温度和CO2浓度升高对荒漠藻结皮光合作用的影响

2007年,对腾格里沙漠东南缘沙坡头地区1956年(51龄)和1981年(26龄)人工植被区及自然植被区的藻结皮净光合速率(P_n)变化,及其与结皮含水量(>100%、40%～60%和<20%)、大气CO₂浓度(360和700 mg·L^-1)和温度(13 ℃、24 ℃ 和28 ℃)的关系进行研究.结果表明：51龄、26龄人工植被区和自然植被区的藻结皮P_n分别为3.4、4.4和3.2 μmol·m^-2·s^-1,且51龄人工植被区藻结皮的P_n显著高于26龄人工植被区和自然植被区;藻结皮含水量对其P_n影响显著,且中等含水量(40%～60%)藻结皮的P_n显著高于低含水量(<20%)和高含水量(>100%);CO₂倍增(700 mg·L^-1)后,中等和高含水量藻结皮的P_n增加了1.8～3.3倍,而低含水量时,藻结皮的P_n变化不明显;高含水量和中等含水量处理时,24 ℃和28 ℃条件下藻结皮的P_n较13 ℃时提高27%～66%,而在低含水量时,不同温度的藻结皮P_n值无显著差异.     

Enamel incremental periodicity in the pig-tailed macaque: A polychrome fluorescent labeling study of dental hard tissues

Bromage and Dean originally outlined a nondestructive method for the study of enamel formation and concluded that early hominids resembled the extant apes more closely than they did modern humans in their rates of growth and maturation. The method used assumed that an enamel circadian rhythmicity was referable to a longer near-weekly period represented by perikymata (periodic surface growth features). This assumption became a matter of debate and discussion. In this study, developing teeth in Macaca nemestrina were labeled with polychrome fluorescent dyes. Examination of the distribution of these dyes in two sectioned teeth provides experimental confirmation of enamel circadian periodicity.     

Prediction of protein coding regions by the 3-base periodicity analysis of a DNA sequence

With the exponential growth of genomic sequences, there is an increasing demand to accurately identify protein coding regions (exons) from genomic sequences. Despite many progresses being made in the identification of protein coding regions by computational methods during the last two decades, the performances and efficiencies of the prediction methods still need to be improved. In addition, it is indispensable to develop different prediction methods since combining different methods may greatly improve the prediction accuracy. A new method to predict protein coding regions is developed in this paper based on the fact that most of exon sequences have a 3-base periodicity, while intron sequences do not have this unique feature. The method computes the 3-base periodicity and the background noise of the stepwise DNA segments of the target DNA sequences using nucleotide distributions in the three codon positions of the DNA sequences. Exon and intron sequences can be identified from trends of the ratio of the 3-base periodicity to the background noise in the DNA sequences. Case studies on genes from different organisms show that this method is an effective approach for exon prediction.     

粤东柘林湾中肋骨条藻(Skeletonema costatum)种群生态学

于2000年5月～2004年12月对粤东大规模养殖区柘林湾的赤潮藻中肋骨条藻（Skeletonema costatum）种群的时空分布进行了长达5a的调查。结果表明,中肋骨条藻种群密度的周年变动模式基本为双峰型,平面分布没有显著的空间差异。调查期间,中肋骨条藻种群密度的站位实测值为0～1．4×10^7cells／dm^3,总均值为3．3×10^5cells／dm^3,占浮游植物总细胞数的67．1％,为调查海区第1优势种。在总共1045份样品中,有中肋骨条藻出现的样品数为1020份。其中,种群密度大于10^6cells／dm^3的样品有65份,大于10^7cells／dm。则有4份。以大于10^6cells／dm^3为中肋骨条藻的赤潮密度标准,在调查期间至少于2000年、2003年发生4次赤潮。运用灰关联理论对中肋骨条藻种群密度与13个环境因子的关系进行排序分析发现,水温、pH值和浮游动物是影响柘林湾中肋骨条藻种群时空分布的关键因子。水温还与中肋骨条藻种群密度的对数值具极显著意义的线性关系,而达到赤潮密度的样品均落在24．5～32．0℃区间,即每年的5～9月份高温季节。由于柘林湾浮游动物的年高峰期也出现在高温季节,说明浮游动物摄食压力的存在可能是柘林湾中肋骨条藻赤潮发生的重要抑制因子。2004年调查海区中肋骨条藻种群密度和在浮游植物群落中的优势度骤然降低,可能与水体营养盐结构和Fe含量的变化有关。因此,长期调查与监测对于研究海湾生态学和赤潮发生机制是极为重要的。     

Microalgal growth enhancement by levoglucosan isolated from the green seaweed <Emphasis Type="Italic">Monostroma nitidum</Emphasis>

Microalgal growth was enhanced by the addition of levoglucosan to the culture medium. The growth-enhancing compound levoglucosan was isolated from the green seaweed Monostroma nitidum using water extraction, molecular fractionation, DEAE-cellulose column chromatography, and high-performance liquid chromatography. Yield of the compound from seaweed powder was 5 × 10⁻³% (w/w). At 10 mM concentration, levoglucosan enhanced cell growth and the specific growth rate of all feed microalgal species tested (Chaetoceros gracilis, Chlorella ellipsoidea, Dunaliella salina, Isochrysis galbana, Nannochloris oculata, Navicula incerta, Pavlova lutheri, Tetraselmis suecica) in most culture media by approximately 150%. Cellular fatty acid profiles and cell size differed marginally between cultures with and without levoglucosan.     

Intraspecific facilitation by allelochemical mediated grazing protection within a toxigenic dinoflagellate population

Dinoflagellates are a major cause of harmful algal blooms (HABs), with consequences for coastal marine ecosystem functioning and services. Alexandrium fundyense (previously Alexandrium tamarense) is one of the most abundant and widespread toxigenic species in the temperate Northern and Southern Hemisphere and produces paralytic shellfish poisoning toxins as well as lytic allelochemical substances. These bioactive compounds may support the success of A. fundyense and its ability to form blooms. Here we investigate the impact of grazing on monoclonal and mixed set-ups of highly (Alex2) and moderately (Alex4) allelochemically active A. fundyense strains and a non-allelochemically active conspecific (Alex5) by the heterotrophic dinoflagellate Polykrikos kofoidii. While Alex4 and particularly Alex5 were strongly grazed by P. kofoidii when offered alone, both strains grew well in the mixed assemblages (Alex4 + Alex5 and Alex2 + Alex5). Hence, the allelochemical active strains facilitated growth of the non-active strain by protecting the population as a whole against grazing. Based on our results, we argue that facilitation among clonal lineages within a species may partly explain the high genotypic and phenotypic diversity of Alexandrium populations. Populations of Alexandrium may comprise multiple cooperative traits that act in concert with intraspecific facilitation, and hence promote the success of this notorious HAB species.     

Severe Karenia brevis red tides influence juvenile bottlenose dolphin (Tursiops truncatus) behavior in Sarasota Bay,Florida

Harmful algal blooms (HABs) are natural stressors in the coastal environment that may be increasing in frequency and severity. This study investigates whether severe red tide blooms, caused by Karenia brevis, affect the behavior of resident coastal bottlenose dolphins in Sarasota Bay, Florida through changes to juvenile dolphin activity budgets, ranging patterns, and social associations. Behavioral observations were conducted on free‐ranging juvenile dolphins during the summer months of 2005–2007, and behavior during red tide blooms was compared to periods of background K. brevis abundance. We also utilized dolphin group sighting data from 2004 to 2007 to obtain comparison information from before the most severe recent red tide of 2005 and incorporate social association information from adults in the study area. We found that coastal dolphins displayed a suite of behavioral changes associated with red tide blooms, including significantly altered activity budgets, increased sociality, and expanded ranging behavior. At present, we do not fully understand the mechanism behind these red tide‐associated behavioral effects, but they are most likely linked to underlying changes in resource availability and distribution. These behavioral changes have implications for more widespread population impacts, including increased susceptibility to disease outbreaks, which may contribute to unusual mortality events during HABs.