Roach K.A.,University of Quebec at Trois - Rivieres |
Winemiller K.O.,University of Quebec at Trois - Rivieres |
Davis S.E.,Everglades Foundation
Freshwater Biology | Year: 2014
Summary: Comparative research and generalisations in lotic ecology are challenged by the dynamic hydrology of fluvial systems. The aim of this study was to understand more fully how factors such as light, nutrients and flow can predict variation in autochthonous production and algal biomass. We measured seasonal changes in percent bankfull discharge, inorganic nutrient concentrations, turbidity, instream primary production, respiration and algal biomass in the littoral zone of five floodplain rivers in one temperate and two tropical regions of the Western Hemisphere. The Brazos, Guadalupe and Neches rivers are in Texas, while the Tambopata River is in Peru and the Cinaruco River in Venezuela. Our study rivers represented a range of hydrological regimes, turbidity levels and nutrient concentrations. Flooding patterns were more seasonal in the tropical rivers than in the (temperate) Texas rivers. Inorganic nutrient concentrations were higher in the temperate rivers, probably due to anthropogenic nutrient loading. Turbidity was higher following periods of high flow in the Brazos, Tambopata and Guadalupe rivers than in the Neches and Cinaruco rivers. Littoral zones in the sediment-laden Brazos and Tambopata rivers became heterotrophic during periods of high discharge, while littoral zones in the Guadalupe, Neches and Cinaruco rivers were consistently autotrophic. Regression tree analysis suggested that algal production and biomass in the water column responded more strongly to seasonal changes in nutrients and temperature than to turbidity, while benthic algae responded more strongly to turbidity. Our findings suggest that during periods of high flow and turbidity in rivers containing fine sediments, autochthonous production is limited and terrestrial-based organic matter may assume greater importance in the aquatic food web. © 2014 John Wiley & Sons Ltd.
Koch G.R.,Florida International University |
Childers D.L.,Arizona State University |
Staehr P.A.,University of Aarhus |
Price R.M.,Florida International University |
And 2 more authors.
Estuaries and Coasts | Year: 2012
Using high-resolution measures of aquatic ecosystem metabolism and water quality, we investigated the importance of hydrological inputs of phosphorus (P) on ecosystem dynamics in the oligotrophic, P-limited coastal Everglades. Due to low nutrient status and relatively large inputs of terrestrial organic matter, we hypothesized that the ponds in this region would be strongly net heterotrophic and that pond gross primary production (GPP) and respiration (R) would be the greatest during the "dry," euhaline estuarine season that coincides with increased P availability. Results indicated that metabolism rates were consistently associated with elevated upstream total phosphorus and salinity concentrations. Pulses in aquatic metabolism rates were coupled to the timing of P supply from groundwater upwelling as well as a potential suite of hydrobiogeochemical interactions. We provide evidence that freshwater discharge has observable impacts on aquatic ecosystem function in the oligotrophic estuaries of the Florida Everglades by controlling the availability of P to the ecosystem. Future water management decisions in South Florida must include the impact of changes in water delivery on downstream estuaries. © 2011 Coastal and Estuarine Research Federation.
Assegid Y.,Florida International University |
Melesse A.M.,Florida International University |
Naja G.M.,Everglades Foundation
Hydrological Processes | Year: 2015
Fluctuations of groundwater levels were used to predict soluble phosphorus concentrations. In-situ observations showed a decrease in soluble phosphorus during groundwater recession and an increase with groundwater rise. A spatial analysis of the simulated soluble phosphorus and groundwater levels indicated similarity of patterns (spatial correlation) 99% of the time. A geographically weighted multivariate analysis of soluble phosphorus using groundwater levels, phosphorus levels of the Kissimmee River, and distance from the Kissimmee River as predictors showed a goodness of fit (R2) ranging from 0.2 to 0.7. Results indicated no significant difference between the simulated and observed soluble phosphorus levels at a p value of 0.01. Among the parameters, the groundwater level explained 70% of the soluble phosphorus variability. The distance to surface waterbodies and their phosphorus levels had significant weights only within a 5-km range from the waterbody. A model generalization is further required to simulate the spatiotemporal groundwater-phosphorus dynamics over meaningful temporal ranges - at least for 3 to 5years - for conclusiveness of the data. © 2014 John Wiley and Sons, Ltd.
Liu C.,Florida International University |
Balsamo V.,Simon Bolivar University of Venezuela |
Sun D.,Florida International University |
Naja M.,Everglades Foundation |
And 3 more authors.
Biosensors and Bioelectronics | Year: 2012
A self-assembled 3D hydrogel-nanoparticle composite integrated surface plasmon resonance (SPR) sensor is reported here. The novel assembled substrate was developed by means of a surface mediated radical co-polymerization process to obtain a highly sensitive hydrogel-based thin film that possesses specific binding sites for target analytes. Initially, amino group modified gold nanoparticles (AuNPs) were covalently linked to acrylic acid monomer. Following this, N-isopropylacrylamide (NIPAAm) and AuNPs linked acrylic acid (AAc) monomers were randomly co-polymerized by the "grafting from" method in the presence of initiator and crosslinker onto the sensing surface. Surface charecterization techniques were utilized to evaluate the thickness and composition of the hydrogel-nanoparticle film. The sensing platform was employed to study the binding kinetics and conformational changes of the ArsA ATPase as a consequence of binding trivalent arsenicals under a variety of conditions. ArsA, the catalytic subunit of the ArsAB arsenite (As(III)) translocating ATPase, is one of the five proteins encoded by the arsenical resistance (ars) operon of plasmid R773 in cells of Escherichia coli, that confers resistance to trivalent and pentavalent salts of the metalloid arsenic. SPR measurements indicate that the 3D hydrogel-nanoparticle coated sensors exhibited a higher sensitivity than that of the 2D AuNPs decorated sensors. Binding of As(III) to ArsA is greatly facilitated by the presence of magnesium ion and ATP. © 2012 Elsevier B.V.
Briceno H.,Florida International University |
Miller G.,Everglades Foundation |
Davis S.E.,Everglades Foundation
Wetlands | Year: 2014
Florida Bay is more saline than it was historically, and reduced freshwater flows may lead to more phosphorus inputs to the mangrove ecotone from the marine endmember. This is important given plans to restore freshwater flow into eastern Florida Bay. We investigated the relationships between salinity, nutrients, and hydrologic variables in the mangrove ecotone of Taylor Slough. We expected that total phosphorus (TP) would increase with salinity, reflecting a downstream marine source, while total nitrogen (TN) would increase with flow in the mangrove ecotone. Despite expectations of increased flows improving the ecological health of lower Taylor Slough and Florida Bay, total nitrogen (TN) and total phosphorus (TP) dynamics may shift in response to new conditions of flow and salinity as well as organic carbon, N, and P availability. Our results showed that TP concentrations are more discharge-driven while TN is more variable and potentially derived from different sources along the flow path from the freshwater Everglades marshes to Florida Bay. Increased flow of freshwater through Taylor Slough will likely decrease TP concentrations in this historically oligotrophic and P-limited ecosystem. However, more studies along the mangrove ecotone is needed to understand how increased flows will affect nitrogen dynamics relative to phosphorus. © Society of Wetland Scientists 2013.