lag mechanism between low and high tide, which can initiate a net sediment flow upstream with each flood tide. The bulk settling velocity showed comparable results at both low and high water. The LAD derived bulk settling velocity as a function of concentration (SSC), yielding a strong positive correlation (r2 = 0.73). Also the importance of flocculation in the bulk settling and clear up of the water column during periods of still water (high and low tide) was demonstrated as all in situ settling velocities (0.33 - 1.75 mm s-1) exceeded single grain approximations (0.47 mm s-1). This research demonstrates the potential for Lagrangian drogue studies as an effective measuring platform for the accurate quantification of estuarine suspended sediment dynamics. The application of the LAD in the Fitzroy River has lead to a significant improvement in the understanding of the system's real sediment transport processes. This research has provided an effective and accurate technique for measuring real settling velocities for input into numerical models or for the validation of existing model outputs. Furthermore, this technique shows great potential for application in other estuarine systems.

The knowledge and understanding of sediment transport is essential for the development of effective management strategies for nutrient and sediment loading in estuarine systems. Estuarine suspended sediment (in high concentrations), has the ability to adversely impact upon surrounding ecosystems, such as the Great Barrier Reef, Australia. Due to a recent decline in water and sediment quality, it has recently been mandated that a number of tropical, coastal estuarine systems in Queensland, such as the Fitzroy River estuary, have their sediment loading reduced. In order to meet these requirements, a greater understanding of the sediment transport dynamics and driving processes (such as flocculation and settling velocity) needs to be achieved, and the accuracy of estimation improved. This research project was motivated by the need to improve the general accuracy of field measurements for estuarine suspended sediment transport and dynamics. Field-based measurements (especially settling velocity) are necessary for the parameterisation of sediment transport models. The difficulty in obtaining accurate, in situ data is well documented and is generally limited to methods that isolate a water sample from its natural environment, removing all influences of estuarine turbulence. Furthermore, the water samples are often extracted from points (Eulerian) where the history of the suspended particles is generally unknown. These sampling methods typically contain intrinsic errors as suspended sediment transport is essentially Lagrangian (i.e., flows with the net motion of flow-field) in nature. An investigation into different drogue systems conducted in parallel with a study into the tidal states of the Fitzroy River estuary led to the development of a novel Lagrangian drogue device, the LAD. Additionally, the water-tracking ability of the LAD was tested and found to accurately follow a parcel of estuarine water over a slack water period. Therefore the LAD was deployed in the Fitzroy River to assist in the further understanding of complex sediment transport processes such as flocculation and settling velocity in a natural estuarine flow field. The final device (the LAD - Lagrangian Acoustic Drogue) was developed, utilizing the principals of acoustic backscatter intensity-derived SSC measurements. The investigation of a series LAD deployments (during slack water) in the Fitzroy River estuary, revealed the dominant suspended sediment processes and also gave an insight into the prevailing flow-patterns. Results showed the presence of a settling lag mechanism between low and high tide, which can initiate a net sediment flow upstream with each flood tide. The bulk settling velocity showed comparable results at both low and high water. The LAD derived bulk settling velocity as a function of concentration (SSC), yielding a strong positive correlation (r2 = 0.73). Also the importance of flocculation in the bulk settling and clear up of the water column during periods of still water (high and low tide) was demonstrated as all in situ settling velocities (0.33 - 1.75 mm s-1) exceeded single grain approximations (0.47 mm s-1). This research demonstrates the potential for Lagrangian drogue studies as an effective measuring platform for the accurate quantification of estuarine suspended sediment dynamics. The application of the LAD in the Fitzroy River has lead to a significant improvement in the understanding of the system's real sediment transport processes. This research has provided an effective and accurate technique for measuring real settling velocities for input into numerical models or for the validation of existing model outputs. Furthermore, this technique shows great potential for application in other estuarine systems.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Engineering
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In recent years there has been an increasing awareness of the role and benefits of scientific fish farming in coastal waters for augmenting fish production of India, although a traditional practice of aquaculture has been prevailing in these waters for a long time. A comprehensive knowledge of the ecology of the different culture systems forms an integral part of the scientific farming because it directly influences the rate of production. The growth and survival of the organisms used for culture depend largely on the overall productivity of the pond, which in turn, is influenced by the various environmental characteristics of the water and the fertility of the pond soil. In short, the water and soil conditions to a great extent determine the success or failure of the culture operation. Further, the information on the various environmental characteristics of the pond water and soil, availability of essential elements and the rate of organic productivity, would not only help to adopt successful management principles and culture techniques but also to manipulate the ecosystem providing the necessary inputs for obtaining better production. Besides providing an overall picture of the productivity of the ponds, studies on soils furnish information on the inputs to enhance the fertility of soils and also help in selection of suitable sites for construction of farms.

The questions on kinematics and morphodynamics of estuarine zones assessment are considered with help of numerical and GIS methods for natural and construction systems monitoring. The monitoring is fulfilled on the basis of the time-spatial database for estuarine part of Danube to Black Sea navigational canal trough the Bystry branch of Cilia delta. To the database we include not only river and reservoir shores and depth but the constantly acting hydrometeorogical parameters as well. The database is used for river and canal navigation analysis, coastal line and fairway stability.As a result we propose the recommendations on protection and training dike structures due to the principle of natural analog type constructures for dredging, seawater rejection and soil deposits utilization as material for artificial offshore structures

Submerged aquatic vegetation (SAV) growing in estuarine and coastal marine systems provides crucial ecosystem functions ranging from sediment stabilization to habitat and food for specific species. SAV systems, however, are sensitive to a number of environmental factors, both anthropogenic and natural. The most common limiting factors are light limitation, water quality, and salinity, as reported widely across the literature. These factors are controlled by a number of complex processes, however, varying greatly between systems and SAV populations. This report seeks to conduct an exhaustive examination of factors influencing estuarine and coastal marine SAV habitats and find the common threads that tie these ecosystems together. Studies relating SAV habitats in the United States to a variety of factors are reviewed here, including geomorphological and bathymetric characteristics, sediment dynamics, sedimentological characteristics, and water quality, as well as hydrologic regime and weather. Tools and methods used to assess each of these important factors are also reviewed. A better understanding of fundamental environmental factors that control SAV growth will provide crucial information for coastal restoration and engineering project planning in areas populated by SAVs.

This report describes the aggregate results from a series of interviews conducted with decision makers involved in governance of the Chesapeake Watershed. Interviews began in June and ended in December of 2021. Information collected will be combined with other data to create and then test a computer model to predict likely policy changes under a range of future scenarios. It is part of a larger project funded by the National Science Foundation called Modeling the Dynamics of Human and Estuarine Systems with Regulatory Feedbacks (Award #2009248). Using the Chesapeake Bay as an example, this project will combine the policy model that we are designing with biophysical models to predict how social, economic and policy changes impact water quality, and how changes in water quality influence human behavior and decision-making.

Estuaries trap much of the fine sediment delivered to them by rivers. This phenomenon presents challenges to the US Army Corps of Engineers (USACE) navigation mission, which maintains navigable waterways for waterborne commerce through estuarine regions. The USACE Regional Sediment Management Program and the USACE Norfolk District are conducting a regional sediment transport modeling study to identify cost-effective sediment management schemes in the James River, a tributary estuary of Chesapeake Bay. A key element of the sediment transport modeling study is the definition of cohesive sediment transport processes, such as erosion and settling velocity. This report describes field-based measurements of cohesive sediment erosion and settling velocity conducted in November 2017. The team conducted erosion testing on 15 cores collected throughout the tidal system. Additionally, two anchor stations were occupied to measure tidal variations in vertical distributions of suspended sediment concentration, particle size, and settling velocity. Recommended cohesive sediment transport parameters were developed from the field measurements.

The US Army Corps of Engineers (USACE) is conducting the “South Shore of Long Island, New York Regional Sediment Management Investigation” to further understand sediment dynamics and to develop a comprehensive regional sediment management plan for the south shore of Long Island, New York. Regional sediment management is a systems approach using best management practices for more efficient and effective use of sediments in coastal, estuarine, and inland environments. This investigation seeks to characterize sediment movement on the south shore of Long Island as a holistic system across the entire study area. It focuses on the regional system post-Hurricane Sandy (October 2012) as the storm significantly altered the physical landscape with severe shoreline erosion, which resulted in the construction of projects to reduce the risk of future storms and stakeholder priorities with a new emphasis on bay-side sediment dynamics, such as channel shoaling and disappearing wetlands. Despite the fact the storm caused severe erosion, the equilibrium beach profile, depth of closure, and general shoreline orientation seem to be unaffected. Previous studies have characterized sediment movement at specific sections of the south shore, but these data have not been incorporated to create a system-wide perspective. Coordinating sediment management across the six Atlantic Ocean inlets, Great South Bay Channel, Intracoastal Waterway, and coastal storm risk management (CSRM) projects could save the federal government millions of dollars in dredging and sand placement actions. This technical note presents the progress the investigation has made to date and will be followed with a more in-depth technical report titled South Shore of Long Island, New York Regional Sediment Management Investigation: A Post-Hurricane Sandy Shoreline Evaluation, currently in preparation.

This report documents a numerical modeling investigation on the transport of sediment material placed on designated disposal sites adjacent to Beaufort Inlet, North Carolina. Historical and newly collected wave and hydrodynamic data around the inlet are assembled and analyzed. The data sets are used to calibrate and validate a coastal wave, hydrodynamic and sediment transport model, the Coastal Modeling System. Model alternatives are developed corresponding to different material placement sites. Sediment transport and sediment plume distribution are evaluated within and around the immediate vicinity of the Beaufort Inlet estuarine system for a representative summer and winter month. Results of model simulations show that high flows occur along navigation channels and low flows occur outside the inlet in open ocean area. Sand materials placed in nearshore sites tend to be trapped in and move along navigation channels entering the inlet. In offshore placement sites the sediment plume shows slow spreading and no significant sand migration from its release locations. Simulations for the summer and winter month present similar distribution patterns of sediments originating from placement sites.