The English–Wabigoon River System: V. Mercury and Selenium Bioaccumulation as a Function of Aquatic Primary Productivity

1983 ◽  
Vol 40 (12) ◽  
pp. 2251-2259 ◽  
Author(s):  
John W. M. Rudd ◽  
Michael A. Turner
Keyword(s):  
Growth Rate ◽  
Primary Productivity ◽  
Growth Rates ◽  
River System ◽  
Whole Body ◽  
Aquatic Food Chain ◽  
Mercury Bioaccumulation ◽  
Aquatic Food ◽  
Stimulation Of

An experiment was carried out in four 100-m3 in situ enclosures to determine the effect of primary production rate on mercury and selenium concentrations of biota and to test the possibility of ameliorating mercury pollution problems by increasing ecosystem primary productivity. Two enclosures were controls. Primary productivity in a third enclosure was increased fourfold by addition of NaNO3 and NaH2PO4. This stimulation was not sufficient to change pH although the growth rate of fish was enhanced. In this enclosure, mercury concentrations in pearl dace (Semotilus margarita) whole body and muscle samples increased two- and five-fold, respectively, exceeding the dilution of mercury by the enhanced growth rates. In the fourth enclosure, at the highest rate of nutrient addition, primary productivity was increased ninefold, pH was elevated from about 7.9 to 9.2, and the growth rate of fish was stimulated. In this case, the elevation of pH retarded the rate of mercury bioaccumulation in comparison with the enclosure of intermediate productivity. Based on these results, stimulation of primary productivity is not recommended as a mercury ameliorating procedure. Stimulation of primary productivity resulted in a general decrease in the concentration of selenium in the aquatic food chain probably resulting from dilution of selenium by enhanced growth rates of fish and other biota.

Single Crystal Silicon Carbide On Silicon Using A Supersonic Gas Jet Of Methylsilane

1997 ◽  
Vol 483 ◽  
Author(s):  
S. A. Ustin ◽  
C. Long ◽  
L. Lauhon ◽  
W. Ho
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Single Crystal Silicon ◽  
Maximum Growth ◽  
X Ray Diffraction ◽  
Crystal Silicon ◽  
Cross Sectional ◽  
Supersonic Molecular Beam ◽  
Transmission Electron

AbstractCubic SiC films have been grown on Si(001) and Si(111) substrates at temperatures between 600 °C and 900 °C with a single supersonic molecular beam source. Methylsilane (H3SiCH3) was used as the sole precursor with hydrogen and nitrogen as seeding gases. Optical reflectance was used to monitor in situ growth rate and macroscopic roughness. The growth rate of SiC was found to depend strongly on substrate orientation, methylsilane kinetic energy, and growth temperature. Growth rates were 1.5 to 2 times greater on Si(111) than on Si(001). The maximum growth rates achieved were 0.63 μm/hr on Si(111) and 0.375μm/hr on Si(001). Transmission electron diffraction (TED) and x-ray diffraction (XRD) were used for structural characterization. In-plane azimuthal (ø-) scans show that films on Si(001) have the correct 4-fold symmetry and that films on Si(111) have a 6-fold symmetry. The 6-fold symmetry indicates that stacking has occurred in two different sequences and double positioning boundaries have been formed. The minimum rocking curve width for SiC on Si(001) and Si(111) is 1.2°. Fourier Transform Infrared (FTIR) absorption was performed to discern the chemical bonding. Cross Sectional Transmission Electron Microscopy (XTEM) was used to image the SiC/Si interface.

Quantitative In Situ Growth Measurements of Chlorine-Activated Homoepitaxial Diamond Cvd

1994 ◽  
Vol 349 ◽  
Author(s):  
Chenyu Pan ◽  
John L. Margrave ◽  
Robert H. Hauge
Keyword(s):  
Growth Rate ◽  
Substrate Temperature ◽  
Growth Rates ◽  
Diamond Growth ◽  
Flow Rates ◽  
Temperature Range ◽  
Quantitative Studies ◽  
Growth Activation ◽  
Lower Temperature

ABSTRACTIn situ quantitative studies of the effects of substrate temperature, methane and chlorine flow rates on homoepitaxial diamond growth rates on (110) surfaces in a chlorine-activated diamond CVD reactor have been carried out using a Fizeau interferometer. The temperature dependence of diamond growth rates was found to display three distinct growth activation energies, ranging from 9±2 kcal/mol in the substrate temperature of 750-950°C, to 3.2±0.2 kcal/mol in the temperature range of 300-650°C, followed by 1.2±0.2 kcal/mol in the temperature range of 102-250°C. Atomic hydrogen is believed to be the dominant activating species in the highest temperature range, and atomic chlorine is believed to be the dominant species in the lower temperature regions. Studies of the methane flow effect on diamond growth rates revealed a linearity, indicating that the diamond growth rate was of the first order in methane flows. Diamond growth rates were also found to increase linearly with the chlorine flow. At high chlorine flow rates, however, an accelerated diamond growth rate was observed. Discussion is given to explain the observed results.

Response of a Brook Trout (Salvelinus fontinalis) Population to a Reduction in Stream Benthos Following an Insecticide Treatment

1990 ◽  
Vol 47 (7) ◽  
pp. 1387-1401 ◽  
Author(s):  
D. P. Kreutzweiser
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Brook Trout ◽  
Food Resource ◽  
Fish Growth ◽  
Invertebrate Drift ◽  
Age Classes ◽  
Insecticide Treatment ◽  
Forest Stream ◽  
Aquatic Food

A forest stream was treated with permethrin to determine the response of brook trout to a reduction in the aquatic food resource following an insecticide treatment. The treatment resulted in massive invertebrate drift and significant reductions of benthos, but did not produce trout mortality or evidence of unusual behaviour. The density, population age structure, movement patterns, and condition of brook trout were not measurably affected by the permethrin treatment. The growth rates of 0 + and 1 + age-classes were significantly lower following the insecticide application than those of trout from the same age-classes of pretreatment years. This reduction in growth rate resulted in significantly smaller trout after treatment. A significant reduction in the growth of trout collected during the same period from a nearby untreated control stream indicated that unusually high summer temperatures were at least partially, if not entirely, responsible for the reduced growth rate of treated fish. Growth rates returned to or exceeded pretreatment levels by the overwinter period of the treatment year.

scholarly journals Determination of In Situ Bacterial Growth Rates in Aquifers and Aquifer Sediments

2003 ◽  
Vol 69 (7) ◽  
pp. 3798-3808 ◽  
Author(s):  
Brian J. Mailloux ◽  
Mark E. Fuller
Keyword(s):  
Growth Rate ◽  
Fluorescence Intensity ◽  
Growth Rates ◽  
Direct Determination ◽  
Shallow Aquifer ◽  
Cell Counting ◽  
Field Scale ◽  
Doubling Times

ABSTRACT Laboratory and field-scale studies with stained cells were performed to monitor cell growth in groundwater systems. During cell division, the fluorescence intensity of the protein stain 5-(and 6-)-carboxyfluorescein diacetate succinimidyl ester (CFDA/SE) for each cell is halved, and the intensity can be tracked with a flow cytometer. Two strains of bacteria, Comamonas sp. strain DA001 and Acidovorax sp. strain OY-107, both isolated from a shallow aquifer, were utilized in this study. The change in the average generation or the average fluorescence intensity of the CFDA/SE-stained cells could be used to obtain estimates of doubling times. In microcosm experiments, the CFDA/SE-based doubling times were similar to the values calculated by total cell counting and were independent of cell concentration. Intact and repacked sediment core experiments with the same bacteria indicated that changes in groundwater chemistry were just as important as growth rates in determining planktonic cell concentrations. The growth rates within the sediment cores were similar to those calculated in microcosm experiments, and preferential transport of the daughter cells was not observed. The experiments indicated that the growth rates could be determined in systems with cell losses due to other phenomena, such as attachment to sediment or predation. Application of this growth rate estimation method to data from a field-scale bacterial transport experiment indicated that the doubling time was approximately 15 days, which is the first known direct determination of an in situ growth rate for bacteria in an aquifer.

Research Progress of Mercury Bioaccumulation in the Aquatic Food Chain, China: A Review

2019 ◽  
Vol 102 (5) ◽  
pp. 612-620 ◽  
Author(s):  
Haiyu Yan ◽  
Qiuhua Li ◽  
Zhenhui Yuan ◽  
Shuang Jin ◽  
Min Jing
Keyword(s):  
Food Chain ◽  
Research Progress ◽  
Aquatic Food Chain ◽  
Mercury Bioaccumulation ◽  
Aquatic Food

scholarly journals The Chemoautotrophically Based Movile Cave Groundwater Ecosystem, a Hotspot of Subterranean Biodiversity

Diversity ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 128
Author(s):  
Traian Brad ◽  
Sanda Iepure ◽  
Serban M. Sarbu
Keyword(s):  
Primary Productivity ◽  
Water Surface ◽  
Energy Input ◽  
Free Swimming ◽  
Invertebrate Species ◽  
Microbial Biofilms ◽  
Oxidation Of Hydrogen ◽  
Aquatic Food ◽  
Movile Cave

Movile Cave hosts one of the world’s most diverse subsurface invertebrate communities. In the absence of matter and energy input from the surface, this ecosystem relies entirely on in situ primary productivity by chemoautotrophic microorganisms. The energy source for these microorganisms is the oxidation of hydrogen sulfide provided continuously from the deep thermomineral aquifer, alongside methane, and ammonium. The microbial biofilms that cover the water surface, the cave walls, and the sediments, along with the free-swimming microorganisms, represent the food that protists, rotifers, nematodes, gastropods, and crustacean rely on. Voracious water-scorpions, leeches, and planarians form the peak of the aquatic food web in Movile Cave. The terrestrial community is even more diverse. It is composed of various species of worms, isopods, pseudoscorpions, spiders, centipedes, millipedes, springtails, diplurans, and beetles. An updated list of invertebrate species thriving in Movile Cave is provided herein. With 53 invertebrate species (21 aquatic and 32 terrestrial), of which 38 are endemic for this unusual, but fascinating environment, Movile Cave is the first known chemosynthesis-based groundwater ecosystem. Therefore, Movile Cave deserves stringent attention and protection.

scholarly journals Plankton community in the western waters of North-Sumatera during the onset monsoon of Asian winter

2020 ◽  
Vol 45 (1) ◽  
pp. 1-12
Author(s):  
Mochamad Ramdhan Firdaus ◽  
Nurul Fitriya ◽  
Praditya Avianto ◽  
Hanif Budi Prayitno ◽  
A'an Johan Wahyudi
Keyword(s):  
Environmental Changes ◽  
Mesh Size ◽  
Environmental Parameters ◽  
Plankton Community ◽  
The North ◽  
Water Characteristics ◽  
Aquatic Food Chain ◽  
Aquatic Food ◽  
North And South

The western waters of North-Sumatera experience dynamic environmental changes during the onset monsoon of the Asian winter. Those changes certainly will affect the distribution of marine organisms, especially the plankton. Plankton is the foundation of the aquatic food chain and plays an important role as the entry gate of solar energy to the water trophic systems. This study aims to investigate the plankton community and its correlation with the environmental factors during the onset monsoon of the Asian winter. Plankton samples were collected, along with water samples and in-situ measurement for environmental parameters determination from western waters of North-Sumatera (95°E – 93°N) in November-December 2017. Plankton samples were taken by vertically hauling (500 m) using Modified Twin Plankton Net with 80 µm mesh size for phytoplankton and 300 µm for zooplankton. Temperature, salinity, and density of waters were measured using CTD SBE 911 – Plus. The nutrients, including orthophosphate, nitrate, and silicate, measured using autoanalyzer Skalar SAN++. Thirty genera of phytoplankton and 44 taxa groups of zooplankton were found. The phytoplankton community dominated by Thallassionema, while the zooplankton dominated by Calanoida. There was a difference in the composition of plankton communities between the north and south parts of the study area. It was probably influenced by different water masses between those two regions indicated by the dissimilarity of their water characteristics. Based on the analysis of the T-S diagram, it is likely that the north community influenced by Bengal Bay Water while the south community influenced by the Indian Equatorial Water.

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