Characterizing juvenile salmon predation risk during early marine residence

Predation mortality can influence the distribution and abundance of fish populations. While predation is often assessed using direct observations of prey consumption, potential predation can be predicted from co-occurring predator and prey densities under varying environmental conditions. Juvenile Pacific salmon Oncorhynchus spp. (i.e., smolts) from the Columbia River Basin experience elevated mortality during the transition from estuarine to ocean habitat, but a thorough understanding of the role of predation remains incomplete. We used a Holling type II functional response to estimate smolt predation risk based on observations of piscivorous seabirds (sooty shearwater [Ardenna griseus] and common murre [Uria aalge]) and local densities of alternative prey fish including northern anchovy (Engraulis mordax) in Oregon and Washington coastal waters during May and June 2010–2012. We evaluated predation risk relative to the availability of alternative prey and physical factors including turbidity and Columbia River plume area, and compared risk to returns of adult salmon. Seabirds and smolts consistently co-occurred at sampling stations throughout most of the study area (mean = 0.79 ± 0.41, SD), indicating that juvenile salmon are regularly exposed to avian predators during early marine residence. Predation risk for juvenile coho (Oncorhynchus kisutch), yearling Chinook salmon (O. tshawytscha), and subyearling Chinook salmon was on average 70% lower when alternative prey were present. Predation risk was greater in turbid waters, and decreased as water clarity increased. Juvenile coho and yearling Chinook salmon predation risk was lower when river plume surface areas were greater than 15,000 km2, while the opposite was estimated for subyearling Chinook salmon. These results suggest that plume area, turbidity, and forage fish abundance near the mouth of the Columbia River, all of which are influenced by river discharge, are useful indicators of potential juvenile salmon mortality that could inform salmonid management.

Cold Model Study on Melting of Ice Made by KCl Solution in Gas-Water Two-Phase Plume Area

With the increasing of scrap usage in steelmaking processes, the melting of scrap becomes a very important phenomenon that limits the productivity and tap-to-tap time. Ice-water systems have been widely used to study the melting of scrap and alloys. In this study, the melting rate of saturated KCl solution ice spheres in gas-water two-phase plume zone are studied as a function of height of location, gas flowrate, and melt temperature. The results show that the shape of the ice sphere gradually changes firstly from spherical to elliptical, and finally becomes an irregular state. 1) The decreasing of the distance between the ice sphere and the bottom plugs, 2) the increasing of the gas flowrate, 3) the slightly increasing of bath temperature will all benefits the melting rate of ice spheres.

A Hybridization of Gravitational Search Algorithm and Particle Swarm Optimization for Odor Source Localization

This paper concerns with the problem of odor source localization by a team of mobile robots. The authors propose two methods for odor source localization which are largely inspired from gravitational search algorithm and particle swarm optimization. The intensity of odor across the plume area is assumed to follow the Gaussian distribution. As robots enter in the vicinity of plume area they form groups using K-nearest neighbor algorithm. The problem of local optima is handled through the use of search counter concept. The proposed approaches are tested and validated through simulation.

A Hybridization of Gravitational Search Algorithm and Particle Swarm Optimization for Odor Source Localization

This paper concerns with the problem of odor source localization by a team of mobile robots. The authors propose two methods for odor source localization which are largely inspired from gravitational search algorithm and particle swarm optimization. The intensity of odor across the plume area is assumed to follow the Gaussian distribution. As robots enter in the vicinity of plume area they form groups using K-nearest neighbor algorithm. The problem of local optima is handled through the use of search counter concept. The proposed approaches are tested and validated through simulation.

Merging of a row of plumes or jets with an application to plume rise in a channel

The physical interpretation of velocity potential is used to propose a model of the mean flow boundary of a row of plumes or jets. Generalised plume equations incorporating the plume area and net entrainment are closed with an entrainment assumption. The resulting model is shown to approach the appropriate limiting similarity solutions above and below the merging height in an unstratified environment. The virtual origin of the far-field flow is hence predicted. An application to plume rise in channels of varying aspect ratio shows that the model may be used to predict the depth of the outflow along the channel.

Optical Breakdown on the Inclined Target: The Features of the Erosive Plume Formation

For oblique incidence of laser radiation on the target, the breakdown of air and erosive jet are separated in time and space. The electron density is higher in the air breakdown area while Al I density is higher in an erosive plume area. We also defined plasma expansion mechanism and estimate the time of erosive plume formation.

Carbonate mineral saturation states in the East China Sea: present conditions and future scenarios

To assess the impact of rising atmospheric CO2 and eutrophication on the carbonate chemistry of the East China Sea shelf waters, saturation states (Ω) for two important biologically relevant carbonate minerals – calcite (Ωc) and aragonite (Ωa) – were calculated throughout the water column from dissolved inorganic carbon (DIC) and total alkalinity (TA) data collected in spring and summer of 2009. Results show that the highest Ωc (∼9.0) and Ωa (∼5.8) values were found in surface water of the Changjiang plume area in summer, whereas the lowest values (Ωc = ∼2.7 and Ωa = ∼1.7) were concurrently observed in the bottom water of the same area. This divergent behavior of saturation states in surface and bottom waters was driven by intensive biological production and strong stratification of the water column. The high rate of phytoplankton production, stimulated by the enormous nutrient discharge from the Changjiang, acts to decrease the ratio of DIC to TA, and thereby increases Ω values. In contrast, remineralization of organic matter in the bottom water acts to increase the DIC to TA ratio, and thus decreases Ω values. The projected result shows that continued increases of atmospheric CO2 under the IS92a emission scenario will decrease Ω values by 40–50% by the end of this century, but both the surface and bottom waters will remain supersaturated with respect to calcite and aragonite. Nevertheless, superimposed on such Ω decrease is the increasing eutrophication, which would mitigate or enhance the Ω decline caused by anthropogenic CO2 uptake in surface and bottom waters, respectively. Our simulation reveals that, under the combined impact of eutrophication and augmentation of atmospheric CO2, the bottom water of the Changjiang plume area will become undersaturated with respect to aragonite (Ωa = ∼0.8) by the end of this century, which would threaten the health of the benthic ecosystem.

Carbonate mineral saturation states in the East China Sea: present conditions and future scenario

To assess the impact of rising atmospheric CO2 and eutrophication on the carbonate chemistry of the East China Sea shelf waters, saturation states (Ω) for two important biologically-relevant carbonate minerals, calcite (Ωc) and aragonite (Ωa) were calculated throughout the water column from dissolved inorganic carbon (DIC) and total alkalinity (TA) data collected in spring and summer of 2009. Results show that the highest Ωc (~9.0) and Ωa (~ 5.8) values were found in surface water of the Changjiang plume area in summer, whereas the lowest values (Ωc=~2.7 and Ωa=~1.7) were concurrently observed in the bottom water of the same area. This divergent behavior of saturation states in surface and bottom waters was driven by intensive biological production and strong stratification of the water column. The high rate of phytoplankton production, stimulated by the enormous nutrient discharge from the Changjiang, acts to decrease the ratio of DIC to TA, and thereby increases Ω values. In contrast, remineralization of organic matter in the bottom water acts to increase the DIC to TA ratio, and thus decreases Ω values. The projected result shows that continued increases of atmospheric CO2 under the IS92a emission scenario will decrease Ω values by 40–50% by the end of this century, but both the surface and bottom waters will remain supersaturated with respect to calcite and aragonite. Nevertheless, superimposed on such Ω decrease is increasing eutrophication, which would mitigate or enhance the Ω decline caused by anthropogenic CO2 uptake in surface and bottom waters, respectively. Our simulation reveals that under the combined impact of eutrophication and augmentation of atmospheric CO2, the bottom water of the Changjiang plume area will become undersaturated with respect to aragonite (Ωa=~0.8) by the end of this century, which would threaten the health of the benthic ecosystem.