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121.
Nocturnal movements of phototactic zooplankton in shallow waters 总被引:2,自引:0,他引:2
D. J. Tranter N. C. Bulleid R. Campbell H. W. Higgins F. Rowe H. A. Tranter D. F. Smith 《Marine Biology》1981,61(4):317-326
Downwardly directed light-traps were used by night, over seagrass and coral sand to investigate the existence and significance of nocturnal peaks in phototactic zooplankton. Samples each half-hour from sunset to sunrise showed that small invertebrates, mostly copepods, were trapped in large numbers once or twice a night. Each period of high catches lasted only 1 to 2 h and was often associated with periods of failing natural light (evening twilight, moonset). This pattern and its variations are explained in terms of nocturnal vertical migration, in which plankton move towards light in response to decreasing light intensity, move away from light in response to increasing light intensity, and disperse at constant light intensity. Some morning peaks are unexplained. 相似文献
122.
Recognition of individual neighbors by song in the song sparrow,a species with song repertoires 总被引:2,自引:0,他引:2
Philip K. Stoddard Michael D. Beecher Cynthia L. Horning S. Elizabeth Campbell 《Behavioral ecology and sociobiology》1991,29(3):211-215
Summary Previous theory and research have suggested that bird species with song repertoires in general, and song sparrows (Melospiza melodia) in particular, cannot readily discriminate between the songs of neighbors and strangers. In a recent study (Stoddard et al. 1991) we showed that song sparrows can in fact discriminate neighbors from strangers on the basis of song. In this study we sought to demonstrate that song sparrows can make the finer discrimination between individual neighbors and that they can do so on the basis of a single song type. We compared the response of territorial males to song playback of neighbors and strangers at three locations: the neighbor's regular boundary, the opposite boundary, and the center of the territory. The birds showed strong neighbor-stranger discrimination at the regular boundary but not at the opposite boundary, nor in the center of the territory. The differences in song discrimination between different boundary locations indicate that song sparrows associate particular songs with particular territories, effectively discriminating between individual neighbors on the basis of song. Song repertoires themselves do not interfere with neighbor recognition to the extent originally postulated. As speakers are moved inside the territory from the border, however, the degree of discrimination diminishes. We believe that differences in speaker placement may have contributed to the variability in neighbor-stranger discrimination observed in previous studies of the song sparrow and perhaps other repertoire species as well. This interpretation is consistent with data from another song sparrow population showing that half the territory takeovers are by immediate neighbors. 相似文献
123.
J. M. Quattro D. S. Stoner W. B. Driggers C. A. Anderson K. A. Priede E. C. Hoppmann N. H. Campbell K. M. Duncan J. M. Grady 《Marine Biology》2006,148(5):1143-1155
Surveys of genetic variation within cosmopolitan marine species often uncover deep divergences, indicating historical separation
and potentially cryptic speciation. Based on broad geographic (coastal eastern North America, Gulf of Mexico, western Africa,
Australia, and Hawaii) and temporal sampling (1991–2003), mitochondrial (control region [CR] and cytochrome oxidase I [COI])
and nuclear gene (lactate dehydrogenase A intron 6 [LDHA6]) variation among 76 individuals was used to test for cryptic speciation
in the scalloped hammerhead, Sphyrna lewini (Griffith and Smith). CR and COI gene trees confirmed previous evidence of divergence between Atlantic and Indo-Pacific scalloped
hammerhead populations; populations were reciprocally monophyletic. However, the between-basin divergence recorded in the
mtDNA genome was not reflected in nuclear gene phylogenies; alleles for LDHA6 were shared between ocean basins, and Atlantic
and Indo-Pacific populations were not reciprocally monophyletic. Unexpectedly, CR, COI, and LDHA6 gene trees recovered a deep
phylogenetic partition within the Atlantic samples. For mtDNA haplotypes, which segregated by basin, average genetic distances
were higher among Atlantic haplotypes (CR: D
HKY=0.036, COI: D
GTR=0.016) than among Indo-Pacific haplotypes (CR: D
HKY=0.010, COI: D
GTR=0.006) and approximated divergences between basins for CR (D
HKY=0.036 within Atlantic; D
HKY=0.042 between basins). Vertebral counts for eight specimens representing divergent lineages from the western north Atlantic
were consistent with the genetic data. Coexistence of discrete lineages in the Atlantic, complete disequilibrium between nuclear
and mitochondrial alleles within lineages and concordant partitions in genetic and morphological characters indicates reproductive
isolation and thus the occurrence of a cryptic species of scalloped hammerhead in the western north Atlantic. Effective management
of large coastal shark species should incorporate this important discovery and the inference from sampling that the cryptic
scalloped hammerhead is less abundant than S. lewini, making it potentially more susceptible to fishery pressure. 相似文献
124.
Of the 18 359 American lobsters (Homarus americanus) tagged and released at three locations in the Bay of Fundy during 1977–1980, 5 375 lobsters (29.3%) were recaptured within 6 yr of release. Mature lobsters (95-mm carapace length, CL) on average moved significantly greater distances than immature lobsters (<95-mm CL). Many (16.4%) of the mature lobsters were recaptured >92.6 km (50 nautical miles) from the release sites; the farthest distance moved was 798 km for a male at liberty for 3.5 yr. Examination of the direction of movements indicates some intermixing of lobsters within the Bay of Fundy, and throughout the Gulf of Maine and the adjoining Continental Shelf and slopes. Mature lobsters were recaptured in deeper waters during winter than during summer. The seasonal shallow-deep migration of mature lobsters in the Bay of Fundy is possibly associated with maximizing degree-days for molting, growth, gonadal development, and egg development. In some areas, mature females on average moved farther and seasonally earlier into deeper waters than mature males. Although the seasonal migration resulted in many lobsters returning to the original release area year after year, some lobsters made extensive long-distance movements away from the Bay of Fundy. Temperature-dependent, seasonal deep-shallow migration can explain both the local returns and the long distance migrations of mature lobsters in the Bay of Fundy and the Gulf of Maine. To achieve appropriate seasonal temperature regimes, mature lobsters have to move different distances and directions, depending on local topography. 相似文献
125.
A brief review of the use of stable lead isotope ratio measurements to identify and apportion sources of lead in human tissue
is followed by examples of the use of inductively coupled plasma source mass spectrometry for such studies.
Inductively coupled plasma source mass spectrometry (ICP-MS) has only recently been used for measurements of coupled ratios
in body tissues and fluids and in environmental sources of lead. Generally, the inaccuracy of these measurements is about
−0.2% and the imprecision less than 0.5%. This analytical performance is sufficient to detect the much larger changes in206Pb:207Pb ratios of −2% or higher, seen in environmental lead exposure and in childhood lead poisoning.
Measurements of lead isotope ratios by ICP-MS have been used to identify specific sources of childhood lead poisoning and
to indicate the relative importance of environmental sources, such as drinking water and lead from petrol. Populations in
the United Kingdom with low lead uptake usually have206:Pb207Pb ratios in body tissues within the range 1.13 ± 0.01. Significant deviations from this range have been seen in response
to increased uptake from lead in: drinking water in parts of Scotland (source ratio ∼1.18 and petrol lead in inner London
(source ratio ∼1.07). The dominant source for some Scottish subjects with high concentrations of lead in blood or in teeth
was water, which contributed approximately 60% to body lead. Petrol lead was shown to be a significant contributor (30–40%)
to the body lead of inner London children. 相似文献
126.
Campbell LM Osano O Hecky RE Dixon DG 《Environmental pollution (Barking, Essex : 1987)》2003,125(2):281-286
Total mercury (THg) concentrations were measured for various fish species from Lakes Turkana, Naivasha and Baringo in the rift valley of Kenya. The highest THg concentration (636 ng g(-1) wet weight) was measured for a piscivorous tigerfish Hydrocynus forskahlii from Lake Turkana. THg concentrations for the Perciformes species, the Nile perch Lates niloticus from Lake Turkana and the largemouth bass Micropterus salmoides from Lake Naivasha ranged between 4 and 95 ng g(-1). The tilapiine species in all lakes, including the Nile tilapia Oreochromis niloticus, had consistently low THg concentrations ranging between 2 and 25 ng g(-1). In Lake Naivasha, the crayfish species, Procambrus clarkii, had THg concentrations similar to those for the tilapiine species from the same lake, which is consistent with their shared detritivore diet. THg concentrations in all fish species were usually consistent with their known trophic position, with highest concentrations in piscivores and declining in omnivores, insectivores and detritivores. One exception is the detritivore Labeo cylindricus from Lake Baringo, which had surprisingly elevated THg concentrations (mean=75 ng g(-1)), which was similar to those for the top trophic species (Clarias and Protopterus) in the same lake. Except for two Hydrocynus forskahlii individuals from Lake Turkana, which had THg concentrations near or above the international marketing limit of 500 ng g(-1), THg concentrations in the fish were generally below those of World Health Organization's recommended limit of 200 ng g(-1) for at-risk groups. 相似文献
127.
The distribution of phycoerythrin-richSynechococcus spp. relative to eukaryotic algae and the contribution ofSynechococcus spp. toin situ primary production were compared at a neritic front, in warm-core eddy 84-E, and at Wilkinson's Basin, during a cruise to the Northwest Atlantic Ocean in July/August 1984. Immunofluorescence analyses ofSynechococcus strains demonstrated the restricted distribution of the tropical oceanic serogroup to the warm-core eddy, while strains of the neritic serogroup and those labelled by antiserum directed against a motile strain, were abundant in all three water masses. Although the majority ofSynechococcus spp. cells were observed in the 0.6 to 1 m fraction, an increasing proportion of the totalSynechococcus spp. cells were found in the 1 to 5 m fraction as nitrate concentrations increased near the base of the thermocline. From immunofluorescence analyses, we determined that the increasing proportion of largerSynechococcus spp. cells at depth was not the result of a change in strain composition, and may therefore be associated with increasing cell volume due to the enhanced nutrient supply. The contribution of the different size fractions to the total standing crop of chlorophyll and thein situ rate of photosynthesis was distincty different for the three water masses. At the neritic front, the larger photoautotrophs of the 1 to 5 m and >5 m fractions were the major contributors to chlorophyll concentrations and primary production.Synechococcus spp. appeared to provide only 6% of the dawn-to-duskin situ primary production at the neritic front. In modified Sargasso water in the warm-core eddy,Synechococcus spp. contributed 25% to thein situ rate of integrated primary production. In this warm-core eddy, the 0.2 to 0.6 m fraction made a major contribution to the standing crop of chlorophyll and primary production that equalled or exceeded that of the larger sze categories. Furthermore, at the bottom of the euphotic layer, eukaryotes numerically dominated the 0.2 to 0.6 m fraction, which contributed 61% of the primary productivity. At Wilkinson's Basin, theSynechococcus spp.-dominated 0.6 to 1.0 m fraction made the greatest contribution to the standing crop of chlorophyll an primary production, while smaller photoautotrophs (0.2 to 0.6 m) accounted for little of the chlorophyll or photosynthetic rates measured over the euphotic layer. Largest numbers ofSynechococcus spp. (2.9x108 cells l-1) occurred at the 18% isolume, coincident with a shoulder in the chlorophyll fluorescence profile and the site of maximumin situ primary productivity. At Wilkinson's Basin,Synechococcus spp. contributed 46% to thein situ photosynthesis integrated over the water-column. 相似文献
128.
McKenney DW Hopkin AA Campbell KL Mackey BG Foottit R 《Environmental monitoring and assessment》2003,88(1-3):445-461
This paper briefly reviews the process of exotic pest risk assessments and presents some examples of emerging opportunities for spatial bioclimatic modeling of exotic species in Canada. This type of analysis can support risk assessments but does not replace the need for on-going high quality field-based observations to validate and update models. Bioclimatic analysis of several exotic pests is provided to illustrate both opportunities and limits. A link is demonstrated to the National Forest Inventory to characterize timber volumes at risk for one exotic species. Challenges' are both scientific and administrative. More accessible and current field survey data are required to improve models. Our experience is that for many exotic species, historical, and even current, data are not always digital or quality controlled for taxonomic identity and accurate geo-referencing. This inhibits their use for integrated spatial modeling applications. 相似文献
129.
The performance of six different bioluminescent bacteria for the assessment of oil bioremediation was compared. Three contained lux genes linked to promoters from hydrocarbon degradation pathways: Pseudomonas fluorescens HK44 (pUTK21), Escherichia coli HMS174 (pOS25) and E. coli DH5 alpha (pGEc74, pJAMA7), responding to naphthalene, isopropylbenzene and octane, respectively. The other three expressed lux constitutively: E. coli HB101 (pUCD607) and P. putida F1 (pUCD607) are genetically engineered, while Vibrio fischeri is naturally bioluminescent and was included to facilitate comparison with previous work. Five different oils (four crude oils plus diesel) were spiked into soil, and the progress of remediation was followed over a period of 119 d by monitoring both hydrocarbon disappearance and changes in the microbial response to soil extracts. The octane bioassay was the only one of the hydrocarbon-responsive bacterial assays to show any appreciable response, with up to 20-fold induction by light crude oils. Heavy crude oil and diesel elicited a much weaker response. The metabolic (lux constitutively expressed) bioassays showed that there was a general increase in toxicity over the course of the experiment, although toxicity to E. coli HB101 (pUCD607) appeared to be decreasing by the final sampling point. The metabolic bioassay response was much less variable between the different oils than for the first three, catabolic, strains. 相似文献
130.
A. S. Hellkamp S. R. Shafer C. L. Campbell J. M. Bay D. A. Fiscus G. R. Hess B. F. McQuaid M. J. Munster G. L. Olson S. L. Peck K. N. Easterling K. Sidik M. B. Tooley 《Environmental monitoring and assessment》1998,51(1-2):317-324
Indicators of the condition and sustainability of agricultural lands in five Mid-Atlantic states were measured in 1994. Indicators were selected to reflect crop productivity and land stewardship on annually harvested herbaceous crop (AHHC) land, which covers almost 10% of the land area in this region. Overall, condition of agricultural lands in the region is good. Crops generally yielded more than those grown in the 1980s, with a mean observed/expected yield index greater than 1. The mean soil quality index was slightly better than a "moderate" rating for crop growth. Almost 2/3 of the AHHC land is covered by crop rotation plans, with the remaining land mostly in hay fields. Insecticides were applied to less than 20% of AHHC land, and less than 20% of the land where pesticides were applied has high to moderately high potential for pesticides leaching into groundwater. However, integrated pest management (IPM) is practiced on less than 20% of AHHC land. Hay showed more efficient use of nitrogen than seed crops, and non-tilled sites, which are mostly hay, had more microbial biomass (suggesting more nutrient cycling) than tilled sites. This information could provide a baseline for a long-term monitoring program for agroecosystems in the region. 相似文献