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231.
Carl Van Colen J. Lenoir A. De Backer B. Vanelslander M. Vincx S. Degraer T. Ysebaert 《Marine Biology》2009,156(10):2161-2171
The role of multi-species benthic diatom films (BDF) in the settlement of late pediveliger larvae of the bivalve Macoma balthica was investigated in still-water bioassays and multiple choice flume experiments. Axenic diatom cultures that were isolated
from a tidal mudflat inhabited by M. balthica were selected to develop BDF sediment treatments characterized by a different community structure, biomass, and amount of
extracellular polymeric substances (EPS). Control sediments had no added diatoms. Although all larvae settled and initiated
burrowing within the first minute after their addition in still water, regardless of treatment, only 48–52% had completely
penetrated the high diatom biomass treatments after 5 min, while on average 80 and 69% of the larvae had settled and burrowed
into the control sediments and BDF with a low diatom biomass (<3.5 μg Chl a g−1 dry sediment), respectively. The percentage of larvae settling and burrowing into the sediment was negatively correlated
with the concentration of Chl a and EPS of the BDF. This suggests higher physical resistance to bivalve penetration by the BDF with higher diatom biomass
and more associated sugar and protein compounds. The larval settlement rate in annular flume experiments at flow velocities
of 5 and 15 cm s−1 was distinctly lower compared to the still-water assays. Only 4.6–5.8% of the larvae were recovered from BDF and control
sediments after 3 h. Nonetheless, a clear settlement preference was observed for BDF in the flume experiments; i.e., larvae
settled significantly more in BDF compared to control sediments irrespective of flow speed. Comparison with the settlement
of polystyrene mimics and freeze-killed larvae led to the conclusion that active selection, active secondary dispersal and,
at low flow velocities (5 cm s−1), passive adhesion to the sediment are important mechanisms determining the settlement of M. balthica larvae in estuarine biofilms. 相似文献
232.
Joshua J. Schwartz Bryant W. Buchanan H. Carl Gerhardt 《Behavioral ecology and sociobiology》2001,49(6):443-455
We studied female mate choice by Hyla versicolor in three venues to examine how acoustic and spatial complexity, background noise, and the calling behavior of males might influence preferences manifest in previous laboratory two-stimulus choice tests. Our laboratory-based two-stimulus choice tests with and without broadcasts of chorus noise demonstrated that females prefer long calls relative to short calls when calling efforts of alternatives are equivalent. Background noise impaired the ability of females to discriminate in favor of longer over shorter calls, but the magnitude of the effect was small. Captures of females at eight speakers broadcasting 6- to 27-pulse calls at the edge of a pond revealed strong discrimination against only the shortest call variant. In natural choruses, females may only rarely encounter males using such unattractive vocalizations. Female phonotaxis at an artificial pond with caged and electronically monitored calling males also indicated that consequences of female preferences for temporal aspects of calling observed in two-stimulus choice tests are much attenuated in choruses and explain only small portions (<10%) of the variation in male mating success. Nevertheless, relatively high call duration and calling effort increased male attractiveness. Acoustic interference emerged as another significant factor influencing male mating success and possibly the differences in female choice observed in laboratory and chorus settings. We suggest that the bias of females against both overlapped and very short calls may help explain why males lengthen their calls but lower their rate of delivery in response to increases in chorus size. 相似文献
233.
234.
Time series of abundance estimates are commonly used for analyses of population trends and possible shifts in growth rate.
We investigate if trends in age composition can be used as an alternative to abundance estimates for detection of decelerated
population growth. Both methods were tested under two forms of density dependence and different levels of environmental variation
in simulated time series of growth in Baltic gray seals. Under logistic growth, decelerating growth could be statistically
confirmed after 16 years based on population counts and 14 years based on age composition. When density dependence sets in
first at larger population sizes, the age composition method performed dramatically better than population counts, and a decline
could be detected after 4 years (versus 10 years). Consequently, age composition analysis provides a complementary method
to detect density dependence, particularly in populations where density dependence sets in late. 相似文献
235.
Hinck JE Norstrom RJ Orazio CE Schmitt CJ Tillitt DE 《Environmental pollution (Barking, Essex : 1987)》2009,157(2):582-591
Organochlorine pesticide and total polychlorinated biphenyl (PCB) concentrations were measured in largemouth bass from the Tombigbee River near a former DDT manufacturing facility at McIntosh, Alabama. Evaluation of mean p,p′- and o,p′-DDT isomer concentrations and o,p′- versus p,p′-isomer proportions in McIntosh bass indicated that DDT is moving off site from the facility and into the Tombigbee River. Concentrations of p,p′-DDT isomers in McIntosh bass remained unchanged from 1974 to 2004 and were four times greater than contemporary concentrations from a national program. Total DDT in McIntosh bass exceeded dietary effect concentrations developed for bald eagle and osprey. Hexachlorobenzene, PCBs, and toxaphene concentrations in bass from McIntosh also exceeded thresholds to protect fish and piscivorous wildlife. Whereas concentrations of DDT and most other organochlorine chemicals in fish have generally declined in the U.S. since their ban, concentrations of DDT in fish from McIntosh remain elevated and represent a threat to wildlife. 相似文献
236.
237.
The incorporation of biochar into soils has been proposed as a means to sequester carbon from the atmosphere. An added environmental benefit is that biochar has also been shown to increase soil retention of nutrients, heavy metals, and pesticides. The goal of this study was to evaluate whether biochar amendments affect the transport of Escherichia coli through a water-saturated soil. We looked at the transport of three E. coli isolates through 10-cm columns packed with a fine sandy soil amended with 2 or 10% (w/w) poultry litter biochar pyrolyzed at 350 or 700°C. For all three isolates, mixing the high-temperature biochar at a rate of 2% into the soil had no impact on transport behavior. When added at a rate of 10%, a reduction of five orders of magnitude in the amount of E. coli transported through the soil was observed for two of the isolates, and a 60% reduction was observed for the third isolate. Mixing the low-temperature biochar into the soil resulted in enhanced transport through the soil for two of the isolates, whereas no significant differences in transport behavior were observed between the low-temperature and high-temperature biochar amendments for one isolate. Our results show that the addition of biochar can affect the retention and transport behavior of E. coli and that biochar application rate, biochar pyrolysis temperature, and bacterial surface characteristics were important factors determining the transport of E. coli through our test soil. 相似文献
238.
239.
Carl M. Shy M.D. Dr. P.H John P. Creason M.S. Martin E. Pearlman M.D. Kathryn E. McClain Ferris B. Benson Marion M. Young M.D. 《Journal of the Air & Waste Management Association (1995)》2013,63(9):582-588
A study of acute respiratory illness was conducted from November 1968 through April 1969 among families residing in an area of relatively high nitrogen dioxide exposure, in an area of elevated suspended particulate exposure, and in two control areas of Greater Chattanooga. Respiratory illness rates were consistently higher in all family segments in the high-nitrogen dioxide exposure area when rates were averaged for the entire 24 weeks of study, the A2/Hong-Kong epidemic period, or post-epidemic interval. A relative excess in respiratory illness of 18.8 percent was found among families exposed to elevated NO2 concentrations and an excess of 10.4 percent was found among families in the elevated-suspended particulate exposure area. 相似文献
240.
John W. Roberts Harry A. Watters Carl A. Mangold August T. Rossano 《Journal of the Air & Waste Management Association (1995)》2013,63(9):948-952
The paving of gravel roads with an average daily traffic (ADT) over 15 is a least cost method for reducing suspended particulate In the air in Seattle. It is also a good business investment when the ADT exceeds 100. Clean roads, gutters, and parking lots may reduce or eliminate Seattle’s most serious environmental constraint on economic development. In a study done in Seattle’s Duwamish Valley the impact of road dust on air quality was measured by obtaining dust emission factors for vehicles traveling at 10, 20, and 30 mph on gravel as well as dusty paved roads. A University of Washington Mark II Cascade Impactor was mounted on a trailer and towed behind a car to determine the concentration and size distribution of this dust. It was found that each vehicle mile at 20 mph on unpaved roads contributed 7.0 Ib of dust to the air, 1.9 Ib consisting of particles smaller than 10 microns in diameter and 0.24 Ib below 2 microns. Three to eight percent by weight of this respirable dust was free silica, which is potentially toxic. The quantity of dust generated varies as an exponent of the speed. The concentrations of dust found in the air near a dry gravel road with an ADT of 250 reached 584 μg/m3 for an 8 hr work day. A 24 hr suspended particulate reading of 463 μg/m3 total and 3.83 μg/m3 free silica was found beside a dusty paved road with an ADT of 18,000. Nineteen miles of gravel roads and 110 miles of dusty paved roads contributed 2700 tons/year of particulate, of which 700 tons were below 10 microns. Paving or oiling such roads will produce benefits of $3,881,000 yearly in household cleaning, health care, sewer, vehicle operation, and road maintenance costs as well as an increase in property values. Clean roads can lower the cost of clean air in Seattle. 相似文献