摘要:

AbstractDense growths of macrophytes are a characteristic feature of chalk streams which may cause problems both to farmers and anglers. Weed is frequently cut to reduce flooding of surrounding land and provide open water for anglers.The objective of this study was to examine short‐term responses of macroinvertebrate faunal assemblages in main flow and marginal samples to both weed‐cutting and the application of herbicide and to compare these with untreated controls.No statistically significant effect could be demonstrated on such faunal parameters as biotic score, richness and abundance and a multivariate analysis of all available data showed that the weed‐cut and herbicide treated sites could not be distinguished from the control sites III and V on the basis of their fauna.It is suggested that for conservation purposes small‐scale management with ‘recovery strips’ separating the treated reaches can achieve the desired objectives of avoiding flooding and providing open water for anglers with minimal effects on the

ISSN:1052-7613    

DOI:10.1002/aqc.3270040202

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractWetlands are under threat from a variety of human activities and in response to this various assessment schemes have been devised. A recent hydrological vulnerability assessment procedure has been advanced by Lloydet al.(1993) for East Anglia, UK, which deals with hydrological threats to fens. The assessment starts with a desk study which classifies a wetland into a particular hydrological class, and from this general statements can be made with regard to the wetland's likely vulnerability to such activities as water abstraction and pollution. No type of desk study, however, will always be able to predict the hydrological consequences of an activity with certainty. Thus, if protection of the wetland is of high priority, Lloydet al.(1993) propose further stages of investigation of increasing expense and difficulty, involving hydrological monitoring and modelling.The purpose of this article is to explore how much desk‐study classifications such as that of Lloydet al.(1993) can reveal about wetland hydrological vulnerability, using East Anglian field investigation and hydrological monitoring evidence. Three sites in East Anglia have been examined over a 2 year period, and the water balance and hydrological processes, together with the hydrological vulnerability of each site, deduced. Comparing these data with the conclusions from the desk study indicates that the classification procedure was able generally to identify the vulnerability of wetlands correctly at the regional scale, but the detailed studies showed that local features, below the scale resolvable by the classification and desk‐study procedure, can easily lead to incorrect assessments.The results of the East Anglian field investigations suggest that although classification procedures are adequate for providing general conclusions about the vulnerability of wetlands in a given region, they cannot be relied upon to be correct for a specific site and ensure its protection against any given hydrological threat. In the case of the assessment of important wetland sites, there is therefore no substitute for detailed hydrological and geological investigations. Because of the importance of seasonal hydrological data for detailed investigations and vulnerability assessment, it is also recommended that hydrological monitoring at a single point on important wetland sites should start well before an impact is envisa

ISSN:1052-7613    

DOI:10.1002/aqc.3270040203

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe Nigerian coastal system—estuaries, lagoons, creeks and wetlands—extends for a distance of approximately 850 km with the Niger Delta (area: 75 000 km2) dominating the entire ecosystem.Human activities—(oil exploration, haphazard mining of sand from coastal areas, sand filling of wetlands for industrial use, heavy pollution by industries)—severely destroyed the breeding and nursery grounds of commercial fish species between 1973 and 1992.As a result, fish landings from capture fisheries decreased from 500 000t in the late 1980s to the present 300 000t.With the Nigerian population increasing at a rate of 3%–4% per year, there is an urgent need for the Federal Government to protect the 850 km coastline, and the riverine wetlands.Conservation education should be vigorously pursued on the socio‐economic benefits of coastal and riverine wetlands.The Federal Government should encourage States and Local Governments to enact environmental laws and regulations. Stiff penalties for violations should be vigorously enforced.Companies involved in exploitation and manufacturing in coastal areas should increase their funding of research directed at minimizing oil spillages and discharge of wastes in their areas o

ISSN:1052-7613    

DOI:10.1002/aqc.3270040204

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effects of freshwater regulation and diversion on the adult and larval stages of fish and invertebrates in coastal marine waters are reviewed.Potential impacts of river modification are highlighted based on our present understanding of the role of fresh water on the physical, chemical and biological processes on the marine environment. These include effects on migration patterns, spawning habitat, species diversity, water quality and distribution and production of lower trophic levels. The effect of dams on anadromous and catadromous fish are also presented.We discuss in detail the marine response to specific river regulation projects on the Nile, Indus and rivers flowing into the Black Sea, San Francisco Bay and James Bay in Canada. A decline in some coastal fisheries with an overall negative impact on the biota is generally associated with reductions in freshwater flow.Extensive ecological considerations are needed during the planning stage of large‐scale freshwater modification projects to minimize potential impact

ISSN:1052-7613    

DOI:10.1002/aqc.3270040205

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractAt present, marine reserves do not represent the full range of community types throughout New Zealand.To assist with the placement of a marine reserve along the Abel Tasman National Park coast (northern South Island), dominant subtidal laminarian and fucoid algae, echinoids and herbivorous molluscs were quantitatively investigated. Results from 100 quadrats collected from 19 random transects at six selected sites showed that algae and grazer assemblages varied between granite and limestone substrata.Granite had a high percentage cover of crustose coralline algae (mean 82%–90%), a sublittoral fringe of brown macroalgae and noEcklonia radiataor red foliose algae. Limestone sites were distinguished by a relatively low percentage cover of coralline algae (mean 13%) and high cover of foliose red algae andE. radiata(2%–36% cover and 0.2–13.9 stipes m−2, respectively).On limestone, molluscsTurbo smaragdusandCookia sulcata, and the echinoidEvechinus chloroticuswere larger than those on granite. On limestone sites with little macroalgae, herbivore size was intermediate. Grazers were more abundant on granite than limestone (mean 34.6 m−2, and 10.8 m−2respectively).Differences in herbivore composition were recorded between granite substrata, while both algal and herbivore composition varied between limestone sites.We suggest that a variety of environmental factors including substratum influence algal and herbivore assemblages along the Abel Tasman coast.It is recommended that selection of a marine reserve site or sites along the coast of Abel Tasman National Park recognizes differences in community structure both between and within limestone and granit

ISSN:1052-7613    

DOI:10.1002/aqc.3270040206

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe restoration or rehabilitation of rivers is currently an expanding area of investment by public water management bodies in the USA and EC. This position has developed from the rapid growth in environmental (and particularly water) awareness, the rise of accountability for environmental degradation within the legislative framework of water institutions and the move away from agricultural over‐production towards sustainable development.The restoration process has been pioneered primarily by aquatic ecologists and landscape designers working in conjunction with civil engineers. Geomorphology, the science of landform development, has much to offer, but at present the contributions are often superficial, concentrating on the scaling and siting of instream fluvial features. This paper argues that it is essential to incorporate the broader geomorpho‐logical wisdom at the design stage so that restoration schemes will be sustainable in the longer t

ISSN:1052-7613    

DOI:10.1002/aqc.3270040207

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractDevelopment pressures in Southeast Asia have been increasing rapidly over recent decades, much at the expense of living resources.Living coastal resources play important biological, ecological and economic roles, but such values, particularly the first two, are difficult to quantify in simple cash terms. Development of built‐up infrastructure on the other hand, enables tangible and usually substantial projected economic gains to be calculated, and these often overshadow estimated benefits of natural habitats through traditional use.This issue has to be addressed, and it can be done through continuing education for all sectors of the population. Institutions of higher learning have a great part to play by packaging research information on living coastal resources for different target groups.Increasing scientific investigations have resulted in a vast amount of knowledge and understanding of the importance of these habitats. Further research can proceed along directions aimed at providing data that will enable better and reliable quantification of biological and ecological benefits.Such information, when made widely available to all, will result in a society that is more appreciative and protective of living coastal resources, and also with a greater understanding of their long‐term significa

ISSN:1052-7613    

DOI:10.1002/aqc.3270040208

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270040209

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270040210

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:1052-7613    

DOI:10.1002/aqc.3270040201

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY