REPLY TO COMMENTS BY DR D H R HELLWIG ON PAPERS BY J.U. GROBBELAAR,M.K. SEELY & O.B. KOK

The aim of this study was to assess and compare the water quality of the Gwebi and Mukuvisi Rivers, on the basis of selected physicochemical variables and macroinvertebrate community structure. Five sites where selected on both rivers and these were sampled on three separate occasions between January and July of 1998. The water variables measured were the concentrations of iron, chromium, zinc, lead, copper, manganese, chlorides, fluorides, sulphates, total phosphates, nitrates, ammonia, total dissolved salts, dissolved oxygen, biological oxygen demand, as well as pH, conductivity, temperature, water surface velocity and discharge. The concentration of most of the chemical variables was relatively similar along the course of the Gwebi River, but there were drastic increases in the levels of iron, chromium, copper, zinc, chlorides, fluorides, sulphates, and ammonia along the Mukuvisi River. The two rivers were different with respect to the physicochemical variables, with the exception of the first site on the Mukuvisi, which was similar to sites on the Gwebi River. This was because of the differences in the levels of human activities on the two rivers. Industrial, sewage and domestic pollution has had an adverse effect on the water quality of the Mukuvisi River. There was a sharp decline in the number of macroinvertebrate taxa along the Mukuvisi River. The lower reaches of the river where dominated by oligochaetes and Chironimidae larvae. Sample score classification of water quality based on the South African Scoring System Version 4 (SASS4) showed that most of the Mukuvisi river had poor quality water quality, whilst much of the Gwebi River had fair quality water. The HABS1 habitat assessment index was used to assess habitat quality at each site. Although much of the Mukuvisi recorded fair to good habitat scores and had generally higher habitat scores than sites on the Gwebi, the SASS scores were generally lower compared to those along the Gwebi. The sample scores and average score per taxon (ASPT) of the SASS4 showed that the Mukuvisi River was of much lower quality than the Gwebi. Both the sample score and ASPT were negatively and significantly (p<0.05) correlated to most of the physicochemical variables. The water quality variables accounted for 61.1% and 59.0% of the differences in the sample score and ASPT respectively. There was a marginal decrease in the Margalef and Shannon indices along the Gwebi River, but the Simpson's index remained relatively constant. Along the Mukuvisi River, there was a clear and distinct decrease in the magnitude of all three diversity indices, indicating decreasing macroinvertebrate community structure. The change in water physicochemical variables accounted for 61.3%, 69.2% and 87.2% of the changes in the Margalef, Shannon and Simpson's index respectively. The study provides evidence that the changes in macroinvertebrate community structure along the Mukuvisi River is due to decline in the water quality. On the Gwebi, water quality is not the main factor determining macroinvertebrate community structure.     

Some aspects of the ecology of the Groot Letaba River in the Northern Province,South Africa

The aim of this pilot study was to evaluate the current ecological status of the Groot Letaba River and to compare this information with historical data. The objective was to determine the effects of various impacts on the fish populations of the river. This was done by analysing the water quality and by considering the effect of weirs and dams, as well as various illegal angling activities, on the fish community.

The Groot Letaba River is not highly polluted and the decline in its flow seems to be the greatest threat to the system. During a preliminary study to develop the river's resource potential, it was stated that the annual water allocation from Tzaneen Dam was 103.9 million m³/annum for irrigation, 8.4 million m³/annum for domestic and industrial use and 14.7 million m³/annum for environmental purposes. However, the yield from Tzaneen Dam was only 98 million m³/annum, suggesting that more water had been allocated than was available. As a result only 20% of the simulated natural flow is observed at Letaba Ranch Weir at the lower end of the river.

Over the past few years many weirs and dams, none of which have fishways, have been constructed in the Groot Letaba River, impacting on the flow regime and on the migration potential of many fish species. Tiger fish (Hydrocynus vittatus) and the largescale yellowfish (Barbus marequensis) are two of the more prominent species influenced negatively by these barriers. This problem is aggravated by the illegal netting of fish stranded below these barriers during their spawning migrations.     

The macroinvertebrates of the Cunene River from the Ruacana Falls to the river mouth and assessment of the conservation status of the river

The proposed construction of a second hydroelectric power-generating dam on the Cunene (Kunene) River on the Namibia-Angola border, more than 100km downstream of the Ruacana hydroelectric power plant, will have a major influence on the aquatic biota of this river. In order to assess the potential impact of this impoundment a more detailed inventory of the biota in the river prior to this development was needed. Unfortunately the river presently does not represent an entirely undisturbed system as the operation of the Ruacana hydroelectric power station since 1970 has had a long-term effect on its biota. In the low-flow mid-summer season in particular, large areas of the river become irregularly inundated and exposed, sometimes on a daily basis, making them unsuitable for macroinvertebrate colonisation. There are six impoundments along the Cunene River upstream of the Ruacana Falls in Angola. These, however, do not have any major disruptive effects on daily flow variation in the Cunene River in Namibia although whole system biological consequences could be considerable but are unstudied. The Cunene River has a diverse freshwater fish fauna but, prior to the surveys reported here, the aquatic macroinvertebrates had been poorly studied. Surveys conducted by staff of the Department of Water Affairs (DWA) of Namibia and the Albany Museum, Grahamstown, in 1997 and 1998 have resulted in 216 aquatic macroinvertebrate species being recorded from Ruacana to the river mouth. The lower Cunene River, flowing through a very arid region, is biogeographically isolated and therefore highly vulnerable to change. The biota recorded reflects a fauna of widespread species and several elements of tropical origin. Several undescribed species may reflect some endemics but because of limited knowledge of the tropical rivers, this cannot be ascertained with certainty. From the aspect of conservation, the river contains a diversity of species with an abundance of filter-feeding species. Further surveys conducted during different seasons will undoubtedly record more taxa.     

Riparian bryophyte communities on Madeira: patterns and determinants of species richness and composition

Abstract

We studied 16 streams evenly distributed over the northern and southern slopes of Madeira in order to investigate the riparian bryoflora. Within each stream, three positions (upper, middle and lower reaches) were delimited and within each position two areas were selected. Within each area two plots (each composed of six microplots of 0.2 m²) were sampled, one in the within-stream habitat (submerged all year round), and the other in the stream-border habitat (submerged only in winter). We found that species composition of the riparian bryophytes is affected by the habitat and position in the stream, but not by the main aspect (northern versus southern slope). Concerning species richness, we found that the stream-border community was clearly richer than the within-stream community, upstream plots were richer than plots downstream, and plots on the northern slope of the island were richer than plots on the southern slope. Habitat type was the most significant factor in determining the richness of the threatened species with more species present in the stream-border habitat. Additive partitioning showed that the between-stream component contributed most to total species richness, especially to the richness of the infrequent and threatened species. However, for the common species, the lowest level, i.e. the within-area component, was the most important. Although northern upstream areas are climatically favourable for many bryophyte species due to their higher humidity, the clear effects found may not only be climate-induced, as these areas are also less disturbed and mostly covered by the natural laurel forest. In the southern, downstream parts only a few species were present. Human impacts are largest in the latter situations and probably contributed to the low species richness. As the streams differed considerably in terms of their bryophyte flora, and most of the species were rare, changes in the riparian areas can greatly affect the bryoflora. Therefore, in order to protect the riparian bryophytes as comprehensively as possible, we emphasize the need for careful monitoring of any changes.     

Physico-chemical conditions and macroinvertebrate fauna in the River Nile from Aswan to Cairo

This paper examines the distribution of benthic macroinvertebrates in relation to physico-chemical conditions along 1 035km of the River Nile from Aswan High Dam to Al Kanater Barrage, Cairo. Total Dissolved Salts and several individual chemical variables showed positive linear regression with distance from Aswan. The creation of the Aswan High Dam has reduced the ionic concentrations discharged to the Nile, but there is a gradual increase as the river flows though Egypt. Benthic macroinvertebrates show overall low taxon richness with taxa typical of a lowland riverine region. Changes in taxon richness appear to be influenced by either pollution and/or sedimentation. Sites downstream of the Kema Factory and downstream of organic discharge from Etsa Drain from Minia city show severe pollution. A Bray-Curtis Diversity Index shows these sites to be biodiversity outliers consistent with the negative impact of pollution. Examination of 95% outlying chemical values confirms gross pollution from these sites and the data as a whole suggest other sites that may also be affected by pollution. A contributor to high macroinvertebrate taxon richness appeared to be increased sedimentation, particularly in midstream samples. It is concluded that the low ionic concentrations resulting from the Aswan High Dam construction, localised pollution, and the occurrence of sediment are the main factors governing macroinvertebrate taxon richness. These factors will require careful monitoring, assessment and management if the biodiversity of the Nile is to be conserved.     

Hydraulic loading,stability and water quality of Nakivubo wetland,Uganda

Nakivubo wetland, which has performed tertiary water treatment for Kampala city for the past 40 years, is ecologically stressed by agricultural and infrastructural developments. Field studies were carried out to assess the hydraulic loading, pollution profile, stability and water quality of this wetland. The upper and lower Nakivubo wetland receive 4.13?7.66 × 10⁴ and 3.50?10.32 × 10⁴m³/day of water respectively, of which 48.3–57.9% of total hydraulic loading to the upper wetland was carried by sampling station S1. The influent water to the upper wetland had a total BOD₅ and NH₄-N loading ranging from 2.6?4.4 × 10³kg BOD/day and 0.79?1.68 × 10³kg NH₄-N/day respectively. The National Water and Sewerage Corporation's effluent constituted a large proportion of BOD and NH₄-N loading into Nakivubo wetland. Zinc, copper and chromium were detected in trace amounts at most sampling stations. However, lead was occasionally detected at Kibira channel (station S5) at a concentration of 0.4mg/l, which is higher than the permitted Ugandan discharge limit of 0.1mg/l (NEMA 1999). The wetland showed a very high removal efficiency for BOD, ranging from 77.4%–86.3%, compared to ammonium-N which ranged from ?66.1% to 33.1% indicating limitations with the nitrification process. A low self-purification for zinc, copper and chromium was also observed in the upper Nakivubo wetland, possibly due to poor plant-wastewater interaction resulting from wetland drainage. In the lower Nakivubo wetland conductivity and dissolved oxygen were generally higher in papyrus- than in Miscanthidium-vegetated zones. However, the BOD and ammonium-N loadings did not vary significantly (P = 0.217 and P = 0.359 respectively) between the two vegetated zones.     

Aftermath of simultaneous toxic spills in the Klein Nyl River,Northern Province,South Africa

In late August 1998, a mechanical malfunction at the Nylstroom Sewage Treatment Works resulted in a massive quantity of untreated sewage flowing into the Klein Nyl River. Simultaneously, 5km upstream, a poly-aromatic hydrocarbon poison was simultaneously leaked into the same river from a 25 litre canister. These spills threatened the Nylsvley Nature Reserve, a newly acclaimed RAMSAR site, situated about 20km downstream of Nylstroom. The Limnological team of the Department of Zoology, University of the North, was asked to assist with the assessment of the effect of these spills, which resulted in a massive fish kill. A monitoring program was implemented in early September 1998 to assess the effect of these spills on the water quality of the receiving water body. The implications of the altered water quality on the aquatic biota are discussed.     

The impact of land use on water quality of the Lwiro River,Democratic Republic of Congo,Central Africa

The water quality of the Lwiro River, Democratic Republic of Congo (DRC), Central Africa, was investigated on a monthly basis from December 1999–October 2000, at six stations along a hydraulic gradient from source to mouth, to evaluate the impact of land use on temperature, Dissolved Oxygen (DO), Biological Oxygen Demand (BOD₅), alkalinity and suspended solids. Upstream, where forests are conserved, minimal changes of physico-chemical parameters of water were observed. Downstream, DO was reduced, due to the increased organic matter content which increased the decomposition rate. BOD₅ and suspended solids increased downstream. Greater changes were found near agricultural areas and villages. Wetlands appear to mitigate BOD₅ and DO impacts.     

EVIDENCE OF FISH SURVIVAL DURING HABITAT DESSICATION IN RHODESIA

Rand Water's chemical water quality data from 1991 to 2000 were used to assess the water quality of the Waterval River, which contributes about 111 x 10⁶m³ of water to the Vaal River annually. Due to a biological community's ability to reflect water quality changes over time, biomonitoring was undertaken to support chemical water quality monitoring. Aspects of the riverine habitat, invertebrates and fish were investigated to give baseline information on the area. Human activities such as mining, industry, agriculture, rural and urban settlements are currently responsible for the deterioration of the ecological integrity of this river system. Habitat degradation was especially evident in the upper reaches of the Waterval River, as indicated by the South African Scoring System, version 4, Average Score Per Taxon and Biotic Integrity scores. In general, the ratings achieved were lower than those expected for the available habitat, which suggests that human activities have influenced the biotic community. By selectively addressing the areas of concern, the state of the environment can be improved, using the current assessment as a benchmark to measure the success or shortcomings of any actions in the years to come.     

Ecological Risk Assessment in Water Resource Management

The US EPA published guidelines for the application of ecological risk assessment (ERA) in the USA in 1998 (US EPA 1998). The process diagram derived by Murray and Claassen (1999) in an evaluation of the US EPA framework is discussed in the context of the South African National Water Act. The evaluation discusses the various steps involved in an ERA and how it can be applied in the implementation of the National Water Act. It is concluded that the application of ERA can make a significant contribution towards sustainable water resource management. Two requirements for this are the need for more demonstration projects and that capacity be developed in risk assessment and risk-based decision making.     

Seasonal variability of macroinvertebrate assemblages in two regions of South Africa: implications for aquatic bioassessment

Seasonal variability of macroinvertebrate assemblages was examined in two regions of South Africa: Western Cape and Mpumalanga. Sampling was undertaken at reference sites using the rapid bioassessment method SASS4 (South African Scoring System, Version 4). This study examined the influence of sampling season on the occurrence of taxa, macroinvertebrate assemblages and SASS scores. In the Western Cape a few taxa were more common at certain times of the year, and multivariate analysis of macroinvertebrate assemblages showed that assemblages grouped by season. The number of taxa and the Average Score per Taxon (ASPT) were significantly different among seasons in the Western Cape, with fewer taxa recorded in winter compared to summer, and significantly higher ASPT values recorded in winter and spring than summer and autumn. Whereas more taxa were recorded in autumn than in spring, a higher proportion of sensitive and high-scoring taxa were recorded in spring. In Mpumalanga macroinvertebrate assemblages did not group by season, and differences in SASS scores were not significant, although more taxa were recorded in winter than in spring or autumn, and ASPTs were slightly higher in winter than in spring. Results are discussed in relation to ecological reference conditions and the interpretation of bioassessment data.     

The Namibian Scoring System (NASS) version 2 rapid bio-assessment method for rivers

This paper presents a rapid bio-assessment method for assessing the ecological condition of streams and rivers in Namibia. The method uses the composition and abundance of aquatic invertebrates, which are identified in the field, mostly to family level. The method is based on the South African Scoring System version 5 (SASS5), which has been modified to account for additional tropical invertebrate taxa that occur in northern Namibia. The method was applied to the Zambezi River near Katima Mulilo and NASS results were found to fluctuate predictably with changes in water level. Training of Namibian personnel to apply the method, as part of the National Water Quality Monitoring Programme, is recommended.     

Spatial variability in macroinvertebrate assemblages: comparing regional and multivariate approaches for classifying reference sites in South Africa

Spatial variability in macroinvertebrate assemblages was examined with the aim of evaluating the utility of regional classification systems in aquatic bioassessment. Sampling was undertaken at reference sites in the Western Cape and Mpumalanga, South Africa, using the rapid bioassessment method SASS4 (South African Scoring System Version 4). Multivariate analysis of macroinvertebrate assemblages showed that assemblages varied regionally with differences most apparent in upland areas, i.e. mountain streams and foothill-cobble beds, with lowland areas less regionally distinct. Within regions, longitudinal zonation into upland and lowland areas was important, with sites grouping on the basis of broad geomorphological zones or subregions. Of the upland sites, differentiation into mountain streams and foothill-cobble beds was not evident, although overall variability of assemblages within upland areas, in particular the Western Cape, was very high. In general, a priori regional classification of sites using the hierarchical spatial framework developed in South Africa provided a useful framework for preliminary classification of reference sites. Groups of sites based on a posteriori analysis of macroinvertebrate data, however, provided a more robust classification than any regional classification. Spatial classifications therefore offer geographic partitions within which to expect somewhat similar conditions, and regional reference sites selected within the context of the spatial framework are likely to be more representative of specific river types than those selected without using the framework. Classification of sites needs to be an iterative process that allows for subjective a priori regional classifications to be modified on the basis of independent, objective a posteriori classification of biological assemblages.     

昆虫基因组及数据库研究进展

基因组序列为昆虫分子生物学研究提供丰富的数据资源,推动系统生物学在古老的昆虫学中蓬勃发展。昆虫基因组学研究已经成为当前的研究热点,目前在NCBI登录注册的昆虫基因组测序计划有494项,其中已提交原始测序数据的昆虫有225种,完成基因组拼接的有215种,具有基因注释的有65种,公开发表的昆虫基因组有43篇。本文综述了测序技术发展的历史及其对昆虫基因组研究的推动作用、昆虫基因组的组装和注释及其存在的问题、昆虫基因组测序进展、昆虫基因组数据库的发展及基因数据挖掘利用的基本思路和对策,以及昆虫基因大数据在害虫防治和资源昆虫利用中的应用前景。     

Towards the development of a macroinvertebrate sampling technique for palustrine wetlands in South Africa: a pilot investigation in the KwaZuluNatal midlands

A study was undertaken in November 2003 to derive a suitable sampling technique for collecting a representative sample of aquatic macroinvertebrates from a selected emergent vegetation biotope in a palustrine wetland, Melmoth Vlei, KwaZulu-Natal, South Africa. The aim was to undertake a preliminary investigation on the development and testing of a macroinvertebrate sampling technique for use in emergent sedge-dominated palustrine wetlands (sensu Cowardin et al. 1979), which could contribute to the development of a South African wetland health biomonitoring programme. Sweep nets and activity traps were evaluated for their effectiveness in terms of macroinvertebrate collection. Sweep net sampling was tested over a range of sweep intensities to determine the minimum number of sweeps required to collect a representative sample. Sampling efficiency of activity traps placed at four depths was tested, and taxon diversity and composition of sweep net and activity trap samples were compared to determine whether activity traps are required to supplement sweep net data. A total of 32 taxa (identified mainly to family level) were identified in the samples collected. Taxon diversity and composition did not differ in the activity traps placed at the four depth locations. Taxon diversity did not differ significantly between different sweep intensities. This may be a result of high variability of macroinvertebrate distribution within a wetland. There is evidence, however, to suggest that this result is due to an inadequate sample size. There was a significant difference in taxon composition between the different sweep intensities (P < 0.05) and between activity trap and sweep net samples (P < 0.05). Sixty-eight percent of taxa appeared more frequently in sweep net sampling than in activity trap sampling. Two taxa were found exclusively in activity traps, although the numbers of these taxa collected were not significant, and they do not represent any unique trophic group. Based on these findings, it was concluded that activity traps are not required to supplement sweep net data, and a technique using a sweep net with a sweep intensity of five would be suitable for collecting a representative sample of macroinvertebrates from a palustrine wetland.     

Physico-chemical and macrobenthic faunal characteristics of Kuramo Water,Lagos, southern Nigeria

A five-month study in 2001 of an enclosed lagoon, Kuramo Water in southern Nigeria, exposed to urban perturbation describes its physical, chemical and macrobenthic invertebrate characteristics. Of the 16 physical and chemical conditions studied at four sites within the bank-root biotope, only BOD and TDS content were significantly different between sites. The elevated level of these perturbation indicators could be related to the raw and treated domestic sewage released directly into Kuramo Water from point and non-point sources. A total of 16 taxa and 691 macrobenthic individuals belonging to 11 families were recognised at the study sites. A naidid and a chironomid species were the most abundant, occurring in high numbers throughout. Other invertebrate groups occurred in low numbers. The diversity indices calculated supported this trend. The generally low diversity further supports the observation that Kuramo Water is a disturbed environment. The absence of molluscs in the benthic invertebrate samples of this study, compared to their dominance in earlier studies of Kuramo Water, reflects a modification in the habitat resulting from a change in the salinity from brackish to freshwater.     

Design,synthesis, antimicrobial activity and anti-HIV activity evaluation of novel hybrid quinazoline–triazine derivatives

Abstract

A series of novel hybrid quinazoline–triazine derivatives was designed and synthesized from cyanuric chloride and anthranilic acid through sequential reactions, which contain different pharmacophores like quinazoline and substituted diaryl triazine (DATA) linked with ethylene diamine. All the newly synthesized compounds were characterized by infrared, ¹H-NMR, ¹³C-NMR, MS and elemental analysis. Further, we evaluated the in vitro anti-HIV activity of the newly synthesized compounds against HIV-1 (III_B) and HIV-2 (ROD) viral strains and as well as in vitro antimicrobial activity against four bacteria (Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, Klebsiella pneumoniae) and two fungi (Aspergillus clavatus, Candida albicans) using the paper agar streak dilution method. The bioassay results indicate that four compounds namely 7d, 7n, 7r and 7s could be considered as possible potential agents.