Kinetics of the polymerization of isoprene with isopropoxyneodymium dichloride/triethylaluminium binary lanthanide catalyst system

The kinetics of the polymerization of isoprene with the heterogeneous rare earth catalyst system isopropoxyneodymium dichloride/triethylaluminium (Nd(OPri)Cl-2-AlEt(3)) was examined in a specially designed dilatometer. The rate of polymerization is expressed as R(p) approximate to -d[M]/dt = k'(p)[Nd](1.40)[M]. The main kinetical parameters such as the concentration of active propagating chain, the efficiency of lanthanide catalyst used (ELCU), the absolute rate constant of propagation as well as the average life time of growing chains, were determined at 30 degrees C, 40 degrees C, 45 degrees C and 50 degrees C.

Effects of Irradiance and Temperature on the Photosynthesis and Vegetative Propagation of Caulerpa serrulata

The photosynthetic oxygen evolution of Caulerpa serrulata was determined with oxygen electrodes. The effects of light and temperature on the growth and regeneration of fragmented C. serrulata thalli were analyzed. The regenerating rate and establishment of different sizes and portions of C. serrulata were studied. The results showed that the light saturation point of C. serrulata was 200 mu mol photons/m(2) per s and the optimum growth temperature was 25-30 degrees C. Under these conditions, the maximum photosynthetic oxygen evolution rate was 15.1 +/- 0.29 mg O-2/mg Chl a/h, the growth rate and elongation rate reached the highest values, 4.67 +/- 0.09 mg FW/d and 0.78 +/- 0.01 mm/d, respectively. The fragmented C. serrulata thalli was regenerated at 20-35 degrees C and survived at 15 degrees C and 200 mu mol photons/m(2) per s. A different survival rate was detected according to fragment size. All of these results indicated that C. serrulata was a candidate to become an invasive species if introduced into a new place. Therefore, we should pay more attention to C. serrulata for its potential threat to marine ecosystem when it is sold for aquarium use.

滤食性贝类筏式养殖对浅海生态环境影响的基础研究

近年来，由于对海区不合理的开发，我国浅海贝类筏式养殖接连遭受重创，这亟需从理论上和实践中确定养殖容量和养殖模式。本文在我国北方典型养殖海湾四十里湾对筏式养殖的贝类开展了现场生理生态学研究，对贝类对浮游植物等悬浮颗粒物的处理过程即贝类对颗粒有机物及营养元素C、N、P的摄食、吸收、排泄、排粪和生长进行了剖析，分析了贝类在沿岸养殖生态系中的物质和营养循环中所扮演的角色，为海区贝类养殖容量和养殖模式的最终确定提供了基础数据。另外，本文还对海水、沉积物及生物体中磷的分析方法进行了大量的实验工作。主要结果如下：① 比较系统地评述了双壳贝类的生物沉积(biodeposition)的原理、测定方法及其生态效应。贝类通过生物沉积在沿岸生态系中的物质和营养循环中扮演着重要的角色。国际上已有不少研究专门报道了贝类在海区现场的生物沉积。而在我国，这方面的研究却罕见。② 综述了双壳贝类各种形态的 N 和 P 排泄及其生态效应。对于我国广泛养殖 的栉孔扇贝、海湾扇贝和牡蛎等双壳贝类的TDN、TP排泄尚未见报道。 ③ 在6～7月，在四十里湾的不同养殖海区(8个站位)对扇贝的生物沉积进行了现场测定。在整个四十里湾海区，一龄栉孔扇贝(壳高 41.1±4.1mm，软体干重 0.48±O.10 g/ind))每个每天所产生生物沉积物干重平均为59.9mg，对颗粒有机质(POM)、颗粒有机碳(POC)、颗粒有机氮(PON)和颗粒有机磷(POP)的生物沉积速率范围及平均值分别为： 6.88、3.09、0.392 和 0.022mg/ind·d。还在一个站位测定了海湾扇贝(壳高 24.6±2.3mm；软体干重 O.14g/ind)的生物沉积速率为 24.3mg/ind·d，或179.2mg/g·d。不同站位一龄栉孔扇贝的生物沉积速率有较大变化，这主要与饵料浓度不同有关。二龄栉孔扇贝(壳高60.9±8.2mm；软体干重1.91±0.32 g/ind)的生物沉积速率平均为 112.7mg/ind·d，对POM、POC、PON和POP的沉积速率分别是一龄扇贝的1.85倍、1.68倍、1.77倍和2.33倍。养殖海区与非养殖海区比较，前者近海底沉积速率是后者的 1.51～3.47 倍。根据以上数据，作者计算了中等规格栉孔扇贝(用壳高 41.1±4.8mm 扇贝估算)在四十里湾在夏季每天的生物沉积量达 162 吨(干重)，或18.6tPOM、8.37tPOC、1.06tPON和60kgPP。在四十里湾的贝类筏式养殖海区，可以估计贝类每年因生物沉积的生产而循环427tN和98.OtP(包括20.0t OP的贡献)，它们能分别满足浮游藻类生产所需求N和P的17.0％和28.3％(其中OP贡献 6.9％)。可见，贝类在养殖生态系的物质和营养盐循环中扮演着重要的角色。高密度、大面积的贝类养殖使大量的生物沉积物聚集于海底，可能对海区环境产生冲击。作者分析，98年8月份烟台养殖区赤潮的发生很可能与海底生物沉积物营养盐的快速释放以及栉孔扇贝大面积死亡而使浮游藻类失去了摄食控制有关，而风平浪静和养殖笼对水流的阻挡也为赤潮的发生提供了有利条件。④ 采用半现场流水系统法测定了栉孔扇贝在不同养殖密度、不同养殖模式(扇贝单养、贝藻混养、贝藻参混养)中的生物沉积。实验时间尺度大，前后计80天。结果说明扇贝的生物沉积速率与其养殖密度呈反比关系。养殖密度的高低影响饵料浓度的变化(两者呈负相关的对数函数关系)，而饵料浓度的高低直接决定着扇贝的生物沉积速率的高低，两者呈正相关关系(生物沉积速率与POC和叶绿 a 分别呈对数和指数函数关系)。不仅生物沉积物的数量与养殖密度(或饵料浓度)有关，生物沉积物的质量同样与养殖密度(或饵料浓度)有关。栉孔扇贝的养殖使沉积物的有机质含量及C、N 和 P 含量降低，且密度越高，它们的含量越低。这反映了扇贝对环境的适应能力。在海带和扇贝的混养模式中，海带对扇贝生物沉积物的数量和质量不构成影响，当然这是在海带不影响浮游植物数量的前提下得出的结果。而实际上在自然海区两者可能是竞争关系。⑤ 对从海区取回到实验室的多种滤食性动物，包括经济双壳贝类(栉孔扇贝、海湾扇贝、长牡蛎、贻贝、菲律宾蛤仔等)和养殖中的污损动物(栖海鞘、玻璃海鞘、藤壶、玟斑稜蛤)的 N 和 P 排泄进行了测定，包括排泄成分和排泄速率。在N排泄中，NH_4-H 占主要部分，如笼式养殖的双壳贝类 NH_4-N 占总N排泄的70％以上，平均值范围为70.8～80.1％。氨基酸是第二大排泄成分，平均占总N排泄的10～25％。其它形态的N，如尿素、亚硝酸盐和硝酸盐也有检出，如双壳贝类尿素氮在总氮排泄中占 2～5％。但在双壳贝类中未检出尿酸氮。比较而言，海鞘、藤壶的尿素氮相对高一些。在P排泄中，OP约占TDP排泄的15～27％。栉孔扇贝TDP排泄速率为0.281μmol/h·ind。作者以实验室测定结果计算，在整个四十里湾的夏季，所养殖的双壳贝类每天将排泄4.54t总溶解氮，其中NH_4-N 3.36t、Amino-N 0.69t、Urea-N 0.2t。 同时每天磷的排泄为0.57t TDP，其中OP O.15t。对面积为1.3 * 10~4hm~2的海区而言，贝类的N、P排泄分别能满足浮游植物生产所需N、P的44％和40％。尽管Urea-N所占比例有限，但也能满足海区浮游植物所需 N 的 2％左右。以上说二月高密度的贝类养殖对海区生态系统营养盐循环的影响是很显著的。附着动物(柄海鞘等)的N、P 排泄也不容忽视，它们分别能满足浮游藻类生产所需 N、P 的 ll％和 12％。它们一方面通过排泄和排粪加速营养盐和物质的循环对浮游植物的生长产生刺激作用；另一方面，对藻类产生摄食控制，如果海区中滤食性动物太多，即使营养盐再丰富也难以使浮游植物大量繁殖，这无疑将影响滤食性动物的生长速率。⑥ 运用近年来发展起来的生物沉积法对四十里湾半现场流水系统中贝类的滤水率、吸收率、生长率、生态效率等生理生态学参数进行了测定。栉孔扇贝(收获时规格0.194～0.412g软体干重/ind)滤水率平均为3.65 1/ind·h。扇贝放养密度和饵料浓度没有显著关系。扇贝的总摄食率平均为3.98mg/ind·h，对POM、POC、PON的 摄食率范围为0.84～1.87、0.335～0.748、0.0515～O.1293mg/ind·h。扇贝的摄食率随放养密度的升高而降低，与POM呈正相关关系。扇贝的吸收速率受密度和饵料浓度的影响不明显。扇贝对N的吸收效率较C、P稍高，对总有机质的吸收效率为75.9±4.1％，如此高的吸收效率与低饵料浓度有关。扇贝氨基酸泄漏所损失的能量高于排氨的能量损失。代谢能与吸收能呈明显的正相关关系。SFG与饵料浓度呈正相关关系。总生长效率K1(* 100)变化较大，范围为20～49；净生长效率K，K_2(* 100)随POM的升高而升高。扇贝对N的总生态效率范围为6.2～12.8％(平均9.9％)，这高于对C(平均5.9％)和P(平均4.1％)的总生态效率。扇贝对POC、PON和PP的生长余力(SFG_C、SFG_N、SFG_P)平均分别为197、46.8和6.2μg/ind·h，它们分别与POC、PON和PP呈正比关系。扇贝对N的净生长率高于对C和P的净生长率。在N的预算中，如果仅考虑NH_4-N的排泄而忽视其它形态氮的排泄，将会产生很大偏差(平均约20％)。扇贝贝壳生长所需的能量在整个扇贝生长所需能量的9.0～15.1％(平均 11.2％)；贝壳C、N和P在扇贝生长中所占的比例分别为10.5～17.8％、9.4～16.1％和8.7～15.O％。可见，贝壳不管在能量预算还是在元素预算中都不应该被忽视。理论计算而得到的SFG和SFG_C、SFG_N、SFG_P与扇贝的实际生长和扇贝C、N、P的实际增长量之间呈正相关关系，但前者明显过高地估计了扇贝的生长。⑦ 运用生物沉积法在四十里湾养殖海区现场对栉孔扇贝的生理生态学特征进行了研究。不同海区扇贝的滤水率有变化，一龄扇贝(41.1±4.1mm，软体干重 0.48±O.10g/ind)滤水率变化范围为 0.72～2.54(平均 1.27)1/ind·h 或 1.65～5.97(平均 2.61)1/g·h。与半现场研究结果一致，滤水率与TPM没有明显关系，而摄食率却与TPM呈正相关关系。二龄扇贝(软体干重 1.91±0.32g/ind)滤水率为 2.09～3.99(平均 3.10)1/ind·h。吸收速率与POM(或TDM)呈正相关关系，与饵料质量(POM/TPM)无明显的相关关系。吸收效率AE_(POM)与TPM(或POM)没有相关关系，却与饵料质量呈明显 的正相关关系。扇贝对POC、PON和PP的吸收效率平均分别为68.9％、64.0％和63.6％。不同海区SFG差别很大。一龄扇贝SFG范围为-O.174～24.08 J/ind·h，SFG与饵料浓度POM呈正相关关系。SFG负值的出现主要与低饵料浓度有关。SFG_C、SFG_N、SFG_P分别与POC、PON和PP呈正相关关系。在N的生长余力计算中，如果仅考虑NH_4-N排泄，而不考虑其它形态N的排泄，就可能产生相当大的偏差，偏差范围为11～360％，这高于半现场的偏差值，显然SFG_N越低，产生的偏差就越大。这说明在饵料不足、扇贝生长受到限制的环境下进行N生长余力的计算时必须考虑其它形态N的排泄。⑧ 对四十里湾养殖海区一些双壳贝类和藻类的化学组成和有机净生产量进行了讨论。不同双壳贝类的软体有机碳含量差别不大，而N含量差异较大。栉孔扇贝N含量最高(占软体干重的12.36％)，而牡蛎、毛蚶软体N含量相对较低，为 8～9％。从双壳贝类贝壳的组成来看，贻贝和菲律宾蛤仔贝壳中N含量最高，分别为 0.55％ 和 0.56％；而栉孔扇贝贝壳N含量相对较低，在 O.1％左右。贻贝贝壳有机磷含量 (308ppm) 也明显高于栉孔扇贝贝壳(62.1 ppm)。不同海区海带的 C/N 比值较高，变化明显，范围为17.36～30.23。石莼与此相似。大型藻类高 C/N 比值说明海区营养元素N的不足。海带的不同部位N含量差别很大，中带部和边叶在不同海区有较大变化，即对环境的营养状况比较敏感。紫贻贝贝壳中C、H、N 和 P 的含量在整个贻贝中占有相对大的比例，分别为 30.4％、30.2％、31.8％和 29．6％。

Seasonal variation of reproduction rates and body size of Calanus sinicus in the Southern Yellow Sea, China

Annual variations of egg production rate (EPR) and clutch size of Calanus sinicus, as well as body size of females (prosome length and dry weight), were investigated at a series of stations in the Southern Yellow Sea by onboard incubation. Calanus sinicus was spawning in all the 11 cruises investigated, and the annual variation of EPR was bimodal. Monthly average EPR was highest from May to July, respectively, 5.97, 5.36 and 6.30 eggs female(-1) d(-1), then decreased dramatically to only 1.37 eggs female(-1) d(-1) in August and attained the lowest 1.07 eggs female(-1) d(-1) in October. In November, average EPR increased again to 4.31 eggs female(-1) d(-1). Seasonal variation of clutch size was similar to EPR, except that it decreased gradually after August rather than dramatically as did EPR. Prosome length of females was maximum in May and minimum in October, but dry weight was highest in November. Monthly average EPR correlated better with prosome length than dry weight, while clutch size was rather determined by dry weight of females. It is suggested that egg production of C. sinicus was active during two discontinuous periods when both surface and bottom temperature fell into its favorite range (i.e. 10-23degreesC), and different reproductive strategies were adopted in these two reproductive peaks: other than the highest EPR, longer prosome length was also achieved by C. sinicus from May to July, while females in November developed shorter bodies but accumulated more energy for reproduction.

A two-stage process with temperature-shift for enhanced anthocyanin production in strawberry cell suspension cultures

A two-stage process with temperature-shift has been developed to enhance the anthocyanin yield in suspension cultures of strawberry cells. The effect of the temperature-shift interval and the shift-time point was investigated for the optimization of this strategy. In this process, strawberry cells were grown at 30 degrees C (the optimum temperature for cell growth) for a certain period as the first stage, with the temperature shifted to a lower temperature for the second stage. In response to the temperature shift-down, anthocyanin synthesis was stimulated and a higher content could be achieved than that at both boundary temperatures but cell growth was suppressed. When the lower boundary temperature was decreased, cell growth was lowered and a delayed, sustained maximum anthocyanin content was achieved. Anthocyanin synthesis was strongly influenced by the shift-time point but cell growth was not. Consequently, the maximum anthocyanin content of 2.7 mg.g-fresh cell(-1) was obtained on day 9 by a temperature-shift from 30 degrees C, after 3-d culture, to 15 degrees C. The highest anthocyanin yield of 318 mg.L-1 on day 12 was achieved when the temperature was shifted from 30 degrees C, after 5-d culture, to 20 degrees C. For a global optimization of both the yield and productivity, the optimum anthocyanin yield and productivity of 272 mg.L-1 and 30.2 mg.L-1.d(-1) on day 9 were achieved by a two-stage culture with a temperature-shift from 30 degrees C after 3 d to 20 degrees C.

玉米农田水热碳通量动态及其环境控制机理研究

陆地生态系统与大气之间的水热碳交换是物质、能量循环的关键过程，一直以来都为研究者们所关注。进入20 世纪以来，特别是随着人们对全球气候变暖的逐步认识，气候变化对水热碳交换过程的影响及其对气候变化的响应研究更加备受关注。本研究以2004~2006 年近三年的涡度相关系统连续观测数据为依托，分析了雨养玉米农田水热碳通量的动态及其影响因子。研究表明，玉米农田水热通量(WHF) 呈显著的单峰型日变化， 日最大值出现在正午12:00~13:00，WHF 变化同步。潜热通量(LE)的季节变化规律与日变化相似，冬季小夏季大，年最大值与最小值分别出现在7 月和1 月。显热通量(Hs) 季节变化也呈单峰型，但年最大值出现在5 月，这主要与降水以及作物生长有关。半小时尺度上，WHF 主要受辐射控制，而日峰值受辐射峰值以及植被生长的双重影响；日尺度上，只要有降水过程，Hs 就会随土壤水分的增大而减小，降水停止后逐渐恢复。而降水对LE 的影响受到可用能量(AE)的干扰，表现出复杂的变化趋势。总的来说，降水持续时间越长AE 越少，对LE 的抑制越大；季节尺度上，WHF 受热量与水分的双重制约。Hs 随着天气回暖后第一次较大降水过程的出现呈现明显下降，而LE 则呈现相反的变化趋势。随着雨季到来和作物的生长，Hs 在7 月出现低谷，而LE 呈现相反的趋势随着降水量的增加而增大；年际间WHF 的分布规律大体一致，但因气象条件等的差异，特别是降水的差异造成年际间WHF 略有不同。在不同水文年型下，水分因子的影响作用有显著差异，且WHF 对热量与水分条件变化的敏感程度也不相同。欠水年，水分因子的作用更显著，是制约WHF 变化的主要控制因子，WHF 对水分的变化更敏感；而丰水年，水分因子的影响减弱，热量的盈亏决定着WHF 变化的主要方向。在不同水文年型下，水热碳通量对水热条件的变化表现出不同的响应方式，为研究生态系统对气候变化的响应提供了参考。 净碳(C)吸收期，玉米农田净碳交换(NEE)呈显著的日变化，在日出以后由CO2 释放转变为CO2 吸收，12:30 左右达到一天中的吸收峰值，日落前出现相反的转换。而净C 释放期内，NEE 均为正值且无明显日变化。NEE 季节变化也呈单峰型二次曲线，在7 月下旬或8 月上旬达到年最大吸收率。根据NEE 的正负，一年分为三个阶段：两个C 排放期与一个C 吸收期。一般C 吸收期从6月开始到9 月结束，此前此后均为C 排放期。在半小时、日时间尺度上，光通量密度(PPFD)与NEE 有着相似的变化规律，是控制NEE 的主要因子；在日、季节尺度上，叶面积指数(LAI)和气孔导度(gs)是影响NEE 的主要生物因子，且gs 的影响程度随着发育期的变化而变化，而不同年份间LAI 对NEE 的影响没有显著的差异。几乎在所有时间步长上，土壤温度(Ts)均为生态系统呼吸(Re)的主要控制因子，时间尺度愈短，二者的相关性愈好。总的来说，在较短时间尺度上，高PPFD 与夏季低温将会促进C 的吸收，有利于C 累积。 玉米农田日最大净C 吸收速率(NEEmax, daily)以及吸收释放转换点(NEE=0)均受PPFD 控制。NEEmax, daily 出现时间与PPFDmax, daily 出现时间几乎完全一致，当PPFD 达到1 日内极大值时，净C 吸收也相应达到了日最大值。但NEEmax, daily的量值还受到其它因子的影响。当水分条件充足时，还将受到LAI、gs 等生物因子的控制。NEE 由正转为负的转换点也是由PPFD 决定。当PPFD 稳定大于PPFD*( PPFD*=100 μmol•m-2s -1)时，净C 吸收开始；当PPFD 稳定小于PPFD*时，净C 吸收由此结束。1 日内，PPFD 稳定通过PPFD*之间的时间间隔决定了日净C 吸收的时间长度。日净C 吸收的时间越长，吸收量也越大，且有明显的季节变化，7 月最长9 月最短。 按照热量水分状况将三年分组，分为I 组(水分状况相似，热量条件不同)与II 组(热量条件相似，水分状况不同)。 I 组年际间PPFD 波动是造成C 交换格局变化的关键原因。而II 组年际间C 交换格局不同是由降水量及其不同分布引起的土壤含水量(SWC)变化是造成。SWC 可以解释年际间NEE 变异的97%，而大气水汽压亏缺(VPD)可以解释30.7%；温度因子通过影响C 收支中的呼吸项，间接影响着生态系统的NEE，它可以解释年际间NEE 变异的73.9%，也是造成年际间C 交换格局不同的原因之一；另外，PPFD 和发育期早晚以及净C吸收期长度等也同样影响着C 交换格局的变化。综合两组情况来看，由水分条件年际变化引起的NEE 的波动大于能量年际变化引起的波动。总之，在较长时间尺度上，NEE 对SWC 变化比其对PPFD 变化更敏感，说明在半干旱地区土壤水分条件仍然是决定C 交换格局的主导因子。 NEE 与LE 呈线性相关，它们之间的相关性主要受温度和NEE 的控制，温度越高，二者的相关性越弱，而NEE 越大二者相关性越好。同时，作物蒸腾与土壤蒸发的比例也是影响NEE 与LE 之间关系的主要因素。蒸腾作用所占的比例越大，二者的线性关系越显著，而土壤蒸发比例越大，二者的相关性越弱。总的来说，NEE 与LE 之间的线性关系有明显的季节变化，生长季好于非生长季，夏天好于冬天。 总之，雨养玉米农田水热碳通量既具有其它农田生态系统共有的动态特征，也具有其特有特征。

Kinetic study of the 2-methyl-3-methoxy-4-phenylbutanoic acid produced by oxidation of microcystin in aqueous solutions

Microcystins (MCs) are a family of related cyclic hepatotoxic heptapeptides, of which more than 70 types have been identified. The chemically unique nature of the C20 beta-amino acid, (2S, 3S, 8S, 9S)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca4,6-dienoic acid (Adda), portion of the MCs has been exploited to develop a strategy to analyze the entirety. Oxidation of MCs causes the cleavage of MC Adda to form 2-methyl-3-methoxy-4-phenylbutanoic acid (MMPB). In the present study, we investigated the kinetics of MMPB produced by oxidation of the most-often-studied MC variant, MC-LR (L = leucine, R = arginine), with permanganate-periodate. This investigation allowed insight regarding the influence of the reaction conditions (concentration of the reactants, temperature, and pH) on the conversion rate. The results indicated that the reaction was second order overall and first order with respect to both permanganate and MC-LR. The second-order rate constant ranged from 0.66 to 1.35 M/s at temperatures from 10 to 30 degrees C, and the activation energy was 24.44 kJ/mol. The rates of MMPB production can be accelerated through increasing reaction temperature and oxidant concentration, and sufficient periodate is necessary for the formation of MMPB. The initial reaction rate under alkaline and neutral conditions is higher than that under acidic conditions, but the former decreases faster than the latter except under weakly acidic conditions. These results provided new insight concerning selection of the permanganate-periodate concentration, pH, and temperature needed for the oxidation of MCs with a high and stable yield of MMPB.

The accumulation and metabolism of astaxanthin in Scenedesmus obliquus (chlorophyceae)

The biosynthesis and metabolism of astaxanthin in coenobium alga Scenedesmus obliquus were investigated using a two-stage culture. The first stage was for the analysis of biosynthesis and accumulation of astaxanthin in alga cells which were cultured under induction conditions (incubation at 30 degrees C and illumination of 180 mu mol m(-2) s(-1)) for 48 h. The composition of the secondary carotenoids in algal cells was analyzed and seven ketocarotenoids were identified. The results implied that S. obliquus synthesized astaxanthin from beta-carotene through three possible pathways. In the second stage, the cultures were transferred to normal conditions (incubation at 25 C and illumination of 80 mu mol m(-2) s(-1)) for 72 h. Algal cells accumulated more chlorophyll and biosynthesis of secondary carotenoids terminated, the content of secondary carotenoids decreased from 59.48 to 6.57%. The results inferred that accumulation and metabolism of astaxanthin could be controlled by cultivated conditions which also could lead the mobilization of secondary carotenoids to support the algal cell growth. The results also implied that presumed conversions from astaxanthin to lutein or antheraxanthin could be modulated by culturing conditions. (C) 2008 Published by Elsevier Ltd.

Combined effects of ultraviolet radiation and temperature on morphology, photosynthesis, and DNA of Arthrospira (Spirulina) platensis (Cyanophyta)

Natural levels of solar UVR were shown to break and alter the spiral structure of Arthrospira (Spirulina) platensis (Nordst.) Gomont during winter. However, this phenomenon was not observed during summer at temperatures of similar to 30 degrees C. Since little has been documented on the interactive effects of solar UV radiation (UVR; 280-400 nm) and temperature on cyanobacteria, the morphology, photosynthesis, and DNA damage of A. platensis were examined using two radiation treatments (PAR [400-700 nm] and PAB [PAR + UV-A + UV-B: 280-700]), three temperatures (15, 22, and 30 degrees C), and three biomass concentrations (100, 160, and 240 mg dwt [dry weight] . L-1). UVR caused a breakage of the spiral structure at 15 degrees C and 22 degrees C, but not at 30 degrees C. High PAR levels also induced a significant breakage at 15 degrees C and 22 degrees C, but only at low biomass densities, and to lesser extent when compared with the PAB treatment. A. platensis was able to alter its spiral structure by increasing helix tightness at the highest temperature tested. The photochemical efficiency was depressed to undetectable levels at 15 degrees C but was relatively high at 30 degrees C even under the treatment with UVR in 8 h. At 30 degrees C, UVR led to 93%-97% less DNA damage when compared with 15 degrees C after 8 h of exposure. UV-absorbing compounds were determined as negligible at all light and temperature combinations. The possible mechanisms for the temperature-dependent effects of UVR on this organism are discussed in this paper.

Seasonal pattern of reproduction of Hizikia fusiformis (Sargassaceae, Phaeophyta) from Nanao Island, Shantou, China

The maturation pattern of sexual reproduction in Hizikia fusiformis (Harvey) Okamura (Sargassaceae, Phaeaophyta) was examined in 2003 at Yunao Bay, Nanao Island, Shantou, China. Maturation began in mid-April (seawater temperature 19-21 degrees C), reached the peak in mid-May (maturation rate ca. 70%, and seawater temperature 23.5-25 degrees C) and finished in late-June (seawater temperature 27.5-30 degrees C). The Hizikia plants continued to gain the length from the beginning of maturation season to reach a maximum mean length of 34.8 cm in mid-May, after which the mean length was reduced drastically due to the senescence and rupture of the larger plants in size. The major portion of the mature plants belonged to the larger plants between April and May, but to the smaller ones in June. It is suggested that the plant must achieve a critical size before reproductive maturation occurred. There was a positive relationship between the number of receptacles (NR), as well as the reproductive allocation (RA), and the plant size of Hizikia population, with the recorded maximum values of NR and RA being 1220 and 64.3% respectively, for a single plant.

Biodegradation of dibenzofuran by Janibacter terrae strain XJ-1

The dibenzofuran (DF)-degrading bacterium, Janibacter terrae strain XJ-1, was isolated from sediment from East Lake in Wuhan, China. This strain grows aerobically on DF as the sole source of carbon and energy; it has a doubling time of 12 hours at 30 degrees C; and it almost completely degraded 100 mg/L-1 DF in 5 days, producing 2,2',3-trihydroxybiphenyl, salicylic acid, gentisic acid, and other metabolites. The dbdA (DF dioxygenase) gene cluster in the strain is almost identical to that on a large plasmid in Terrabacter sp. YK3. Unlike Janibacter sp. strain YY-1, XJ-1 accumulates gentisic acid rather than catechol as a final product of DF degradation.

Photosynthetic characteristics of the economic brown seaweed Hizikia fusiforme (Sargassaceae, Phaeophyta), with special reference to its "leaf" and receptacle

Photosynthetic responses to irradiance and temperature of "leaves" and receptacles were compared in February ( vegetative stage) and May ( reproductive stage) in the seaweed, Hizikia fusiforme ( Harvey) Okamura (Sargassaceae, Phaeophyta) from Nanao Island, Shantou, China. Irradiance-saturated photosynthesis (P-max) was significantly higher in receptacles than in "leaves" on a fresh weight basis, and that of "leaves" was greater in May than in February at ambient seawater temperatures. The optimum temperature for P-max was 30 degrees C for both "leaves" and receptacles, being 5 - 10 degrees C higher than the ambient seawater temperature. The apparent photosynthetic efficiencies were greater in receptacles than in "leaves" within the tested temperature range of 10 - 40 degrees C. The irradiance for saturating photosynthesis for both "leaves" and receptacles was temperature-dependent, with the highest values ( about 200 mu mol photons m(-2) s(-1)) at 30 degrees C.

Kinetics of the oxidation of MCRR by potassium permanganate

The occurrence of the microcystins in the water bodies, especially in drinking water resources, has received considerable attentions. In situ chemical oxidation is a promising cost-effective treatment method to remove MC from water body. This research investigated the reaction kinetics of the oxidation of MCRR by permanganate. Experimental results indicate that the reaction is second order overall and first order with respect to both permanganate and MCRR, and has an activation energy of 18.9 kJ/mol. The second-order rate constant ranges from 0.154 to 0.225 l/mg/min at temperature from 15 to 30 degrees C. The MCRR degradation rates can be accelerated through increasing reaction temperature and oxidant concentration. The reaction under acid conditions was slightly faster than under alkaline conditions. The half-life of the reaction was less than 1 min, and more than 99.5% of MCRR was degraded within 10 min. (c) 2005 Elsevier Ltd. All rights reserved.

Effect of body size on growth and energy budget of Nile tilapia, Oreochromis niloticus

A growth trial was conducted at 30 degrees C to investigate the effect of body size on growth and energy budget of Nile tilapia. The average initial body weights of the four size groups tested were 9.3, 34.1, 80.3 and 172.4 g, respectively. Fish were fed to satiation twice a day with a diet containing 35.6% crude protein. Food consumption (C-max: kJ/day) increased with body size (W: g) according to the relationship: Ln C-max = 1.45 + 0.42 LnW. The final body contents of dry matter, crude protein and ash per unit body weight increased with increasing body size while contents of fat and energy were independent of body size. Specific growth rates of wet weight, dry weight, protein and energy decreased as the fish increased in size. Feed efficiencies in wet weigh, dry weight and crude protein decreased with increasing body size, while that of energy remained unchanged. The proportions of energy intake allocated to the various components (faecal energy, excretory energy, heat production and recovered energy) of the energy budget were not significantly affected by body size, and the average budget was: 100IE-18.5(+/- 1.33)FE + 5.9 (+/- 3.09)(ZE + UE) + 49.3(+/- 3.77)HE + 26.3(+/- 6.23)RE, where IE, FE, (ZE + UE), HE and RE represent gross energy intake, faecal energy, excretory (non-faecal) energy loss, heat production and recovered energy (growth), respectively. It is suggested that the decrease in growth rate in larger fish is mainly due to the decrease in relative food intake. (C) 1997 Elsevier Science B.V.

Energy budget of Nile tilapia (Oreochromis niloticus) in relation to ration size

Nile tilapia weighing 8.29-11.02 g were fed a practical diet at seven ration levels (starvation, 0.5, 1, 2, 3, 4% body weight per day and satiation) twice a day at 30 degrees C. Feed consumption, apparent digestibility, nitrogenous excretion and growth were determined directly, and heat production was calculated by difference of energy budget. The relationship between specific growth rate in wet weight (SGR(w), percentage per day) and ration size (RL, percentage per day) was a decelerating curve described as SGR(w) = 2.98 (1 - e(-0.61(RL-0.43))). The apparent digestibility coefficients for dry matter and protein showed a decreasing pattern with increasing ration while the apparent digestibility coefficient of energy was not significantly affected by ration size. The proportion of gross energy intake lost in nitrogenous excretion tended to decrease with increasing ration. Feed efficiency was highest, and the proportion of gross energy intake channelled to heat production was lowest, at an intermediate ration level (2% per day). The energy budget at the satiation level was: 100IE = 16.9FE + 1.2(ZE + UE) + 62.3HE + 19.6RE, where IE, FE, (ZE + UE), HE and RE represent gross energy intake, faecal energy, excretory (non-faecal) energy loss, heat production and recovered energy (growth), respectively. (C) 1997 Elsevier Science B.V.