The Experts below are selected from a list of 31125 Experts worldwide ranked by ideXlab platform
Wenzhao Liang - One of the best experts on this subject based on the ideXlab platform.
-
phytoplankton size structure in the western south china sea under the influence of a jet eddy system
Journal of Marine Systems, 2018Co-Authors: Wenzhao Liang, Danling Tang, Xin LuoAbstract:Abstract A northeastward jet in the western South China Sea (SCS) usually induces phytoplankton blooms during summertime. This jet is often sandwiched by a cyclonic eddy in the north and an anticyclonic eddy in the south. Using in situ and satellite data, the present study analyzes the combined impact of the northeastward jet and two eddies on the phytoplankton size structure (PSS) from August to September 2014. Generally, picophytoplankton is the major size fraction in surface Water, contributing 73% of the total chlorophyll a concentration. The data showed that a high chlorophyll a belt (av. 0.29 ± 0.18 μg L−1) with a large percentage of microphytoplankton (av. 14%) appeared in the northeastward jet. Meanwhile, similar chlorophyll a concentrations were observed in the cyclonic (av. 0.072 ± 0.019 μg L−1) and anticyclonic eddies (av. 0.087 ± 0.02 μg L−1), but microphytoplankton contributed 6.7% more in the anticyclonic eddy. Below the surface, however, the dominant size of phytoplankton switched from pico to nano and micro with increasing depth. In contrast to the observations at the surface, the jet and anticyclonic eddy presented a lower microphytoplankton contribution than the cyclonic eddy. Horizontally, advection of coastal Upwelling Water by the northeastward jet enhanced the growth of phytoplankton and influenced the surface PSS. Meanwhile, divergence/convergence in cyclonic/anticyclonic eddy interaction with the northeastward jet formed the high chlorophyll a belt at the edge of the eddy and increased the microphytoplankton contribution through Water mass transport and mixing. Nutrient supply and weakening of the light intensity below the surface layer synergistically influenced the concentration and size structure of phytoplankton in the cyclonic/anticyclonic eddies at different depths. Finally, this study proposed a ‘jet-eddy system’ to explain summer spatial characteristics of PSS in the western SCS. Source Water (riverine and coastal Upwelling Water) that feeds the ‘jet-eddy system’ is another key factor affecting phytoplankton biomass and its size structure.
David R Geist - One of the best experts on this subject based on the ideXlab platform.
-
physicochemical characteristics of the hyporheic zone affect redd site selection by chum salmon and fall chinook salmon in the columbia river
North American Journal of Fisheries Management, 2002Co-Authors: David R Geist, Timothy P Hanrahan, Evan V Arntzen, Geoffrey A Mcmichael, Christopher J Murray, Yiju ChienAbstract:Abstract Chum salmon Oncorhynchus keta and fall chinook salmon O. tshawytscha spawned at separate locations in a side channel near Ives Island, Washington, in the Columbia River downstream of Bonneville Dam. We hypothesized that measurements of Water depth, substrate size, and Water velocity would not sufficiently explain the separation in spawning areas and began a 2-year investigation of physicochemical characteristics of the hyporheic zone. We found that chum salmon spawned in Upwelling Water that was significantly warmer than the surrounding river Water. In contrast, fall chinook salmon constructed redds at downwelling sites, where there was no difference in temperature between the river and its bed. An understanding of the specific factors affecting chum salmon and fall chinook salmon redd site selection at Ives Island will be useful to resource managers attempting to maximize available salmonid spawning habitat within the constraints imposed by other Water resource needs.
-
hyporheic discharge of river Water into fall chinook salmon oncorhynchus tshawytscha spawning areas in the hanford reach columbia river
Canadian Journal of Fisheries and Aquatic Sciences, 2000Co-Authors: David R GeistAbstract:Fall chinook salmon (Oncorhynchus tshawytscha) spawned predominantly in areas of the Hanford Reach of the Columbia River where hyporheic Water discharged into the river channel. This Upwelling Water had a dissolved solids content (i.e., specific conductance) indicative of river Water and was presumed to have entered highly permeable riverbed substrate at locations upstream of the spawning areas. Hyporheic discharge zones composed of undiluted ground Water or areas with little or no Upwelling were not used by spawning salmon. Rates of Upwelling into spawning areas averaged 1,200 L?m-2?day-1 (95% C.I.= 784 to 1,665 L?m-2?day-1) as compared to approximately 500 L?m-2?day-1 (95% C.I.= 303 to 1,159 L?m-2?day-1) in non-spawning areas. Dissolved oxygen content of the hyporheic discharge near salmon spawning areas was about 9 mg?L-1 (+ 0.4 mg?L-1) whereas in non-spawning areas dissolved oxygen values were 7 mg?L-1 (+ 0.9 mg?L-1) or lower. In both cases dissolved oxygen of the river Water was higher (11.3+ 0.3 mg?L-1). Physical and chemical gradients between the hyporheic zone and the river may provide cues for adult salmon to locate suitable spawning areas. This information will help fisheries managers to describe the suitability of salmon spawning habitat in large rivers.
Xin Luo - One of the best experts on this subject based on the ideXlab platform.
-
phytoplankton size structure in the western south china sea under the influence of a jet eddy system
Journal of Marine Systems, 2018Co-Authors: Wenzhao Liang, Danling Tang, Xin LuoAbstract:Abstract A northeastward jet in the western South China Sea (SCS) usually induces phytoplankton blooms during summertime. This jet is often sandwiched by a cyclonic eddy in the north and an anticyclonic eddy in the south. Using in situ and satellite data, the present study analyzes the combined impact of the northeastward jet and two eddies on the phytoplankton size structure (PSS) from August to September 2014. Generally, picophytoplankton is the major size fraction in surface Water, contributing 73% of the total chlorophyll a concentration. The data showed that a high chlorophyll a belt (av. 0.29 ± 0.18 μg L−1) with a large percentage of microphytoplankton (av. 14%) appeared in the northeastward jet. Meanwhile, similar chlorophyll a concentrations were observed in the cyclonic (av. 0.072 ± 0.019 μg L−1) and anticyclonic eddies (av. 0.087 ± 0.02 μg L−1), but microphytoplankton contributed 6.7% more in the anticyclonic eddy. Below the surface, however, the dominant size of phytoplankton switched from pico to nano and micro with increasing depth. In contrast to the observations at the surface, the jet and anticyclonic eddy presented a lower microphytoplankton contribution than the cyclonic eddy. Horizontally, advection of coastal Upwelling Water by the northeastward jet enhanced the growth of phytoplankton and influenced the surface PSS. Meanwhile, divergence/convergence in cyclonic/anticyclonic eddy interaction with the northeastward jet formed the high chlorophyll a belt at the edge of the eddy and increased the microphytoplankton contribution through Water mass transport and mixing. Nutrient supply and weakening of the light intensity below the surface layer synergistically influenced the concentration and size structure of phytoplankton in the cyclonic/anticyclonic eddies at different depths. Finally, this study proposed a ‘jet-eddy system’ to explain summer spatial characteristics of PSS in the western SCS. Source Water (riverine and coastal Upwelling Water) that feeds the ‘jet-eddy system’ is another key factor affecting phytoplankton biomass and its size structure.
Patrick Byrne - One of the best experts on this subject based on the ideXlab platform.
-
diffusive equilibrium in thin films provides evidence of suppression of hyporheic exchange and large scale nitrate transformation in a groundWater fed river
Hydrological Processes, 2015Co-Authors: C M Heppell, Andrew Binley, A L Heathwaite, Patrick Byrne, Hao Zhang, Sami Ullah, Katrina Lansdown, Mark TrimmerAbstract:The hyporheic zone of riverbed sediments has the potential to attenuate nitrate from Upwelling, polluted groundWater. However, the coarse-scale (5–10 cm) measurement of nitrogen biogeochemistry in the hyporheic zone can often mask fine-scale (<1 cm) biogeochemical patterns, especially in near-surface sediments, leading to incomplete or inaccurate representation of the capacity of the hyporheic zone to transform Upwelling NO3−. In this study, we utilised diffusive equilibrium in thin-films samplers to capture high resolution (cm-scale) vertical concentration profiles of NO3−, SO42−, Fe and Mn in the upper 15 cm of armoured and permeable riverbed sediments. The goal was to test whether nitrate attenuation was occurring in a sub-reach characterised by strong vertical (Upwelling) Water fluxes. The vertical concentration profiles obtained from diffusive equilibrium in thin-films samplers indicate considerable cm-scale variability in NO3− (4.4 ± 2.9 mg N/L), SO42− (9.9 ± 3.1 mg/l) and dissolved Fe (1.6 ± 2.1 mg/l) and Mn (0.2 ± 0.2 mg/l). However, the overall trend suggests the absence of substantial net chemical transformations and surface-subsurface Water mixing in the shallow sediments of our sub-reach under baseflow conditions. The significance of this is that Upwelling NO3−-rich groundWater does not appear to be attenuated in the riverbed sediments at <15 cm depth as might occur where hyporheic exchange flows deliver organic matter to the sediments for metabolic processes. It would appear that the chemical patterns observed in the shallow sediments of our sub-reach are not controlled exclusively by redox processes and/or hyporheic exchange flows. Deeper-seated groundWater fluxes and hydro-stratigraphy may be additional important drivers of chemical patterns in the shallow sediments of our study sub-reach. © 2015 The Authors. Hydrological Processes Published by John Wiley & Sons Ltd.
-
control of river stage on the reactive chemistry of the hyporheic zone
Hydrological Processes, 2014Co-Authors: C M Heppell, Andrew Binley, A L Heathwaite, Patrick Byrne, Hao Zhang, Sami Ullah, Katrina Lansdown, Mark TrimmerAbstract:We examined the influence of river stage on subsurface hydrology and pore Water chemistry within the hyporheic zone of a groundWater-fed river during the summer baseflow period of 2011. We found river stage and geomorphologic environment to control chemical patterns in the hyporheic zone. At high river stage, the flux of Upwelling Water in the shallow sediments (> 20 cm) decreased at samples sites in the upper section of our study reach and increased substantially at sites in the lower section. This differential response is attributed to the contrasting geomorphology of these sub-reaches which affects the rate of the rise and fall of river stage relative to subsurface head. At sites where streamward vertical flux decreased, concentration profiles of a conservative environmental tracer suggest surface Water infiltration into the riverbed below depths recorded at low river stage. An increase in vertical flux at sites in the lower sub-reach is attributed to the movement of lateral subsurface Waters originating from the adjacent floodplain. This lateral-moving Water preserved or decreased the vertical extent of the hyporheic mixing zone observed at low river stage. Down welling surface Water appeared to be responsible for elevated dissolved organic carbon (DOC) and Mn concentrations in shallow sediments (0 – 20 cm); however, lateral subsurface flows were probably important for elevated concentrations of these solutes at deeper levels. Results suggest that DOC delivered to hyporheic sediments during high river stage from surface Water and lateral subsurface sources could enhance heterotrophic microbial activities. This article is protected by copyright. All rights reserved.
R Mcewen - One of the best experts on this subject based on the ideXlab platform.
-
autonomous detection and sampling of Water types and fronts in a coastal Upwelling system by an autonomous underWater vehicle
Limnology and Oceanography-methods, 2012Co-Authors: Yanwu Zhang, John P Ryan, James G Bellingham, Julio B J Harvey, R McewenAbstract:Coastal Upwelling occurs under the combined effect of wind stress and Earth's rotation. The nutrients carried up by Upwelling have great impact on primary production and fisheries. For using autonomous underWater vehicles (AUVs) to investigate complex coastal Upwelling ecosystems, we have developed algorithms for an AUV to autonomously distinguish between Upwelling and stratified Water columns based on the vertical temperature difference between shallow and deep depths, and to accurately detect an Upwelling front based on the horizontal gradient of the vertical temperature difference in the Water column. During a June 2011 experiment in Monterey Bay, California, the Dorado AUV flew on a transect from an Upwelling shadow region (stratified Water column), through an Upwelling front, and into an Upwelling Water column. Running our algorithms, the AUV successfully classified the three distinct Water types, accurately located the narrow front, and acquired targeted Water samples from the three Water types. Molecular analysis of the AUV-acquired Water samples shows that mussels, calanoid copepods, and podoplean copepods were most abundant in the Upwelling shadow region and nonexistent in the Upwelling Water column. Calanoid copepods were moderately abundant in the Water samples collected from the Upwelling front. These results are largely consistent with previous findings from zooplankton population surveys conducted with the Dorado AUV in Monterey Bay in 2009. The novel detecting and targeted sampling capabilities permit an AUV to autonomously conduct “surgical sampling” of a complex marine ecosystem.
