Prolonged inundation and ecological changes in an Avicennia mangrove: implications for conservation and management

The mangrove around Sungei Pemburongunan, just west of Tanjong Batu and Istana Darul Aman in the Brunei-Muara District, is unique in that it contains the only pure stand of Avicennia marina in Brunei Darussalam. In mid-October, 1990 the mouth of Sungei Pemburongunan was closed due to a natural build-up of a sandbar across it. The mangrove quickly became flooded and adverse effects on the flora and fauna were observed during the following weeks. In mid-December a channel was dug across the sand bar to reduce the flooding and normalise the ecology. Some of the dying Avicennia and Lumnitzera have since recovered but others such as Acrostichum and Casuarina have not. Avicennia showed some interesting responses to prolonged inundation. Many of the Avicennia that had flowered during the flood produced seedlings which are now well rooted and 40–80 cm in height. The survival of large numbers of these seedlings is attributed to the floor-related decrease in the number of grapsid and sesarmid crabs which predate on them. The crab and mollusc populations have largely recovered. Unlike periodic short-term flooding which does not seem to have any apparent adverse affect on the ecosystem, prolonged inundation can result in the loss of the Avicennia and its associated flora and fauna. Thus, fragile mangrove ecosystems such as this need to be monitored and managed closely.This work demonstrates that contrary to conventional wisdom, human intervention and management can be beneficial to more fragile ecosystems, which could otherwise succumb to natural processes. Furthermore, it highlights the importance of the dynamic nature of the environment which should be considered in management and conservation programmes.     

Measurement of luminescence in coral skeletons

Luminescent lines in skeletons of the massive coral Porites record periods when seawater was significantly diluted by land runoff. Records developed from such lines would be useful in a wide range of areas, including climatology, oceanography, civil engineering, agriculture, water resources and reef management. To realise this enormous potential, we built an instrument for routine, reliable recovery of luminescence information from coral skeletons. Skeletal slices were laid on a table that moved in 0.25 mm steps. The coral skeleton was illuminated with ultra-violet light (UV) at 390 nm and luminescent emissions at 490 nm were recorded. Light at 490 nm was then shone on the same 2 mm diameter point on the skeleton and the reflection of 490 nm light was recorded. Luminescent emissions from a point were then standardised by the reflectivity of that same point.Slices cut from three corals that grew at an inshore reef had many strong luminescent lines. Measurements of luminescence in these colonies were nearly identical, both for multiple tracks across one slice and for tracks across slices from the different corals. There was a clear link with discharge from a nearby river. Slices cut from two corals that grew at a reef 56 km offshore had occasional, weak luminescent lines that were also linked with river discharge. Tracks across these slices were similar but the weak luminescence due to river discharge was partially obscured by weak luminescence associated with the annual density banding pattern that characterises massive coral skeletons. The technique recovered excellent information about skeletal luminescence. However, there is a need to gain better understanding of the link between seawater dilution and luminescence and to develop procedures for data processing before the technique can be used to construct useful proxy environmental records.     

Seasonal changes in haematology and metabolic resources in the tench

Significant variations in the number of white and red blood cells, haematocrit and haemoglobin were found throughout the year in sexually mature male and female tench Tinca tinca . In general, the lowest values were observed during autumn–winter and the highest during summer, with males exhibiting higher values than females. Plasma glucose, cholesterol and triglycerides were lower during the winter than during the summer–autumn seasons in both sexes. Gonado-somatic and hepato-somatic indices were inversely correlated in female tench throughout the year. Seasonal patterns in liver metabolic resources were very similar for both sexes. For males and females, liver glycogen and proteins increased during the autumn, whereas the liver stored lipid during spring. Dorsal muscle mainly deposited glycogen, whereas lipid was mainly stored in the ventral muscle. Relations between seasonal changes in environmental factors, such as feeding and temperature are discussed.     

不同土地类型下重金属随暴雨径流迁移过程及速率对比

选择太湖上游西苕溪流域最具代表性的5种土地类型,利用野外人工降雨装置,研究了不同形态重金属(Cu,Cr,Pb,Zn)随暴雨径流水相及沉积物相的迁移过程,对比了流域内不同土地利用／土地覆被条件下重金属的迁移特征,并估算了流失速率。结果表明,在相同的降雨条件下,桑林Cu、Zn和Pb随地表径流水相的迁移量最大。分别达0．21、0．45和0．15mg·m^-2·min^-1;水田Cr迁移量最大,达0．06mg·m^-2·min^-1;松林重金属迁移量都很小,而且重金属随地表径流水相的迁移主要是通过悬浮细颗粒态。地表径流沉积物相的重金属流失量远高于水相。水相迁移速率仅占沉积物相迁移率的0．1％～4．9％;从地表径流水相重金属迁移量占沉积物相迁移量的比例来看,Cu较高,Cr、Pb、Zn较低。     

浑善达克沙地高西马格剖面孢粉分析及植被演化的初步探讨

 为了探讨浑善达克沙地5 000年以来的植被演化过程, 我们对内蒙古正蓝旗境内高西马格湖人工挖掘2.0 m深的剖面进行了较高时间分辨率的孢粉分析,并参考孢粉组合与植被之间的对应关系,得出: 该期的植被和气候演化大致可以划分为3个阶段：阶段 I（约5 010～4 040 aBP）,孢粉组合     

表达阳离子抗菌肽的转基因棉花表型异常

用基因枪轰击茎尖法将人工合成的阳离子抗菌肽CEMA基因导入棉花中,获得3株转基因棉花,它们均出现嵌合体表型。在表型不正常的枝条上,叶片扭曲畸形,出现灰绿色与绿色条纹相间的花叶,花器发育异常、无花粉、人工授粉不能结实。花叶区的叶绿素含量降低约20％,叶肉栅栏组织细胞局部缺损,维管束及其管状分子数目减少。叶片灰绿色区叶肉细胞的次生壁明显增厚,局部区域吞噬现象明显,叶绿体内基粒片层数目较少,嗜锇小体明显较多,类囊体腔不明显。PCR分析表明,仅在不正常枝条的花叶中检测到外源CEMA基因。     

Seasonal variations in the behavioural thermoregulation of roosting Humboldt penguins ( Spheniscus humboldti) in north-central Chile

We examined the thermoregulatory behaviour (TRB) of roosting Humboldt penguins (Spheniscus humboldti) in north central Chile during summer and winter, when ambient temperatures (T_a) are most extreme. Each body posture was considered to represent a particular TRB, which was ranked in a sequence that reflected different degrees of thermal load and was assigned an arbitrary thermoregulatory score. During summer, birds exhibited eight different TRBs, mainly oriented to heat dissipation, and experienced a wide range of T_a (from 14 to 31°C), occasionally above their thermoneutral zone (TNZ, from 2 to 30°C), this being evident by observations of extreme thermoregulatory responses such as panting. In winter, birds exhibited only three TRBs, mainly oriented to heat retention, and experienced a smaller range of T_a (from 11 to 18°C), always within the TNZ, even at night. The components of behavioural responses increased directly with the heat load which explains the broader behavioural repertoire observed in summer. Since penguins are primarily adapted in morphology and physiology to cope with low water temperatures, our results suggest that behavioural thermoregulation may be important in the maintenance of the thermal balance in Humboldt penguins while on land.     

The effects of temperature changes on the oxygen consumption of juvenile Chinese shrimp Fenneropenaeus chinensis Osbeck

The effects of temperature changes on oxygen consumption of Chinese shrimp (Fenneropenaeus chinensis Osbeck) were studied. The response of oxygen consumption to a temperature rise was conformed to partial metabolic compensation. No compensatory response was observed at lower temperature. A sudden temperature increase by 12 °C resulted an overshoot in oxygen consumption in shrimp adapted to 19 °C, while a sudden decrease by 12 °C in shrimp adapted to 19 °C resulted in an undershoot in oxygen consumption. The shrimp adapted to 31 °C responded with an undershoot in oxygen consumption when a sudden temperature drop by 12 °C occurred. But overshoot in oxygen consumption did not occur when the shrimps were transferred back from 19 to 31 °C. The amplitude of oxygen consumption was reduced in shrimp during the process of acclimation to the temperature diel fluctuation. After the shrimp had adapted to the temperature fluctuation, the daily mean oxygen consumption of shrimp at diel temperature fluctuation from 24 to 30 °C was significantly lower than those adapted to the constant temperature at 27 °C (P<0.05). The decrease in metabolic rate may account for the increase in the growth rate of shrimp at a diel fluctuating thermal regime.     

Molecular Morphology of Eukaryotic Class-1 Translation Termination Factor eRF1 in Solution

The integral structural parameters and the shape of the molecule of human translation termination factor eRF1 were determined from the small-angle X-ray scattering in solution. The molecular shapes were found by bead modeling with nonlinear minimization of the root-mean-square deviation of the calculated from the experimental scattering curve. Comparisons of the small-angle scattering curves computed for atomic-resolution structures of eRF1 with the experimental data on scattering from solution testified that the crystal and the solution conformations are close. In the ribosome, the distance between the eRF1 motifs GGQ and NIKS must be shorter than in crystal or solution (75 versus 100–107 Å). Therefore, like its bacterial counterpart RF2, the eukaryotic eRF1 must change its conformation as it binds to the ribosome. The conformational mobility of eukaryotic and prokaryotic class-1 release factors is another feature making them functionally akin to tRNA.