Evidence for Atmospheric Deposition Impacts On the Enchytraeid Worm Population of Uk Upland Ombrotrophic Peats

The results of four experiments on acidification effects upon the Enchytraeid worm populations of ombrotrophic peats are reported. in the first, populations were measured in peats from Calluna vulgaris-dominated microcosms collected from along a gradient in N deposition in the UK and subjected for 18 months to simulated precipitation with a solute composition appropriate for their site of collection. There was a significant decline in Enchytraeid population along the N deposition gradient for Calluna-dominant microcosms, but when grasses took over from the Calluna, Enchytraeid numbers increased significantly. in the second experiment, two sets of peat moorland microcosms from a single site, supporting Calluna and Calluna-grass mixed vegetation, were subjected for 12 months to ambient and 2- and 6-times the ambient N deposition. Additional N was added in two forms, as ammonium sulphate and as nitric acid. the high N treatments significantly reduced the Enchytraeid populations for both vegetation types. in a third experiment, the pH preference for the Enchytraeids was assessed using interconnected tubes of peat covering the pH range 2.2–8.7. the preferred pH range after 8 months was 2.7–3.7. in the final experiment, it was found that recolonization with Enchytraeids after initial removal was more rapid under grass dominant vegetation than under Calluna dominant vegetation.     

Pyrrolizidine alkaloid content in <Emphasis Type="Italic">Senecio</Emphasis>: ontogeny and developmental constraints

Summary. The ontogeny of pyrrolizidine alkaloid (PA) synthesis and constraints on defence level during the seedling stage were examined in the annual Senecio vulgaris and the monocarpic perennial Senecio jacobaea. In both species, PAs were actively synthesized from the onset of seedling growth so that juvenile stages did not go through an undefended stage. Roots are known to be the exclusive sites where PAs are produced. Root biomass was the single most important biomass parameter explaining variation in total PAs per seedling. All correlation coefficients between—relative growth rate and PA concentration were negative, but none was significant. However, a significant negative—correlation was found between shoot to root ratio and PA concentration in S. jacobaeaseedlings, suggesting a dilution effect of the PAs. Earlier studies have shown that the shoot to root ratio is positively correlated with relative growth—rate of established S. jacobaea plants. It is therefore suggested that young S. jacobaea plants with a high shoot to root ratio and hence a high growth capacity necessarily have lower PA defence levels than plants with a low shoot to root ratio. Received 10 July 2002; accepted 16 November 2002.     

On the tolerance of charophytes to high-nitrate concentrations

Currently a debate exists about whether the reduced growth of macrophytes with increased nitrogen loading in shallow ecosystems is determined by ecological or physiological factors. To discover whether nitrate in the water is detrimental per se to charophytes, we subjected Chara hispida and Chara vulgaris specimens, collected from two habitats greatly differing in nitrate concentrations (1.5 and 10?mg NO₃-N/L, annual means), to a wide nitrate range (0.5–50?mg NO₃-N/L) in two experiments (with free-floating specimens using nitrate as the sole N source, and with planted specimens, with other N sources in sediment). Charophytes grew both unplanted and planted in all treatments, and growth reductions occurred at the highest concentration in all cases. Some charophyte responses when faced with nitrate increases were different depending on (i) the species and (ii) population origin. Under the most realistic situation, the growth of both planted C. vulgaris populations was higher than that of C. hispida populations. C. vulgaris specimens from the nitrate-rich waterbody adapted best to the highest nitrate concentrations when they grew floating. Despite charophytes being vital and growing under high-nitrate concentrations in short-term laboratory experiments, such a situation in the environment may eventually not be sustainable, since ecological factors act in the field.     

Female choice for complex song in the European starling: a field experiment

Male European starlings Sturnus vulgaris sing long complex songs that appear to be important in the courtship of females but which also influence competitive interactions between males. We tested the hypothesis that females choose mates on the basis of the complexity of their songs, rather than on the quality of the territories the males defended. In order to determine whether certain territories were preferred over others, the first set of birds to settle in the experimental nest-boxes was removed and a second set allowed to settle. Consistent preferences for certain nest-boxes were indicated by correlations between the settlement patterns of the first and second sets of birds. However, males with the most complex song did not necessarily occupy the most preferred nest sites. Males with more complex song acquired mates faster. This relationship remained significant when nest-site preference was statistically controlled, indicating that female starlings chose males with complex song rather than those that defended preferred nest sites. A number of morphological variables were also found to be uncorrelated with female choice. Song complexity in European starlings increases with age, and the evolution of song complexity in this species is consistent with an age-indicator model of sexual selection. Males with larger repertoires were also in better condition, indicating that females obtain high-quality mates by choosing on the basis of male song. Received: 29 April 1995/Accepted after revision: 9 September 1995     

味精废水异养培养小球藻的初步研究

味精废液经过除菌体,石灰水沉淀除去硫酸根和调ｐＨ等预处理后,加入有机碳源对小球藻进行异养培养,培养效果很好,可达到甚至超过合成培养基。     

含氮杂环化合物对水生生物的毒性作用研究

研究了6种典型含氮杂环化合物对水生生物的急性毒性,获得了吲哚、吡啶、喹啉、异喹啉、2-甲基喹啉和8-羟基喹啉对小球藻的48 hEC50、对大型蚤的48 h LC50、对斑马鱼的96h LC50及对发光细菌的15min EC50值.6种物质对大型蚤、斑马鱼及发光细菌的毒性与其价分子连接性指数、辛醇/水分配系数显著相关.发光细菌毒性结果与大型蚤、斑马鱼的毒性结果显著相关,而与小球藻不相关.     

川蔓藻对两种常见浮游藻类的化感作用

选取沉水植物川蔓藻与浮游藻类普通小球藻、铜绿微囊藻为研究对象,测定在川蔓藻共培养胁迫下2种藻单独存在和按1：1（V：V）混合情况下的光密度、叶绿素a、最大光化学量子产量、相对电子传递速率、可溶性糖、丙二醛以及超氧化物歧化酶活性的变化.结果表明：在川蔓藻存在的条件下,普通小球藻、铜绿微囊藻和二者混合藻的生长被快速强烈抑制,抑制率在第6d时达到最大值,分别为80.95%、94.18%和94.01%.3个处理组的光密度值、叶绿素a、可溶性糖及最大光化学量子产量等指标均低于对照组,且随时间呈明显的下降趋势,说明其光合能力逐渐减弱.而丙二醛和超氧化物歧化酶指标在0~6d却高于对照组,表明可能发生了浮游藻类膜质过氧化过程.     

大气污染对悬铃木叶绿素及抗氧化酶系的影响

大气污染会影响悬铃木叶片内叶绿素含量以及活性氧清除系统,致使植物体内叶绿素含量降低,抗氧化酶系统活性上升,并使植物体内丙二醛积累增加。交通污染对植物的影响程度与工业污染相当,应引起重视。绿化可减少空气污染,提高环境质量。     

小球藻生产生物柴油关键培养条件的摸索

当今世界能源的短缺和水体富营养化的发生严重阻碍了社会经济的发展。基于微藻培养的污水深度处理和生物柴油生产耦合系统,可以在很大程度上减缓这两方面的压力。在模拟实验条件,以不同氮磷比、光周期、光强及温度对小球藻生产生物柴油关键培养条件进行探索。培养小球藻至生长稳定期后,提取脂类物质,计算脂类物质占小球藻的干重比,从而摸索出微藻合成脂类物质最优条件。通过对实验结果处理和分析,得出在氮磷比为16,光周期为16:08,光照强度为4 000 Lux,温度为20℃条件下培养小球藻,用索氏提取器提取脂类物质,产生的脂类物质的含量最高,可以为高效的生物柴油生产提供基本的信息。     

栅藻和小球藻在4种养殖废水中的生长及净化效果对比研究

利用经过处理的鸡场养殖废水、猪场沼液（简称猪沼）、池塘养殖废水和BG-11培养基分别培养斜生栅藻和普通小球藻,对比2种微藻在各培养液中的生长、对废水中氮磷的净化效果以及微藻油脂的积累情况。结果表明：经过23 d的培养,小球藻处理组中,小球藻+猪沼培养液中可收获藻粉0.353 1 g·L-1,小球藻+BG-11中可收获藻粉0.189 8 g·L-1,高于其他3种培养液中的收获量。栅藻处理组中,栅藻+BG-11中收获的藻粉最多,为0.168 5 g·L-1,其次为栅藻+猪沼培养液（0.131 1 g·L-1）。2种微藻对不同废水培养液的净化效果不同,但总体来说,栅藻和小球藻对总磷的去除效果最好,去除率在89.32%~98.69%。对硝氮的去除率也在60%以上。另外,利用猪沼培养的小球藻油脂含量最高,达到50.34%;培养的栅藻油脂含量与BG-11中相近,并高于其他培养液。因此,利用猪场沼液培养栅藻和小球藻具有可行性。