Identification of factors affecting the growth and survival of the settling Japanese flounder larvae, Paralichthys olivaceus

A series of experiments were conducted to identify the factors that affected the growth and survival of the settling flounder larvae Paralichthys olivaceus. Settling larvae 24 days after hatching (DAH) were reared in 10-l experimental tanks up to 40 DAH, and two of the following factors were changed as controlled factors in each experiment: light regime (24L:0D or 12L:12D), prey density (1500, 3000, or 5000 Artemia l(-1)), shelter (sand or no sand) and stocking density (5, 10, or 15 fish l(-1)). Early settling larvae (24-35 DAH) experienced little mortality (less than 10% of the overall mortality) that was not significantly affected by above factors. In contrast, late settling larvae (36-40 DAH) suffered high cannibalistic mortality which was significantly influenced by each of the above factors. Larvae experienced significantly lower mortality at 10 fish l(-1) level than at other densities. Larvae at 15 fish l(-1) level had higher mortality than at 5 fish l(-1) when all other factors were identical. Larvae at 3000 and 5000 Artemia l(-1) treatments survived significantly better than at 1500 Artemia l(-1), but no significant differences in larval mortality were found between the two higher densities. Larvae suffered higher mortality at low prey density or at the absence of sand when they were exposed to longer photoperiod. Low stocking density significantly improved the growth of the settling larvae. The average daily instantaneous growth rate (G) at 5 and 15 fish l(-1) treatments were 0.050 and 0.034, with the coefficient of variation (CV) in final length at 16.4 and 23.5, respectively. Daily instantaneous growth rate increased significantly from 0.033 in the 1500 Artemia l(-1) to 0.041 and 0.045 in the 3000 and 5000 Artennia l(-1), respectively, but no significant difference in larval growth existed between the two higher prey densities. These findings suggested that the optimal prey density for growth and survival of the settling flounder larvae at a stocking density of 5 - 15 fish l(-1) was around 3000 Artemia l(-1) . Larvae that were exposed to 24L showed 20% increase in growth ( G = 0.046, CV = 18.7) than those exposed to 12L ( G = 0.037, CV = 20.5). Longer exposure to light significantly improved larval growth, provided sufficient food was available. Sand substrate did not show significant effects on larval growth, possibly because the larvae spent most of the time swimming or feeding in the water column during this stage. (C) 2003 Elsevier Science B.V. All rights reserved.

Impact of microzooplankton and Calanus sinicus (Brodsky, 1962) on phytoplankton in the Yellow Sea during early summer

Dilution incubations and Calanus sinicus addition incubations were simultaneously conducted at five stations in the Yellow Sea in June of 2004 to evaluate the impact of microzooplankton and Calanus sinicus on phytoplankton based on the Chlorophyll a (Chl-a) levels. The Chl-a growth rates (k) ranged from 0.60-1.67 d(-1), while microzooplankton grazed the Chl-a at rates (g) of 0.29-0.62 d(t-1). The addition of C. sinicus enhanced the Chl-a growth rate (Z) by 0.004-0.037 d(-1) ind.(-1) L. C. sinicus abundance ranged from 84.1-160.9 ind. m(-3), which occupied 90.7%-99.1% of the copepod (> 500 mu m) population. The in-situ increase in phytoplankton by C. sinicus community was estimated to be 0.000 4-0.005 9 d(-1). These results showed that microzooplankton were the main grazers of phytoplankton, while C. sinicus induced a slight increase in the levels of phytoplankton.

Determination of aliphatic amines from soil and wastewater of a paper mill by pre-column derivatization using HPLC and tandem mass spectrometry (HPLC-MS/MS)

A pre-column derivatization method for the sensitive determination of aliphatic amines using the labeling reagent 1,2-benzo-3,4-dihydrocarbazole-9-ethyl chloroformate (BCEOC) followed by HPLC with fluorescence detection and APCI/NIS identification in positive-ion mode has been developed. The chromophore of 2-(9-carbazole)-ethyl chloroformate (CEOC) reagent was replaced by the 1,2-benzo-3,4-dihydrocarbazole functional group, which resulted in a sensitive fluorescence derivatizing reagent, BCEOC, that could easily and quickly label amines. Derivatives were stable enough to be efficiently analyzed by HPLC and showed an intense protonated molecular ion corresponding m/z [M + H](+) with APCI/MS in positive-ion mode. The collision induced dissociation of the protonated molecular ion formed characteristic fragment ions at m/z 264.1, m/z 246.0 and m/z 218.1, corresponding to the cleavages of CH2CH2O-CO, CH2CH2-OCO, and N-CH2CH2O bonds. Studies on derivatization conditions demonstrated that excellent derivatization yields close to 100% were observed with a 3 to 4-fold molar reagent excess in acetonitrile solvent, in the presence of borate buffer (pH 9.0) at 40 degrees C for 10 min. In addition, the detection responses for BCEOC derivatives were compared with those obtained with CEOC and FMOC as labeling reagents. The ratios I-BCEOC/I-CEOC and I-BCEOC/I-FMOC were, respectively, 1.40-2.76 and 1.36-2.92 for fluorescence responses (here, I was the relative fluorescence intensity). Separation of the amine derivatives had been optimized on an Eclipse XDB-C-8 column. Detection limits calculated from an 0.10 pmol injection, at a signal-to-noise ratio of 3, were 18.65-38.82 fmol (injection volume 10 mu L for fluorescence detection. The relative standard deviations for intraday determination (n = 6) of standard amine derivatives (50 pmol) were 0.0063-0.037% for retention times and 3.36-6.93% for peak areas. The mean intra-and inter-assay precision for all amines were <5.4% and 5.8%, respectively. The recoveries of amines ranged from 96 to 113%. Excellent linear responses were observed with correlation coefficients of >0.9994. The established method provided a simple and highly sensitive technique for the quantitative analysis of trace amounts of aliphatic amines from biological and natural environmental samples.

贵州省喀斯特地区水库中CO2﹑CH4﹑N2O的产生与释放研究－以红枫湖﹑百花湖为例

大气中不断增加的温室气体浓度，将对气候、生态环境和人类活动等一系列问题产生重大影响，因此其“源”﹑“汇”效应备受关注。水库，作为人为活动对大气温室气体浓度影响的一个重要方面，也越来越受到国、内外学者的关注。本论文对贵州省喀斯特地区两个富营养水库(红枫湖、百花湖)中主要温室气体（CO2﹑CH4﹑N2O）在不同月份的水体中的分布规律进行研究，并结合两湖具体水环境条件，分析了影响两湖水体中CO2﹑CH4﹑N2O变化的因素，进而阐明两湖水体中CO2﹑CH4﹑N2O产生与释放的机理。本论文得到的结论如下： 1.由于地理位置和气候条件类似，所以两库水体中pCO2变化规律类似：两库表层水中pCO2在6月、8月明显低于大气CO2分压，其他月份则明显高于大气CO2分压。从全年角度来说，红枫湖表层水pCO2为874.2±774.4µatm，百花湖为1131.7±1164.0µatm，都是大气CO2的“源”。两湖pCO2与Chla之间存在的显著负相关，说明浮游植物光合作用与细菌呼吸作用共同影响是两湖pCO2出现季节变化的主要原因。 2.夏季，水体中光合作用产生的有机质发生降解产生CO2对温跃层中CO2的增加起重要作用；沉积物中有机质降解导致静水层中CO2积累，这种作用在秋﹑冬季有所降低，可能与水温有关。而秋冬季，随着温跃层的消失，在水体混合作用下，夏季水体中积累的CO2重新释放到表层水中使其pCO2升高。 3.通过与国内、外其他地区湖泊（水库）表层水中CO2的比较，发现：（1）由于红枫湖与百花湖地处喀斯特山区，陆源输入的有机碳比北部温带地区少，所以表层水中CO2低，对大气CO2释放的贡献较小。（2）由于富营养化现象，两库夏季表层水体成为大气CO2的“汇”。并且，就全年而言，表层水中CO2低于北部温带地区，说明两库光合作用固定的C返回大气的程度可能较低。 4.两湖表层水中CH4浓度的变化规律为：枯水期>丰水期，但在所有采样期间两湖始终是大气CH4的“源”。就全年而言，红枫湖两采样点HF-N和HF-S表层水中CH4浓度分别为0.19±0.09µmol/L和0.48±0.53µmol/L，百花湖两采样点BH-1和BH-2分别为0.32±0.29µmol/L和0.29±0.20µmol/L。两湖表层水中CH4浓度变化可能由以下几方面原因造成：（1）枯水期，水体滞留时间长，水体中的CH4得到积累；（2）丰水期，藻类初级生产造成表层水中DO含量增加，表层水体中CH4被氧化的程度较高；（3）丰水期，径流及降雨的增加也可能造成表层水体中CH4被稀释。 5.两湖湖底水体中CH4浓度的变化规律为：枯水期〈丰水期。就全年而言，HF-N和HF-S点底层水中CH4浓度分别为16.49±26.16µmol/L和8.80±15.30µmol/L，BH-1和BH-2分别为6.03±7.07µmol/L和4.41±7.00µmol/L。浮游植物光合作用产生的有机物及湖底水温﹑含氧状况是影响CH4产生的主要因素。SO42-也对湖底CH4的产生起一定抑制作用。 6.夏季，两湖湖水表层藻类的初级生产与湖水底层沉积物的降解对水体中CH4产生有影响。而热分层和两湖静水层中缺氧环境使得CH4得到积累。而到了秋冬季节，在水体混合作用下这部分CH4在水体中重新分布，并且由于氧化作用加强而被损耗。 7.两湖表层水中N2O的变化规律为：夏季N2O明显低于其他季节，但在所有采样期间内两湖都是大气N2O的“源”。从全年来看，红枫湖HF-N和HF-S两采样点表层水中N2O浓度分别为；46.31±29.65nmol/L，36.93±18.41nmol/L；百花湖BH-1和BH-2两采样点表层水中N2O浓度分别为102.13±79.53nmol/L，99.51±75.77nmol/L。硝化反应是影响两湖表层水中N2O季节变化的主要原因，并受表层水温﹑DO及NO3－等共同影响。 8.通过比较水体中NO3-﹑NH4+及N2O的分布特征，发现：春季,红枫湖水体中以硝化反应为主；夏季,两湖温跃层以上水体中以硝化反应为主，湖底以反硝化作用为主；秋﹑冬季节，虽然有个别采样点出现硝化或反硝化反应，但总体上两湖水体中N2O以水体混合作用为主。