scholarly journals Temporal changes in nutrients in a deep oligomictic lake: the role of external loads versus internal processes

2021 ◽  
Vol 80 (3) ◽  
Author(s):  
Michela Rogora ◽  
Martina Austoni ◽  
Rossana Caroni ◽  
Paola Giacomotti ◽  
Lyudmila Kamburska ◽  
...  
Keyword(s):  
Water Column ◽  
Total Phosphorus ◽  
Inorganic Nitrogen ◽  
Lake Maggiore ◽  
Deep Mixing ◽  
Long Term Study ◽  
Mixing Patterns ◽  
The Impact ◽  
External Loads

The impact of climate change on stratification and mixing patterns has important effects on nutrient availability and plankton dynamics in deep lakes. We demonstrate this in a long-term study of Lake Maggiore, a deep oligomictic lake located in the subalpine lake district in Northern Italy. Studies on physical, chemical and biological features of the lake have been performed continuously since the 1980s. The lake recovered from eutrophication in response to a reduction of catchment nutrient loads and reached a stable oligotrophic status by the end of the 1990s, with average total phosphorus concentrations in the water column around 10 µg L-1. However, both reactive and total phosphorus have slightly increased since 2010, leading to a shift in the lake trophic state towards mesotrophy. The increase in phosphorus has been limited to the hypolimnetic layers, concentrations being fairly stable or decreasing in the epilimnion. Reactive silica also progressively increased in the hypolimnion, while nitrate and total nitrogen concentrations have steadily decreased in both deep and surface layers, especially in the summer period. These changes were assessed in relation to catchment loads, atmospheric deposition and climate-related variations in stratification and mixing patterns and in nutrient retention. Long-term changes in primary production, represented by chlorophyll levels, and biovolume of the main algal groups were also considered. During the eutrophication period and until the 1990s, in-lake phosphorus concentrations were tightly related to external loads; successively, phosphorus and its vertical distribution up the water column became more controlled by internal processes, in particular by stratification and mixing regime. An increase of thermal stability and a reduced frequency and intensity of deep mixing events has fostered oxygen depletion and phosphorus and silica accumulation in the hypolimnion. Another consequence of reduced deep mixing events, has been a reduction in nutrient replenishment of the upper layers at spring mixing. External loads are still the main driver of change for nitrogen compounds: the decrease in the atmospheric load of nitrogen that occurred in the Lake Maggiore area over the last decade, as an effect of reduced nitrogen emissions, has caused decreasing concentration of inorganic nitrogen in the lake. However, the phytoplankton community changes observed might also play a role in nitrogen dynamics, particularly in the nitrate minima observed during summer in recent years.

scholarly journals Nutrient retention behind a tropical mega-dam: a case study of the Sardar Sarovar Dam, India

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Harish Gupta ◽  
S. Kiran Kumar Reddy ◽  
Mounika Chiluka ◽  
Vamshikrishna Gandla
Keyword(s):  
Arabian Sea ◽  
Inorganic Nitrogen ◽  
Nutrient Retention ◽  
Significant Loss ◽  
N Removal ◽  
Narmada River ◽  
Sardar Sarovar ◽  
The Impact

AbstractIn this study, we demonstrate the impact of the construction of a mega-dam on the nutrient export regime of a large tropical river into the Arabian Sea. Long-term (11 years) fortnight nutrient parameters, upstream and downstream to Sardar Sarovar (SS) Dam, were examined to determine the periodical change in nutrient fluxes from the Narmada River, India. During this 11-year period, the average discharge of the Narmada River upstream to Rajghat (35.3 km3 year−1) was higher than that of downstream at Garudeshwar (33.9 km3 year−1). However, during the same period, the suspended sediment load was reduced by 21 million tons (MT) from 37.9 MT at Rajghat to 16.7 MT at Garudeshwar. Similarly, mean concentrations of dissolved silica (DSi) reduced from 470 (upstream) to 214 µM (downstream), dissolved inorganic phosphate (DIP) from 0.84 to 0.38 µM, and dissolved inorganic nitrogen (DIN) from 43 to 1.5 µM. It means that about 54%, 55%, and 96% flux of DSi, DIP, and DIN retained behind the dam, respectively. The estimated denitrification rate (80,000 kg N km−2 year−1) for the reservoir is significantly higher than N removal by lentic systems, globally. We hypothesize that processes such as biological uptake and denitrification under anoxic conditions could be a key reason for the significant loss of nutrients, particularly of DIN. Finally, we anticipated that a decline in DIN fluxes (by 1.13 × 109 mol year−1) from the Narmada River to the Arabian Sea might reduce the atmospheric CO2 fixation by 7.46 × 109 mol year−1.

Long-term prognosis of patients withJ-wave syndrome

Heart ◽  
2019 ◽  
Vol 106 (4) ◽  
pp. 299-306
Author(s):  
Tsukasa Kamakura ◽  
Tetsuji Shinohara ◽  
Kenji Yodogawa ◽  
Nobuyuki Murakoshi ◽  
Hiroshi Morita ◽  
...  
Keyword(s):  
High Amplitude ◽  
Long Term Study ◽  
St Segment ◽  
History Of ◽  
Provocation Testing ◽  
Long Term Prognosis ◽  
Electrocardiographic Parameters ◽  
The Impact

ObjectiveLimited data are currently available regarding the long-term prognosis of patients with J-wave syndrome (JWS). The aim of this study was to investigate the long-term prognosis of patients with JWS and identify predictors of the recurrence of ventricular fibrillation (VF).MethodsThis was a multicentre retrospective study (seven Japanese hospitals) involving 134 patients with JWS (Brugada syndrome (BrS): 85; early repolarisation syndrome (ERS): 49) treated with an implantable cardioverter defibrillator. All patients had a history of VF. All patients with ERS underwent drug provocation testing with standard and high intercostal ECG recordings to rule out BrS. The impact of global J waves (type 1 ECG or anterior J waves and inferolateral J waves in two or more leads) on the prognosis was evaluated.ResultsDuring the 91±66 months of the follow-up period, 52 (39%) patients (BrS: 37; ERS: 15) experienced recurrence of VF. Patients with BrS and ERS with global J waves showed a significantly higher incidence of VF recurrence than those without (BrS: log-rank, p=0.014; ERS: log-rank, p=0.0009). The presence of global J waves was a predictor of VF recurrence in patients with JWS (HR: 2.16, 95% CI 1.21 to 3.91, p=0.0095), while previously reported high-risk electrocardiographic parameters (high-amplitude J waves ≥0.2 mV and J waves associated with a horizontal or descending ST segment) were not predictive of VF recurrence.ConclusionsThis multicentre long-term study showed that the presence of global J waves was associated with a higher incidence of VF recurrence in patients with JWS.

Fire and its impact on avian population dynamics

1997 ◽  
Vol 3 (3) ◽  
pp. 206 ◽  
Author(s):  
G. Barry Baker ◽  
E. Belinda Dettmann ◽  
Stephen J. Wilson
Keyword(s):  
Population Size ◽  
Fire Regimes ◽  
Long Term Study ◽  
Sclerophyll Forest ◽  
In Fire ◽  
Avian Populations ◽  
The Impact ◽  
Term Monitoring ◽  
Probability Of Capture

Survival rate, population size, recruitment and probability of capture, derived from a long-term study of 20 passerine species in wet sclerophyll forest near Canberra, were used to measure the impact of a high intensity wildfire which burnt 70% of the study area. The wildfire significantly affected the population size of 13 species for a period of up to six years following the fire. Survival and recruitment were the least sensitive measures of impact and indicated a significant response to fire for only 2 of 10 species. We detected measurable effects of the fire for 17 of the 20 species studied. Many of these species had returned to prefire levels within three years, but for nine species the effects were still apparent six years later. Mark-recapture methodology provides an effective way of measuring the impact of fire regimes in forest environments. Long-term monitoring programmes should be established in fire-prone forest environments to contribute toward our understanding of fire, and its effect on avian populations. Such programmes have resource implications and researchers are urged to encourage the participation of the amateur bird banding community to contribute to such projects.

scholarly journals Effects of eutrophication on size and biomass of crustacean zooplankton in a tropical reservoir

2005 ◽  
Vol 65 (2) ◽  
pp. 325-338 ◽  
Author(s):  
R. M. Pinto-Coelho ◽  
J. F. Bezerra-Neto ◽  
C. A. Morais-Jr.
Keyword(s):  
Total Phosphorus ◽  
Temporal Variations ◽  
Crustacean Zooplankton ◽  
Tropical Reservoir ◽  
Term Study ◽  
Qualitative And Quantitative ◽  
Long Term Study ◽  
Quantitative Changes ◽  
Significant Size

This is a long-term study (1993-1998) on the effects of increasing eutrophication on the crustacean zooplankton structure in a eutrophic reservoir. The study first demonstrates that the eutrophication increase verified is a phenomenon well described by a single abiotic variable: total phosphorus. During the study period, zooplankton suffered extensive qualitative and quantitative changes. Significant size and biomass responses of certain zooplankton groups to the temporal variations of total phosphorus were found. These findings suggest that the variables size and biomass of major zooplankton groups should always be considered simultaneously in order to assess impacts caused by eutrophication on the structure of zooplankton.

Haemoproteusinfected birds have increased lifetime reproductive success

Parasitology ◽  
2015 ◽  
Vol 142 (8) ◽  
pp. 1033-1043 ◽  
Author(s):  
M. ZYLBERBERG ◽  
E. P. DERRYBERRY ◽  
C. W. BREUNER ◽  
E. A. MACDOUGALL-SHACKLETON ◽  
J. M. CORNELIUS ◽  
...  
Keyword(s):  
Reproductive Success ◽  
Lifetime Reproductive Success ◽  
Parasitic Infections ◽  
Host Fitness ◽  
Return Rates ◽  
Long Term Study ◽  
In The Wild ◽  
The Impact ◽  
The Relationship

SUMMARYThe impact of haematozoan infection on host fitness has received substantial attention since Hamilton and Zuk posited that parasites are important drivers of sexual selection. However, short-term studies testing the assumption that these parasites consistently reduce host fitness in the wild have produced contradictory results. To address this complex issue, we conducted a long-term study examining the relationship between naturally occurring infection withHaemoproteusandPlasmodium, and lifetime reproductive success and survival of Mountain White-crowned Sparrows. Specifically, we tested the hypothesis that birds infected with haematozoan parasites have reduced survival (as determined by overwinter return rates) and reproductive success. Contrary to expectation, there was no relationship betweenHaemoproteusandPlasmodiuminfection and reproduction or survival in males, nor was there a relationship betweenPlasmodiuminfection and reproduction in females. Interestingly,Haemoproteus-infected females had significantly higher overwinter return rates and these females fledged more than twice as many chicks during their lifetimes as did uninfected females. We discuss the impact of parasitic infections on host fitness in light of these findings and suggest that, in the case of less virulent pathogens, investment in excessive immune defence may decrease lifetime reproduction.

Long-term study on the impact of temperature on enhanced biological phosphorus and nitrogen removal in membrane bioreactor

2015 ◽  
Vol 84 ◽  
pp. 8-17 ◽  
Author(s):  
N. Sayi-Ucar ◽  
M. Sarioglu ◽  
G. Insel ◽  
E.U. Cokgor ◽  
D. Orhon ◽  
...  
Keyword(s):  
Nitrogen Removal ◽  
Membrane Bioreactor ◽  
Term Study ◽  
Long Term Study ◽  
The Impact ◽  
Biological Phosphorus

scholarly journals Data Warehouse Design to Support Customer Relationship Management Analyses

2009 ◽  
pp. 702-724
Author(s):  
Colleen Cunningham ◽  
Il-Yeol Song ◽  
Peter P. Chen
Keyword(s):  
Data Warehouse ◽  
Data Warehousing ◽  
Customer Relationship ◽  
Data Warehouses ◽  
Design Decisions ◽  
Long Term Study ◽  
Percent Success ◽  
The Impact

CRM is a strategy that integrates concepts of knowledge management, data mining, and data warehousing in order to support an organization’s decision-making process to retain long-term and profitable relationships with its customers. This research is part of a long-term study to examine systematically CRM factors that affect design decisions for CRM data warehouses in order to build a taxonomy of CRM analyses and to determine the impact of those analyses on CRM data warehousing design decisions. This article presents the design implications that CRM poses to data warehousing and then proposes a robust multidimensional starter model that supports CRM analyses. Additional research contributions include the introduction of two new measures, percent success ratio and CRM suitability ratio by which CRM models can be evaluated, the identification of and classification of CRM queries, and a preliminary heuristic for designing data warehouses to support CRM analyses.

scholarly journals Small Reservoir Impact on Simulated Watershed-Scale Nutrient Yield

2007 ◽  
Vol 2007 ◽  
pp. 1-4 ◽  
Author(s):  
Shane J. Prochnow ◽  
Joseph D. White ◽  
Thad Scott ◽  
Christopher Filstrup
Keyword(s):  
Total Phosphorus ◽  
Nutrient Loading ◽  
Assessment Tool ◽  
Agricultural Runoff ◽  
Surface Flow ◽  
Long Term Storage ◽  
Nutrient Yield ◽  
Potential Strategy ◽  
The Impact

The soil and water assessment tool (SWAT) is used to assess the influence of small upland reservoirs (PL566) on watershed nutrient yield. SWAT simulates the impact of collectively increasing and decreasing PL566 magnitudes (size parameters) on the watershed. Totally removing PL566 reservoirs results in a 100%increase in total phosphorus and an 82%increase in total nitrogen, while a total maximum daily load (TMDL) calling for a 50%reduction in total phosphorus can be achieved with a 500%increase in the magnitude of PL566s in the watershed. PL566 reservoirs capture agriculture pollution in surface flow, providing long-term storage of these constituents when they settle to the reservoir beds. A potential strategy to reduce future downstream nutrient loading is to enhance or construct new PL566 reservoirs in the upper basin to better capture agricultural runoff.

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