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21.
Douglas Faulkner Sherwood McIntyre 《Journal of the American Water Resources Association》1996,32(4):817-829
ABSTRACT: The Buffalo River is a tributary to the Mississippi River in west-central Wisconsin that drains a watershed dominated by agricultural land uses. Since 1935, backwater from Lock and Dam 4 on the Mississippi River has inundated the mouth of the Buffalo's valley. Resurveys of a transect first surveyed across the lake in 1935 and cesium-137 dating of backwater sediments reveal that sedimentation rates at the Buffalo's mouth have remained unchanged since the mid-1940s. Study results indicate that sediment yields from the watershed have persisted at relatively high levels over a period of several decades despite pronounced trends toward less cultivated land and major efforts to control soil erosion from agricultural land. The maintenance of sediment yields is probably due to increased channel conveyance capacities resulting from incision along some tributary streams since the early 1950s. Post-1950 incision extended the network of historical incised tributary channels, enhancing the efficient delivery of sediment from upland sources to downstream sites. 相似文献
22.
Copper contamination in surface waters is common in watersheds with mining activities or agricultural, industrial, commercial, and residential human land uses. This widespread pollutant is neurotoxic to the chemosensory systems of fish and other aquatic species. Among Pacific salmonids (Oncorhynchus spp.), copper-induced olfactory impairment has previously been shown to disrupt behaviors reliant on a functioning sense of smell. For juvenile coho salmon (O. kisutch), this includes predator avoidance behaviors triggered by a chemical alarm cue (conspecific skin extract). However, the survival consequences of this sublethal neurobehavioral toxicity have not been explored. In the present study juvenile coho were exposed to low levels of dissolved copper (5-20 microg/L for 3 h) and then presented with cues signaling the proximity of a predator. Unexposed coho showed a sharp reduction in swimming activity in response to both conspecific skin extract and the upstream presence of a cutthroat trout predator (O. clarki clarki) previously fed juvenile coho. This alarm response was absent in prey fish that were exposed to copper. Moreover, cutthroat trout were more effective predators on copper-exposed coho during predation trials, as measured by attack latency, survival time, and capture success rate. The shift in predator-prey dynamics was similar when predators and prey were co-exposed to copper. Overall, we show that copper-exposed coho are unresponsive to their chemosensory environment, unprepared to evade nearby predators, and significantly less likely to survive an attack sequence. Our findings contribute to a growing understanding of how common environmental contaminants alter the chemical ecology of aquatic communities. 相似文献
23.
This paper examines the dependability of the Event Assessment Tool over time. The latter is part of a CD-ROM--Emergency Risk Communication CDCynergy--distributed primarily to public information officers in the United States by the Centers for Disease Control and Prevention. The Event Assessment Tool is designed to aid emergency professionals in identifying the magnitude of a crisis event and to suggest appropriate actions to confront such a situation. Applied twice during the 2001 anthrax bioterrorism crisis in Boca Raton, Florida, the tool functioned in a binary manner by first indicating a moderate crisis level (on 4 October) and then four days later (on 8 October) a highly intense crisis, suggesting that it is time sensitive. This anthrax event provides an opportunity for crisis and disaster managers to understand the dynamic nature of crises. Rapid changes during these types of events suggest that any metric used to predict intensity must account for this variability. Additional limitations and implications of the tool are discussed. 相似文献
24.
Three analytical methods have been evaluated for the determination of volatile organic compounds in water. These techniques have been subsequently applied to the study of a trade effluent discharge problem. 相似文献
25.
The seasonal successions of standing crop and floral assemblage were studied for oceanic coccolithophores at 5 weather stations in the western North Atlantic Ocean. The coccolithophores were less populous during winter at the northern stations, whereas they became scarce during summer at the southern stations. The average standing crop in the surface water was quite consistent throughout all climatic regions, being a few tens of thousand cells per liter. The average standing crop at the 100 m level showed a clear trend of increasing southwards. The population at this depth was only one-tenth as large as that of the surface level at the northernmost station, whereas it was almost two-thirds as large as the surface levels at the southernmost station. Many of the major species exhibited seasonally biased occurrences. The trend was mostly repeated in consecutive years, although the magnitude of their abundances fluctuated from year to year in some case. The average species composition was obtained for the 5 weather stations at the surfacewater (surface and 20 m levels combined) and 100 m levels; Emiliania huxleyi dominated the flora at all stations. The relationship between occurrences of major species and ambient water temperature was also studied. Although some species were stenothermal, the majority exhibited eurythermal characteristics; this accounts for the high specific diversity of the coccolithophore community throughout the wide range of waters studied.Contribution No. 2899 of the Lamont-Doherty Geological Observatory of Columbia University. 相似文献
26.
Sherwood C. McIntyre James W. Naney 《Journal of the American Water Resources Association》1990,26(2):227-232
ABSTRACT: The three basins of Reelfoot Lake, which is located in northwestern Tennessee, were investigated using the Cs-137 tracer technique to determine rates of sediment deposition and to estimate the time before the basins will fill with sediment. Blue Basin, the largest of the three basins with 2922 ha, had an average annual sedimentation rate of 0.9 cm/yr from 1984 to 1984. The basin will become too shallow for most boating and recreational activities in about 200 years. Buck Basin, the central basin with 774 ha, had an average annual sedimentation rate of 1.1 cm/yr and will become too shallow for most recreational uses in about 100 years. Upper Blue Basin, the most upstream and smallest basin with 439 ha, had an average annual sedimentation rate of 1.7 cm/yr and will become too shallow for most recreational uses in about 60 years. Two important sources of sediment to Reelfoot Lake are erosion from a large number of soybean fields and channelization of many of the streams that flow into the lake. Changes in land management that would reduce erosion could increase the time the lake would remain usable for recreational activities. 相似文献
27.
Coastal development and engineering projects preclude ecosystem processes that provide habitat for beach nesting birds. Management
for coastal species may depend on actions that attempt to restore important habitat features and mitigate disturbance effects.
However, species response to restoration or other management actions may be difficult to predict or measure. At Jones Beach
State Park, on Long Island, New York, a 0.49 ha restoration project provided moist substrate foraging habitat for breeding
Piping Plovers (Charadrius melodus) from 2002 to 2005. We examined whether foraging habitat restoration affected Piping Plover breeding population size, productivity,
and fledgling production within 300 m of the restoration site. We found a positive relationship between habitat restoration
and the number of fledglings produced per year. However, foraging habitat restoration did not significantly increase the number
of Plover pairs breeding at Jones Beach. Our ability to evaluate restoration effects on Plovers depended on: 1) use of multiple
performance criteria; 2) a design that allowed comparison of pre- and post-restoration data; and 3) a spatial control that
allowed comparison of similar areas that were near and far from the restoration site. Despite the small size of the restoration
project, there were measurable benefits to Plovers, indicating that foraging habitat restoration may be an effective tool
for species recovery. 相似文献
28.
Wesley M. Knapp Anne Frances Reed Noss Robert F. C. Naczi Alan Weakley George D. Gann Bruce G. Baldwin James Miller Patrick McIntyre Brent D. Mishler Gerry Moore Richard G. Olmstead Anna Strong Kathryn Kennedy Bonnie Heidel Daniel Gluesenkamp 《Conservation biology》2021,35(1):360-368
Extinction rates are expected to increase during the Anthropocene. Current extinction rates of plants and many animals remain unknown. We quantified extinctions among the vascular flora of the continental United States and Canada since European settlement. We compiled data on apparently extinct species by querying plant conservation databases, searching the literature, and vetting the resulting list with botanical experts. Because taxonomic opinion varies widely, we developed an index of taxonomic uncertainty (ITU). The ITU ranges from A to F, with A indicating unanimous taxonomic recognition and F indicating taxonomic recognition by only a single author. The ITU allowed us to rigorously evaluate extinction rates. Our data suggest that 51 species and 14 infraspecific taxa, representing 33 families and 49 genera of vascular plants, have become extinct in our study area since European settlement. Seven of these taxa exist in cultivation but are extinct in the wild. Most extinctions occurred in the west, but this outcome may reflect the timing of botanical exploration relative to settlement. Sixty-four percent of extinct plants were single-site endemics, and many occurred outside recognized biodiversity hotspots. Given the paucity of plant surveys in many areas, particularly prior to European settlement, the actual extinction rate of vascular plants is undoubtedly much higher than indicated here. 相似文献
29.
Density estimates based on point processes are often restrained to regions with irregular boundaries or holes. We propose a density estimator, the lattice-based density estimator, which produces reasonable density estimates under these circumstances. The estimation process starts with overlaying the region with nodes, linking these together in a lattice and then computing the density of random walks of length k on the lattice. We use an approximation to the unbiased crossvalidation criterion to find the optimal walk length k. The technique is illustrated using walleye (Sander vitreus) radiotelemetry relocations in Lake Monroe, Indiana. We also use simulation to compare the technique to the traditional kernel density estimate in the situation where there are no significant boundary effects. 相似文献
30.
Franke Alastair Falk Knud Hawkshaw Kevin Ambrose Skip Anderson David L. Bente Peter J. Booms Travis Burnham Kurt K. Ekenstedt Johan Fufachev Ivan Ganusevich Sergey Johansen Kenneth Johnson Jeff A. Kharitonov Sergey Koskimies Pertti Kulikova Olga Lindberg Peter Lindström Berth-Ove Mattox William G. McIntyre Carol L. Mechnikova Svetlana Mossop Dave Møller Søren Nielsen Ólafur K. Ollila Tuomo Østlyngen Arve Pokrovsky Ivan Poole Kim Restani Marco Robinson Bryce W. Rosenfield Robert Sokolov Aleksandr Sokolov Vasiliy Swem Ted Vorkamp Katrin 《Ambio》2020,49(3):762-783
Ambio - The peregrine falcon (Falco peregrinus) and the gyrfalcon (Falco rusticolus) are top avian predators of Arctic ecosystems. Although existing monitoring efforts are well established for both... 相似文献