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121.
Diane K. Stoecker Jason E. Adolf Allen R. Place Patricia M. Glibert Donald W. Meritt 《Marine Biology》2008,154(1):81-90
The bloom-forming dinoflagellates Prorocentrum minimum and Karlodinium veneficum can have detrimental effects on some marine life, including shellfish, but little is known about their effects on early life
history stages of bivalves. In the Chesapeake Bay region, blooms of these dinoflagellates overlap with the spawning season
of the eastern oyster, Crassostrea virginica. In laboratory experiments, we compared the effects of P. minimum and K. veneficum on the survival and development of embryos and larvae of the eastern oyster. At 104 cells ml−1, P. minimum did not have a negative effect on embryos and larvae in 2-day exposures. The yield of D-hinge larvae was equal to or greater
than in control treatments. At 2 × 104 cells ml−1 (approximately equal biomass to the P. minimum treatment) K. veneficum caused significant mortality to oyster embryos within 1 day and almost no embryos developed into D-hinge larvae. This effect
was not alleviated by the provision of an alternate food source (Isochrysis sp.). Significant mortality was observed when larvae were exposed to K. veneficum at concentrations of 104 cells ml−1 (approximately 5 ng ml−1 of karlotoxin). The K. veneficum cultures used in these experiments were relatively low in toxin content, more toxic strains could be expected to cause mortality
at lower cell concentrations. Survival and maturation of embryos and larvae may be reduced when spawns of the eastern oyster
coincide with high bloom densities of K. veneficum. 相似文献
122.
Christopher J. Williams Patricia J. Heglund 《Environmental and Ecological Statistics》2009,16(4):495-513
Habitat association models are commonly developed for individual animal species using generalized linear modeling methods
such as logistic regression. We considered the issue of grouping species based on their habitat use so that management decisions
can be based on sets of species rather than individual species. This research was motivated by a study of western landbirds
in northern Idaho forests. The method we examined was to separately fit models to each species and to use a generalized Mahalanobis
distance between coefficient vectors to create a distance matrix among species. Clustering methods were used to group species
from the distance matrix, and multidimensional scaling methods were used to visualize the relations among species groups.
Methods were also discussed for evaluating the sensitivity of the conclusions because of outliers or influential data points.
We illustrate these methods with data from the landbird study conducted in northern Idaho. Simulation results are presented
to compare the success of this method to alternative methods using Euclidean distance between coefficient vectors and to methods
that do not use habitat association models. These simulations demonstrate that our Mahalanobis-distance-based method was nearly
always better than Euclidean-distance-based methods or methods not based on habitat association models. The methods used to
develop candidate species groups are easily explained to other scientists and resource managers since they mainly rely on
classical multivariate statistical methods. 相似文献
123.
124.
Patricia C. Henshaw Derek B. Booth 《Journal of the American Water Resources Association》2000,36(6):1219-1236
ABSTRACT: Stream channels are known to change their form as a result of watershed urbanization, but do they restabilize under subsequent conditions of constant urban land use? Streams in seven developed and developing watersheds (drainage areas 5–35 km2) in the Puget Sound lowlands were evaluated for their channel stability and degree of urbanization, using field and historical data. Protocols for determining channel stability by visual assessment, calculated bed mobility at bankfull flows, and resurveyed cross‐sections were compared and yielded nearly identical results. We found that channel restabilization generally does occur within one or two decades of constant watershed land use, but it is not universal. When (or if) an individual stream will restabilize depends on specific hydrologic and geomorphic characteristics of the channel and its watershed; observed stability is not well predicted by simply the magnitude of urban development or the rate of ongoing land‐use change. The tendency for channel restabilization suggests that management efforts focused primarily on maintaining stability, particularly in a still‐urbanizing watershed, may not always be necessary. Yet physical stability alone is not a sufficient condition for a biologically healthy stream, and additional rehabilitation measures will almost certainly be required to restore biological conditions in urban systems. 相似文献
125.
Stefano Raccanelli Simone Libralato Maurizio Favotto 《Environmental Chemistry Letters》2008,6(4):251-258
Rearing benthic bivalves that are contaminated by persistent organic pollutants (POPs) in areas with low pollution levels
permits their natural detoxification. Here, we present the results of novel detoxification experiments conducted with the
Manila clam (Tapes philippinarum) in the Venice Lagoon; these experiments were conducted both in summer and winter. Measurements of dioxins (PCDD), furans
(PCDF), polychlorinated biphenyl (PCB) and hexachlorobenzene (HCB) concentrations in clam flesh over time after their resettlement
in cleaner areas allowed for determining the minimum time required to reach safe toxicity levels. Moreover, dioxin fingerprint
dynamics demonstrated successful detoxification from industrial contaminants. A simple bioaccumulation/detoxification model
applied to the collected data provided for the first time estimation of detoxification rates and half-lives for POP congeners
in clam flesh. This work provides a basis for considering natural detoxification as a viable solution for safely exploiting
resources otherwise restricted from human consumption due to associated health risks. 相似文献
126.
Phosphates for Pb immobilization in soils: a review 总被引:9,自引:0,他引:9
In its soluble ionic forms, lead (Pb) is a toxic element occurring in waters and soils mainly as the result of human activities.
The bioavailability of lead ions can be decreased by complexation with various materials in order to decrease their toxicity.
Pb chemical immobilization using phosphate addition is a widely accepted technique to immobilize Pb from aqueous solution
and contaminated soils. The application of different P amendments cause Pb in soils to shift from forms with high availability
to the most strongly bound Pb fractions. The increase of Pb in the residual or insoluble fraction results from formation of
pyromorphite Pb5(PO4)3X where X = F, Cl, Br, OH, the most stable environmental Pb compounds under a wide range of pH and Eh natural conditions.
Accidental pyromorphite ingestion does not yield bioavailable lead, because pyromorphite is insoluble in the intestinal tract.
Numerous natural and synthetic phosphates materials have been used to immobilize Pb: apatite and hydroxyapatite, biological
apatite, rock phosphate, soluble phosphate fertilizers such as monoammonium phosphate, diammonium phosphate, phosphoric acid,
biosolids rich in P, phosphatic clay and mixtures. The identification of pyromorphite in phosphate amended soils has been
carried out by different non destructive techniques such as X-ray diffraction, scanning electron microscopy coupled with energy
dispersive X-ray spectroscopy, X-ray absorption fine structure, transmission electron microscopy and electron microprobe analysis.
The effectiveness of in situ Pb immobilization has also been evaluated by selective sequential extraction, by the toxicity
leaching procedure and by a physiologically based extraction procedure simulating metal ingestion and gastrointestinal bioavailability
to humans. Efficient Pb immobilization using P amendments requires increasing the solubility of the phosphate phase and of
the Pb species phase by inducing acid conditions. Although phosphorus addition seems to be highly effective, excess P in soil
and its potential effect on eutrophication of surface water, and the possibility of As enhanced leaching remains a concern.
The use of mixed treatments may be a useful strategy to improve their effectiveness in reducing lead phyto- and bioavailability. 相似文献
127.
Linda A. Joyce Curtis H. Flather Patricia A. Flebbe Thomas W. Hoekstra Stan J. Ursic 《Environmental management》1990,14(4):489-500
The impact of timber management and land-use change on forage production, turkey and deer abundance, red-cockaded woodpecker
colonies, water yield, and trout abundance was projected as part of a policy study focusing on the southern United States.
The multiresource modeling framework used in this study linked extant timber management and land-area policy models with newly
developed models for forage, wildlife, fish, and water. Resource production was integrated through a commonly defined land
base that could be geographically partitioned according to individual resource needs. Resources were responsive to changes
in land use, particularly human-related, and timber management, particularly the harvest of older stands, and the conversion
to planted pine. 相似文献
128.
The paper investigates the scientific knowledge divide in the environmental sciences between developed and developing countries and explores the implications and impacts on both science and policymaking. Quantitative data analysis of more than 6400 scientific papers published in 1993–2003 yield evidence for a growing divide in authorship, publication rates, and location of scientific research in nine environmental journals with high impact factor ratings. In addition to this severe imbalance in publication rates between developed and developing countries, we also find a research bias toward certain eco-climatic zones. More than 80% of papers are published in and about temperate and cold eco-climatic zones. Only 13% of the papers in our study are based on research in the dry sub-tropical and tropical zones, although these eco-climatic zones account for more than 52% of the world's land area. Based on these results, we discuss how the limited empirical source and focus of environmental research undermine the claims of universality of environmental science and what consequences this may have on policymaking processes at different levels. Finally, we briefly explore some short- and long-term strategies to address the knowledge divide. 相似文献
129.
Jozien T. J. Brons Hans J. Van Der Harten Herman P. Van Geijn Juri W. Wladimiroff Martinus F. Niermeuer Dick Lindhout Patricia A. Stuart Chris J. L. M. Meijer Nico F. Th Arts 《黑龙江环境通报》1990,10(5):279-288
Radial-ray reduction malformations (RRRMs) may occur isolated or in association with other anomalies. The data of seven fetuses born with RRRMs were collected. Six fetuses had associated lethal abnormalities of the central nervous system, urogenital system, and/or heart, detected by ultrasound. In five cases, it was possible to establish the precise diagnosis, enabling an informed prognosis and subsequent genetic counselling. The diagnoses were: Edwards syndrome (n=3), VACTERL association (n=1), and Poland-Moebius-like complex (n= 1). In two cases, a complete diagnosis was not possible because of inadequate evaluation of these fetuses before and/or after birth. A proposal is given for the diagnostic approach for infants with RRRMs detected in the antenatal period by means of ultrasonography. 相似文献
130.
Dr Harini Narayan Richard De Chazal Margaret Barrow Patricia McKeever Edmund Neale 《黑龙江环境通报》1993,13(10):893-901
Congenital diaphragmatic hernia (CDH) is a developmental defect of as yet unknown aetiology which accounts for 8 per cent of all major congenital anomalies and is associated with up to 80 per cent mortality despite optimal postnatal treatment. The risk of recurrence of CDH for future sibs after one affected infant is about 2 per cent. A multifactorial/threshold inheritance pattern with an observed high male:female sex ratio is currently favoured for the rare occurrence of familial CDH, although other modes of inheritance have also been described. We report three cases of familial CDH, two of whom were brother and sister sibs and the third was a first cousin, born within 18 months of each other. The diagnosis was by ultrasound and there were several factors predicting a poor outcome. The mortality in this group was 100 per cent. The prenatal diagnosis, treatment options, the unusual genetic aspects, outcome, and the pathology involved are discussed. 相似文献