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991.
Mud crabs of the genus Scylla are commercially important mangrove residents that are extensively fished throughout their range in the Indo-West Pacific.
Despite this high level of exploitation very little is known about the population dynamics of any of the Scylla species. The present study concentrated on an exploited population of Scylla
paramamosain in a natural estuarine mangrove on Can Coc Island in the mouth of the Hau River, Mekong Delta, Vietnam. A total of 6,114
juvenile crabs captured on the seaward mangrove fringe were internally tagged by injection of coded microwire tags and released
over a period of 29 days. Recaptures were monitored over the following 144 days. There was little migratory movement within
the estuary; of 285 recaptured crabs, 93% were recovered within the island mangrove study area and only two individuals were
recovered from mangroves lining the opposite mainland riverbanks. A von Bertalanffy growth function was fitted to growth increment
data from recaptured crabs, with L
max = 150 mm to derive a growth constant, k = 2.39 year−1. The theoretical age at which carapace width is zero (t
0) was derived from known size at recruitment at instar 1, giving a value of −0.0095 years. Previous studies of the same population
have shown that female S. paramamosain reach maturity at a mean size of 102 mm carapace width. The present study indicates that they attain this size at around
160 days from first settlement in the mangrove fringe. Abundance of juvenile crabs in the study area was estimated by the
Petersen method as 1,101,500 (95% CI 4,17,300–1,785,800, representing 1,102 crabs ha−1 of mangrove. Estimation of mortality from tag returns and from the age-catch curves during a period of constant recruitment
were comparable (Z = 1.11 and 1.04 month−1, respectively). Fishing only accounted for 14% of total mortality, suggesting that at the time exploitation was not at a
critical level despite the apparent high level of fishing activity. 相似文献
992.
Zooplankton of tikehau atoll (Tuamotu archipelago) and its relationship to particulate matter 总被引:2,自引:0,他引:2
The standing stock and taxonomic composition of zooplankton (>200 m) were monitored in the lagoon of Tikehau atoll from April 1985 to April 1986. These data were supplemented by two 10 d studies on the variability, structure and functioning of the pelagic ecosystem. The biomass of animals >200 m comprised 50% of the total biomass of all organisms from 35 to >2000 m. The zooplankton populations were characterized by successive blooms of copepods, larvaceans, pteropods and salps, probably arising from the periodic input of detritus from the reef during windy periods. As a result, the ecosystem was not in a steady state and the data for the fluxes of organic matter are presented separately for April 1985 and April 1986. Using the C:N:P ratio method, net growth efficiencies, K
2, were calculated for total mesozooplankton, mixed copepods, and two planktonic species, Undinula vulgaris and Thalia democratica. Combined with nitrogen and phosphorus excretion rates, these K
2 values enabled the assessment of production rates. On a 24 h basis, P:B ratios (%) were close to 100 for the total zooplankton and 54, 34 and 800 for mixed copepods, U. vulgaris and T. democratica, respectively. These ratios are 5.7 times lower than that recorded for phytoplankton. High productivity may be ascribable to the high density of seston, the high temperature (29.5°C), and the kind of organisms present. Zooplankton production equalled 38 and 30% of 14C uptake during April 1985 and April 1986, respectively. Ingestion of animals >35m was calculated by means of assimilation efficiencies and amounted to 17 and 7% of particulate organic carbon, 100 and 38% of living carbon, and 64 and 140% of primary production during the two periods, respectively. Finally, inorganic exduring was 32 and 18% of phytoplankton nitrogen and phosphorus requirements. A model based on the dimensional structure of the pelagic food-web, has been drawn to illustrate the biomass and carbon, nitrogen and phosphorus fluxes in the study area. The lagoon appears to export part of its planktonic biomass, which is 4.2 times lower one sea mile outside the main pass connecting the lagoon to the open ocean. 相似文献
993.
994.
Bertrand Segues Jean-Michel Rozet Brigitte Gilbert Pascale Saugier-Veber Daniel Rabier Jean-Marie Saudubray Mireille Carré Françoise Parrot Rouleau Alain Menget Jean-Michel Bonardi Stanislas Lyonnet Jean-Paul Bonnefont Arnold Munnich 《黑龙江环境通报》1995,15(8):757-761
Ornithine transcarbamylase (OTC) deficiency is an X-linked disorder of the urea cycle mapped to chromosome Xp21.1. Here, we show that apparent segregation of null alleles at the OTC locus and flanking polymorphic loci mimicked false maternity or false paternity in three affected families. Based on these observations, we suggest giving consideration to gene deletion when dealing with segregation of null alleles in OTC deficiency. 相似文献
995.
Louis V. Verchot Meine Van Noordwijk Serigne Kandji Tom Tomich Chin Ong Alain Albrecht Jens Mackensen Cynthia Bantilan K. V. Anupama Cheryl Palm 《Mitigation and Adaptation Strategies for Global Change》2007,12(5):901-918
Agriculture is the human enterprise that is most vulnerable to climate change. Tropical agriculture, particularly subsistence
agriculture is particularly vulnerable, as smallholder farmers do not have adequate resources to adapt to climate change.
While agroforestry may play a significant role in mitigating the atmospheric accumulation of greenhouse gases (GHG), it also
has a role to play in helping smallholder farmers adapt to climate change. In this paper, we examine data on the mitigation
potential of agroforestry in the humid and sub-humid tropics. We then present the scientific evidence that leads to the expectation
that agroforestry also has an important role in climate change adaptation, particularly for small holder farmers. We conclude
with priority research questions that need to be answered concerning the role of agroforestry in both mitigation and adaptation
to climate change. 相似文献
996.
Maria Paola Iampieri Rita Mingarelli Eric Le Guern Giuseppe Novelli Professor Bruno Dallapiccola 《黑龙江环境通报》1994,14(4):285-289
Five pregnancies at risk for X-linked retinitis pigmentosa (RP) have been monitored by first-trimester prenatal diagnosis using DNA markers flanking the RP2 and RP3 loci. Three affected and two unaffected fetuses, including a female carrying a wild-type genotype, were predicted on the basis of marker segregation and estimation of the recombination fraction. 相似文献
997.
M. Salvy Y. Capowiez Y. Le Conte M. Salvy J.-L. Clément 《Die Naturwissenschaften》1999,86(11):540-543
Varroa jacobsoni is an ectoparasite of honey bees which reproduces in capped brood cells. Multi-infestation is frequently observed in worker
brood and can be interpreted as an aggregative phenomenon. The aim of this study was to determine whether the distribution
of V. jacobsoni in worker brood cells relies on a random or an aggregative process. We studied the distribution of Varroa females in capped worker brood at similar age by comparing, by a Monte Carlo test, the observed frequency distribution of
mites per cell to simulated distributions based on a random process. A complementary approach, using the "nearest neighbor
distances" (NND) with Monte Carlo tests, was investigated to study the spatial distribution (a) between mites in different
cells and (b) between infested cells in brood. The observed distributions did not differ significantly from that expected
by a random process, and we conclude that there is no aggregation during invasion of V. jacobsoni in worker brood.
Received: 29 April 1999 / Accepted in revised form: 26 August 1999 相似文献
998.
铁铝盐基离子对土壤中水溶性氟环境效应的影响 总被引:1,自引:0,他引:1
氧化物或粘土矿物可吸附氟离子,但磷酸根离子与氟离子存在竞争吸附效应,造成氟的环境存在量、存在形态及生物效应更加复杂,影响了环境中氟污染的治理.试验选用典型贵州黄壤和石灰土,通过向模拟高氟污染土壤中添加铁铝盐基离子和磷酸盐,采用两因素最优设计,研究外源物质对土壤中水溶性氟的影响.结果表明,FeCl3·6H2O或AlCl3·6H2O都能降低土壤中水溶性氟,而KH2PO4使土壤中水溶性氟增加,对黄壤和石灰土中水溶性氟影响效果大小依次为FeCl3·6H2O(AlCl3·6H2O)、KH2PO4.同时表明,采用铁铝盐基离子改变黄壤性质,达到降氟效果仍有很大潜力,而石灰土环境在高添加铁铝盐基离子水平下继续添加FeCl3·6H2O或AlCl3·6H2O降低土壤中水溶性氟的作用较弱.从土壤pH看,黄壤水溶性氟受试验因子影响复杂,土壤pH低水溶性氟不一定低,pH在4~6时,氟元素的形态及有效性尤其复杂,而石灰土中水溶性氟基本随pH降低而降低. 相似文献
999.
Adsorption and precipitation of tetracycline with struvite. 总被引:1,自引:0,他引:1
Sibel Ba?ak?ilardan-Kabakci Andrew Thompson Elise Cartmell Kristell Le Corre 《Water environment research》2007,79(13):2551-2556
The interaction of tetracycline with struvite during adsorption and precipitation processes was investigated. Tetracycline removal by adsorption was affected by solution pH, contact time, and struvite concentration. The lowest tetracycline removal (8.4%) was observed at pH 7.7, the dissociation constant (pKa2) of tetracycline. Because of the electrostatic repulsion, the amount of tetracycline adsorbed on the surface was low. The small amount of adsorption was the result of surface complexation between tetracycline ions and metal ions. Calcium (Ca2+) ions in the adsorbent enhanced the binding of tetracycline. Freundlich (KF: 0.04, n: 1.49) and Redlich-Peterson (KR: 0.08, alphaR: 0.98, betaR: 0.49) models best defined the equilibrium data. In the case of struvite precipitation, approximately 22% of tetracycline was removed as a result of binding to struvite alongside struvite formation. 相似文献
1000.