ISSN:0730-7268    

DOI:10.1002/etc.5620121201

出版商:Wiley Periodicals, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractWetlands have been intricately linked with humankind throughout the ages. Evidence of rice culture dates to the earliest age of humans, long before the era of historical records. Drain‐field and raised‐field agriculture occurred in wetlands throughout large areas of Mesoamerica before Hispanic exploration of the region. About 40% of the world's population uses rice as a major staple; rice culture currently occupies about 15% of the world's wetland area. Wetlands are valued for high biological productivity; as filters, sinks, and transformers for sediments, nutrients, and pollutants; and as buffers between aquatic systems and human activities on upland areas. Because of their varied ecological functions, wetlands are of interest to ecotoxicologists as potential sites for detoxifying pollutants. Estimates are that wetlands occupy about 3 to 6% of the world's land area. Attempts to define, delineate, monitor, and regulate the use of wetlands in the United States have proven to be extremely complex. Considerable progress has been made in classifying and monitoring changes in wetland areas on a nationwide basis, but less success has been achieved in defining and delineating wetlands. The United States experience should be a useful model for developing countries to study as they attempt to deal with wetland management and protection. As long as the world's population continues to grow at exponential rates, it seems highly probable that pressure to use wetlands to meet society's demands will increase. Consequently, opportunities to set aside reserves will decrease, and the role that wetlands play in maintaining quality of life will depend more and more on our collective ability to develop and promote compatible uses on wetla

ISSN:0730-7268    

DOI:10.1002/etc.5620121202

出版商:Wiley Periodicals, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractSalt marshes are found between the high tide and the near‐shore sublittoral zones along the coasts and up estuaries of continents, primarily in the temperate zone. They flourish in regions where much silt is carried to the coastal regions by rivers or where geological processes favor erosion and suspension of silt. Salt marshes have multiple ecological and economic values. They have a high rate of primary productivity; provide habitats for many marine species (including commercially important organisms); assist in flood and erosion control; lessen the effects of stormwater surges; and improve water quality by filtering pollutants, excess nutrients, and disease‐causing microorganisms. In addition, this habitat is used for recreational and educational purposes by millions of people who spend millions of dollars. Although the myriad functions and uses of this habitat attest to its tremendous importance, legal protection of salt marshes varies significantly throughout the world. Salt‐marsh processes are governed by the interactions between “natural” physical, chemical, geological, and biological factors. Of importance to ecotoxicologists and other scientists is understanding the intimate interaction between these various abiotic and biotic factors. This paper reviews the functional processes of salt marshes and discusses recent research advances under the following major headings: (a) physical, geological, and chemical factors; (b) biotic factors (including productivity of vascular plants, phytoplankton, epibenthic algae, and attached macrophytes; secondary production of primary and secondary consumers; and decomposition; (c) material cycling, biogeo‐chemical cycling, and nutrients; (d) long‐term changes; and (e) interaction with adjace

ISSN:0730-7268    

DOI:10.1002/etc.5620121203

出版商:Wiley Periodicals, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractSoil reduction caused by flooding has profound effects on species adaptation and mineral nutrition of higher plants. Anaerobic conditions inhibit normal root respiration of higher plants. Alternate metabolic pathways may be utilized in combination with the development of anatomical characteristics that result in the internal movement of oxygen to the roots. Soil organisms use other oxidants when the oxygen supply is interrupted, which results in profound changes in oxidative states of many metals and nonmetals, and changes in soil reaction and conductivity. The products of reduction are primarily nitrogen gas, manganous manganese, ferrous iron, sulfide sulfur, methane, and organic acids. These reduction products alter the availability of soil nutrients and can drastically alter the soil acidity. Plant‐soil interactions on flooded soils can sometimes be altered, as has been demonstrated by the use of phosphorus fertilizer on southern pine and zinc on ric

ISSN:0730-7268    

DOI:10.1002/etc.5620121204

出版商:Wiley Periodicals, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe term wetlands refers to a mosaic of important ecosystems that typically form transition zones between uplands and aquatic environments. These areas provide support functions for natural and living resources and mediate biogeochemical transformations of global significance. It is becoming clear that the introduction of toxic and other contaminants to large wetland areas has contributed to a series of undesirable trends in habitat quality; availability of valuable fish and wildlife; and quality of associated resources, including surface and ground waters. The purpose of this review is to indicate the importance of wetlands to regional and global ecology and discusses research on the effects of contaminants in wetland ecosystems. Areas of needed future research also are suggested.

ISSN:0730-7268    

DOI:10.1002/etc.5620121205

出版商:Wiley Periodicals, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractCoastal wetland habitats may receive pesticide inputs indirectly from agricultural and forest control of weeds and insects in upland drainage areas; indirectly or directly from weed, insect, and biofouling control from development of adjacent lands for agricultural, recreational, or residential uses; and directly from control activities practiced within wetlands for protection of public health or for nuisance abatement. Persistent and bioaccumulative pesticides used at upland sites have threatened coastal wetland biota. For more biodegradable contemporary pesticides, concerns for ecological impact are more a function of the proximity of the site of application relative to the wetland, and time available for degradation and sorption. In addition, the rate and extent of localized mixing, flushing, and stratification within the wetland can greatly affect exposure concentrations and durations for wetland biota. The short‐term, direct toxic effects of pesticides on aquatic biota inhabiting coastal wetlands have been characterized in laboratory and field studies; however, assessment of the cumulative and indirect effects of repeated exposures to multiple chemicals at sublethal concentrations is a major research nee

ISSN:0730-7268    

DOI:10.1002/etc.5620121206

出版商:Wiley Periodicals, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractImportant selenium data in the literature are discussed with reference to the biogeochem‐ical processes affecting selenium cycling in wetlands. Selenium oxidation‐reduction reactions are shown to be the most important biogeochemical processes controlling speciation, precipitation/dissolution, sorption/desorption, methylation, and volatilization of selenium. Furthermore, bioavailability and toxicity of selenium, with reference to wetland ecosystems, are summarized. Based on the information available in the literature, a conceptual model depicting selenium chemistry and behavior in wetlands is descri

ISSN:0730-7268    

DOI:10.1002/etc.5620121207

出版商:Wiley Periodicals, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThis literature review borrows from diverse fields because of the paucity of freshwater wetland studies on mercury cycling and effects. Peat cores provide an excellent means of dating mercury deposition temporal patterns. Conclusions about cycling suggest that a biogeochemical model would prove useful for evaluating wetland processes of mercury transformation and accumulation. Mercury methylation and the association of mercury with organic matter require additional research. Wetlands trap and release mercury, and its association with organic matter seems to affect the release rate. At high exposure, usually associated with laboratory studies or waste discharges, a variety of biotic toxic responses are observed. Predator species accumulate mercury predictably, and residue‐effect relationships seem useful for an index of ecologic damage. More definitive conclusions require additional research to define the ecosystem properties that affect mercury transfer to wetland predator

ISSN:0730-7268    

DOI:10.1002/etc.5620121208

出版商:Wiley Periodicals, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractArid wetlands are being contaminated by subsurface agricultural irrigation drainage throughout the western United States. Historic freshwater inflows have been diverted for agricultural and municipal use, and remaining freshwater supplies are not sufficient to maintain the integrity of these important natural areas once they are degraded by irrigation drainwater. Waterfowl populations are threatened in the Pacific and Central Flyways; migratory birds have been poisoned by drainwater contaminants on at least six national wildlife refuges. Subsurface irrigation drainage is the most widespread and biologically important source of contaminants to wetlands in arid regions of the country. The case history of poisoning at Kesterson National Wildlife Refuge in California and studies at other locations by the U.S. Department of the Interior provide detailed information on the toxicity of drainwater contaminants to fish and wildlife. Biogeochemical conditions favorable for the production of toxic drainage are found throughout the western states. Two actions seem necessary to prevent further drainage‐related degradation of arid wetlands. First is a reduction in the amount of contaminants reaching these wetlands, possibly involving regulatory intervention through the National Pollutant Discharge Elimination System permit process. Second, a better balance must be achieved in the way fresh water is allocated between agriculture and wildlife. Federally subsidized water has supported agriculture at the expense of wetlands for nearly 100 years in the western United States. This trend must be reversed if arid wetlands and their fish and wildlife populations are to surviv

ISSN:0730-7268    

DOI:10.1002/etc.5620121209

出版商:Wiley Periodicals, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractEarly efforts at modeling wetland ecosystems were aimed primarily at reflecting biomass or nutrient dynamics. A number of models have been developed for different wetland types, including coastal salt marshes, mangrove wetlands, freshwater marshes, swamps, and riparian wetlands. The early ecosystem models were mostly simple compartment models with linear, constant‐coefficient differential equations used to simulate biomass or nutrient dynamics. Practically no contaminant flux was incorporated into these models. With few exceptions, the ecosystems were considered spatially homogeneous. At the same time that the ecosystem models were being developed, considerable effort was given to modeling various wetland processes, such as circulation and sediment transport. Other process‐level modeling included plant and animal uptake and elimination of both organic chemicals and heavy metals. The level of detail in these process models, however, has not been applied to most ecosystem models. There has been a recent trend, however, to increase the complexity of ecosystem‐level models and to incorporate spatial dynamics. These developments should greatly enhance the ability to simulate contaminant transport and effects in wet

ISSN:0730-7268    

DOI:10.1002/etc.5620121210

出版商:Wiley Periodicals, Inc.    

年代:1993

数据来源: WILEY