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Pelagic metabolism of the Douro estuary (Portugal) - Factors controlling primary production

Azevedo, Isabel C.; Duarte, Pedro; Bordalo, A.A.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2006 ENG
Relevância na Pesquisa
37.15%
The pelagic metabolism of the Douro estuary (Portugal) and the factors influencing primary production (PP) and community respiration (CR) in this system were studied during an annual cycle (December 2002 - December 2003). Sampling surveys were conducted twice a month during ebb and flood spring tides and water samples were collected for PP and CR assessments at three stations along the estuary (lower, middle and upper stretches). During the study period, PP values were in the range of 4.7-1878.5 mg C m-2 d-1 (average, 319.9 mg C m-2 d-1). River discharge controlled phytoplankton biomass inputs into the estuary as well as residence time. A decreasing trend in water column PP from the upper to the lower estuary related to higher nitrogen concentrations and phytoplankton biomass from riverine origin was observed. An inverse trend was found for CR, i.e., higher values were found in the lower, more urbanized stretch. During the study period, averaged CR values reached 1154 mg C m-2 d-1. In general, heterotrophy dominated the entire estuary, except in the upper stretch from May through July, when increased PP, but also lower CR values were recorded. A positive correlation between chlorophyll a and Pmax was found which is unusual in coastal ecosystems...

The contribution of scientific research for integrated coastal management: the Mondego estuary as study case

Costa, Sonia; Azeiteiro, Ulisses; Pardal, Miguel
Fonte: APRH Publicador: APRH
Tipo: Artigo de Revista Científica
Publicado em //2013 ENG
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The present paper quantifies and summarizes the research performed in the Mondego estuary (Portugal) over the last decades. Online databases were used to quantitatively assess the international publications, the master dissertations and PhD theses focused in the research about that estuary, from 1989 to 2012. In general, there had been a notable growth trend in publication output. Estuarine, Coastal and Shelf Science was the most active journal publishing on Mondego estuary. Field studies were the predominant type of research and the population/community dynamics and functioning have been one of the main research topics. Towards the time, the estuary has been used as local for several studies and the existing database has been useful to test theoretical ecological hypotheses and to support some management decisions and ecosystem restoration schemes. The efforts intended to its preservations are justified by its high ecological value, presenting large diversity of habitats and biodiversity, and its socio-economic importance, providing goods and services to population. The published research results cover several aspects of the system including the hydrology, the nutrient cycling, the communities’ structure, diversity and dynamics. Moreover...

Hydrodynamics and suspended sediment transport in the Camboriú estuary - Brazil: pre jetty conditions

SIEGLE, Eduardo; SCHETTINI, Carlos A. F.; KLEIN, Antonio H. F.; TOLDO JR., Elírio E.
Fonte: Universidade de São Paulo, Instituto Oceanográfico Publicador: Universidade de São Paulo, Instituto Oceanográfico
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.15%
Estuarine hydrodynamics is a key factor in the definition of the filtering capacity of an estuary and results from the interaction of the processes that control the inlet morphodynamics and those that are acting in the mixing of the water in the estuary. The hydrodynamics and suspended sediment transport in the Camboriú estuary were assessed by two field campaigns conducted in 1998 that covered both neap and spring tide conditions. The period measured represents the estuarine hydrodynamics and sediment transport prior to the construction of the jetty in 2003 and provides important background information for the Camboriú estuary. Each field campaign covered two complete tidal cycles with hourly measurements of currents, salinity, suspended sediment concentration and water level. Results show that the Camboriú estuary is partially mixed with the vertical structure varying as a function of the tidal range and tidal phase. The dynamic estuarine structure can be balanced between the stabilizing effects generated by the vertical density gradient, which produces buoyancy and stratification flows, and the turbulent effects generated by the vertical velocity gradient that generates vertical mixing. The main sediment source for the water column are the bottom sediments...

HYDRODYNAMICS AND SUSPENDED SEDIMENT TRANSPORT IN THE CAMBORIU ESTUARY - BRAZIL: PRE JETTY CONDITIONS

SIEGLE, Eduardo; SCHETTINI, Carlos A. F.; KLEIN, Antonio H. F.; TOLDO JR., Elirio E.
Fonte: INST OCEANOGRAFICO, UNIV SAO PAULO Publicador: INST OCEANOGRAFICO, UNIV SAO PAULO
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.15%
Estuarine hydrodynamics is a key factor in the definition of the filtering capacity of an estuary and results from the interaction of the processes that control the inlet morphodynamics and those that are acting in the mixing of the water in the estuary. The hydrodynamics and suspended sediment transport in the Cambori estuary were assessed by two field campaigns conducted in 1998 that covered both neap and spring tide conditions. The period measured represents the estuarine hydrodynamics and sediment transport prior to the construction of the jetty in 2003 and provides important background information for the Cambori estuary. Each field campaign covered two complete tidal cycles with hourly measurements of currents, salinity, suspended sediment concentration and water level. Results show that the Cambori estuary is partially mixed with the vertical structure varying as a function of the tidal range and tidal phase. The dynamic estuarine structure can be balanced between the stabilizing effects generated by the vertical density gradient, which produces buoyancy and stratification flows, and the turbulent effects generated by the vertical velocity gradient that generates vertical mixing. The main sediment source for the water column are the bottom sediments...

Dinâmica de sedimentos coesivos em um estuário altamente estratificado: rio Araranguá, SC; Dynamic of cohesive sediment at stratified estuary: Araranguá River, SC

Couceiro, Mariana Afonso Abade
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 24/04/2015 PT
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37.29%
O objetivo deste estudo é compreender a dinâmica das partículas no estuário do rio Araranguá (SC) em termos de transporte em suspensão, deposição e exportação, em diferentes condições físico-químicas da água, com pH baixo (<4,5) e normal (>=7), e sob condições de regime transiente da descarga fluvial. O estuário do rio Araranguá é classificado como altamente estratificado e dominado pela descarga fluvial. Um aspecto fundamental nos processos que controlam a dinâmica de materiais em suspensão no estuário é a atividade de lavra e beneficiamento do carvão, que gera uma drenagem ácida no rio Mãe Luzia. O seu pH baixo (˜3) indica que o processo de floculação é intensificado no interior do estuário. Com o objetivo de melhor entender a hidrodinâmica do estuário, um modelo tridimensional foi implementado para a região. O modelo foi calibrado e validado com dados observados. Simulações com diferentes picos de descarga fluvial (100, 400, 700 e 1000 m3.s-1) e baixa descarga (30 m3.s-1) foram realizadas. Para calcular o transporte do material particulado em suspensão foi desenvolvido um modelo Lagrangeano da trajetória da partícula. O modelo da trajetória utiliza os resultados do modelo hidrodinâmico e a velocidade de decantação das partículas. O estuário respondeu rapidamente às variações da descarga fluvial. A cunha salina foi transportada para fora do estuário durante os picos de 700 e 1000 m3.s-1. A descarga fluvial é o fator dominante no controle da intrusão da salinidade no estuário e...

Hydrodynamics and suspended sediment transport in the Camboriú Estuary - Brazil : prejetty conditions

Toldo Junior, Elirio Ernestino; Siegle, Eduardo; Schettini, Carlos Augusto França; Klein, Antonio Henrique da Fontoura
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: application/pdf
ENG
Relevância na Pesquisa
37.15%
As trocas de água e materiais através das desembocaduras de estuários são de difícil quantificação e são de fundamental importância para o entendimento do funcionamento de estuários e da zona costeira. A hidrodinâmica e transporte de sedimentos em suspensão no estuário do rio Camboriú foram estudados através da realização de duas campanhas de campo em 1998 cobrindo as condições de quadratura e sizígia. O período do levantamento foi anterior à obra de construção do molhe em 2003 que alterou a morfologia da desembocadura, fornecendo assim importantes informações base sobre o sistema. Cada experimento cobriu dois ciclos de maré com medições horárias de correntes, salinidade, concentrações de sedimentos em suspensão e nível de água. Os resultados mostram que o estuário é parcialmente misturado com estrutura vertical variando em função da amplitude e fase da maré. A estrutura dinâmica do estuário é balanceada entre os efeitos estabilizadores gerados pelo gradiente vertical de densidade, que permite produzir fluxo de empuxo e estratificação, e os efeitos turbulentos gerados pelo gradiente vertical de velocidade, que gera mistura vertical. A principal fonte de sedimentos para a coluna de água são os sedimentos de fundo...

The unexpected occurrence of late Sardina pilchardus (Walbaum, 1792) (Osteichthyes: Clupeidae) larvae in a temperate estuary

Morais, P.; Faria, Ana Margarida da Silva; Chícharo, Alexandra; Chícharo, Luís
Fonte: Universidade do Algarve Publicador: Universidade do Algarve
Tipo: Artigo de Revista Científica
Publicado em //2009 ENG
Relevância na Pesquisa
37.15%
The presence of sardine larval stages inside estuaries has generally been regarded as accidental and restricted to the lower part of estuaries. Sampling done with a zooplankton net in the Guadiana estuary corroborated this hypothesis. Late sardine larvae (32.8 ± 2.0 mm) were, however, unexpectedly collected with an otter trawl, 14 km upstream from the mouth of the estuary. Thus, this work intends to: (1) discriminate and compare the abiotic characteristics of the sites where maximum abundance of sardine larval stages were registered, when captured with a zooplankton net, with the characteristics of the sites where late sardine larvae were collected with an otter trawl; (2) demonstrate that the presence of the late sardine larvae inside the Guadiana estuary was not accidental. The average salinity of the site were late larvae where collected was 4.2 ± 2.3, i.e. 87.3% lower than the average salinity where maximum abundance of early larvae was registered. We suggest that the presence of the late sardine larvae inside the Guadiana estuary was not accidental. In order to migrate to that location and remain in the estuary, counteracting river inflow, these late larvae must have employed active migration and retention strategies. New methodologies need to be implemented for routine sampling of all larval stages of sardine...

Liver oxidative stress of the grey mullet Mugil cephalus presents seasonal variations in Ennore estuary

Padmini,E.; Vijaya Geetha,B.; Usha Rani,M.
Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/11/2008 EN
Relevância na Pesquisa
37.19%
The objective of this study was to determine the liver oxidative stress status of grey mullets living in heavy-metal-rich polluted Ennore estuary compared with unpolluted Kovalam estuary. Fish were collected from both estuaries during the monsoon and summer seasons from October 2004 to September 2006. Fish liver homogenate (N = 20 per group) was prepared for evaluating oxidative stress parameters. Fish living in the polluted estuary had significantly higher lipid oxidation products, conjugated dienes (0.346 ± 0.017 vs 0.141 ± 0.012 DA233/mg protein), lipid hydroperoxides (0.752 ± 0.032 vs 0.443 ± 0.03 nmol/mg protein), and lipid peroxides (3.447 ± 0.14vs 1.456 ± 0.096 nmol MDA/mg protein) than those of the unpolluted estuary during the summer. In contrast, significantly lower levels of superoxide dismutase (20.39 ± 1.14 vs 53.63 ± 1.48 units/mg protein) and catalase (116 ± 6.87vs 153 ± 8.92 units/mg protein) were detected in the liver of fish from the polluted estuary (Ennore) compared to fish from the unpolluted estuary (Kovalam) during the summer. Variations in most of the oxidative stress parameters were observed between the summer and monsoon seasons, indicating the importance of seasonal variation for estuaries and their inhabitants.

Distribution and abundance of Cladocera (Branchiopoda) in the Paraíba do Sul River estuary, Rio de Janeiro, Brazil

Sterza,José Mauro; Fernandes,Luiz Loureiro
Fonte: Universidade de São Paulo, Instituto Oceanográfico Publicador: Universidade de São Paulo, Instituto Oceanográfico
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2006 EN
Relevância na Pesquisa
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To characterize the cladoceran community of the Paraíba do Sul River estuary, located in the district of São João da Barra, Rio de Janeiro, Brazil, cladocerans were collected monthly in nine sampling stations from September 2002 until August 2003. Samples were obtained by subsurface tows using a plankton net with a 30 cm opening mouth and 70 micron mesh size, fitted with a mechanical flowmeter. Environmental parameters such as salinity and temperature were also obtained. Seventeen species of Cladocera were identified: Pseudoevadne tergestina, Penilia avirostris, Macrothrix triserialis, Moina micrura, Simocephalus kerhervei, Simocephalus vetalus, Simocephalus latirostris, Simocephalus serrulatus, Alona rectangula, Alona quadrangularis, Bosmina longirostris, Bosminopsis deitersi, Camptocercus dadayi, Ceriodaphnia richardi, Diaphanosoma fluviatile, Kurzia latissima and Pleuroxus similis. The highest total abundance of Cladocera occurred in April in the marine zone of the estuary. The most abundant species during this period was Penilia avirostris. At the mixing and freshwater zones of the estuary, the most abundant species were Moina micrura, mainly in January; and Simocephalus vetalus and Bosmina longirostris during spring. From this scenario...

Hydrodynamics and suspended sediment transport in the Camboriú estuary - Brazil: pre jetty conditions

Siegle,Eduardo; Schettini,Carlos A. F.; Klein,Antonio H. F.; Toldo Jr.,Elírio E.
Fonte: Universidade de São Paulo, Instituto Oceanográfico Publicador: Universidade de São Paulo, Instituto Oceanográfico
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2009 EN
Relevância na Pesquisa
37.15%
Estuarine hydrodynamics is a key factor in the definition of the filtering capacity of an estuary and results from the interaction of the processes that control the inlet morphodynamics and those that are acting in the mixing of the water in the estuary. The hydrodynamics and suspended sediment transport in the Camboriú estuary were assessed by two field campaigns conducted in 1998 that covered both neap and spring tide conditions. The period measured represents the estuarine hydrodynamics and sediment transport prior to the construction of the jetty in 2003 and provides important background information for the Camboriú estuary. Each field campaign covered two complete tidal cycles with hourly measurements of currents, salinity, suspended sediment concentration and water level. Results show that the Camboriú estuary is partially mixed with the vertical structure varying as a function of the tidal range and tidal phase. The dynamic estuarine structure can be balanced between the stabilizing effects generated by the vertical density gradient, which produces buoyancy and stratification flows, and the turbulent effects generated by the vertical velocity gradient that generates vertical mixing. The main sediment source for the water column are the bottom sediments...

The attenuation of tidal and subtidal oscillations in the patos lagoon estuary

Fernandes, Elisa Helena Le??o; Mari??o-Tapia, Ismael; Dyer, Keith Richard; M??ller Junior, Osmar Olinto
Fonte: Universidade Federal do Rio Grande Publicador: Universidade Federal do Rio Grande
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.19%
Abstract The single, long and narrow channel that usually connects choked coastal lagoons to the ocean can serve as a natural hydraulic low-pass filter that reduces or eliminates tidal and subtidal effects inside the lagoon. This study proposes an alternative method of estimating the attenuation of the tidal and subtidal oscillations throughout the Patos Lagoon estuary. The attenuation is estimated for conditions of contrasting river runoff and weather (summer and winter). A highpass/ low-pass filter (fast fourier transformation technique ??? FFT) is applied to time series of sea-surface elevation (SSE) measured at the mouth of the Patos Lagoon. The resulting high-frequency (tidal) and lowfrequency (subtidal) signals are used in independent simulations to force the TELEMAC-2D model. Attenuation of the tidal and subtidal signals throughout the estuary is estimated by applying cross-spectral analysis between the model-generated SSE time series at different locations throughout the estuary and the filtered SSE time series measured at the mouth. Results from the proposed method suggest that: (1) the low-frequency (subtidal) oscillations are less attenuated and propagate further than the high-frequency (tidal) oscillations in the Patos Lagoon estuary; (2) the filtering capability of the Patos Lagoon estuary is expected to follow a seasonal pattern...

Impact of Potentially Contaminated Sediments From The Sado Estuary in Human Health: Cytotoxic And Genotoxic Assays in a Human Cell Line

Pinto, Miguel; Louro, Henriqueta; Costa, Pedro; Caeiro, Sandra; Lavinha, João; Silva, Maria João
Fonte: Instituto Nacional de Saúde Doutor Ricardo Jorge, IP Publicador: Instituto Nacional de Saúde Doutor Ricardo Jorge, IP
Tipo: Conferência ou Objeto de Conferência
Publicado em 18/10/2011 ENG
Relevância na Pesquisa
37.27%
As many estuaries in industrialized countries, the river Sado Estuary (W Portugal) is affected by various sources of pollution, such as heavy-industry, urbanism, mining, agriculture and maritime traffic. Mostly classified as a natural reserve, it also remains a privileged site for fishing activities performed by the local population, who not only consume but distribute their fishery. Previous studies revealed sizable amounts of contaminants in the estuary sediments, namely metals, pesticides and polycyclic aromatic hydrocarbons. These compounds can be accumulated in the edible parts of estuarine species with commercial value or local agricultural products and enter the human food chain, posing a public health concern. The present study is part of a broader project whose objective is to evaluate the environmental risk, including ecologic and human health risk, associated with the estuarine benthic environment, complemented with the analysis of a target population from a small village located near the estuary shore. This study aims to assess the cytotoxic and genotoxic potential of sediments from the Sado Estuary through the neutral red uptake assay and the alkaline comet assay (coupled with DNA repair endonucleases) in a human cell line respectively...

Characterization of cytotoxicity and genotoxicity of sediments from a potentially contaminated estuary

Pinto, Miguel
Fonte: Instituto Nacional de Saúde Doutor Ricardo Jorge Publicador: Instituto Nacional de Saúde Doutor Ricardo Jorge
Tipo: Dissertação de Mestrado
Publicado em //2011 ENG
Relevância na Pesquisa
37.25%
Dissertação de mestrado apresentada à Faculdade de Ciências da Universidade de Lisboa, 2011; The Sado Estuary (W Portugal) is affected by various sources of pollution, associated with the existence of an urban center, heavy-industry, mining activities and agriculture. It also remains a privileged site for fishing activities that are responsible for the supplying of consumable resources either locally or externally. Previous studies revealed sizable amounts of contaminants in the estuary sediments, namely metals, pesticides and polycyclic aromatic hydrocarbons. These compounds can be absorbed and accumulated in the edible parts of estuarine species and in local agricultural products, thus entering the human food chain and posing a public health problem. This study aims to assess the cytotoxic and genotoxic effects of sediments from the Sado Estuary in a human cell line, in order to contribute to hazard identification. Sediments were collected in 4 distinct fishing sites (P, E, A, C) of the Sado Estuary; a reference (Mf) and a potentially contaminated sample (M) from a different estuary (Mira Estuary, W Portugal) were also included. Total organic and inorganic contaminants were extracted with a mixture of methanol:dicholomethane and recovered in DMSO. HepG2 cells were exposed for 48h to several concentrations of each extract. Cytotoxicity was measured by the neutral red assay and genotoxicity by the comet assay. A dose-related decrease in cell viability was observed for extracts P...

Radionuclide Indicators of Sediment Dynamics in the Delaware Estuary

Humberston, Joshua
Fonte: Universidade de Delaware Publicador: Universidade de Delaware
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
37.19%
Christopher K. Sommerfield; This report describes the methods and results of a seasonal study of suspended sediment dynamics in the Delaware Estuary using radionuclides as sediment tracers. Specifically, Be-7, I-131, and Pb-210 were used to determine if the estuary at selected coring sites was depositional, and if so, what were the rates of recent deposition. Be-7/Pb-210xs ratios were used to determine relative ages, or time since the sediment was in contact with the water column. Cores from eight sites in the middle to lower estuary were collected in summer, fall, and winter of 2011. Deposition rates varied among coring sites and over time. The absence of Be-7 and I-131 in bed deposits suggest that the estuary at the sampling locations is experiencing no net accumulation. An analysis of deposition variations among cores between seasons suggests large freshwater discharges following Hurricane Irene and Tropical Storm Lee moved the usual depositional zone about 50 kilometers seaward to the lower estuary. Iodine-131 was used to determine general transport distances since it is only sourced in the urbanized estuary.; Geological Sciences

Sedimentary response of the Delaware Estuary to tropical cyclones Irene and Lee in 2011

Duval, Daniel
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
Relevância na Pesquisa
37.25%
Sommerfield, Christopher K.; Tropical cyclones have a major influence on the hydrodynamics of MidAtlantic rivers and estuaries, and by extension on processes and rates of sediment transport. In 2011 the passage of Hurricane Irene and Tropical Storm Lee through the Delaware River Basin was recorded by sensors deployed throughout the region, and the resulting observations provided unique insights into the coupled hydrodynamic and sedimentary response of the Delaware Estuary. The combined suspended sediment input of the two main tributaries, the Delaware and Schuylkill rivers, was over 1,300,000 metric tons during the two-week storm period. Time series records of sediment transport along the axis of the estuary suggested that most of the sediment transported during the storms was bed material resuspended within the estuary, not new material delivered from above the head of tide. Significantly, the resuspended sediment flux was equal to or greater than the river influx. Despite the large volume of freshwater delivered to the estuary, salt was not completely flushed from the mouth of Delaware Bay, and the resident suspended sediment inventory was retained. The storm-produced sediment pulse was attenuated and assimilated during passage from the upper to lower estuary...

Economic Value of the Delaware Estuary Watershed - Summary Document

Kauffman, Gerald; Homsey, Andrew; Chatterson, Sarah; McVey, Erin; Mack, Stacey
Fonte: Universidade de Delaware Publicador: Universidade de Delaware
Tipo: Outros
EN_US
Relevância na Pesquisa
37.25%
prepared for the Partnership for the Delaware Estuary; What do Boeing, Sunoco, Campbell’s Soup, DuPont, Wawa, Starbucks, Iron Hill Brewery, the Philadelphia Eagles, Salem Nuclear Power Plant, and the United States Navy have in common? They all depend on the waters of the Delaware Estuary to sustain their business. The natural resources of the Delaware Estuary watershed provide tremendous economic value to our region. This report examines that value in three distinct ways: • Economic value directly related to the Delaware Estuary’s water resources and habitats: Using economic activity as a measure of value, the Delaware Estuary contributes over $10 billion in annual economic activity from recreation, water quality and supply, hunting and fishing, forests, agriculture and parks. • Value of the goods and services provided by the Delaware Estuary’s ecosystems: Using ecosystem goods and services as a measure of value, the ecosystems of the Delaware Estuary (such as wetlands, forests, farms, and water) provide $12 billion annually in goods and services in 2010 dollars, with a net present value of $392 billion calculated over a 100-year period. • Employment related to the Delaware Estuary’s water resources and habitats: Using employment as a measure of value...

Economic Value of the Delaware Estuary Watershed - Comprehensive Report

Kauffman, Gerald J.
Fonte: Universidade de Delaware Publicador: Universidade de Delaware
Tipo: Outros
EN_US
Relevância na Pesquisa
37.25%
prepared for the Partnership for the Delaware Estuary, funded by DNREC; What do Boeing, Sunoco, Campbell’s Soup, DuPont, Wawa, Starbucks, Iron Hill Brewery, the Philadelphia Eagles, Salem Nuclear Power Plant, and the United States Navy have in common? They all depend on the waters of the Delaware Estuary to sustain their business. The natural resources of the Delaware Estuary watershed provide tremendous economic value to our region. This report examines that value in three distinct ways: • Economic value directly related to the Delaware Estuary’s water resources and habitats. Using economic activity as a measure of value, the Delaware Estuary contributes over $10 billion in annual economic activity from recreation, water quality and supply, hunting and fishing, forests, agriculture and parks. • Value of the goods and services provided by the Delaware Estuary’s ecosystems. Using ecosystem goods and services as a measure of value, the ecosystems of the Delaware Estuary provide $12 billion annually in goods and services in 2010 dollars, with a net present value of $392 billion calculated over a 100-year period. • Employment related to the Delaware Estuary’s water resources and habitats. Using employment as a measure of value...

Seasonal patterns of delta15N and delta18O-NO3- in the Murderkill River Watershed and Estuary, DE

Fischer, Sarah Jane L.
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
Relevância na Pesquisa
37.19%
Ullman, William J.; The stable isotopes of dissolved nitrate ??15 N and ?? 18 O-NO3- together with nitrogen speciation can be used to track sources and to determine the processes controlling nitrogen attenuation. Five seasonal surveys of ??15 N and ?? 18 O-NO3- , NO3- , and related biogeochemical parameters were conducted to investigate nitrogen sources and cycling in surface waters across connected, but distinct, hydrodynamic settings of the Murderkill Watershed, DE. In the upper watershed, little systematic change in NO 3- concentrations and isotopic composition was observed in streams, but four to fifteen fold NO3- decreases and 2-4 / ??15 N and ??18 O-NO 3- enrichment occurred in the ponds during summer months. The ratio of ??15 N:??18 O enrichment occurred in either a 2:1 or 1:1 ratio or somewhere in between, consistent with plant uptake and/or denitrification. During summer periods, chlorophyll a and dissolved oxygen levels also increased by several factors and therefore some of the first observations of ?? 15 N and ?? 18 O-NO3- dynamics are reported for freshwater algal blooms. Novel application of a distance-based multi-segmented estuarine model was used to propose ??15 N and ??18 O-NO 3- distribution in the marsh-lined estuary due to mixing of 3-end members: the upper watershed...

The response of microalgal biomass and community composition to environmental factors in the Sundays Estuary

Kotsedi,Daisy; Adams,Janine B; Snow,Gavin C
Fonte: Water SA Publicador: Water SA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2012 EN
Relevância na Pesquisa
37.22%
The Sundays Estuary is permanently open to the sea and experiences regular freshwater inflow in the form of agricultural return flows with large supplies of nutrients. The objectives of this study were to measure microalgal biomass and community composition and relate these to freshwater inflow, water quality and other environmental variables. These data can then be used in setting the ecological water requirements of the estuary. Surveys in August 2006, March 2007, February, June and August 2008 showed that salinity less than 10, expressed in practical salinity units, mostly occurred from 12.5 km from the mouth in the middle reaches of the estuary, which was also where the highest water column chlorophyll a (>20 μg.ℓ-1) was found. The study showed that different groups of microalgae formed phytoplankton blooms during individual sampling sessions. These included blooms of green algae (August 2006), flagellates (March 2007), dinoflagellates (June 2008) and diatom species (February and August 2008). The estuary was then sampled over 5 consecutive weeks from March to April 2009 to identify environmental factors that support different microalgal bloom species. Phytoplankton blooms were found during Weeks 1, 4 and 5 from the middle to the upper reaches of the estuary. It was shown that diatoms occurred in blooms during warm...

Insights into the bacterial diversity in a freshwater-deprived permanently open Eastern Cape estuary, using 16S rRNA pyrosequencing analysis

Matcher,GF; Dorrington,RA; Henninger,TO; Froneman,PW
Fonte: Water SA Publicador: Water SA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/07/2011 EN
Relevância na Pesquisa
37.19%
The aim of this study was to conduct an investigation into the bacterial diversity in the freshwater-deprived Kariega Estuary, situated along the Eastern Cape coastline, using ribosomal RNA gene sequences obtained by pyrosequencing. Shifts in the microbial diversity were correlated to selected physico-chemical variables along the length of the estuary. More than 27 000 sequences were obtained and rarefaction analyses confirmed a comprehensive appraisal of the microbial diversity present in the Kariega Estuary. Distinct patterns in phylotype distribution from the hypersaline upper reaches to the mouth of the estuary were observed; notably, the importance of the detrital food web within the Kariega Estuary was highlighted by the high occurrence of Bacteroidetes and Actinomycetes. Moreover, while the observed chlorophyll-a concentrations were low (< 0.1 µg·ℓ-1), the presence of Pelagibacter and Flavobacteria amongst the microbial community suggests a potentially important contribution of these microbes towards the total primary productivity of the ecosystem. No human pathogenic microbes were detected within waters of the system. We conclude that pyrosequencing provides a versatile and efficient tool for assessing the microbial diversity in the Kariega Estuary and propose that this technology may provide valuable information on the ecosystem functioning and health of aquatic ecosystems.