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221.
Combining field and laboratory work, this study investigated the reproductive cycle, aggregative behavior, spawning periodicity,
development and early growth of the sea star Henricia lisa living at bathyal depths off eastern Canada. Marked differences were found between individuals from ~1,300 and ~600 m deep.
The former had a male biased sex ratio and an aperiodic reproductive cycle, whereas the latter displayed an equal sex ratio
and a biannual breeding pattern. Furthermore, the maximum size was larger and female fecundity roughly five times higher in
shallower compared to deeper populations. In the tanks, aggregative behavior was recorded twice a year during the summer and
winter breeding periods. The onset of aggregations and spawning coincided with a temperature of 3–4°C. Males spawned first
and females typically responded inside 30–60 min. Between 12 and 20 eggs were retained to be brooded under the arched arms
of the female, whereas the remainder were broadcasted and developed without parental care. The fertilized eggs underwent a
first cleavage after 12 h, reached the brachiolaria stage in 1 month, became juveniles within 3–4 months and reached ~ 4 mm
in diameter after 14–17 months of growth. The embryos and juveniles developed at the same rate whether brooded or not, and
development of winter cohorts was typically slower due to lower prevailing temperatures. This study of H. lisa provides the first evidence of lecithotrophy in a seasonally breeding deep-sea echinoderm and of brooding in a deep-sea asteroid. 相似文献
222.
This study examines the composition and activity of the planktonic community during the polar night in the high Arctic Kongsfjord,
Svalbard. Our results are the first published evidence of bioluminescence among zooplankton during the Arctic polar night.
The observations were collected by a bathyphotometer detecting bioluminescence, integrated into an autonomous underwater vehicle,
to determine the concentration and intensity of bioluminescent flashes as a function of time of day and depth. To further
understand community dynamics and composition, plankton nets were used to collect organisms passing through the bathyphotometer
along with traditional vertical net tows. Additionally, using a moored bathyphotometer closed to the sampling site, the bioluminescence
potential itself was shown not to have a diurnal or circadian rhythm. Rather, our results provide evidence for a diel vertical
migration of bioluminescent zooplankton that does not correspond to any externally detectable changes in illumination. 相似文献
223.
Pascal D. Leroy Ahmed Sabri Fran?ois J. Verheggen Fr��d��ric Francis Philippe Thonart Eric Haubruge 《Chemoecology》2011,21(3):113-122
In natural environment, semiochemicals are involved in many interactions between the different trophic levels involving insects,
plants and hosts for parasitoids or prey for predators. These volatile compounds act as messengers within or between insect
species, inducing particular behaviours, such as the localisation of a source of food, the orientation to an adequate oviposition
site, the selection of a suitable breeding site and the localisation of hosts or prey. In this sense, bacteria have been shown
to play an important role in the production of volatile compounds which ones act as semiochemicals. This review, focusing
on the semiochemically mediated interactions between bacteria and insects, highlights that bacterial semiochemicals act as
important messengers for insects. Indeed, in most of the studies reported here, insects respond to specific volatiles emitted
by specific bacteria hosted by the insect itself (gut, mouthparts, etc.) or present in the natural environment where the insect
evolves. Particularly, bacteria from the families Enterobacteriaceae, Pseudomonaceae and Bacillaceae are involved in many
interactions with insects. Because semiochemicals naturally produced by bacteria could be a very interesting option for pest
management, advances in this field are discussed in the context of biological control against insect pests. 相似文献
224.
Elaine S. Carvalho Rubén J. Sánchez Maria I. B. Tavares álano C. Lam?nica 《Journal of Polymers and the Environment》2010,18(4):661-667
The chemical modification of Acrylamidomethyl Cellulose Acetate Propionate (AMCAP) was carried out by radical addition of
acrylic acid. The structural modification was confirmed with the aid of FTIR, MS and NMR techniques. Thermal properties of
hydrophilic cellulose derivative (AMCAP–H2O2) such as glass transition (Tg 153 °C) and thermal stability (372.7 °C) were determined by DSC and TGA techniques, respectively. These thermal properties
confirmed the introduction of carboxylic groups into AMCAP structure, which causes an impact in their properties. The AMCAP–H2O2 shows minor contact angle compared to AMCAP, giving a more hydrophilic characteristic, due to acrylic acid addition into
the side chains of AMCAP polymer. 相似文献
225.
226.
Negative effects of noise on individuals, the inevitable result of urbanization, have become a significant urban problem in our day. Introduction of an approach to the noise problem on an urban-planning scale lightens the burden of measures required to be taken against noise at the stages of regional and developmental planning. Stadiums, which should be also evaluated from the point of noise problem when planning decisions are made on the urban planning scale, may cause very serious problems differing depending on the region they are located in. In this article, various dimensions of the noise problem caused by stadiums have been exemplified by making an assessment on Ali Sami Yen football stadium located in Mecidiyeköy district which is among important residential and commercial centres of ?stanbul or Turkey. When the simulation results obtained for ordinary days and match days are evaluated, it has been found out that the people living in the area are exposed to noise levels substantially exceeding the acceptable values. Results of the survey conducted in the area have clearly revealed the existence of noise problem, too. 相似文献
227.
Recovery of lotic macroinvertebrate communities from disturbance 总被引:7,自引:0,他引:7
J. Bruce Wallace 《Environmental management》1990,14(5):605-620
Ecosystem disturbances produce changes in macrobenthic community structure (abundances, biomass, and production) that persist
for a few weeks to many decades. Examples of disturbances with extremely long-term effects on benthic communities include
contamination by persistent toxic agents, physical changes in habitats, and altered energy inputs. Stream size, retention,
and local geomorphology may ameliorate the influence of disturbances on invertebrates. Disturbances can alter food webs and
may select for favorable genotypes (e.g., insecticidal resistance). Introductions of pesticides into lotic ecosystems, which
do not result in major physical changes within habitats, illustrate several factors that influence invertebrate recovery time
from disturbance. These include: (1) magnitude of original contamination, toxicity, and extent of continued use; (2) spatial
scale of the disturbance; (3) persistence of the pesticide; (4) timing of the contamination in relation to the life history
stages of the organisms; (5) vagility of populations influenced by pesticides; and (6) position within the drainage network.
The ability of macroinvertebrates to recolonize denuded stream habitats may vary greatly depending on regional life histories,
dispersal abilities, and position within the stream network (e.g., headwaters vs larger rivers). Although downstream drift
is the most frequently cited mechanism of invertebrate recolonization following disturbance in middle- and larger-order streams,
evidence is presented that shows aerial recolonization to be potentially important in headwater streams. There is an apparent
stochastic element operating for aerial recolonization, depending on the timing of disturbance and flight periods of various
taxa. Available evidence indicates that recolonization of invertebrate taxa without an aerial adult stage requires longer
periods of time than for those that possess winged, terrestrial adult stages (i.e., most insects). Innovative, manipulative
experiments are needed in order to address recolonization mechanisms of animals inhabiting streams that differ in size, latitude,
disturbance frequency and magnitude, as well as the potential influence of early colonists on successional sequences of species
following disturbance. 相似文献
228.
CHANGING RAINFALL-RUNOFF RELATIONSHIPS IN THE URBANIZING PEACHTREE CREEK WATERSHED,ATLANTA, GEORGIA1
Bruce K Ferguson Philip W. Suckling 《Journal of the American Water Resources Association》1990,26(2):313-322
ABSTRACT: Peachtree Creek is a gaged watershed that has experienced a substantial increase in urbanization. The relationships of runoff to rainfall were studied for total annual flows, low flows, and peak flows. For each type of flow the relationship in the later, more urbanized period was compared to that in the earlier, less urbanized period. An increase in total runoff in wet years was observed as urbanization increased, but a decrease occurred during dry years. For low flows a similar decrease of runoff in dry years was found. An increase in peak runoff was observed over most of the range of precipitation. Increasing peak flows and declining low flows can be adequately explained by urban hydrologic theoryshed. which focuses on the effects of urban impervious surfaces upon direct runoff and infiltration. However, a decline of total runoff in dry years can be explained only by taking into account evapotranspiration as well. The concept of advectively assisted urban evapotranspiration, previously discovered by climatologists, is needed to explain such a loss of total runoff. Urban hydrologic theory must take into account vegetation and evapotranspiration, as well as impervious surfaces and their direct runoff, to explain the magnitude of total annual flows and low flows. Urban stormwater management should address the restoration of low flows, as well as the control of floods. 相似文献
229.
Thomas Carlisle George Mulamoottil Bruce Mitchell 《Journal of the American Water Resources Association》1991,27(3):419-427
ABSTRACT: The objective was to survey individuals from different interest groups in Ontario to ascertain attitudes towards the use of artificial wetlands for stormwater management and to provide waterfowl habitat. In total, 166 questionnaires were distributed and 124 cempleted returns were received. The results of the survey show that the provision of wetlands as waterfowl habitats in the context of stormwater impoundments is severely limited and is not considered an important management option. The overwhelming rejection of this integrated approach seems to be due to a lack of understanding and its comparative newness. Some of the perceived problems and concerns could be addressed by improvements in the design of the artificial wetlands. The design and implementation of an artificial wetland prototype as part of an education program in Ontario is recommended. A few research opportunities also are outlined. 相似文献
230.
Peter M. Allen Jeffrey C. Arnold Bruce W Byars 《Journal of the American Water Resources Association》1994,30(4):663-671
ABSTRACT: There is considerable potential for use of channel dimension data in planning-level models for resource and impact assessment. The channel dimension data is used to route flows and sediment through the basin. The cost of obtaining actual surveyed data for large watersheds is typically prohibitive. Predictive equations have been developed based on 674 stations from watersheds across the United States which encompass a wide variety of channel types and sizes. These equations were tested against an independent data set and found to be adequate for use in planning-level models. Future research is advocated which would include data from regions and stream types not included in this study. 相似文献