The enigma of progress in denitrification research.

Humans have dramatically increased the amount of reactive nitrogen (primarily ammonium, nitrogen oxides, and organically bound N) circulating in the biosphere and atmosphere, creating a wide array of desirable products (e.g., food production) and undesirable consequences (e.g., eutrophication of aquatic ecosystems and air pollution). Only when this reactive N is converted back to the chemically unreactive dinitrogen (N2) form, do these cascading effects of elevated reactive N cease to be of concern. Among the quantitatively most important processes for converting reactive N to N2 gas is the biological process of classical denitrification, in which oxides of nitrogen are used as terminal electron acceptors in anaerobic respiration. This Invited Feature on denitrification includes a series of papers that integrate our current state of knowledge across terrestrial, freshwater, and marine systems on denitrification rates, controlling factors, and methodologies for measuring and modeling denitrification. In this paper, we present an overview of the role of denitrification within the broader N cycle, the environmental and health concerns that have resulted from human alteration of the N cycle, and a brief historical perspective on why denitrification has been so difficult to study. Despite over a century of research on denitrification and numerous recent technological advances, we still lack a comprehensive, quantitative understanding of denitrification rates and controlling factors across ecosystems. Inherent problems of measuring spatially and temporally heterogeneous N2 production under an N2-rich atmosphere account for much of this slow progress, but lack of interdisciplinary communication of research results and methodological developments has also impeded denitrification research. An integrated multidisciplinary approach to denitrification research, from upland terrestrial ecosystems, to small streams, river systems, estuaries, and continental shelf ecosystems, and to the open ocean, may yield new insights into denitrification across landscapes and waterscapes.     

The life cycle of the commensal hydromedusa Eutima sapinhoa n. sp.

Eutima sapinhoa n. sp. is a small hydroid, which lives attached by a basal disc to the mantle, foot, gills and labial palps of the bivalve Tivela mactroides (Born, 1778), found on the northern littoral of São Paulo State, Brazil. This bivalve, locally known as “sapinhoá”, is used as food by the coastal inhabitants. The hydroid produces a leptomedusa which belongs to the family Eutimidae. The medusa bud develops as a small knob-like protuberance near the base of the polyp and, after 61/2 days, reaches the free-swimming stage in covered preparation dishes containing about 200-ml filtered sea water at a temperature of 20° to 22°C. After 25 days the medusa is 4 mm high, 4-mm in diameter, and possesses 4 radial tentacles —each about 2 to 3 times as long as the bell diameter, 8 marginal vesicles — 2 in each quadrant, and 28 small marginal swellings — 7 in each quadrant. The peduncle is as long as the height of the bell, 4 single long gonads develop on the subumbrella on each radial canal. The nematocysts are small atrichous isorhizae, with capsules averaging 7 μm in length.     

Megafaunal Extinctions: The Conservation Message from 11,000 Years B.P.

Abstract: At the end of the Pleistocene, the Americas, northern Eurasia: and Australia experienced a vast decline in large mammal diversity, while Africa and tropical Asia were hardly affected. The elimination of the megaberbivores (animals weighing >1000 kg, probably by human predation, removed the vegetation impact of these species. The resultant reduction in habitat mosaic diversity and in forage quality probably precipitated the extinctions of lesser large mammalian species. Surviving megaherbivores in the form of elephants and rhinoceroses are currently being exterminated from many African conservation areas. African savanna ecosystems could prove more resistant to species losses than north temperate ecosystems, because geomorphic factors plus low and erratic rainfall enhance spatial heterogeneity and vegetation quality independently of large herbivore impact Nevertheless, the history of the Hluhluwe Game Reserve in South Africa suggests that certain African ecosystems may become susceptible to an inexorable decline in populations of some large herbivores following the extermination of elephants. If elephants and rhinoceroses cannot be conserved active habitat manipulation will be needed to retain a diverse fauna of large mammals in such regions.     

Ultrastructure of the corallinaceae. I. The vegetative cells of Corallina officinalis and C. cuvierii

A technique utilizing combined fixation and gentle decalcification has been employed to study the ultrastructure of the vegetative cells of the articulated calcareous coralline algae Corallina officinalis Linnaeus and C. cuvierii Lamouroux (Rhodophyta: Cryptonemiales). The epidermal cells are distinctive, with many cell wall inggrowths which pass between the chloroplasts. It is suggested that these cells function as transfer cells. The epidermal cells contain no starch, although the chloroplasts have well developed photosynthetic lamellae. Damage to these epidermal cells leads to formation of new cells by renewed division of sub-epidermal meristematic cells. The outer cortical cells have few small vacuoles and many plastids, with an extensive photosynthetic lamellar system. Deeper into the thallus, the vacuoles increase in size and free cytoplasmic starch grains occur. The medullary cells have a very large vacuole and in older tissue often appear dead. The long genicular cells have calcareous walls at either end while the wall in the middle of these cells is non-calcareous and has an inner fibrillar layer and a thin outer cuticle. In partially decalcified material, the orientation of the CaCO₃ (calcite) crystals next to the cells can clearly be seen. Immediately next to the cell the crystals are fairly small and arranged at right angles to the plasmalemma. Further away from the cell the crystal size is larger and their orientation is more random. The crystals are surrounded by organic material, and the possible rôle of this material in calcification in coralline algae is discussed.     

The biology of colonial hydroids. I. The morphology of the polyp of Eirene viridula (Thecata: Campanulinidae)

The colonial marine hydroid Eirene viridula Peron and Lesueur (Thecata, Campanulinidae) is readily maintained under laboratory conditions and reproduces in both vegetative and sexual modes. Polyps from these colonies displayed 4 distinct body regions, which were studied by comparison of light and electron micrographs of semi-thin and ultra-thin sections. Attention was directed chiefly to the epitheliomuscular and digestive muscle cells, found in all 4 regions and characterized by the presence of a central vacuole. Particular emphasis has been placed upon the coated vesicles and discoidal coated vesicles, which appear side by side in the digestive muscle cells of the stomach, and upon the central vacuoles typical of the muscle cells of the contractile parts of the body. The possible functional significance of these structures is discussed.This work was supported by the Deutsche Forschungsgemeinschaft.     

Sublittoral epifaunal communities at Signy Island,Antarctica. I. The ice-foot zone

Photographs were taken every 0.5 m along three transects of 5.5 m length on shallow rock faces at Signy Island, Antarctica, during the austral summer of 1991/1992. The percentage cover of substratum ranged from 0 to 100% and the colonising communities included representatives of ten phyla. The zone from mean low-water neap level to 1.5 m depth was mostly devoid of organisms as a result of the seasonal formation of the encrusting ice foot. Coralline and macroalgae dominated from 2 to 3 m, and animal groups from 3.5 to 5.5 m. Bryozoans, and to a lesser extent sponges, were the most abundant animal phyla. Within the bryozoans a succession of colonisation of different species was observed, the most abundant two of which occupied >80% of substratum in places. Substratum type seemed to be the main factor influencing community development in the shallow sublittoral at Signy Island, although ice impact prevents community development in the top 1.5 m and limits it over the rest of the transect down to 5.5 m. Depth and profile of substratum also influenced communities within this depth range (particularly taxonomic composition).     

The Estuarine Component of the Us E.P.A.'S Environmental Monitoring and Assessment Program

The US Environmental Protection Agency's Office of Research and Development has initiated the Environmental Monitoring and Assessment Program (EMAP) to monitor status and trends in the condition of the nation's near coastal waters, forests, wetlands, agro-ecosystems, surface waters, deserts and rangelands. the programme is also intended to evaluate the effectiveness of Agency policies at protecting ecological resources occurring in these systems. Monitoring data collected for all ecosystems will be integrated for regional and national status and trends assessments. the near coastal component of EMAP consists of estuaries, coastal waters, and the Great Lakes. Near coastal ecosystems have been regionalized and classified, and an integrated sampling strategy has been developed. EPA and NOAA have agreed to coordinate and, to the extent possible, integrate the near coastal component of EMAP with the NOAA National Status and Trends Program. A demonstration project was conducted in estuaries of the mid-Atlantic region (Chesapeake Bay to Cape Cod) in the summer of 1990. in 1991, monitoring continued in mid-Atlantic estuaries and was initiated in estuaries of a portion of the Gulf of Mexico. Preliminary results indicate: there are no insurmountable logistical problems with sampling on a regional scale; several of the selected indicators are practical and sensitive on the regional scale; and an efficient effort in future years will provide valuable information on condition of estuarine resources at regional scales.     

The short-run impact of environmental protection costs on U.S. product prices

Using an input-output framework, this paper investigates the magnitude of the impact that environmental protection costs had on prices in the United States in 1977. With the imposition of environmental protection costs, the projected total price increases for individual industries range from 0.12% to 6.58%. Due to data limitations, the constraints of input-output analysis, and the structural changes that occurred in the economy from 1972 to 1977, the results should not be taken as definitive. However, the results do indicate the typical sort of variation in impact likely to occur across industries and that the average impact on prices was modest.     

The Estuarine Component of the Us E.P.A.'S Environmental Monitoring and Assessment Program

The US Environmental Protection Agency's Office of Research and Development has initiated the Environmental Monitoring and Assessment Program (EMAP) to monitor status and trends in the condition of the nation's near coastal waters, forests, wetlands, agro-ecosystems, surface waters, deserts and rangelands. the programme is also intended to evaluate the effectiveness of Agency policies at protecting ecological resources occurring in these systems. Monitoring data collected for all ecosystems will be integrated for regional and national status and trends assessments. the near coastal component of EMAP consists of estuaries, coastal waters, and the Great Lakes. Near coastal ecosystems have been regionalized and classified, and an integrated sampling strategy has been developed. EPA and NOAA have agreed to coordinate and, to the extent possible, integrate the near coastal component of EMAP with the NOAA National Status and Trends Program. A demonstration project was conducted in estuaries of the mid-Atlantic region (Chesapeake Bay to Cape Cod) in the summer of 1990. in 1991, monitoring continued in mid-Atlantic estuaries and was initiated in estuaries of a portion of the Gulf of Mexico. Preliminary results indicate: there are no insurmountable logistical problems with sampling on a regional scale; several of the selected indicators are practical and sensitive on the regional scale; and an efficient effort in future years will provide valuable information on condition of estuarine resources at regional scales.     

The life cycle of Eutima commensalis sp. nov. (Eutimidae,Hydromedusae)

Developmental stages of the medusa Eutima commensalis sp. nov. were obtained from plankton collections made at 2 fixed stations, one at Fareway Buoy and the other at Aroor in the Cochin backwater system. Six stages were arbitrarily assigned and described. The hydroid and the medusa of this form were found to occur in these waters throughout the year, except during the monsoon months from June to September. The hydroid is endocommensalic on wood-boring molluscs such as Nausitora hedleyi, Teredo furcifera and Martesia striata.     

The Robert H. MacArthur Award Lecture. Timescales, dynamics, and ecological understanding

Explicit consideration of timescales and dynamics is required for an understanding of fundamental issues in ecology. Endogenous dynamics can lead to transient states where asymptotic behavior is very different from dynamics on short timescales. The causes of these kinds of transients can be placed in one of three classes: linear systems with different timescales embedded or exhibiting reactive behavior, the potentially long times to reach synchrony across space for oscillating systems, and the complex dynamics of systems with strong density-dependent (nonlinear) interactions. It is also important to include the potentially disparate timescales inherent in ecological systems when determining the endogenous dynamics. I argue that the dynamics of ecological systems can best be understood as the response, which may include transient dynamics, to exogenous influences leading to the observed dynamics on ecologically relevant timescales. This view of ecosystem behavior as responses of ecological systems governed by endogenous dynamics to exogenous influences provides a synthetic way to unify different approaches to population dynamics, to understand mechanisms that determine the distribution and abundance of species, and to manage ecosystems on appropriate timescales. There are implications for theoretical approaches, empirical approaches, and the statistical approaches that bridge theory and observation.     

桂牧1号杂交象草研究进展

系统综述了桂牧1号杂交象草(Pennisetum purpureumcv.Guimu-1)生物学特性、丰产栽培技术、营养品质、饲喂效果等方面的研究状况,并针对生产实际中存在的问题,提出了桂牧1号杂交象草今后生产和研究的主要方向.     

The biology of colonial hydroids. II. The morphology and ultrastructure of the medusa of Eirene viridula (Thecata-Leptomedusa: Campanulinidae)

The free-swimming medusae of Eirene viridula are typical marine hydroids, with distinct subdivisions into body regions, which were studied by comparison of light and electron microscopy. Particular attention is given to the epithelio-muscular and digestive muscle cells. The epidermis — apart from a few nerve cells and cnidocytes-consists of epitheliomuscular cells. At their bases these cells form a musculature and at the apex many secretory vesicles. In the velum, large expansions of the intercellular space are found. The gastrodermis — apart from the mucous and zymogen cells in the manubrium — consists of digestive muscle cells, the structure of which corresponds in principle to that of the epitheliomuscular cells. In its apex, this type of cells contains both normal coated vesicles and discoidal coated vesicles. In the solid tentacles, the digestive muscle cells form a turgescent vesicular tissue. The central nervous system consists of the exumbrellar, subumbrellar, and gastrodermal nerve rings. They are composed of ganglion cells, their processes, and intraepithelial flagella. The static organs are purely ectodermal statocysts which have only one lithocyte and only one sensory cell.     

The role of scientists in statutory interpretation of the U.S. Endangered Species Act

Like many federal statutes, the U.S. Endangered Species Act (ESA) contains vague or ambiguous language. The meaning imparted to the ESA's unclear language can profoundly impact the fates of endangered and threatened species. Hence, conservation scientists should contribute to the interpretation of the ESA when vague or ambiguous language contains scientific words or refers to scientific concepts. Scientists need to know at least these 2 facts about statutory interpretation: statutory interpretation is subjective and the potential influence of normative values results in different expectations for the parties involved. With the possible exception of judges, all conventional participants in statutory interpretation are serving their own interests, advocating for their preferred policies, or biased. Hence, scientists can play a unique role by informing the interpretative process with objective, policy‐neutral information. Conversely, scientists may act as advocates for their preferred interpretation of unclear statutory language. The different roles scientists might play in statutory interpretation raise the issues of advocacy and competency. Advocating for a preferred statutory interpretation is legitimate political behavior by scientists, but statutory interpretation can be strongly influenced by normative values. Therefore, scientists must be careful not to commit stealth policy advocacy. Most conservation scientists lack demonstrable competence in statutory interpretation and therefore should consult or collaborate with lawyers when interpreting statutes. Professional scientific societies are widely perceived by the public as unbiased sources of objective information. Therefore, professional scientific societies should remain policy neutral and present all interpretations of unclear statutory language; explain the semantics and science both supporting and contradicting each interpretation; and describe the potential consequences of implementing each interpretation. A review of scientists’ interpretations of the phrase “significant portion of its range” in the ESA is used to critique the role of scientists and professional societies in statutory interpretation.     

城市固体废弃物堆肥化处理的影响因素

城市固体废弃物的堆肥化处理已经成为各国越来越重视的方法。堆肥化处理是通过控制堆腐过程条件,使废弃物在短时间内最有效地达到稳定,杀灭病原菌,使产品可以安全地使用。本文对堆肥的原理及基本机理进行了介绍,同时对堆肥过程的重要参数（ 水分含量、有机质含量、 Ｃ／ Ｎ 比、ｐ Ｈ 值、通气量等） 进行了综述。