Comparative effects of herbicides on photosynthesis and growth of tropical estuarine microalgae

Pulse amplitude modulation (PAM) fluorometry is ideally suited to measure the sub-lethal impacts of photosystem II (PSII)-inhibiting herbicides on microalgae, but key relationships between effective quantum yield [Y(II)] and the traditional endpoints growth rate (mu) and biomass increase are unknown. The effects of three PSII-inhibiting herbicides; diuron, hexazinone and atrazine, were examined on two tropical benthic microalgae; Navicula sp. (Heterokontophyta) and Nephroselmis pyriformis (Chlorophyta). The relationships between Y(II), mu and biomass increase were consistent (r(2)0.90) and linear (1:1), validating the utility of PAM fluorometry as a rapid and reliable technique to measure sub-lethal toxicity thresholds of PSII-inhibiting herbicides in these microalgae. The order of toxicity (EC(50) range) was: diuron (16-33nM)>hexazinone (25-110nM)>atrazine (130-620nm) for both algal species. Growth rate and photosynthesis were affected at diuron concentrations that have been detected in coastal areas of the Great Barrier Reef.     

Is the connectivity function a good indicator of soil infiltrability distribution and runoff flow dimension?

Among the studies on runoff connectivity of soils with heterogeneous properties, the need to understand the relationships between soil heterogeneity and the associated runoff organization and amount is frequently mentioned. In this study, we simulate the stationary runoff–runon process on bi‐dimensional (2D) flat slopes for five infiltrability distributions, one of them correlated, as a function of rainfall intensity and flow dimension. We define flow dimension by 1 + ε, where ε is the outflow fraction transferred from one pixel to each of the two lateral downslope pixels. Our aim is to assess the effect of ε and soil heterogeneity on the connectivity function compared to the mean runoff flow rate, the wet area and the number of runoff patterns. The analysis of connectivity is carried within the percolation framework. The results show that the integral connectivity scale is more sensitive to the flow dimension and soil heterogeneity compared to the other variables. The wet area fraction does not depend on ε. Unlike previous studies, we find that increased runoff production is not necessarily related to increased connectivity. The use of the connectivity function within the percolation framework appears to be a valuable method for assessing the impact of soil heterogeneity and flow dimension on the runoff organization during a rainfall event. Copyright © 2014 John Wiley & Sons, Ltd.     

Trends in indicators of eutrophication in Western Long Island Sound and the Hudson-Raritan Estuary

Significant improvements in water quality have been observed for several decades throughout much of the Hudson-Raritan Estuary, primarily as a result of regional abatement of municipal and industrial discharges. These improvements include area-wide, order-of-magnitude reductions in ambient coliform concentrations and significant increases in dissolved oxygen (DO) concentrations. In contrast to these improvements, DO in bottom waters of the western Long Island Sound (WLIS) appears to have decreased in the last two decades. Although there is no consensus as to why hypoxia in WLIS may have recently become more severe, several related hypotheses have been suggested, including an increase in eutrophication, increased density stratification, and changes in wastewater loads. To determine if eutrophication has increased in WLIS, trends in several indicators of eutrophication were examined from a long-term water quality data set. Since the mid-1980s surface DO supersaturation has increased, bottom minimum DO has decreased, and vertical DO stratification has increased in WLIS. Other areas of the Hudson-Raritan Estuary, such as Jamaica Bay and Raritan Bay, exhibit similar evidence of declining water quality and may be experiencing increasing eutrophication. Temporal changes in vertical density stratification indicate that surface to bottom temperature differences have increased to a greater extent and have had a more significant impact on bottom DO depletion in WLIS than in the shallower Jamaica Bay and Raritan Bay. Additional factors contributing to the observed decline in water quality include recent changes in wastewater loads and possible increases in upstream and nonpoint source loads.     

An ultraviolet-selected galaxy redshift survey – II. The physical nature of star formation in an enlarged sample

We present further spectroscopic observations for a sample of galaxies selected in the vacuum ultraviolet (UV) at 2000 Å from the FOCA balloon-borne imaging camera of Milliard et al. This work represents an extension of the initial study by Treyer et al. Our enlarged catalogue contains 433 sources (≃3 times as many as in our earlier study) across two FOCA fields. 273 of these are galaxies, nearly all with redshifts z ≃0–0.4. Nebular emission-line measurements are available for 216 galaxies, allowing us to address issues of excitation, reddening and metallicity. The UV and H α luminosity functions strengthen our earlier assertions that the local volume-averaged star formation rate is higher than indicated from earlier surveys. Moreover, internally within our sample, we do not find a steep rise in the UV luminosity density with redshift over 0< z <0.4. Our data are more consistent with a modest evolutionary trend, as suggested by recent redshift survey results. Investigating the emission-line properties, we find no evidence for a significant number of AGN in our sample; most UV-selected sources to z ≃0.4 are intense star-forming galaxies. We find that the UV flux indicates a consistently higher mean star formation rate than that implied by the H α luminosity for typical constant or declining star formation histories. Following Glazebrook et al., we interpret this discrepancy in terms of a starburst model for our UV-luminous sources. We develop a simple algorithm which explores the scatter in the UV flux–H α relation in the context of various burst scenarios. Whilst we can explain most of our observations in this way, there remains a small population with extreme UV–optical colours which cannot be understood.     

湿地景观变化过程与累积环境效应研究进展

湿地在流域中处于水陆交错的特殊过渡区域,是地表重要的景观覆盖类型和生态系统。湿地具有独特的水文、土壤和植被特征,在维护区域/流域生态平衡和环境稳定方面发挥巨大作用。湿地景观变化过程主要表现为景观格局和过程在时间和空间尺度上的相互作用过程。该过程对系统的能量流动、物质循环以及物种迁移产生作用,对地理环境也产生巨大环境效应。湿地景观变化与土地利用/覆盖变化紧密相关,与人类活动影响息息相联。至今,人类已把天然的湿地景观格局改变为受人类支配的土地利用格局。自然湿地景观格局的变化过程对湿地生态系统以及其他系统的生物多样性、初级生产力产生显著影响,对局地、区域及全球气候环境、水文环境、生物多样性等方面产生显著而深刻的影响。湿地景观变化是全球变化研究的重要内容,尤其对认识全球气候变化、土地利用/覆盖变化和生物多样性变化的区域响应具有重大意义。     

The He i 10 830 Å chromosphere and filament associated structures

Full disk, He I 10 830 Å solar spectroheliograms have been generated using the Haleakala Stokes polarimeter-spectrometer. The spectroheliograms, with spatial resolution of 10 × 16 arc sec and wavelength bandpass of 0.53 Å, were developed for the detection of coronal holes, and have been compared with nearly simultaneous H and Ca K flltergrams.Areas of reduced helium absorption have been noted in the neighborhood of filaments and neutral zones in the longitudinal solar magnetic field. The existence of these helium lanes is discussed in terms of their relationship to H filament channels or to the coronal cavities which surround prominences.     

珠江口万顷沙晚第四纪沉积及古环境重建

选取位于珠江口万顷沙ZK316-2钻孔进行孢粉、硅藻和岩性等分析,重建了珠江口晚更新世以来的海侵海退旋回和古环境特征。孢粉和硅藻分析表明：晚更新世期间该区域主要经历了一次大的海侵海退,期间有2次小的海平面波动。晚更新世地层海相特征明显,孢粉组合指示了温暖湿润的气候环境,其植被以南亚热带常绿林为主,孢粉组合以青冈属、蕈树属、金缕梅科等亚热带种属为主,期间出现的海桑属推测为滨海相沉积,指示了当时海平面的位置。晚更新世的海相沉积尽管14C测年结果为老于30 ka左右,但经过区域孢粉组合、硅藻特征、海平面高度等因素的综合对比分析后认为：下部海相层的年代更可能属于MIS 5期,而期间2次短暂的低海面记录可能与5b和5d海平面波动有关。钻孔上部13.9 m以上为全新世2 232 cal. a B.P.以来的沉积,孢粉分析表明植被仍以亚热带常绿林为主,但人类干扰因素的禾本科、松属、芒箕和火灾记录（炭屑）大量增加,指示了沿海人类活动增强和大规模农业的发展,这与全新世晚期海平面下降和三角洲的快速加积作用基本同步进行。     

海南岛南部MIS-5海相沉积地层的发现及其意义

通过对海南岛三亚地区铁炉港海湾TLG01钻孔沉积物的AMS 14C和OSL测年,以及对地层岩性特征、亮度、粒度、海生贝壳、有孔虫丰度等进行研究,发现全新世海相层较薄,以砂质潮坪相沉积为主;而下伏晚更新世海相层厚度超过38 m,OSL测年结果显示为MIS-5e及MIS-5d沉积。晚更新世海进―海退系列自下而上依次为砂质潮坪―潮下带―泥质潮坪―砂质潮坪,其中可见较深水的软体动物。MIS-5e细粒的粉砂黏土体积分数先陡增、后缓降,结合粒度及有孔虫丰度、亮度L*等指标,判断MIS-5e初期为最高海平面时期,水深较大,其后海平面逐渐降低;沉积物中陆源粗砂的体积分数不断增加,显示进入了MIS-5d相对低海面时期。MIS-1及MIS-5沉积物粒度三角图,分别与湛江海岛潮间带及不同深度南海表层沉积物同类沉积环境有较好的对照,指示2类不同水深的海相环境。     

闽江下游全新世孢粉记录的植被与环境变化

为了揭示闽江下游闽侯盆地第四纪沉积环境演变与人类活动历史,对闽江下游闽侯盆地庄边山遗址附近的FZ5钻孔进行了孢粉、硅藻分析。结果表明：闽侯盆地全新世海侵初始发生时间约为9 000 cal. a B.P.,至7 500 cal. a B.P.达到最大海侵范围,晚全新世海退的发生时间在闽侯盆地大约为1 900 cal. a B.P.。孢粉分析证实了当地早中全新世温暖的亚热带气候以及浓密的常绿阔叶林植被。在7 500―1 900 cal. a B.P.之间无论植被覆盖还是气候环境均比较稳定,高海平面时期的适宜气候以及海湾环境也有利于当地以渔猎经济方式为主的新石器文化（昙石山文化）的兴起和发展。自1 900 cal. a B.P.以后,孢粉组合突变为以先锋植物芒萁属（Dicranopteris）、禾本科（Poaceae）、松属（Pinus）等类型为主,揭示了当地植被受到人类农业刀耕火种的影响而发生显著变化。高含量的禾本科花粉（含一定数量的水稻）仅在剖面上部明显增加这一事实,证实了闽侯和福州一带水稻种植的大面积发展始于距今1 900 a前后。     

粤北岩溶区连江流域降雨侵蚀力

对连江流域35个气象站1980―2013年逐日雨量数据进行整理,利用日雨量、月雨量和年雨量方法计算得出RA、RB、RC,通过有效系数M检验得出最优R值;然后利用反距离加权、张力样条函数和普通克里金进行空间插值,通过检验确定最准确的插值方法,最后对其进行插值分析。结果表明：基于月降雨量的计算方法和反距离加权插值法更加适合于连江流域降雨侵蚀力的计算和估算;连江流域降雨侵蚀力时空变化明显,降雨侵蚀力变化与年际降水量变化基本一致;中上游高大山脉存在的地区,多年平均降雨侵蚀力明显高于其他地区;下游多年平均降雨量丰富,其多年平均降雨侵蚀也较严重。