scholarly journals Spatial distribution and diversity of phytoplankton community in Eastern Obolo River Estuary, Niger Delta

2018 ◽  
Vol 9 (1) ◽  
pp. 1-14 ◽  
Author(s):  
K. S. Effiong ◽  
A. I. Inyang ◽  
U.U. Robert
Keyword(s):  
Spatial Distribution ◽  
Niger Delta ◽  
Phytoplankton Community ◽  
River Estuary

scholarly journals Spatial and Temporal Variability of Soil Salinity in the Yangtze River Estuary Using Electromagnetic Induction

2021 ◽  
Vol 13 (10) ◽  
pp. 1875
Author(s):  
Wenping Xie ◽  
Jingsong Yang ◽  
Rongjiang Yao ◽  
Xiangping Wang
Keyword(s):  
Electrical Conductivity ◽  
Spatial Distribution ◽  
Soil Salinity ◽  
Yangtze River ◽  
Laboratory Data ◽  
River Estuary ◽  
Yangtze River Estuary ◽  
Soil Electrical Conductivity ◽  
The Yangtze River ◽  
The Yangtze River Estuary

Soil salt-water dynamics in the Yangtze River Estuary (YRE) is complex and soil salinity is an obstacle to regional agricultural production and the ecological environment in the YRE. Runoff into the sea is reduced during the impoundment period as the result of the water-storing process of the Three Gorges Reservoir (TGR) in the upper reaches of the Yangtze River, which causes serious seawater intrusion. Soil salinity is a problem due to shallow and saline groundwater under serious seawater intrusion in the YRE. In this research, we focused on the temporal variation and spatial distribution characteristics of soil salinity in the YRE using geostatistics combined with proximally sensed information obtained by an electromagnetic induction (EM) survey method in typical years under the impoundment of the TGR. The EM survey with proximal sensing method was applied to perform soil salinity survey in field in the Yangtze River Estuary, allowing quick determination and quantitative assessment of spatial and temporal variation of soil salinity from 2006 to 2017. We developed regional soil salinity survey and mapping by coupling limited laboratory data with proximal sensed data obtained from EM. We interpreted the soil electrical conductivity by constructing a linear model between the apparent electrical conductivity data measured by an EM 38 device and the soil electrical conductivity (EC) of soil samples measured in laboratory. Then, soil electrical conductivity was converted to soil salt content (soil salinity g kg−1) through established linear regression model based on the laboratory data of soil salinity and soil EC. Semivariograms of regional soil salinity in the survey years were fitted and ordinary kriging interpolation was applied in interpolation and mapping of regional soil salinity. The cross-validation results showed that the prediction results were acceptable. The soil salinity distribution under different survey years was presented and the area of salt affected soil was calculated using geostatistics method. The results of spatial distribution of soil salinity showed that soil salinity near the riverbanks and coastlines was higher than that of inland. The spatial distribution of groundwater depth and salinity revealed that shallow groundwater and high groundwater salinity influenced the spatial distribution characteristics of soil salinity. Under long-term impoundment of the Three Gorges Reservoir, the variation of soil salinity in different hydrological years was analyzed. Results showed that the area affected by soil salinity gradually increased in different hydrological year types under the impoundment of the TGR.

scholarly journals DIVERSIDADE E DISTRIBUIÇÃO ESPACIAL DE BROMELIÁCEAS EPIFÍTICAS DO ALTÍSSIMO RIO TIBAGI – PARANÁ – BRASIL

FLORESTA ◽  
2010 ◽  
Vol 40 (1) ◽  
Author(s):  
Annete Bonnet ◽  
Gustavo Ribas Curcio ◽  
Franklin Galvão ◽  
Carina Kozera
Keyword(s):  
Spatial Distribution ◽  
River Estuary ◽  
Horizontal Distribution ◽  
Variable Number ◽  
Climatic Factor ◽  
Atmospheric Humidity ◽  
Floristic Survey ◽  
Microclimatic Conditions ◽  
Definition Of ◽  
Epiphytic Bromeliads

O presente estudo teve como objetivo caracterizar a diversidade e a distribuição espacial das bromeliáceas epifíticas na região do altíssimo rio Tibagi, considerando os fatores geomorfológicos, pedológicos, climáticos e vegetacionais. A avaliação fitossociológica das bromeliáceas foi realizada mediante instalação de parcelas em número variável nas três áreas de estudo. O levantamento florístico foi complementado por observações nas áreas adjacentes às parcelas, respeitando a compartimentação geomorfológica, pedológica e vegetacional. Foram registradas onze espécies de bromeliáceas no total, tendo sido sete delas observadas na área da cabeceira do rio Tibagi, oito no cânion e nove na floresta da foz do rio Bugio. A riqueza foi relacionada, principalmente, com as condições macro e microclimáticas. A umidade fornecida pelas nuvens e chuvas formadas na cuesta do segundo planalto, assim como, em microescala, a umidade atmosférica gerada pelas cachoeiras existentes no cânion e originada da evaporação da água dos Organossolos, é o fator climático fundamental na definição dos padrões encontrados. Considerando a distribuição horizontal das espécies, a diminuição de bromeliáceas da porção mais próxima ao canal para a mais distante está atrelada ao gradiente microclimático, formado pela redução em umidade relativa associada à diminuição em luminosidade. Palavras-chave: Bromeliáceas; distribuição espacial; umidade; rio Tibagi.   Abstract Diversity and spatial distribution of epiphytic bromeliads of the high Tibagi river, Paraná, Brazil. The present study aims to characterize the diversity and the spatial distribution of epiphytic bromeliads on the region of the high Tibagi river, considering geomorphologic, pedologic, climatic and vegetacional factors. The phytossociological evaluation was achieved with installation of variable number of plots in the three study areas. The floristic survey was complemented by observations in adjacent areas, respecting the geomorphologic, pedologic and vegetacional compartimentation. Eleven bromeliad species were found in total, being seven species in headwater of Tibagi river area, eight in canyon area and nine in the forest of the Bugio river estuary. The richness was related, mainly, with the macro and microclimatic conditions. The humidity supplied by clouds and rains formed in the cuesta of the second platean, as will as, in microscale, the atmospheric humidity generated by canyons waterfalls and originated of the Organossolos water, is the fundamental climatic factor in the definition of the found standards. Considering the species horizontal distribution, the bromeliads reduction of the closer portion to the stream to the most distant ones is related to the microclimatic gradient, formed by the decreasing of relative humidity associated with luminosity.Keywords: Bromeliads; spatial distribution; humidity; Tibagi river.

scholarly journals Phytoplankton Dynamics in the Middle Adriatic Estuary, with a Focus on the Potentially Toxic Genus Pseudo-nitzschia

2020 ◽  
Vol 8 (8) ◽  
pp. 608
Author(s):  
Jasna Arapov ◽  
Mia Bužančić ◽  
Sanda Skejić ◽  
Jelena Mandić ◽  
Ana Bakrač ◽  
...  
Keyword(s):  
Domoic Acid ◽  
Phytoplankton Community ◽  
River Estuary ◽  
Environmental Parameters ◽  
Late Summer ◽  
Diatom Genus ◽  
Human Intoxication ◽  
Stratified Estuary ◽  
Special Environment ◽  
Variable Layer

The Krka River estuary is a karstic, permanently stratified estuary due to the strong freshwater inflow. It is a special environment in which to study the phytoplankton community, especially because this area is an important aquaculture site. Among other potentially toxic phytoplankton species, the diatom genus Pseudo-nitzschia occurs frequently and is a potential source of domoic acid (DA), causing shellfish toxicity and human intoxication. The main objective was to examine the dynamics of the phytoplankton community and, in particular, the genus Pseudo-nitzschia in the upper part of the Krka estuary, through monthly sampling over two years. The phytoplankton community was analysed using light microscopy and scanning electron microscopy to determine the diversity of Pseudo-nitzschia species and characterise the environmental parameters associated with a high abundance of Pseudo-nitzschia species. Seven Pseudo-nitzschia species were identified in the investigation, with higher frequencies and abundances in the less variable layer, at a 7 m depth. Blooms of Pseudo-nitzschia were noted in the late summer/early autumn, dominated by P. delicatissima/arenysensis. Winter assemblages were characterised by P. pseudodelicatissima/cuspidata, P. calliantha, and P. subfraudulenta, and were associated with domoic acid occurrence in shellfish.

Nutrient limitation of phytoplankton in the upper Swan River estuary, Western Australia

1996 ◽  
Vol 47 (4) ◽  
pp. 659 ◽  
Author(s):  
PA Thompson ◽  
W Hosja
Keyword(s):  
Nutrient Limitation ◽  
Chlorophyll A ◽  
Phytoplankton Community ◽  
River Estuary ◽  
Early Summer ◽  
Phosphate Silicate ◽  
Cell Densities ◽  
And Control ◽  
Swan River ◽  
Second Peak

During 1993-94 the phytoplankton community in the upper Swan River estuary had a peak chlorophyll a concentration of 57 mg m-3 during early summer (December 1993) and a second peak of 35 mg m-3 during late autumn (May 1994). Mid summer was characterized by low cell densities and low chlorophyll a concentrations. The potential of the phytoplankton community for nutrient limitation was assessed with dilution bioassays given nutrient mixes deficient in one of the following: nitrogen, phosphate, silicate, iron, trace metals, chelators, or vitamins. During the mid-summer period of low phytoplankton abundance, nitrogen was the nutrient with the greatest potential to limit algal biomass. During mid summer, ambient N:P ratios tended to be near unity and bioassays indicated that the available pool of N was up to 20 times more limiting to biomass development than was available P. Also during mid summer, bioassay treatments given no nitrogen and control treatments given no nutrients showed little growth, reaching chlorophyll a concentrations -1/30th of those given a full suite of nutrients. Chlorophyll a concentrations in the bioassay control treatments given no nutrients were correlated (r2 = 0.74) with measured surface nitrate concentrations; this suggested that nitrate inputs may be a major factor controlling phytoplankton biomass in this ecosystem. The correlation between surface nitrate concentration and rainfall (r2 = 0.69) further suggests that rainfall may be the most important mechanism supplying nitrate to the surface waters of this estuary.

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