WETLANDS AND PUBLIC HEALTH

SUMMARY

Various facets of public health involvement with wetlands in South Africa are considered. Emphasis is however given to the role of these systems in human disease transmission. With the possible exception of bilharzia, too little is known of the biology of either the pathogens or their intermediate vectors (if they have one) in the aquatic environment for transmission to be adequately understood and for the most cost-effective control strategies to be developed. Insufficient liaison between limnologists and the public health authorities is seen as contributing to this difficulty.     

FISH AND FISHERIES OF WETLANDS

SUMMARY

The three major wetland types have characteristic fish communities. River-associated wetlands harbour a rich diversity of fishes which can either survive habitat desiccation during the dry-down, or migrate to and fro with the flood. Endorheic wetlands have a lower diversity of species which are typically ‘r’-selected relative to mainstream riverine or lacustrine forms. Marine wetlands have a variety of peripheral or marine forms, but are not discussed in this account. The dynamics of wetland fish communities are determined by periodically changing abiotic factors, especially water temperature and water level, and biotic factors, especially food availability. Water level fluctuations have several important functions and result in pulses of nutrient input and fish abundance. Wetland fish stocks can usually be sustained as long as the pristine flood regime is retained, but disruption of the flooding pattern interferes with fish breeding and nutrient flow. Fishing yields may be directly correlated with the flood history during the previous two years. Wetland fishes play an important role by converting the resource at the base of the food chain, i.e. living plants, detritus or epiphytes, into food for higher trophic levels. The need to identify and conserve key food supplies is emphasized. Wetland fisheries are relatively poorly developed in southern Africa with notable exceptions, e.g. Pongolo floodplain, Okavango swamp, Lake Liambezi, Elephant Marsh on the Shire River, but even in these systems the resource is probably underutilized.

The need to consider the socio-economic implications of upgrading a subsistence fishery are emphasized, and further study on the effect of water level fluctuations on major trophic pathways and on multispecies fisheries is encouraged. Because of the urgent need to manage wetland fisheries, various short-cut methods to obtain first-order estimates of fish production, yields and growth rates should be used until more data are available. The need to manage a floodplain holistically for both the aquatic and terrestrial phases is stressed. In addition, inocula (re-colonizing life history stages) should be conserved to accelerate the recovery of endorheic wetland fish stocks after a drought. As wetlands are of fundamental importance to lake or river metabolism and provide vital breeding and feeding areas for fishes, they should be given the highest conservation priority. Cost-benefit analyses should therefore be performed before any large scale manipulations of wetlands are performed.     

WETLANDS AS ACCRETING SYSTEMS: NUTRIENT CYCLING IN WETLANDS

SUMMARY

The major concepts involved in nutrient cycling in wetlands are discussed using phosphorus and nitrogen as examples. The differences in nutrient cycling patterns between hydrologically contrasting wetlands, and the significance of fluctuating water levels in wetlands, are stressed. In South Africa, some research into nutrient cycling in submerged aquatic macrophyte communities has been undertaken, but very little information is available on these processes in wetlands dominated by emergent vegetation forms. Generally, the information available on nutrient cycling processes in South African wetlands is of limited applicability to the assessment of nutrient cycling in whole wetland systems. Therefore, rational wetland management strategies require further research on nutrient cycling.     

甲壳质,壳聚糖在农业上的应用

本文综述了甲壳质、壳聚糖作为降解性地膜、植物生长调节剂、肥料和土壤改良剂、农药、食物保鲜剂及饲料、饵料添加剂等在农业方面的应用。     

现代农业中的激光技术和激光育种

现代农业中的激光技术是一项新技术。激光农用的开拓领域相当广泛。激光育种在我国始于70年代初,据不完全统计到1986年为止,已育成粮、油、棉、蔬菜、果树、桑、蚕等新品种(系)36个,对农业生产起到了良好作用。为了在现代农业中发挥激光技术的应用优势,从育种的角度来说,应该在加强激光生物学多学科之间合作的前提下,大力开展激光生物工程的研究,这也是激光应用于农业发展的希望所在。     

THE CONSERVATION OF WETLANDS

Diplotaxodon limnothrissa is a widely distributed species occurring throughout Lake Malawi and is probably the most abundant cichlid in the pelagic zone of the lake. The species is exploited commercially in the south-east arm of the lake, but since the fishery's inception the resource has never been assessed. Per-recruit analysis indicated that the resource is under-exploited, with current spawner biomass per-recruit between 55% and 74% of pristine levels.     

青藏高原天然湿地水环境特征和水质净化能力分析

研究以拉萨市拉鲁湿地及其相连干渠和茶巴朗湿地水体为研究对象, 分别于2020年8月(夏季)和2021年4月(春季)各采集22个水样, 测定水体氮磷营养盐和高锰酸盐指数, 分析了夏季和春季湿地的水环境特征和水质净化能力。结果表明, 拉鲁湿地和茶巴朗湿地由于流域人为污染水平不同进水水质存在差异, 拉鲁湿地进水水质主要受氮磷营养盐影响, 茶巴朗湿地水质主要受耗氧有机物影响。两湿地对水质都具有净化作用, 不同季节湿地对不同污染物的去除效果也有所差异。夏季, 拉鲁湿地对TN、NH₃-N、NO₃-N、TP和SRP的最大去除率分别为75.0%、65.2%、89.5%、82.2%和35.3%。茶巴朗湿地对TN、NH₃-N、NO₃-N、TP和SRP的去除率分别为60.7%、73.5%、12.7%、35.9%和5.0%。夏季两湿地对COD_Mn均未表现出去除作用。春季, 拉鲁湿地对TN、NH₃-N、NO₃-N、TP、SRP和COD_Mn的最大去除率分别为35.2%、65.9%、56.8%、59.5%、62.3%和17.9%。茶巴朗湿地的水质净化效果较差, 对TN、NH₃-N、NO₃-N、TP、SRP和COD_Mn的去除率分别为2.2%、10.2%、11.3%、11.3%、9.0%和26.0%。湿地水生植物、湿地结构、特殊的水动力特征及水污染负荷都可能影响高原湿地的水质净化能力, 春季高原湿地较低的水温、植物丰度和水文条件可能会降低湿地对污染物的去除效果。     

PLANNING THE RATIONAL USE OF WETLANDS

SUMMARY

A conceptual approach to planning is outlined. It is a cyclical process in which we start with a goal, examine it and express it more clearly, assemble information, evaluate the information, work out alternative lines of action, choose the one most likely to lead to success and then try it out.

This approach is applied to wetlands. The importance of establishing a “unity of action” and a body to co-ordinate activities is stressed. Planning the conservation of estuaries in Natal is given as a practical example.

A number of research projects is given in relation to the planning process. A comprehensive and methodical means of determining research projects is advocated.

The paper concludes with a call for committment, else planning is an exercise in futility.     

中国北回归线附近岛屿及沿海初夏鸟类报告

于2001年6月8日至19日对位于北回归线附近的粤闽沿海岛屿及沿海湿地(东迄福建省南部的东山岛,西至广东省东部汕头地区的牛田洋湿地和南澳及其附近诸岛)进行鸟类调查,后又于2004年6月做了补充调查.共记录到鸟类77种,其中海岛鸟11种,湿地鸟25种,陆地鸟41种,包括国家一、二级保护种类分别为白腹军舰鸟Fregata andrewsi和岩鹭Egretta sacra.观察新增了10种以往未曾在该地区记录到的鸟类,首次记录到岩鹭在南澳及其附近诸岛的繁殖,再次印证了粉红燕鸥Sterna dougallii、黑枕燕鸥.Sterna sumatrana、褐翅燕鸥Sterna anaethetus和黑叉尾海燕Oceanodroma monorhis在该地区的繁殖记录.通过对比该地区一个多世纪以来鸟类记录(包括繁殖记录)的差异,探讨该地区鸟类区系的演替过程.     

WETLANDS AS ACCRETING SYSTEMS: INORGANIC SEDIMENTS

SUMMARY

Concepts dealing with factors affecting the origin, transport and deposition of inorganic sediments as well as their role in the functioning of wetland systems are discussed. The lack of quantitative data, particularly for South African systems, is emphasised. Research priorities, which will lead to a better understanding of inorganic sediment: wetland interactions and allow for rational exploitation of wetlands, are proposed.     

WETLANDS AS ACCRETING SYSTEMS: WASTEWATER TREATMENT

SUMMARY

Considerable attention has been directed in the last decade to the use of wetlands for wastewater treatment. They are generally very effective in reducing (by up to 95%) the concentrations of nitrogen, pathogenic bacteria and heavy metals but their efficiencies in reducing phosphorus and organic matter vary widely. While most of the processes which result in removal of wastewater constituents are qualitatively understood, quantitative data are lacking. It is therefore impossible to predict the potential of any wetland for wastewater treatment or to manage wetlands for optimum treatment efficiency. Little is known of either short- or long-term effects of wastewater addition on wetland ecosystems.

In view of the substantial economic benefits of using wetlands for wastewater treatment, it is suggested that studies on wastewater treatment by both artificial and natural wetlands in South Africa are urgently required.     

GRADIENT ANALYSIS OF DIATOM ASSEMBLAGES IN WESTERN KENTUCKY WETLANDS1

Diatom and water chemistry data from 35 wetland sites in western Kentucky were used to assess diatoms as indicators of ecological conditions in wetlands. The wetlands were affected by different degrees of acid mine drainage and agriculture. Canonical correspondence analysis indicated that the distribution of diatoms was highly correlated with conductivity and total phosphorus (TP), two variables commonly associated with acidic mine drainage and agriculture, respectively. Diatom-based inference models were developed for use as quantitative indicators of two important environmental variables in wetlands: conductivity and TP. Diatom-inferred conductivity and TP values were highly correlated with measured values. Cross-validation with jackknifing procedures suggested that high apparent r² between inferred and measured conductivity was overly optimistic and should be treated with caution. Jackknifing-derived TP inference models performed poorly in predicting TP toward the ends of low and high TP concentrations. In general, the conductivity inference models based on plankton had better predictability than those based on epiphyton. Epiphyton-based inference models can predict TP better than plankton. Therefore, diatoms in planktonic and epiphytic assemblages could provide complementary information on ecological conditions. Our data suggest that diatoms can reflect major regional environmental gradients and therefore can be used as indicators of the ecological conditions in wetlands. Quantitative inference models with known predictive power can aid the development of realistic and ecologically sound biotic indices for this region.     

THE DISTRIBUTION OF WETLANDS IN THE SOUTH-WESTERN CAPE PROVINCE,SOUTH AFRICA

Summary

The hydrological and habitat value of wetlands is beginning to be recognised in South Africa, but only in parts of Natal Province has an effort been made to map wetlands and to record their status over large areas. While the most accurate method of mapping wetlands is a combination of photogrammetry and field surveys, this is time-consuming and expensive. An alternative “desktop” method was therefore used to draw up a preliminary distribution of wetlands in the south-western Cape Province, and this approach consisted of summarising the information contained on 1:50 000 topographical survey maps. The summary shows that shallow, vegetated wetlands (vleis) occur mainly in the wetter south and south-west of the region, while the non-perennial wetlands (pans) predominate inland, where the land is dryer and flatter. There are many estuarine wetlands along the coast, resulting from the tendency of river mouths to be blocked by sand-bars. Farming requirements and suitable topography account for the many small artificial wetlands (farm dams) in the central southern parts. Farm dams predominate in the region (15067 were counted), followed by pans (1741), riverine wetlands (261), vleis (216) and estuarine wetlands (15).