How do abiotic environmental variables shape benthic diatom assemblages in subtropical streams?

2017 ◽  
Vol 68 (5) ◽  
pp. 863 ◽  
Author(s):  
Wing Ying Tsoi ◽  
Wade L. Hadwen ◽  
F. Sheldon
Keyword(s):  
Environmental Gradients ◽  
Critical Role ◽  
Benthic Diatom ◽  
Base Flow ◽  
Diatom Assemblage ◽  
Environmental Drivers ◽  
Diatom Assemblages ◽  
Physical And Chemical Variables ◽  
Ecological Importance ◽  
Physical And Chemical

Diatoms (Division Bacillariophyta) commonly dominate benthic algal communities in upland streams and are the major primary producers that sit at the base of food webs. Given their ecological importance, the aim of the present study was to investigate the spatial patterns of freshwater biofilm biomass and diatom assemblage composition in response to differences in physical and chemical variables in the Bremer, Logan and Albert catchments in south-east Queensland. Patterns in benthic diatom assemblage structure were examined during base flow conditions and the focus was on relating the spatial hierarchical interrelationships among ultimate (i.e. catchments and geology) and proximate (i.e. flow, nutrients, light, conductivity, pH and turbidity) environmental drivers. The spatial difference observed in the benthic diatom assemblages was predominantly driven by proximate environmental drivers, which, in turn, were affected by ultimate drivers. Flow played a critical role in controlling both biofilm biomass and affecting the occurrence of diatom taxa. Nutrients and light also played roles as limiting resources structuring biofilm biomass and the relative abundance of diatoms. Diatom growth form, cell size and attachment mode can be used to create a more quantitative and predictive approach to establishing relationships between diatoms and environmental gradients.

scholarly journals Epipsammic diatoms in streams influenced by urban pollution, São Carlos, SP, Brazil

2010 ◽  
Vol 70 (4) ◽  
pp. 920-930 ◽  
Author(s):  
T. Bere ◽  
JG. Tundisi
Keyword(s):  
Environmental Gradients ◽  
Urban Pollution ◽  
Base Flow ◽  
Stepwise Multiple Regression ◽  
Study Region ◽  
Diatom Communities ◽  
Physical And Chemical Variables ◽  
Forward Stepwise ◽  
Lotic Environments ◽  
Physical And Chemical

Epipsammic diatoms have important implications for ecosystem processes in lotic environments. Most of the studies on benthic diatoms concentrate on epilithic diatoms and very little is known about epipsammic diatoms. The objective of this study was to assess epipsammic diatom communities in streams in relation to environmental conditions. Epipsammic diatoms and water quality sampling was done at 7 sites during summer base flow period (2008). Forward stepwise multiple regression and canonical correspondence analysis (CCA) were used to determine environmental gradients along which species vary with physical and chemical variables. A total of 112 diatom species distributed among 44 genera were recorded. Altitude and the process of eutrophication played a significant role in structuring diatom communities in the study region.

Effects of Didymosphenia geminata blooms on benthic diatom assemblages in the Restigouche River Watershed, eastern Canada

Botany ◽  
2015 ◽  
Vol 93 (5) ◽  
pp. 317-323 ◽  
Author(s):  
Branaavan Sivarajah ◽  
Joshua Kurek ◽  
Kathleen M. Rühland ◽  
John P. Smol
Keyword(s):  
Benthic Diatom ◽  
Diatom Assemblage ◽  
Diatom Assemblages ◽  
Eastern Canada ◽  
Didymosphenia Geminata ◽  
Assemblage Composition ◽  
River Watershed ◽  
And Function ◽  
Riverine Systems ◽  
The Impact

Nuisance Didymosphenia geminata (Lyngbye) M. Schmidt (didymo) blooms were first reported in 2006 from the Restigouche River Watershed (RRW), eastern Canada. Although government agencies and recreational users are concerned about these blooms, little is known about the impact on biota and (or) the structure and function of the relatively pristine riverine systems of the RRW. Here, we assess whether didymo blooms affect overall benthic diatom assemblage composition by examining epilithic samples from middle stretches of the Patapedia and Upsalquitch rivers. Significant (albeit minor) differences (P < 0.05) in diatom assemblage composition between sites, with and without didymo blooms, were only observed from the Patapedia River. Rarefied diatom species diversity (Hill’s N2) and rarefied richness did not differ significantly among sites, regardless of the presence or absence of blooms. Our data show that didymo blooms have minimal effect on benthic diatom assemblage composition in the RRW.

scholarly journals Limnological study of Piraquara river (Upper Iguaçu basin): spatiotemporal variation of physical and chemical variables and watershed zoning

2003 ◽  
Vol 46 (3) ◽  
pp. 383-394 ◽  
Author(s):  
Paulo Henrique C. Marques ◽  
Haydée Torres de Oliveira ◽  
Eunice da Costa Machado
Keyword(s):  
River Basin ◽  
Oxygen Demand ◽  
Principal Component ◽  
Serra Do Mar ◽  
Spatial Gradients ◽  
Water Composition ◽  
Physical And Chemical Variables ◽  
Nitrite Nitrate ◽  
Physical And Chemical ◽  
Iguaçu River

The Piraquara river basin (Upper Iguaçu River basin - Brazil) was studied as an ecological system throughout a complete seasonal cycle, comprising the rainy and dry season. Analyzes of 16 physical and chemical water variables (dissolved oxygen, biochemical oxygen demand, temperature, pH, conductivity, total nitrogen, total phosphorus, ortophosphates, nitrite, nitrate, ammonium, reagent silicate, total suspended solids, chlorophyll - a, flow velocity and depth) showed correlations between water composition and watershed physiographic features, and the Principal Component Analysis allowed to evidence spatial gradients and seasonal differences. The sampling points were clustered in patches with homogeneous behavior, according to ecologycal concepts: patch 1, with strong influence of Serra do Mar mountains; patch 2, medium course, under Piraquara Dam influence and patch 3, under wetlands influence. Two main factors of serial discontinuity were identified: the Piraquara dam effect and the influence of wetlands. The watershed zoning based on limnological characteristics seeks to subsidize research and biomonitoring for this public springs area.

scholarly journals Water quality and potamoplankton evaluation of the Nile River in Upper Egypt

2015 ◽  
Vol 27 (2) ◽  
pp. 171-190 ◽  
Author(s):  
Ahmed Mohamed El-Otify ◽  
Isaac Agaiby Iskaros
Keyword(s):  
Community Structure ◽  
Zooplankton Community ◽  
Water Level Fluctuations ◽  
Main Stream ◽  
Upper Egypt ◽  
Physical And Chemical Variables ◽  
Different Seasons ◽  
High Current Velocity ◽  
Major Nutrients ◽  
Physical And Chemical

Aim: The composition, abundance, community structure of potamoplankton and major physical and chemical variables of the Nile water in Upper Egypt were investigated to assess its status in different seasons during 2007.MethodsWater samples were collected seasonally during 2007 from six investigated sites from variable depths at levels of 0, 2.5 and 5 m. The area of this investigation is defined as the southern 120 Km of the main stream of the Nile in Upper Egypt (24° 04’ – 25° 00’ latitudes and 32° 51’ – 32° 54’ longitudes), downstream of Aswan Old Dam.ResultsAltogether, 121 potamoplankton species, of which 85 related to phytoplankton and 36 appertaining to zooplankton were recorded. Most numerous phytoplankton were Chlorophyceae (42 species) followed by Bacillariophyceae (30 species). Cyanobacteria and Dinophyceae were less numerous with only 11 and 2 species, respectively. Zooplankton species were mainly belonging to three systematic groups namely; Rotifera (24 species), Copepoda (3 species) and Cladocera (9 species). Besides, other rare zooplankton including Platyhelminthes, Nemata and Ciliophora were sparsely encountered. The main hydrological conditions characterizing the investigated area include water level fluctuations (˂82 - ˃85 m above sea level), relatively high current velocity (0.8 - 1.3 m sec–1) and disposal of wastewater. Plankton populations were variably but rather weakly dependent on the major nutrients due to their excessive availability in accessible form for uptake by the producers. For phytoplankton, the community structure was categorized in relation to temperature, pH, SO42– and Mg2+. For zooplankton, the community structure was categorized in relation to conductivity as well as Mg2+. Sampling intervals were inadequate to demonstrate the existing successional pattern of the Nile potamoplankton community. Alterations in the phytoplankton community structure accompanied changes in water temperature represented by the alternate dominance between diatoms and cyanobacteria, while zooplankton community was always dominated by rotifers. Phytoplankton populations were numerically more abundant in autumn and zooplankton peaked in spring.ConclusionsWastewater disposal restricted the abundance of the Nile zooplankton assemblages mainly due to the numerical decline of Rotifera and Cladocera. Otherwise, wastewater did not exert major limits for phytoplankton. The data obtained in this investigation will be crucial to understand potamoplankton regulation and contribute to the knowledge regarding the Limnology of the Nile basin.

scholarly journals Phytoplankton abundance, dominance and coexistence in an eutrophic reservoir in the state of Pernambuco, Northeast Brazil

2011 ◽  
Vol 83 (4) ◽  
pp. 1313-1326 ◽  
Author(s):  
Giulliari A. S. T. Lira ◽  
Elcida L. Araújo ◽  
Maria Do Carmo Bittencourt-Oliveira ◽  
Ariadne N. Moura
Keyword(s):  
Rainy Season ◽  
Phytoplankton Community ◽  
Dry Season ◽  
Cylindrospermopsis Raciborskii ◽  
Phytoplankton Abundance ◽  
Vertical Variation ◽  
Total Phytoplankton ◽  
Physical And Chemical Variables ◽  
Different Depths ◽  
Physical And Chemical

The present study reports the phytoplankton abundance, dominance and co-existence relationships in the eutrophic Carpina reservoir, Pernambuco, Brazil. Sampling was carried out at six different depths bimonthly at a single reservoir spanning two climatic periods: dry season (January, September, and November 2006) and rainy season (March, May, and July 2006). Density, abundance, dominance, specific diversity and equitability of the community were determined, along with chlorophyll a, and physical and chemical variables of the environment. Eight species were considered abundant, and their densities corresponded to more than 90% of the total phytoplankton community quantified. Cyanobacteria represented more than 80% of this density. Cylindrospermopsis raciborskii was the only dominant taxon in the dry season, and was co-dominant in the rainy season. C. raciborskii, Planktothrix agardhii and Geitlerinema amphibium had the greatest densities and lowest vertical variation coefficients. The statistical analysis indicated relationships with vertical and seasonal variations in the phytoplankton community and the following variables: total dissolved solids, water temperature, electrical conductivity and pH. The changes in the environmental variables were discrete and regulated by the establishment of precipitation however, they were able to promote vertical and seasonal instability in the structure of the phytoplankton community.

scholarly journals Environmental quality evaluation of lakes in the Rio Grande do Sul coastal plain

2007 ◽  
Vol 50 (4) ◽  
pp. 673-685 ◽  
Author(s):  
Catarina da Silva Pedrozo ◽  
Odete Rocha
Keyword(s):  
Environmental Quality ◽  
Sewage Treatment ◽  
Principal Component ◽  
Organic Pollution ◽  
Physical And Chemical Variables ◽  
Environmental Element ◽  
Different Characteristics ◽  
Physical And Chemical ◽  
The Town

The purpose of the present work was to evaluate the environmental quality of Marcelino, Pinguela, Peixoto, Palmital, Malvas and Do Passo lakes, interconnected by canals and located in the district of Osório, RS. In this context, 29 physical and chemical variables were analyzed with sampling carried out in January, May, July and October 1997 to verify the environmental quality of the system and the existence of a gradient of quality. Canonical Analysis was applied to the data of all environmental variables measured, and showed that the lakes had different characteristics as a consequence of the organic pollution received. Marcelino lake received continuous input of organic matter from the sewage treatment works in the town of Osório, whereas Peixoto, Pinguela, Palmital, Malvas and Do Passo lakes resembled other water bodies described in the region, not showing, so far, signs of degradation caused by the input of effluents. Principal Component Analysis selected environmental element were directly linked to organic pollution, that reflected sequential non-recent effects of contamination.

scholarly journals Predictive Models to Estimate Carbon Stocks in Agroforestry Systems

Forests ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1240
Author(s):  
Maria Fernanda Magioni Marçal ◽  
Zigomar Menezes de Souza ◽  
Rose Luiza Moraes Tavares ◽  
Camila Viana Vieira Farhate ◽  
Stanley Robson Medeiros Oliveira ◽  
...  
Keyword(s):  
Land Use ◽  
Random Forest ◽  
Carbon Stock ◽  
Agroforestry System ◽  
Agroforestry Systems ◽  
Forest Fragment ◽  
Random Forest Algorithm ◽  
Land Use Systems ◽  
Physical And Chemical Variables ◽  
Physical And Chemical

This study aims to assess the carbon stock in a pasture area and fragment of forest in natural regeneration, given the importance of agroforestry systems in mitigating gas emissions which contribute to the greenhouse effect, as well as promoting the maintenance of agricultural productivity. Our other goal was to predict the carbon stock, according to different land use systems, from physical and chemical soil variables using the Random Forest algorithm. We carried out our study at an Entisols Quartzipsamments area with a completely randomized experimental design: four treatments and six replites. The treatments consisted of the following: (i) an agroforestry system developed for livestock, (ii) an agroforestry system developed for fruit culture, (iii) a conventional pasture, and (iv) a forest fragment. Deformed and undeformed soil samples were collected in order to analyze their physical and chemical properties across two consecutive agricultural years. The response variable, carbon stock, was subjected to a boxplot analysis and all the databases were used for a predictive modeling which in turn used the Random Forest algorithm. Results led to the conclusion that the agroforestry systems developed both for fruit culture and livestock, are more efficient at stocking carbon in the soil than the pasture area and forest fragment undergoing natural regeneration. Nitrogen stock and land use systems are the most important variables to estimate carbon stock from the physical and chemical variables of soil using the Random Forest algorithm. The predictive models generated from the physical and chemical variables of soil, as well as the Random Forest algorithm, presented a high potential for predicting soil carbon stock and are sensitive to different land use systems.

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