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101.
Alternate dense and less-dense skeletal bands in massive corals have been used for many years to record the history of growth in species such as Porites lutea and Montastrea annularis, based on the assumption that one dense band and one less-dense band is equivalent to a year's growth. This report demonstrates that specimens of Porites lutea Edwards and Haime (collected from the same neighbourhood in Phuket, Thailand, from November 1983 through November 1984) produce skeletal bands asynchronously and that one year's growth in corals from certain sites may regularly consist of four bands of varying density. The annual banding pattern observed at all sites includes the deposition of a dense band in response to high sedimentation loads and, probably, reduced light levels. 相似文献
102.
Stereophotography for the field biologist: measurement of lengths and three-dimensional positions of free-swimming sharks 总被引:1,自引:0,他引:1
A stereophotographic technique for determining size and relative position of free-swimming sharks is described and illustrated for schooling scalloped hammerhead sharks (Sphyrna lewini). The method yields total length and nearest-neighbor, interindividual distance; and each of these dimensions is expressed as a function of the shark's distance into a school on the vertical and horizontal planes. Stereopairs of photographs were taken by an aligned, beam-mounted pair of cameras (Nikonos III). The scale to determine the length of a shark from the paired photographic images was obtained from the horizontal displacement between the images. Displacement was correlated with optical axis separation from photographs of a scaled staff at known distances from the camera. Image dimensions on the photographs were measured by projecting a scale onto the stage through a camera lucida. The precision of repeated measurements of a 50 cm section of a scaled staff at increasing distances from the cameras of 2, 4, and 8 m was ±5.0%. Lengths of the sharks ranged from 109 to 371 cm, with a median of 178 cm, for 3 offshore sites in the Gulf of California during July and August 1979. At one site, El Bajo Gorda, lengths increased with both distance from the camera and distance into the group; in contrast, the interindividual distances (head-to-head) did not vary with distance into the group and possessed a median of 232 cm. 相似文献
103.
This study was undertaken to investigate the natural variation of heavy metals in the polychaete Nereis diversicolor O. F. Müller and to examine this variation with respect to physiological and environmental parameters. During a 2 yr period from October 1980 to October 1982, concentrations of copper, zinc and iron in N. diversicolor from the Tees Estuary, North East England, were found to vary significantly with time. A seasonal influence on whole body copper concentration, in part related to the reproductive cycle, was observed. Zinc concentrations in N. diversicolor increased during periods of rapid growth and may represent a physiological demand for this metal. Whole body concentrations of iron appeared to be independent of size of worm, sexual maturation and sediment concentrations. 相似文献
104.
Oxygen consumption rates of the deep-sea fish Sebastolobus altivelis were measured in situ on pelagic juveniles at mesopelagic depths (608 m) and on demersal adults at bathyal depths (1 300 m) in the Santa Catalina Basin in March 1982. Two pelagic juveniles were individually collected, and respiration was measured continuously for approximately 2 d with a slurp gun respirometer manipulated from the submersible “Alvin”. Oxygen consumption rates of these juveniles were highly variable and were 1.5 to 1.8 times higher during the night than during the day. Gut contents of the juveniles were mainly euphausiids (Euphausia pacifica and Nematoscelis difficilis). Four demersal adults were collected by “Alvin” and individually placed in fish-trap respirometers on the bottom where respiration was measured continuously for approximately 1 d. Weight-specific O2 consumption rates for adults decreased with increasing body weight and were consistent in magnitude throughout the incubation period. Population O2 consumption for demersal S. altivelis (calculated from abundance, size-frequency distribution, and O2 consumption regression equation) was 11.01 μl O2 m-2 h-1, which is two orders of magnitude less than the O2 consumption rate for the population of the most abundant epibenthic megafaunal species in the Santa Catalina Basin, the ophiuroid Ophiophthalmus normani. O. normani is a principal prey for adults of S. altivelis based on gutcontent analysis. Given the population O2 consumption rate as an estimate of food energy demand, the demersal population of S. altivelis would assimilate only 0.007% of the standing crop of O. normani per day. 相似文献
105.
The marine pseudomonad bacterium PL1 contains an intracellular pool of free amino acids which consist mainly of glutamate with small amounts of glutamine and aspartate when grown in a nutrient medium containing 0.2 M NaCl. When the NaCl concentration of the growth medium is increased to 0.8 M, proline becomes a major component of the intracellular pool together with glutamate—at this molarity and under suitable nutrient conditions these amino acids comprise 20% of total bacterial amino acid nitrogen. When grown in a nutrient growth medium containing a constant level of NaCl, the intracellular pool size can vary by a factor of 4 depending on the concentration of carbon and nitrogen in the medium. Experiments show that the amino acid pool can act as a nitrogen reserve but has little function as a carbon reserve. At high NaCl concentrations there is a marked dependence for growth on the presence of sufficient potassium in the medium. However, no correlation between K+ and glutamate concentration in either nitrogen or K+-limited cultures has been found. None of the enzymes associated with glutamate biosynthesis was influenced by NaCl levels between 0.2 and 0.5 M. Neither Na+ or K+ stimulated the activity of these enzymes when tested in vitro. 相似文献
106.
An important topic in the registration of pesticides and the interpretation of monitoring data is the estimation of the consequences of a certain concentration of a pesticide for the ecology of aquatic ecosystems. Solving these problems requires predictions of the expected response of the ecosystem to chemical stress. Up until now, a dominant approach to come up with such a prediction is the use of simulation models or safety factors. The disadvantage of the use of safety factors is a crude method that does not provide any insight into the concentration–response relationships at the ecosystem level. On the other hand, simulation models also have serious drawbacks like that they are often very complex, lack transparency, their implementation is expensive and there may be a compilation of errors, due to uncertainties in parameters and processes. In this paper, we present the expert model prediction of the ecological risks of pesticides (PERPEST) that overcomes these problems. It predicts the effects of a given concentration of a pesticide based on the outcome of already performed experiments using experimental ecosystems. This has the great advantage that the outcome is more realistic. The paper especially discusses how this model can be used to translate measured and predicted concentrations of pesticides into ecological risks, by taking data on measured and predicted concentrations of atrazine as an example. It is argued that this model can be of great use to evaluate the outcome of chemical monitoring programmes (e.g. performed in the light of the Water Framework Directive) and can even be used to evaluate the effects of mixtures. 相似文献
107.
Charles?R.?BrownEmail author Mary?Bomberger?Brown 《Behavioral ecology and sociobiology》2004,56(5):498-511
Little is known in general about how group size or ectoparasitism affect survival in colonial animals. We estimated daily within-season survival probabilities for nesting adult and recently fledged juvenile cliff swallows (Petrochelidon pyrrhonota) at 239 colonies from 1983 to 2003 in southwestern Nebraska, USA. Some colonies had been fumigated to remove ectoparasites. We conducted mark-recapture at each colony site to estimate daily survival. There were no systematic differences between males and females in daily survival. Adults and juveniles occupying parasite-free colonies had, on average, 4.4% and 62.2% greater daily survival, respectively, than their counterparts in naturally infested colonies. Daily survival of all birds increased with colony size for both parasite-free colonies and those under natural conditions, although the effect was stronger for adults at fumigated sites and for juveniles. Average daily survival probability for adults tended to increase during warmer and drier summers. Although daily survival varied at some sites over the course of the nesting cycle, there were no strongly consistent within-year temporal effects on survival. Even small differences in daily survival probability can translate into large effects on mean lifespan. The deleterious effects of ectoparasites on daily survival within the season represent a previously unknown cost of ectoparasitism. The increase in within-season survival with colony size reflects the net effects of many costs and benefits associated with colony size. Ectoparasitism is probably the most important cost that tends to partly balance the positive effects of large colonies. The greater survival of cliff swallows in the larger colonies is a previously unknown advantage of colonial nesting.Communicated by P. Heeb 相似文献
108.
M.?A.?Kvitrud S.?D.?Riemer R.?F.?Brown M.?R.?Bellinger M.?A.?BanksEmail author 《Marine Biology》2005,147(6):1459-1466
We used a PCR-based species test and microsatellite genotyping to determine salmonid species composition and quantity of Chinook
among Pacific harbor seal (Phoca vitulina) prey. Tests were applied to DNA extracted from all salmonid bones recovered from scat (fecal) samples. Condition of bone
samples and quantity of DNA varied substantially. Although DNA extraction and species identification was only successful for
just over half of the bone samples, 93% of all scat samples had bones that were identified to species. Most often only a single
salmonid prey species was evident within a scat sample (39% exclusively coho and 46% exclusively Chinook) but 13% contained
bones from more than one species of salmonid. For scat samples that contained Chinook bones, 68% had skeletal remains from
the same fish and 32% had bones from more than one individual Chinook, varying in number from two to four individuals per
scat. In one case, bones from one individual Chinook were recovered in three different scat samples. 相似文献
109.
Aneil?F.?AgrawalEmail author Jeremy?M.?Brown Edmund?D.?BrodieIII 《Behavioral ecology and sociobiology》2004,57(2):139-148
Maternal-offspring interactions are important in a variety of animals. Understanding the evolution of these interactions requires that we also study the broader social context in which they occur. To date, behavioral studies on burrower bugs, Sehirus cinctus, have focused exclusively on interactions between mothers and offspring. Here we ask whether these interactions occur in a social context that extends beyond the family unit of a mother and her own genetic offspring. Such social structure can arise from behaviors that occur before eggs are laid, or from actions of individuals that occur post-hatching. We present field data showing that lay sites of mothers are spatially aggregated on a scale that would lead to behavioral interactions among families. Microsatellite markers suggest neighboring mothers are unrelated. Laboratory experiments do not support the hypothesis that spatial aggregation results from a direct attraction of females to one another. Other laboratory studies reported here indicate that, after hatching, unrelated clutches sometimes join together to form multifamily groups. Experiments reveal that mothers are not necessary for these joining events to occur. In sum, these data suggest that both mothers and offspring play active, but different, roles in generating the social environment in which offspring rearing occurs.Communicated by N. Wedell 相似文献
110.
M. A. Arthur G. B. Coltharp D. L. Brown 《Journal of the American Water Resources Association》1998,34(3):481-495
ABSTRACT: Forest land managers are concerned about the effects of logging on soil erosion, streamflow, and water quality and are promoting the use of Best Management Practices (BMPs) to control impacts. To compare the effects of BMP implementation on streamwater quality, two of three small watersheds in Kentucky were harvested in 1983 and 1984, one with BMPs, the other without BMPs. There was no effect of clearcutting on stream temperatures. Streamflow increased by 17.8 cm (123 percent) on the BMP watershed during the first 17 months after cutting and by 20.6 cm (138 percent) on the Non-BMP watershed. Water yields remained significantly elevated compared to the uncut watershed 8 years after harvesting. Suspended sediment flux was 14 and 30 times higher on the BMP and Non-BMP Watersheds, respectively, than on the uncut watershed during treatment, and 4 and 6.5 times higher in the 17 months after treatment was complete. Clearcutting resulted in increased concentrations of nitrate, and other nutrients compared to the uncut watershed, and concentrations were highest on the non-BMP watershed. Recovery of biotic control over nutrient losses occurred within three years of clearcutting. The streamside buffer strip was effective in reducing the impact of clearcutting on water yield and sediment flux. 相似文献