Soil water depletion under various leguminous cover crops in the derived savanna of West Africa

Leguminous cover crops have the potential of making cropping systems in the tropics sustainable if they would not deplete resources such as soil water and nutrients to the detriment of companion crops. Therefore, a study was carried out at Alabata, Ibadan, southwestern Nigeria, to evaluate the effects of leguminous cover crops on soil water suctions in 1993 and 1994 in order to assess the possibility of integrating them into the farming systems of the savanna zone of West Africa. In 1993, 13 leguminous cover crops (Aeschynomene histrix, Centrosema brasilianum, Centrosema pascuorum, Chamaecrista rotundifolia, Cajanus cajan, Crotalaria verrucosa, Crotalaria ochroleuca, Lablab purpureus, Mucuna pruriens, Psophocarpus palustris, Pseudovigna argentea, Pueraria phaseoloides and Stylosanthes hamata) were planted in a randomized complete block design with four replications. Maize and natural fallow (mainly Chromolaena odorata and Imperata cylindrica) were included as comparisons. Only six of the legumes (A. histrix, C. pascuorum, C. cajan, C. ochroleuca, M. pruriens, and P. phaseoloides) were included in the measurements in the 1994 new plots. Soil water suctions at various stages of legume growth were measured at daily or weekly intervals (depending on the frequency of rainfall events) using tensiometers installed at 0–15 and 15–30 cm soil depths. Soil water suctions exceeding 10 kPa (theoretical field capacity) were observed mainly between 6 and 12 weeks after planting (WAP), and by 20 WAP when cover crops had matured and rainfall frequency was very low. Soil water suctions were significantly related (r²>0.80) to dry matter between 8 and 10 WAP. The studied cover crops were classified in three groups which can be used as a guide for choosing the legumes in tropical farming systems. Soil water depletion was markedly influenced by growth characteristics of legumes and distribution of rainfall during the rainy season. Leguminous cover crops conserved soil water after their growth needs were satisfied.     

连云港港口渔船防污工作的调查与思考

通过对连云港港口渔船防污工作的现场调查，分析了存在的问题，对渔船的污染危害进行了评估，并提出了对策。     

川西南阿什及尔期地层中的Ce异常及其古海洋学意义

川西南阿什及尔期地层中的全岩REE分配模式显示 ,含有浮游笔石和小型无铰纲腕足类的黑色页岩具有较低的Ce异常值 (0 .6 2～ 0 .74) ,而含有底栖三叶虫、有铰纲腕足类和藻类的非黑色页岩则具有较高的Ce异常值 (0 .92～ 1.30 )。Ce与其他元素的相关分析进一步揭示 ,Ce与Fe的相关性最好 (r =0 .85 ) ,与P的相关性次之 (r =0 .6 1) ,与Al的相关性较差 (r =0 .2 9) ,而与Mn和Ca几乎不相关 (r =0 .14,r =- 0 .0 2 )。实际观察可能表明 ,研究区底层水体在氧化和碱性条件下 ,Ce氧化为Ce4 + 并进入Fe的氢氧化物和磷酸盐的晶格中 ,或者被吸附到它们的表面 ,造成Ce在氧化水体中呈现负异常而在同期氧化沉积物中呈现正异常或负异常不明显 ;相反 ,在还原和酸性条件下 ,Ce在水体中以 +3价状态富集 ,引起Ce在同期缺氧沉积物中呈现明显负异常。作为古海水氧化还原指示的全岩Ce异常 ,通常限定于解释远洋细粒沉积物的沉积环境。我们的研究结果说明 ,移去化石骨骼 (通常是磷酸盐化石骨骼 )的浅海细粒沉积物同样可以用于全岩REE分析 ,以获得可靠的能够指示古海水氧化还原条件变化的Ce异常     

A Blueprint for the Oceans: Implications of Two National Commission Reports for Conservation Practitioners

Abstract:  In the first comprehensive reviews since 1969, two high-level reports on the status of U.S. marine ecosystems and resources have been released: that of the nongovernmental Pew Oceans Commission in 2003 and that of the congressionally mandated U.S. Commission on Ocean Policy in 2004 . Although the two commissions differed in the breadth and depth of their mandates, their findings on the state of our oceans and need for new management approaches are similar, and their major recommendations for science, governance, management and conservation, and education echo and reinforce each other. The history behind the two commissions and the structure and objectives of each remind us of the crucial roles conservation practitioners and scientists must play in the implementation of report recommendations. The reports suggest priorities for conservation practitioners to improve science, management, conservation, governance, and education to better manage and protect ocean resources and ecosystems. To redirect activities affecting the state of global marine resources, integrated research; education and outreach by terrestrial, aquatic, and marine conservation practitioners; and a clear definition of their roles in the implementation of recommendations is essential. Marine ecosystems provide a test case of society's ability to manage complexity in human and natural systems in an integrated manner, with extensive opportunities for participation by conservation practitioners from all disciplines.     

Detection and delineation of critical areas using echelons and spatial scan statistics with synoptic cellular data

Geographical surveillance for hotspot detection and delineation has become an important area of investigation both in geospatial ecosystem health and in geospatial public health. In order to find critical areas based on synoptic cellular data, geospatial ecosystem health investigations apply recently discovered echelon tools. In order to find elevated rate areas based on synoptic cellular data, geospatial public health investigations apply recently discovered spatial scan statistic tools. The purpose of this paper is to conceptualize a joint role for these together in the spirit of a cross-disciplinary cross-fertilization to accomplish more effective and efficient geographical surveillance for hotspot detection and delineation, and early warning system.     

Historical perspectives on contemporary human–environment dynamics in southeast Africa

The human communities and ecosystems of island and coastal southeast Africa face significant and linked ecological threats. Socioecological conditions of concern to communities, governments, nongovernmental organizations, and researchers include declining agricultural productivity, deforestation, introductions of non-native flora and fauna, coastal erosion and sedimentation, damage to marine environments, illegal fishing, overfishing, waste pollution, salinization of freshwater supplies, and rising energy demands, among others. Human–environment challenges are connected to longer, often ignored, histories of social and ecological dynamics in the region. We argue that these challenges are more effectively understood and addressed within a longer-term historical ecology framework. We reviewed cases from Madagascar, coastal Kenya, and the Zanzibar Archipelago of fisheries, deforestation, and management of human waste to encourage increased engagement among historical ecologists, conservation scientists, and policy makers. These case studies demonstrate that by widening the types and time depths of data sets we used to investigate and address current socioecological challenges, our interpretations of their causes and strategies for their mitigation varied significantly.     

Applying artificial neural network methodology to ocean color remote sensing

Artificial neural networks (ANN) are widely used as continuous models to fit non-linear transfer functions. In this study we used ANN to retrieve chlorophyll pigments in the near-surface of oceans from Ocean Color measurements. This bio-optical inversion is established by analyzing concomitant sun-light spectral reflectances over the ocean surface and pigment concentration. The relationships are complex, non-linear, and their biological nature implies a significant variability. Moreover, the sun-light reflectances are usually measured by satellite radiometers flying at 800 km over the ocean surface, which affect the data by adding radiometric noise and atmospheric correction errors. By comparison with the polynomial fit usually employed to treat this problem, we show the advantages of neural function approximation like the association of non-linear complexity and noise filtering.     

Bioaccumulation of Hg, Cu, and Zn in the Azores triple junction hydrothermal vent fields food web

In this work, mercury (Hg), copper (Cu) and zinc (Zn) concentrations and tissue distribution are determined in seven benthic invertebrates species (the key species) from the Mid Atlantic Ridge (MAR) hydrothermal vent fields. The samples were collected from three hydrothermal vent fields – Menez Gwen, 840 m; Lucky Strike, 1700 m and Rainbow, 2300 m – near the Azores Triple Junction. These fields are characterized by different depths, geological context and chemical composition of the hydrothermal fluid, particularly the metal content, which is reflected by the metal concentrations in the organisms. Indeed, our results show that organisms from Menez Gwen presented the highest Hg concentrations, while those from Lucky Strike and Rainbow were richer in Cu and Zn. The potential transfer of these metals through two trophic links are also evaluated and include (1) the mussel Bathymodiolus azoricus and the commensal worm Branchipolynoe seepensis, and (2) three different species of shrimps and the crab Segonzacia mesatlantica. No evidence of Hg biomagnification in either of the vent food chains is clearly observed but an increase in Hg accumulation from prey to predator in the crustacean food chain. The same pattern was observed for Cu and Zn, even though these metals are not known to be generally biomagnified in food chains.     

FRESH GROUND WATER STORED IN AQUIFERS UNDER THE CONTINENTAL SHELF: IMPLICATIONS FROM A DEEP TEST,NANTUCKET ISLAND,MASSACHUSETTS1

ABSTRACT: A deep water-resource and stratigraphic test well near the center of Nantucket Island, about 40 miles (64 km) off the New England Coast, has encountered freshwater at greater depth than predicted by the Ghyben-Herzberg principle. An uppermost lens of fresh-water, which occupies relatively permeable glacial-outwash sand and gravel to a depth of 520 ft. (158 m), is probably in hydrodynamic equilibrium with the present level of the sea and the height of the water table. However, two zones of freshwater between 730-820 ft. (222-250 m) and 900-930 ft. (274-283 m) are anomalously deep. A third zone extending from 1150-1500 ft. (350-457 m) contains slightly salty ground water (2 to 3 parts per thousand dissolved solids). Several explanations are possible, but the most likely is that large areas of the Continental Shelf were exposed to recharge by precipitation during long periods of low sea level in Pleistocene time. After the last retreat of glacial ice, seawater rapidly drowned the shelf around Nantucket Island. Since then, about 8000 years ago, the deep freshwater zones which underlie dense clay layers have not had time to adjust to a new equilibrium. Under similar circumstances freshwater may remain trapped under extensive areas of the Continental Shelf wherever clay confining beds have not permitted saltwater to intrude rapidly to new positions of hydrodynamic equilibrium. The implications are far reaching because all continental shelfs were exposed to similar hydrologic influences during Pleistocene time.     

Inventory of ocean monitoring in the Southern California Bight

Monitoring of the ocean environment in southern California, USA, has been conducted by a diverse array of public and private organizations with different motivations, working on a variety of spatial and temporal scales. To create a basis from which to integrate information from these diverse programs, we conducted an inventory of ocean monitoring activities in the Southern California Bight to address the following questions: (1) How much money is being expended annually on marine monitoring programs? (2) Which organizations are conducting the most monitoring? (3) How are resources allocated among the different types of monitoring programs? This inventory focused on programs existing, or those expected to be in existence, for at least 10 years and that were active at any time between 1994 and 1997. For each program identified for inclusion in this study, information was collected on the number of sites, sampling intensity, parameters measured, and methods used. Levels of effort were translated into cost estimates based upon a market survey of local consulting firms. One hundred fourteen marine monitoring programs, conducted by 65 organizations and costing US $31 million annually, were identified. Most of the effort (81 programs, 65% of samples, 70% of costs) was expended by ocean dischargers as part of their compliance with National Pollutant Discharge Elimination System (NPDES) permit requirements. Federal programs (11 programs, 25% of samples, 10% of total expenditures) expended more than state or local government programs. More than one quarter of monitoring expenditures were conducted to measure concentrations and mass of effluent inputs to the ocean. The largest effort expended on receiving water monitoring was for measuring bacteria, followed by sediments, fish/shellfish, water quality, and intertidal habitats. The large level of expenditures by individual agencies has presented opportunities for integrating small, site-specific ocean monitoring programs into regional- and national-scale monitoring and assessment programs.