Nutrients in the sediments of a tropical north-eastern Australian estuary, catchment and nearshore coastal zone

1993 ◽  
Vol 44 (6) ◽  
pp. 845 ◽  
Author(s):  
B Eyre
Keyword(s):  
Seasonal Variability ◽  
River Estuary ◽  
Agricultural Practices ◽  
Distribution Patterns ◽  
Phosphorus Concentration ◽  
Wet Season ◽  
Sediment Phosphorus ◽  
Anthropogenic Inputs ◽  
Nitrogen Concentrations ◽  
Australian Estuary

The distribution, transport, accumulation, modification and seasonal variability of sediment nutrients was studied in the Moresby River Estuary, catchment and nearshore zone. Phosphorus was examined by using a quick and analytically simple three-stage sequential extraction scheme that allows for natural environmental processes and differences in bio- availability. Elevated sediment phosphorus concentrations in the catchment during the wet season reflect the application of phosphate fertilizers to the agricultural lands that dominate the catchment. It is suggested that the dispersion and seasonal variability in concentration and distribution of phosphorus are controlled by sedimentary processes (e.g. erosion and transport of sediment) that are intimately linked to hydrological conditions. The physical processes that operate on a time-scale of hours (e.g, tidal currents) dominate sediment phosphorus concentration in the estuary and preclude chemical and biological equilibrium from becoming established in the sediment phosphorus along the length of the estuary. Elevated sediment total Kjeldahl nitrogen concentrations in the catchment reflect the application of nitrogenous fertilizers (mainly urea). The nitrogen distribution patterns differ from those of phosphorus, suggesting that different processes operate to control sediment nitrogen and sediment phosphorus. Low phosphorus concentrations in the sediments suggest that agricultural practices in the catchment and associated anthropogenic inputs are having little, if any, impact on the catchment, river and estuary.

Dynamics of the Swan River Estuary: The seasonal variability

1996 ◽  
Vol 47 (3) ◽  
pp. 517 ◽  
Author(s):  
R Stephens ◽  
J Imberger
Keyword(s):  
Seasonal Variability ◽  
Nutrient Loading ◽  
River Estuary ◽  
Estuarine System ◽  
Fluid Exchange ◽  
Salt Wedge ◽  
Wedge Condition ◽  
Intensive Investigation ◽  
Australian Estuary ◽  
Swan River

The Swan River is a south-westem Australian estuary that undergoes a distinct seasonal stratification cycle. Motivated by the increasing nutrient loading of the estuarine system, an intensive investigation into the hydrodynamics was performed with the aim of understanding the physical processes responsible for transport within the estuary. The seasonal variability of the stratification was documented with regular conductivity-temperature-depth-dissolved oxygen transects that were used to piece together an overview of the dynamics. The estuarine dynamics were classified into a gravitational overflow produced by the winter rains, a salt wedge condition governed by both discharge and topographic constraints, tidal dynamics that influence the degree of flushing, and the roles of two sills that control fluid exchange between the estuary and the ocean and control the propagation of the salt wedge and the gravitational overflow.

scholarly journals An update on the distribution of Glossina (tsetse flies) at the wildlife-human-livestock interface of Akagera National Park, Rwanda

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Richard S. Gashururu ◽  
Samuel M. Githigia ◽  
Methode N. Gasana ◽  
Richard Habimana ◽  
Ndichu Maingi ◽  
...  
Keyword(s):  
National Park ◽  
Control Strategies ◽  
Glossina Pallidipes ◽  
Distribution Patterns ◽  
Tsetse Flies ◽  
Wet Season ◽  
Chi Square ◽  
Large Numbers ◽  
Surrounding Areas ◽  
Biconical Traps

Abstract Background Glossina (tsetse flies) biologically transmit trypanosomes that infect both humans and animals. Knowledge of their distribution patterns is a key element to better understand the transmission dynamics of trypanosomosis. Tsetse distribution in Rwanda has not been well enough documented, and little is known on their current distribution. This study determined the current spatial distribution, abundance, diversity, and seasonal variations of tsetse flies in and around the Akagera National Park. Methods A longitudinal stratified sampling following the seasons was used. Biconical traps were deployed in 55 sites for 6 consecutive days of each study month from May 2018 to June 2019 and emptied every 48 h. Flies were identified using FAO keys, and the number of flies per trap day (FTD) was used to determine the apparent density. Pearson chi-square (χ2) and parametrical tests (t-test and ANOVA) were used to determine the variations between the variables. The significance (p < 0.05) at 95% confidence interval was considered. Logistic regression was used to determine the association between tsetse occurrence and the associated predictors. Results A total of 39,516 tsetse flies were collected, of which 73.4 and 26.6% were from inside Akagera NP and the interface area, respectively. Female flies accounted for 61.3 while 38.7% were males. Two species were identified, i.e. G. pallidipes [n = 29,121, 7.4 flies/trap/day (FTD)] and G. morsitans centralis (n = 10,395; 2.6 FTD). The statistical difference in numbers was significant between the two species (p = 0.000). The flies were more abundant during the wet season (15.8 FTD) than the dry season (4.2 FTD). Large numbers of flies were trapped around the swamp areas (69.1 FTD) inside the park and in Nyagatare District (11.2 FTD) at the interface. Glossina morsitans was 0.218 times less likely to occur outside the park. The chance of co-existing between the two species reduced outside the protected area (0.021 times). Conclusions The occurrence of Glossina seems to be limited to the protected Akagera NP and a narrow band of its surrounding areas. This finding will be crucial to design appropriate control strategies. Glossina pallidipes was found in higher numbers and therefore is conceivably the most important vector of trypanosomosis. Regional coordinated control and regular monitoring of Glossina distribution are recommended. Graphic Abstract

Nitrogen cycling in a Venezuelan tropical seasonally flooded forest: soil nitrogen mineralization and nitrification

1994 ◽  
Vol 10 (3) ◽  
pp. 399-416 ◽  
Author(s):  
Barrios E. ◽  
Herrera R.
Keyword(s):  
Soil Nitrogen ◽  
Nitrogen Availability ◽  
Inorganic Nitrogen ◽  
Nitrogen Concentration ◽  
Ammonium Nitrogen ◽  
Wet Season ◽  
Flooded Forest ◽  
Nitrogen Concentrations ◽  
Minimum Stress ◽  
Seasonally Flooded

ABSTRACTSeasonally flooded forests represent a transition between terrestrial and aquatic ecosystems. The Mapire river, a tributary of the Orinoco river, floods its surrounding forests during the wet season (May–December). The soils are very acid and the total nitrogen concentration (0.1%) is only half that found in nearby soils flooded by Orinoco waters. Ammonium-nitrogen predominates in the soil during the flooded period while nitrate-nitrogen concentrations are higher in the dry period. Wide fluctuations in the inorganic nitrogen fractions did not considerably affect the annual course of soil nitrogen.The predominance of mineralization versus nitrification (56 and 5 μgsoil month−1respectively) and possibly the synchronization of nitrogen availability with plant demand could be considered as nitrogen conserving mechanisms.In synchrony with the hydrologic cycle, the seasonally flooded forest studied shows a nitrogencycle where inputs and accumulation are maximized when the system is under minimum stress (dry season). During flooding, the system enters a period of dormancy making minimal use of nutrient and energy to avoid or tolerate anaerobiosis.

scholarly journals Shifts of Bacterioplankton Metabolic Profiles along the Salinity Gradient in a Subtropical Estuary

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Hidetoshi Urakawa ◽  
Jaffar Ali ◽  
Rheannon D. J. Ketover ◽  
Spencer D. Talmage ◽  
Juan C. Garcia ◽  
...  
Keyword(s):  
Salinity Gradient ◽  
Water Discharge ◽  
River Estuary ◽  
Metabolic Profiles ◽  
Wet Season ◽  
Biolog Ecoplates ◽  
Utilization Patterns ◽  
Subtropical Estuary ◽  
Discharge Patterns ◽  
Bacterioplankton Communities

Understanding the biodegradation potential of river bacterioplankton communities is crucial for watershed management. We investigated the shifts in bacterioplankton metabolic profiles along the salinity gradient of the Caloosahatchee River Estuary, Florida. The carbon source utilization patterns of river bacterioplankton communities were determined by using Biolog EcoPlates. The number of utilized substrates was generally high in the upstream freshwater dominated zone and low in the downstream zone, suggesting a shift in metabolic profiles among bacterioplankton assemblages along the estuarine gradient. The prokaryotic cell numbers also decreased along the estuarine salinity gradient. Seasonal and site-specific differences were found in the numbers of utilized substrates, which were similar in summer and fall (wet season) and winter and spring (dry season). Bacterioplankton assemblages in summer and fall showed more versatile substrate utilization patterns than those of winter and spring communities. Therefore, our data suggest that microbial metabolic patterns in the subtropical estuary are likely influenced by the water discharge patterns created by dry and wet seasons along the salinity gradient.

scholarly journals THE IMPACT OF AGRICULTURAL PRACTICES ON GROUNDWATER QUALITY: A CRITICAL STUDY BASED ON NAVITHANVELI DS DIVISION IN AMPARA DISTRICT IN SRI LANKA

2017 ◽  
Vol 5 (9) ◽  
pp. 36-43 ◽  
Author(s):  
Nijamir K ◽  
Kaleel MIM
Keyword(s):  
Groundwater Quality ◽  
Groundwater Contamination ◽  
Agricultural Practices ◽  
Primary Objective ◽  
Phosphate Concentration ◽  
Critical Study ◽  
Wet Season ◽  
Traditional Agricultural Practices ◽  
The Impact ◽  
Chemical Testing

This study was proceeded to identify the groundwater contamination based on the primary and secondary objectives. The primary objective is “identifying the groundwater contamination by the utilization of agro-chemicals, and the secondary objectives are “finding out Nitrate and Phosphate concentration to identify the Groundwater quality depletion by the chemical testing, identifying adverse agricultural practices and to make awareness among agro-chemical users by inducing traditional agricultural practices and recommend favorable solutions to the groundwater oriented problems in study area. For this study five parameters such as NO3, PO4, EC, pH and Turbidity were analyzed. All the parameters varied from wet season to dry season. Particularly, NO3 and PO4 concentration has deviated from both seasons. The conclusion of the study is that the application of the agrochemicals has impacted on the groundwater quality drastically.

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