scholarly journals Modeling the Impact of Extreme River Discharge on the Nutrient Dynamics and Dissolved Oxygen in Two Adjacent Estuaries (Portugal)

2019 ◽  
Vol 7 (11) ◽  
pp. 412
Author(s):  
Vítor H. Oliveira ◽  
Magda C. Sousa ◽  
Fernando Morgado ◽  
João M. Dias
Keyword(s):  
Dissolved Oxygen ◽  
River Discharge ◽  
Nutrient Dynamics ◽  
Winter Season ◽  
Limiting Factor ◽  
Dissolved Oxygen Concentration ◽  
The North ◽  
Nutrient Patterns ◽  
Freshwater Inflows ◽  
The Impact

The Minho and Lima are adjacent estuaries located in the north of Portugal, with high ecological and economic importance. To address gaps in knowledge about changes in nutrient patterns in adjacent estuaries subject to different freshwater inflows, a numerical model, Delft3D, was implemented and developed, using a single domain, which allowed physical communication between estuaries. Calibration and validation of the model was successfully performed. Three numerical simulations were carried out, in which only river flows were varied (1st corresponds to a baseline numerical run, the 2nd a flood scenario, and the 3rd a drought scenario). Under flooding conditions, similar patterns were verified in both estuaries, with high fluvial discharges showing to have a reduced impact on both estuarine dynamics. In this case the nutrients were not a limiting factor for the biota, both for summer and winter seasons, since there was no significant decrease in dissolved oxygen concentration. For the drought scenario, it was observed that the estuary with the lower inflow of freshwater (Lima) was the most affected, with a significant decrease in the concentration of nutrients and oxygen dissolved in the winter season (decrease of 2 mg O2/L). In conclusion, this work reveals that it is essential to continuously monitor dam-controlled estuarine systems, as a significant decrease in river discharge will cause significant changes in the variables analysed (O2, PO4, and NO3) and may cause loss of biodiversity.

Impact of hypolimnetic oxygenation on profundal macroinvertebrates in a eutrophic lake in central Alberta. I. Changes in macroinvertebrate abundance and diversity

1997 ◽  
Vol 54 (9) ◽  
pp. 2157-2169 ◽  
Author(s):  
W P Dinsmore ◽  
E E Prepas
Keyword(s):  
Dissolved Oxygen ◽  
Water Temperature ◽  
Eutrophic Lake ◽  
Water Bodies ◽  
Macroinvertebrate Communities ◽  
South Basin ◽  
The North ◽  
Hypolimnetic Oxygenation ◽  
Abundance And Diversity ◽  
The Impact

Hypolimnetic oxygenation from 1988 to 1991 in the north basin of Amisk Lake increased mean summer (June-August) dissolved oxygen (DO) concentrations in the deep hypolimnion (25 m) from <0.4 mg ·L-1 during pretreatment years (1980-1987) to 2.7 mg ·L-1 during treatment. Mean summer hypolimnetic temperatures at 25 m also increased from 6.3 (pretreatment) to 8.1°C (treatment). Profundal (15-25 m) Chironomus spp. abundance in the treated basin increased from <100 to >2000 ·m-2 from 1988 to 1991 whereas Chaoborus spp., Tubificidae, and other taxa remained uncommon at similar depths. Shannon-Weaver indices of diversity decreased as oxygenation progressed, in contrast with previous studies. Similar patterns in densities and diversity were observed in the south basin of Amisk Lake, although the increase in DO concentrations was smaller relative to the north basin. The impact of increased water temperature on macroinvertebrates appeared minor relative to the effects of increased DO concentrations. No changes in macroinvertebrate communities were noted in a nearby reference lake during the study period. Responses to hypolimnetic oxygenation in Amisk Lake differed markedly from those reported for smaller, single-basined water bodies.

scholarly journals Detection of low bottom water oxygen concentrations in the North Sea; implications for monitoring and assessment of ecosystem health

2009 ◽  
Vol 6 (4) ◽  
pp. 8411-8453 ◽  
Author(s):  
N. Greenwood ◽  
E. R. Parker ◽  
L. Fernand ◽  
D. B. Sivyer ◽  
K. Weston ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Oxygen Concentration ◽  
North Sea ◽  
Mixed Layer ◽  
Ecosystem Health ◽  
Bottom Water ◽  
Dissolved Oxygen Concentration ◽  
The North ◽  
The North Sea ◽  
Oxygen Concentrations

Abstract. This paper presents new results from high temporal resolution observations over two years (2007 and 2008) from instrumented moorings deployed in the central North Sea, at the Oyster Grounds and on the northern slope of Dogger Bank (North Dogger). The water column was stratified in the summer at both sites, leading to limited exchange of the water in the bottom mixed layer. Data from these moorings revealed the variable nature of summer oxygen depletion at the Oyster Grounds. The combination of in situ and ship-based measurements allowed the physical and biological conditions leading to decreasing dissolved oxygen concentrations in bottom water to be examined. The concentration of dissolved oxygen in the bottom water at both sites was observed to decrease throughout the summer period after the onset of stratification. Depleted dissolved oxygen concentration (6.5 mg l−1, 71% saturation) was measured at the North Dogger, a site which is not significantly influenced by anthropogenic nutrient inputs. Lower oxygen saturation (5.2 mg l−1, 60% saturation) was measured for short durations at the Oyster Grounds. Increasing bottom water temperature accounted for 55% of the decrease in dissolved oxygen concentration at the Oyster Grounds compared to 10% at North Dogger. Dissolved oxygen concentration in bottom water at the Oyster Grounds was shown to be strongly influenced by short term events including storm events and pulses of biomass input. In contrast, dissolved oxygen concentration in bottom water at the North Dogger reflected longer seasonal processes such as gradual temperature increases and a more steady supply of biomass to the bottom mixed layer. The differences between the study sites shows the need for an improved understanding of the mechanisms driving these processes if the use of oxygen in marine management and ensuring ecosystem health is to be meaningful and successful in the future. These observations provide greater understanding of the nature of the depletion in bottom oxygen concentration in the North Sea.

scholarly journals Detection of low bottom water oxygen concentrations in the North Sea; implications for monitoring and assessment of ecosystem health

2010 ◽  
Vol 7 (4) ◽  
pp. 1357-1373 ◽  
Author(s):  
N. Greenwood ◽  
E. R. Parker ◽  
L. Fernand ◽  
D. B. Sivyer ◽  
K. Weston ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Oxygen ◽  
Oxygen Concentration ◽  
North Sea ◽  
Particulate Organic Matter ◽  
Ecosystem Health ◽  
Bottom Water ◽  
Dissolved Oxygen Concentration ◽  
The North ◽  
The North Sea

Abstract. This paper presents new results from high temporal resolution observations over two years (2007 and 2008) from instrumented moorings deployed in the central North Sea, at the Oyster Grounds and on the northern slope of Dogger Bank (North Dogger). The water column was stratified in the summer at both sites, leading to limited exchange of the water in the bottom mixed layer. Data from these moorings revealed the variable nature of summer oxygen depletion at the Oyster Grounds. The combination of in situ and ship-based measurements allowed the physical and biological conditions leading to decreasing dissolved oxygen concentrations in bottom water to be examined. In 2007 and 2008, the concentration of dissolved oxygen in the bottom water at both sites was observed to decrease throughout the summer period after the onset of stratification. Depleted dissolved oxygen concentration (6.5 mg l−1, 71% saturation) was measured at the North Dogger, a site which is not significantly influenced by anthropogenic nutrient inputs. Lower oxygen saturation (5.2 mg l−1, 60% saturation) was measured for short durations at the Oyster Grounds. The seasonal increase in bottom water temperature accounted for 55% of the decrease in dissolved oxygen concentration at the Oyster Grounds compared to 10% at North Dogger. Dissolved oxygen concentration in bottom water at the Oyster Grounds was shown to be strongly influenced by short term events including storms and pulses of particulate organic matter input. In contrast, dissolved oxygen concentration in bottom water at the North Dogger reflected longer seasonal processes such as a gradual temperature increase over the summer and a more steady supply of particulate organic matter to the bottom mixed layer. The differences between the study sites shows the need for an improved understanding of the mechanisms driving these processes if the use of oxygen in marine management and ensuring ecosystem health is to be meaningful and successful in the future. These high frequency observations provide greater understanding of the nature of the depletion in bottom oxygen concentration in the North Sea.

scholarly journals Reconstruction of Atlantic historical winter coastal storms in the Spanish coasts of the Gulf of Cadiz, 1929–2005

2011 ◽  
Vol 11 (6) ◽  
pp. 1715-1722 ◽  
Author(s):  
P. Ribera ◽  
D. Gallego ◽  
C. Pena-Ortiz ◽  
L. Del Rio ◽  
T. A. Plomaritis ◽  
...  
Keyword(s):  
Winter Season ◽  
Positive Trend ◽  
Gulf Of Cadiz ◽  
Atlantic Sector ◽  
Coastal Storms ◽  
The North ◽  
Gulf Of Cádiz ◽  
Instrumental Period ◽  
The North Atlantic Oscillation ◽  
The Impact

Abstract. This paper presents the reconstruction of a climatological series of winter coastal storms on the northern coasts of the Gulf of Cadiz. This series has been put together using information extracted from regional and local Spanish newspapers. It includes all the storms coming from the Atlantic sector that have been detected during the winter season, from October to March, between 1929 and 2005. In order to validate this historical storm series, it has been compared with storms series identified from quasi-observational data and using different wave heights as thresholds to decide what is to be considered as a coastal storm. Nearly 2.6 reports per year about coastal storms are published in the press which correspond to waves of 3.6 m high or more and to prevailing winds from a direction ranging between SSW and WNW. A long- term positive trend has been detected for the complete storm series. If only the instrumental period is analysed, no significant trend is detected. It is suggested that this difference might be associated with the impact of the North Atlantic Oscillation over the occurrence of storms in this area.

scholarly journals Aedes species (Diptera: Culicidae) ecological and host feeding patterns in the north-eastern parts of South Africa, 2014–2018

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
M. M. Guarido ◽  
M. A. Riddin ◽  
T. Johnson ◽  
L. E. O. Braack ◽  
M. Schrama ◽  
...  
Keyword(s):  
South Africa ◽  
Limiting Factor ◽  
Sequence Information ◽  
Host Feeding ◽  
Entomological Surveillance ◽  
North East ◽  
The North ◽  
North Eastern ◽  
Control And Prevention ◽  
The Impact

Abstract Background There is a paucity of recent data and knowledge on mosquito diversity and potential vectors of arboviruses in South Africa, with most of the available data dating back to the 1950s–1970s. Aedes and Culex species are the major vectors of some of the principal arboviruses which have emerged and re-emerged in the past few decades. Methods In this study we used entomological surveillance in selected areas in the north-eastern parts of South Africa from 2014 to 2018 to assess mosquito diversity, with special emphasis on the Aedes species. The impact of trap types and environmental conditions was also investigated. Identification of the blood meal sources of engorged females collected during the study period was carried out, and DNA barcodes were generated for selected species. Results Overall, 18.5% of the total Culicidae mosquitoes collected belonged to the genus Aedes, with 14 species recognised or suspected vectors of arboviruses. Species belonging to the Neomelaniconion subgenus were commonly collected in the Bushveld savanna at conservation areas, especially Aedes mcintoshi and Aedes circumluteolus. Aedes aegypti was present in all sites, albeit in low numbers. Temperature was a limiting factor for the Aedes population, and they were almost exclusively collected at temperatures between 18 °C and 27 °C. The cytochrome oxidase subunit I (COI) barcode fragment was amplified for 21 Aedes species, and for nine of these species it was the first sequence information uploaded on GenBank. Conclusion This study provides a better understanding of the diversity and relative abundance of Aedes species in the north-east of South Africa. The information provided here will contribute to future arboviral research and implementation of efficient vector control and prevention strategies. Graphical abstract

scholarly journals ALTERACIONES FISICO-QUIMICAS DE LA COLUMNA DE AGUA, GENERADAS POR EL USO DEL BOLICHE (METODO DE PESCA ARTESANAL) EN LA CIENAGA GRANDE DE SANTA MARTA, CARIBE COLOMBIANO

2016 ◽  
Vol 24 ◽  
Author(s):  
Mario Enrique Rueda ◽  
José Ernesto Mancera P.
Keyword(s):  
Dissolved Oxygen ◽  
Water Column ◽  
Oxygen Concentration ◽  
Coastal Lagoon ◽  
Water Transparency ◽  
Dissolved Oxygen Concentration ◽  
Artisanal Fishing ◽  
Physical Chemical ◽  
Before And After ◽  
The Impact

With the purpose of assessing the impact generated by the use of an artisanal fishing method populary called "boliche", in the tropical coastal lagoon Ciénaga Grande de Santa Marta, different aspects were quantified; being one of them designed to analyze some physical-chemical alterations of the water column, produced during the fishing operations. The dissolved oxygen concentration, water transparency and seston composition and concentration, before and after of 70 boliche's thrusts were determinated. The results showthat fishing operations generate some momentary changes of little repercution to the ecosystem, such as particle resuspention principally inorganic an increase in seston concentration and a consequen water column transparency decrease. The dissolved oxygen concentration does not show appreciable alteration.

Spatial differences in the impact of the North Atlantic Oscillation on the flow of rivers in Europe

2011 ◽  
Vol 42 (1) ◽  
pp. 30-39 ◽  
Author(s):  
Dariusz Wrzesiński ◽  
Rafał Paluszkiewicz
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Winter Season ◽  
Winter Period ◽  
The North ◽  
The North Atlantic ◽  
Positive Correlations ◽  
The North Atlantic Oscillation ◽  
River Profiles ◽  
The Impact

The article presents regional differences in the impact that the North Atlantic Oscillation (NAO) exerts on the flow of European rivers. The impact is determined by temporal variations in the strength of relations expressed by coefficients of correlation between monthly or seasonal NAO indices and discharges recorded at 510 river profiles. The results of the correlation analysis were arranged using Ward’s method of hierarchical grouping. The classification of river profiles thus obtained made it possible to distinguish seven regions differing in the nature of the dependence between streamflow and the intensity of the NAO. The most statistically significant positive correlations are displayed by the rivers of Fennoscandia, Denmark and the northwest part of the British Isles in the winter period, while the most significant negative correlations (also in winter) are recorded for streams of the Mediterranean Basin, western France and the southeast of England. In the southeast part of the Baltic Sea drainage basin, significant positive correlations of streamflow with the NAO indices can be observed in the winter season and negative correlations are observed in spring.

scholarly journals River Discharge into the Mediterranean Sea: Climatology and Aspects of the Observed Variability

2004 ◽  
Vol 17 (24) ◽  
pp. 4740-4751 ◽  
Author(s):  
Maria Vittoria Struglia ◽  
Annarita Mariotti ◽  
Angelo Filograsso
Keyword(s):  
River Discharge ◽  
Adriatic Sea ◽  
Aegean Sea ◽  
Early Spring ◽  
Catchment Basin ◽  
The North ◽  
Gulf Of Lion ◽  
The Mediterranean ◽  
The North Atlantic Oscillation ◽  
The Impact

Abstract River discharge across the Mediterranean catchment basin is investigated by means of an extensive dataset of historical monthly time series to represent at-best discharge into the sea. Results give an annual mean river discharge into the Mediterranean of 8.1 × 103 m3 s−1, or at most a value that should not exceed 10.4 × 103 m3 s−1. The seasonal cycle has an amplitude of 5 × 103 m3 s−1, with a dry season in midsummer and a peak flow in early spring. Dominant contributions are from Europe with a climatological annual mean of 5.7 × 103 m3 s−1. Discharge in the Adriatic Sea, the Gulf of Lion, and the Aegean Sea together account for 62% of Mediterranean discharge, which mostly occurs in the Adriatic (2.7 × 103 m3 s−1). The North Atlantic Oscillation (NAO) impacts Mediterranean discharge primarily in winter, with most river discharges across the Mediterranean catchment being anticorrelated with the NAO. Related winter anomalies are about 10%–20% of the winter means. During the period 1960–90, Mediterranean winter discharge as a whole may have undergone year-to-year NAO-related variations of up to 26% of the seasonal mean, while about 17% on decadal time scales. These variations are expected to have occurred mostly in the Gulf of Lion and the Adriatic Sea, together with the Balearic Sea, where the impact of the NAO is greatest.

McFAN experiment: An integrated analysis of the multiphase chemistry experiment in Fogs and Aerosols in the North China Plain

2020 ◽  
Author(s):  
Hang Su ◽  
Nan Ma ◽  
Yele Sun ◽  
Jiangchuan Tao ◽  
Pingqing Fu ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Winter Season ◽  
Direct Determination ◽  
Organic Aerosol ◽  
Integrated Analysis ◽  
The North ◽  
The North China Plain ◽  
The Impact ◽  
Chemistry Experiment

&lt;p&gt;Fine-particle pollution associated with winter haze threatens the health of more than 400 million people in the North China Plain. The Multiphase chemistry experiment in Fogs and Aerosols in the North China Plain (McFAN) investigated the physical-chemical mechanisms leading to the haze formation with a focus on the contributions of multiphase processes in aerosol and fogs. We integrated multiple platform observations with regional and box models to identify the key oxidation process producing sulfate, nitrate and secondary organic aerosols, and their impact. A new environmental chamber was deployed to conduct kinetic experiments with real atmospheric compositions in comparison to literature kinetic data from laboratory studies. The experiments were carried out for multiple years since 2017 at the Gucheng site in the center of polluted areas and have performed experiments in the winter season. The location of the site minimizes fast transition between clean and polluted air masses (e.g., in Beijing), and helps to maintain a pollution regime representative for the North China Plain. The multi-year consecutive experiments documented the trend of PM2.5 pollution and corresponding change of aerosol physical and chemical properties, and allowed to investigate newly proposed mechanisms. The preliminary results show new proofs of the key role of aqueous phase reactions in regulating the aerosol compositions during haze events.&lt;/p&gt;&lt;p&gt;Reference:&lt;/p&gt;&lt;p&gt;Zheng et al., Exploring the severe winter haze in Beijing: the impact of synoptic weather, regional transport and heterogeneous reactions. Atmospheric Chemistry and Physics &lt;strong&gt;15&lt;/strong&gt;, 2969-2983 (2015).&lt;/p&gt;&lt;p&gt;Cheng et al., Reactive nitrogen chemistry in aerosol water as a source of sulfate during haze events in China. Science Advances &lt;strong&gt;2&lt;/strong&gt;,&amp;#160; (2016).&lt;/p&gt;&lt;p&gt;Li et al., Multifactor colorimetric analysis on pH-indicator papers: an optimized approach for direct determination of ambient aerosol pH. Atmos. Meas. Tech. Discuss. &lt;strong&gt;2019&lt;/strong&gt;, 1-19 (2019).&lt;/p&gt;&lt;p&gt;Kuang et al., Distinct diurnal variation of organic aerosol hygroscopicity and its relationship with oxygenated organic aerosol. Atmos. Chem. Phys. Discuss. &lt;strong&gt;2019&lt;/strong&gt;, 1-33 (2019).&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

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