Über relative Sexualität bei Ectocarpus siliculosus

The Science of Nature -     

Ambient toxicity due to chlorpyrifos and diazinon in a central California coastal watershed

The Salinas River watershed along the central coast of California, U.S.A., supports rapidly growing urban areas and intensive agricultural operations. The river drains to an estuarine National Wildlife Refuge and a National Marine Sanctuary. The occurrence, spatial patterns, sources and causesof aquatic toxicity in the watershed were investigated by sampling four sites in the main river and four sites in representative tributaries during 15 surveys between September1998 and January 2000. In 96 hr toxicity tests, significant Ceriodaphnia dubia mortality was observed in 11% of the mainriver samples, 87% of the samples from a channel draining anurban/agricultural watershed, 13% of the samples fromchannels conveying agricultural tile drain runoff, and in 100% of the samples from a channel conveying agricultural surface furrow runoff. In six of nine toxicity identificationevaluations (TIEs), the organophosphate pesticides diazinon and/or chlorpyrifos were implicated as causes of observed toxicity, and these compounds were the most probable causes oftoxicity in two of the other three TIEs. Every sample collectedin the watershed that exhibited greater than 50% C. dubia mortality (n = 31) had sufficient diazinon and/or chlorpyrifos concentrations to account for the observed effects.Results are interpreted with respect to potential effects on other ecologically important species.     

Cars and fuels for tomorrow: a comparative assessment

Light duty vehicles, i.e. passenger cars and light trucks, account for approximately half of global transportation energy demand and, thus, a major share of carbon dioxide and other emissions from the transport sector. Energy consumption in the transport sector is expected to grow in the future, especially in developing countries. Cars with alternative powertrains to internal combustion engines (notably battery, hybrid and fuel-cell powertrains), in combination with potentially low carbon electricity or alternative fuels (notably hydrogen and methanol), can reduce energy demand by at least 50%, and carbon dioxide and regulated emissions much further. This article presents a comparative technical and economic assessment of promising future fuel/vehicle combinations. There are several promising technologies but no obvious winners. However, the electric drivetrain is a common denominator in the alternative powertrains and continued cost reductions are important for widespread deployment in future vehicles. Development paths from current fossil fuel based systems to future carbon-neutral supply systems appear to be flexible and a gradual phasing-in of new powertrains and carbon-neutral fluid fuels or electricity is technically possible. Technology development drivers and vehicle manufacturers are found mainly in industrialised countries, but developing countries represent a growing market and may have an increasingly important role in shaping the future.     

Decision support in urban water management based on generic scenarios: The example of NoMix technology

Urine source separation (NoMix technology) followed by processing the concentrated nutrient solution has the potential to become a cost-efficient alternative to conventional end-of-pipe nutrient elimination. A choice of processing technologies can only be made for specific scenarios, and there is currently no methodology for analyzing generic situations. In setting up a formalized decision-support methodology (based on STEEPLED analysis), we discuss how to create such generic scenarios, how to couple them with process engineering objectives, how to define the technology requirements, and finally how to produce a realistic subset of technology alternatives. The methodology is tested in five real scenarios. We also touch on the criteria for a final choice of technology taking into account large uncertainties about the performance of real technologies. We conclude that technology development is one of the most important requirements for implementing urine source separation in practice. There is an urgent need to develop cost-efficient processing technologies that satisfy the requirements of stakeholders.     

Pyrodinium大量繁殖现象会在东南亚地区重新发生和扩散吗?——千年末的见解

迄今20年来,Pyrodinium bahamense ( var.compressum)一直是造成东南亚地区重大公众健康问题和经济问题的唯一的腰鞭毛虫物种.它产生石房蛤毒素,即一系列造成麻痹性贝毒(PSP)的毒素.这是一个影响世界上许多国家的严重的毒理学问题,轻者,会在30分钟内发生中毒现象,重者,可能在食用中毒贝类后的2～24小时内由于呼吸系统麻痹而致死.在马来西亚、文莱、菲律宾以及印度尼西亚均有关于这种生物大量繁殖的报道.自1976年首次在马来西亚沙巴发生以来,东盟-加拿大赤潮网已在26个地区记录到31次该种生物大量繁殖事件.截止1999年,受影响最严重的国家是菲律宾,其受影响的地区最多[18]、发生麻痹性贝素(PSP)事件最多(约1995起)马来西亚报道总共发生609起PSP事件,造成44人死亡,而文莱则记录有14起PSP事件,但没有死亡事故.印度尼西亚记录有427起PSP事件,17人死亡.在该地区迄今没有开展关于这些大量繁殖事件对生态/环境的影响的研究.对经济影响的估算表明,损失可高达每天30万美元.有助于了解Pyrodinium大量繁殖动态的大部分信息来自己已经在受到影响的地区各国不同程度地开展的有害/有毒藻类监测与研究.区域性的合作研究与监测工作可有助于协调当地的数据集并保证其用于比较分析和模拟所要求的质量和有效性.对地方和区域尺度上大量繁殖的时间模型以及Pyrodinium大量繁殖发生/再发生和扩散的可能征兆和趋势可以进行调查.可能通过改进和优化现有的Pyrodinium大量繁殖描述性和简单的预报模型,来帮助管理这里的人民赖以为日常食物来源和生计的野生捕捞和人工养殖的贝类.     

Modeling fecundity in birds: Conceptual overview, current models, and considerations for future developments

Fecundity is fundamental to the fitness, population dynamics, conservation, and management of birds. For all the efforts made to measure fecundity or its surrogates over the past century of avian research, it is still mismeasured, misrepresented, and misunderstood. Fundamentally, these problems arise because of partial observability of underlying processes such as renesting, multiple brooding, and temporary emigration. Over the last several decades, various analytical approaches have been developed to estimate fecundity from incomplete and biased data. These, include scalar arithmetic formulae, partial differential equations, individual-based simulations, and Markov chain methodology. In this paper, we: (1) identify component processes of avian reproduction; (2) review existing methods for modeling fecundity; (3) place these diverse models under a common conceptual framework; (4) describe the parameterization, validation, and limitations of such models; and (5) point out future considerations and challenges in the application of fecundity models. We hope this synthesis of existing literature will help direct researchers toward the most appropriate methods to assess avian reproductive success for answering questions in evolutionary ecology, natural history, population dynamics, reproductive toxicology, and management.