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141.
142.
Summary There are large numbers of reproductively mature female tree swallows (Tachycineta bicolor) which do not breed due to limits of suitable nesting cavities. Many of these floaters are one-year-old females that have a distinctive subadult plumage. This study examines the behavioral tactics that these subadult female floaters use to obtain breeding opportunities. Early in the season, subadult floaters tended to intrude briefly (Fig. 4) on many nest sites in succession (Figs. 2, 3), although they rarely gained close access to nest sites (Fig. 5). Subadults responded very quickly to vacant nest sites, where the resident female had been experimentally removed, by entering the nest cavity and defending it from conspecifics. We argue that the early season exploratory behavior increases a subadult's chances of discovering a vacant nest site, rather than increasing its success in evicting resident females or laying eggs in other females' nests. During the nestling period, subadult females intruded on fewer nest sites for longer periods, and often gained close access to the nest site. Late in the season, subadult floaters may be gathering information on the quality of nest sites for the next breeding season, rather than searching for current breeding opportunities. The reproductive tactics of subadult female tree swallows are consistent with the breeding threshold model for the evolution of delayed plumage maturation in passerines.  相似文献   
143.
The lipids of 2 species and 1 group of copepods, 4 species of euphausiids, 2 species of mysids, and 6 species of decapods, taken from different depths in the North-eastern Atlantic Ocean and Western Mediterranean Sea, have been analysed specifically for their wax ester content. The mid-water animals living below 500 m contained large amounts of wax ester (30 to 80% total lipid), while those animals living in the upper 600 to 700 m or on the sea floor had only small wax ester fractions (5 to 10% total lipid). It is suggested that the wax esters are laid down by those animals living in areas of low food density, where energy conservation is important, partly to achieve a more neutral buoyancy. In addition, it would appear that wax esters can function as energy reserves.  相似文献   
144.
Megalopae (postlarvae) of the blue crab Callinectes sapidus Rathbun use flood-tide transport (FTT) for movement into and up estuaries. Since they settle around the time of slack water at the end of flood tide during FTT, it was predicted that orientation toward primary nursery areas of aquatic vegetation occurs at this time. This study tested the hypotheses that megalopae locate nursery areas by swimming upstream in the presence of chemical odors from potential nursery areas and avoid adverse microhabitats by swimming downstream when predator or adverse environmental odors are present. Megalopae were tested in a flume where they were exposed to the sequence of cues mediating FTT (i.e. 2 psu increase in salinity followed by an increase and a decrease in current speed and turbulence). The flume contained odor water either from the developmental area (offshore water), nursery area vegetation (seagrass, Zostera marina; salt marsh cord grass, Spartina alterniflora), predators (fiddler crab, Uca pugilator; mud crab, Panopeus herbstii; grass shrimp, Palaemonetes pugio), or chemicals associated with adverse environments (ammonium). Vertical positions of premolt and intermolt megalopae were similar in water devoid of estuarine chemical cues (offshore water) and water containing seagrass odor. Upstream swimming behavior (orientation) of intermolt megalopae was also similar in these waters. However, there was an ontogenetic behavioral change, as the proportion of premolt megalopae oriented upstream generally increased as the concentration of seagrass and salt marsh cord grass odor increased and as current speed decreased. Upstream orientation of premolt megalopae in response to seagrass odor decreased significantly (i.e. downstream swimming increased) in the presence of odor from U. pugilator, P. pugio, and ammonium, but not from P. herbstii. Thus, the hypothesis was supported. These results suggest premolt megalopae orient toward nursery areas by swimming upstream in response to odors from aquatic vegetation as current speeds decrease at the end of nocturnal flood tides. Moreover, these results also indicate that megalopae may discriminate among microhabitats and avoid adverse settlement habitat, as orientation toward nursery areas is reversed by predator odors and ammonium.  相似文献   
145.
146.
Laser mass spectrometry has been applied for on-line monitoring of traces of aromatic compounds from flue gas of incineration plants. The experiments have been carried out at two sampling sites in an industrial hazardous-waste incinerator. With laser mass spectrometry resonance-enhanced multiphoton ionization (REMPI) with time-of-flight mass spectrometry (TOFMS) (REMPI-TOFMS), using the group selective multi-component monitoring approach, aromatic compounds are selectively ionized from the complex flue-gas matrix. In this case, the result of an REMPI-TOFMS on-line measurement is a distinct pattern of aromatic compounds. These patterns are dependent on: (i) the point of measurement, (ii) the incineration plant, (iii) the temperature, and (iv) the fuel. This contribution focuses on the fuel dependence of the pattern. The most transient behavior can be observed when containers filled with hazardous waste are burnt, leading to puffs. Real-time monitoring results of puffs are given. Furthermore, as an approach towards on-line monitoring of the TEQ (PCDD/F toxicity equivalent), REMPI-TOFMS on-line analysis results of chlorobenzene are presented.  相似文献   
147.
Paper sludges were traditionally landfilled or burned. Over the years, the use of paper sludges on soils has increased, as well as the concerns about their environmental effects. Therefore, the chemical characterization of paper sludges and their young (immature) compost needed to be investigated, and over 150 inorganic and organic chemicals were analyzed in de-inking paper sludge (DPS). In general, nitrogen, phosphorus and potassium contents were low but variable in raw DPS and its young compost. The contents of arsenic, boron, cadmium, cobalt, chromium, manganese, mercury, molybdenum, nickel, lead, selenium, and zinc were also low and showed low variability. However, the copper contents were above the Canadian compost regulation for unrestricted use and required a follow-up. The fatty- and resin acids, and polycyclic aromatic hydrocarbons were the organic chemicals measured at the highest concentrations. For resinic acids, care should be taken to avoid that leachates reach aquatic life. For polycyclic aromatic hydrocarbons, naphthalene should be followed until soil content reaches 0.1 microg g(-1), the maximum allowed for soil use for agricultural purposes according to Canadian Environmental Quality Guidelines. In young compost, the concentration of these chemical families decreased over time and most compounds were below the detection limits after 24 weeks of composting. In raw DPS, among the phenol, halogenated and monoaromatic hydrocarbons, dioxin and furan, and polychlorinated biphenyl families, most compounds were below the detection limits. The raw DPS and its young compost do not represent a major threat for the environment but can require an environmental follow-up.  相似文献   
148.
It has been frequently demonstrated that mercury (Hg) concentrations in fish rise in newly constructed hydroelectric reservoirs in the Northern Hemisphere. In the present work, we studied whether similar effects take place also in a tropical upland reservoir during impoundment and discuss possible causes and implications. Total Hg concentrations in fish and several soil and water parameters were determined before and after flooding at Rio Manso hydroelectric power plant in western Brazil. The Hg concentrations in soil and sediment were within the background levels in the region (22-35 ng g(-1) dry weight). There was a strong positive correlation between Hg and carbon and sulphur in sediment. Predatory fish had total Hg concentrations ranging between 70 and 210 ng g(-1) f.w. 7 years before flooding and between 72 and 755 ng g(-1) f.w. during flooding, but increased to between 216 and 938 ng g(-1) f.w. in the piscivorous and carnivorous species Pseudoplatystoma fasciatum, cachara, and Salminus brasiliensis, dourado, 3 years after flooding. At the same time, concentrations of organic carbon in the water increased and oxygen concentrations decreased, indicating increased decomposition and anoxia as contributing to the increased Hg concentrations in fish. The present fish Hg concentrations in commonly consumed piscivorous species are a threat to the health of the population dependent on fishing in the dam and downstream river for sustenance. Mercury exposure can be reduced by following fish consumption recommendations until fish Hg concentrations decrease to a safe level.  相似文献   
149.
Fine sediments in shallow water bodies such as Lake Okeechobee are prone to resuspension. Predominantly inorganic "mud" sediment that covers approximately 670 km2 of the lake has been recognized as a persistent source of turbidity. The objective of this study was to determine if mineral components of sediments in Lake Okeechobee and water conveyances of the northern Everglades also occur as suspended sediment and hence constitute a potential abiotic contributor to turbidity. Sediment samples were collected from nine stations within the lake and eight locations north of Water Conservation Area 2A in the Everglades. Water samples were also collected at selected locations. The silt and clay mineralogy of sediment and suspended particles was determined using X-ray diffraction, thermogravimetry, scanning-electron microscopy, energy-dispersive X-ray elemental microanalysis, and high-resolution transmission-electron microscopy. Clay fractions of the lake sediment contained the Mg silicate minerals sepiolite and palygorskite, along with smectite, dolomite, calcite, and kaolinite. Sediment silt fractions were dominated by carbonates and/or quartz, with smaller amounts of Ca phosphates and sepiolite. Mineralogy of the mud sediment was similar to that reported for geologic phosphate deposits. This suggests that the mud sediment might have accumulated by stream transport of minerals from these deposits. Suspended solids and mud-sediment mineralogy were similar, except that smectite was more abundant in suspended solids. Everglade samples also contained Mg-rich minerals. The small size, low density, and fibrous or platy nature of the prevalent mud sediment minerals make them an abiotic, hydrodynamically sensitive source of persistent turbidity in a shallow lake. Mitigation efforts focused exclusively on P-induced biogeochemical processes do not address the origin or effects of these minerals. Ecological management issues such as turbidity control, P retention, geologic P input, and suitability of dredging are related to mud-sediment properties and provenance.  相似文献   
150.
In-situ feeding habits of the copepods Temora turbinata and T. stylifera were investigated by scanning electron microscope examination of fecal pellets, the contents of which reflected copepod gut contents upon capture. Pellet contents were compared with assemblages of available phytoplankton in the water column at the times of zooplankton sampling. Samples were collected in continental shelf and slope waters of the Gulf of Mexico near the mouth of the Mississippi River. Both species ingested a wide size range and taxonomic array of phytoplankters, and to a lesser extent, other crustaceans. Fecal pellets contained primarily the remains of the phytoplankters that were most abundant in the water at times of collection. There was considerable overlap in the food items ingested by adult females of both copepod species, or two stages of T. turbinata copepodites. Thus, T. turbinata and T. stylifera are omnivores, but primarily opportunistic herbivores.  相似文献   
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