THE STATE OF KNOWLEDGE OF WATER QUALITY AND MAJOR BIOTIC COMPONENTS OF THE MHLATHUZE ESTUARY

Summary

This note briefly introduces the concept of the Environmental Reserve of the New Water Act as well as the set of papers hereafter which deal with specific components of the ecology of the Mhlathuze Estuary. These were prepared for an Estuarine Flow Requirements study of the system. Each forms an up-to-date review of the specific topic it deals with.     

ZOOPLANKTON OF THE MHLATHUZE (RICHARDS BAY) ESTUARY: AN OVERVIEW,WITH COMMENTS ON FRESHWATER REQUIREMENTS

Summary

The Mhlathuze estuary in its present form was established during construction of the Richards Bay harbour during the early 1970s. This paper summarises available data on the zooplankton community as part of a study on the freshwater requirements of the estuary. The zooplankton community indicates a strong marine influence. The large tidal exchange prevents the establishment of a stable estuarine zooplankton community. The possible influences of changes in freshwater input are discussed.     

A REVIEW OF THE MACROBENTHIC FAUNA OF THE MHLATHUZE ESTUARY: SETTING THE ECOLOGICAL RESERVE

Summary

This paper reviews historical and current ecological information on macrobenthos from the Mhlathuze Estuary before and after development of the Richards Bay Harbour. The fauna is described in terms of the potential influence of a change in freshwater inflow to the system and the requirements for the setting of an Ecological Reserve. Over 95% of the species recorded were primarily marine and to a lesser extent estuarine in origin. Fauna typical of sheltered, soft-bottomed marine environments inhabited the estuary, whereas estuarine fauna was limited to the canalised sections of the Mhlathuze River. Certain areas were characterised by opportunistic species indicative of disturbed or organically enriched sediments while others sustained a high diversity of more sensitive climax species, several of which are endemic to southern Africa. The majority of species belonged to the Class Polychaeta but the estuarine mudcrab Paratylodiplax blephariskios dominated the benthic biomass. The pre-feasibility stage of the Ecological Reserve Determination indicated that a reduction in freshwater input would negatively impact upon the already reduced estuarine component at the head of the estuary. Conversely, if freshwater flow to the estuary is augmented, sediment transport via the river could increase without there being an. improved catchment management policy in place.     

DIATOMS AS INDICATORS OF WATER QUALITY IN THE UPPER HENNOPS RIVER (Transvaal,South Africa)

SUMMARY

The water quality of the upper Hennops River was determined by applying the method of Lange-Bertalot (1978; 1979), which is based on groups of diatom species with similar tolerances towards pollution. A definite improvement in the water quality was indicated between the upper reaches of the river, which receives secondary treated sewage effluent discharges, and Rietvlei Dam, some 25 km downstream. According to the water quality classification of Lange-Bertalot, this represented an improvement from class III – IV (α-meso- to polysaprobic) to class II – III (α- to β-mesosaprobic). These results were in general agreement with chemical analyses, which suggests that Lange-Bertalot's method for classifying the quality of running waters can be adapted, to South African conditions. The pollution tolerances of some species not included in Lange-bertalot's classification are suggested.     

MASS MORTALITY OF MARINE AND ESTUARINE FISH IN THE SWARTVLEI AND WILDERNESS LAKE SYSTEMS,SOUTHERN CAPE.

Summary

Two incidences of mass mortality of fish were recorded in two saline waterbodies (Swartvlei estuary and Rondevlei) in the Wilderness National Park. Species affected were the Knysna seahorse (Hippocampus capensis) and longsnout pipefish (Syngnathus acus) in the Swartvlei estuary, and Cape stumpnose (Rhabdosargus holubi) and white steenbras (Lithognathus lithognathus) in Rondevlei. Comparison of water quality parameters during fish mortalities to past ranges and reported species tolerances indicated that the probable causes for the mortalities were high water temperature in the Swartvlei estuary, and low dissolved oxygen concentration in Rondevlei.     

THE INFLUENCE OF P-RETENTION BY SOILS AND SEDIMENTS ON THE WATER QUALITY OF THE LIONS RIVER

SUMMARY

The soils of Midmar dam catchment and the sediments of the Lions river are shown to have high P-retention properties. Present conditions result in little leaching of PO₄ ^?4 from the soils and favour a net transport of P from overlying water to the sediments. P levels in the water are likely to remain low even if the loading rate of P were increased substantially. It is postulated however that other factors may induce a release of P from the sediments and adversely affect the load carried by the water.     

Mathematical modelling as a management tool for water quality control [2pt] of the tropical Beberibe estuary,NE Brazil

Sewage disposal in natural waters is a common problem in most countries. Large inputs of organic matter and nutrients from raw sewage to a weak hydrodynamic environment may lead to deterioration of the water quality. Widely available riverine and estuarine models such as QUAL-2E and MUDLARK can be used to adequately model these situations. Beberibe is a low hydrodynamic estuary that runs through a densely populated region in the Recife Metropolitan Area (RMA), Northeast Brazil, and receives untreated domestic sewage from aproximately 200000 inhabitants. The mouth of the estuary is shallow and tortuous, causing a large reduction in tidal propagation. The low river flow is strongly influenced by rain seasonality at the upstream boundary, with mean values varying from 4.9 m³ s^–1 in the wet winter to 1.4 m³ s^–1 during the dry summer. A major program to build sewage plants was planned to increase the water quality of the RMA rivers. This study focuses on water quality modelling of the Beberibe estuary basin, formed by the Beberibe River and two small tributaries. Numerical simulations of temperature, dissolved oxygen, biochemical oxygen demand, nitrate, ammonia, phosphate and faecal coliforms were carried out, targeting the expected population growth in the following 20 years. The QUAL-2E and the MUDLARK models were coupled at the tidal intrusion limit, with the estuarine sector modelled by the MUDLARK while QUAL-2E was used in the upper river. A longitudinal dispersion coefficient related to tidal excursion was introduced into the MUDLARK algorithm to better determine the tidal effect on the distribution of water quality variables. Both models were calibrated successfully and verified with a 4 year water quality data series from the Pernambuco State Environmental Agency (Companhia Pernambucana do Meio Ambiente – CPRH). Results showed that the river flow is a major factor controlling the water quality. Even the most efficient treatment applied was not able to bring water quality up to all desirable levels during dry summer months, mainly considering dissolved oxygen and biochemical oxygen demand. Results also confirm that the spring-neap cycle does not significantly affect water quality, probably due to the strong tidal attenuation at the estuary mouth.     

A REVIEW OF THE AQUATIC AVIFAUNA OF THE MHLATHUZE ESTUARY

Summary

This paper is the first published review of the aquatic avifauna of the Mhlathuze Estuary. It also uses a regional approach in order to determine the potential for certain hitherto unrecorded species to occur there. The study shows that there appear to have been significant changes in the aquatic avifauna over the past 15 years and that these have, by and large, been negative. However, information on the current status of the avifauna is lacking and it is considered important to determine this as soon as possible.     

THE EFFECT OF SEASON ON A BIOTIC WATER QUALITY INDEX: A CASE STUDY OF THE YELLOW JACKET AND MAZOWE RIVERS,ZIMBABWE.

Summary

The effect of season on the South African Scoring System (SASS) biotic index for rapid assessment of water quality using benthic macroinvertebrates was investigated using the Yellow Jacket and Mazowe Rivers in Zimbabwe as a case study. Several impacts in the area degraded water quality. These were habitat destruction, acid mine drainage and organic pollution. SASS score at all sites changed with season. At and downstream from polluted sites, water quality determined using SASS was best at the end of the rainy season and it deteriorated steadily into the dry season. SASS scores from sites upstream of pollution appeared to improve towards the end of the rainy season. Average Score Per Taxon indices did not have a significant pattern of seasonal variation. SASS was designed to monitor water quality in South African rivers, so when implementing any monitoring programme, selection of sampling season and the interpretation of results in areas with similar climate patterns should take seasonal effects into account, It must be appreciated that water quality at impacted sites is a dynamic variable related both to the activities of polluters and to season.     

Ecology and Assessment of the Benthic Diatom Communities of Four Lake Erie Estuaries using Lange-Bertalot Tolerance Values

Diatom composition of four Lake Erie estuaries was related to seasonal factors, year, location within the estuaries, and water quality parameters including nutrient and metals concentrations. Canonical correspondence analysis (CCA) revealed seasonality as the most important factor determining variability in diatom species composition among sites and dates. Alkalinity, pH, silicate, orthophosphate, and nitrite concentrations were water chemistry parameters correlated with diatom community composition. Eigenvalues for the first two CCA axes of nutrient/physical data and species data were higher than the first two CCA axes of metals data and species data. In addition, the water quality of these estuaries was evaluated using an index composed of Lange-Bertalot pollution tolerance values. The Lange-Bertalot index scores indicated that the Ashtabula estuary had the best water quality of the study sites. Lange-Bertalot index scores were highly correlated with a gradient of disturbance represented by the first axis of a principle components analysis of sites and nutrient data (Spearman ρ = 0.7). The Lange-Bertalot tolerance values could be useful for discriminating ‘good’ sites from “bad” sites among the Lake Erie estuaries.     

Qualité des eaux en milieu estuarien: Suivi annuel de critères physiques et chimiques dans les eaux de l'estuaire de la Loire

Chemical composition and physical parameters of waters from the Loire estuary were examined in 1981–1982 in order to assess water quality. It appears that riverflow is of first importance on suspended matter load, dissolved nutrient concentrations and oxygenation. The annual hydrological cycle is made of two periods. During the first one low riverflow, low nutrient concentrations, high suspended matter load and oxygen depletion are noticed. During the second one higher riverflows occur accompanied with increasing nutrient concentrations, decreasing turbidity and restoration of dissolved oxygen. Results indicate that annual inputs of dissolved nutrients attain 60 000 t a^–1 for nitrogen, 2 400 t a^–1 for phosphorus and 100 000 t a^–1 for silica. It is suggested that the high suspended matter loading (¹ million t a^–1) is a significant factor disturbing oxygenation and by the way limiting water quality within the estuary.

     

Biogeography of dinoflagellate cysts in northwest Atlantic estuaries

Few biogeographic studies of dinoflagellate cysts include the near‐shore estuarine environment. We determine the effect of estuary type, biogeography, and water quality on the spatial distribution of organic‐walled dinoflagellate cysts from the Northeast USA (Maine to Delaware) and Canada (Prince Edward Island). A total of 69 surface sediment samples were collected from 27 estuaries, from sites with surface salinities >20. Dinoflagellate cysts were examined microscopically and compared to environmental parameters using multivariate ordination techniques. The spatial distribution of cyst taxa reflects biogeographic provinces established by other marine organisms, with Cape Cod separating the northern Acadian Province from the southern Virginian Province. Species such as Lingulodinium machaerophorum and Polysphaeridinium zoharyi were found almost exclusively in the Virginian Province, while others such as Dubridinium spp. and Islandinium? cezare were more abundant in the Acadian Province. Tidal range, sea surface temperature (SST), and sea surface salinity (SSS) are statistically significant parameters influencing cyst assemblages. Samples from the same type of estuary cluster together in canonical correspondence analysis when the estuaries are within the same biogeographic province. The large geographic extent of this study, encompassing four main estuary types (riverine, lagoon, coastal embayment, and fjord), allowed us to determine that the type of estuary has an important influence on cyst assemblages. Due to greater seasonal variations in SSTs and SSSs in estuaries compared to the open ocean, cyst assemblages show distinct latitudinal trends. The estuarine context is important for understanding present‐day species distribution, the factors controlling them, and to better predict how they may change in the future.     

THE USE OF TOXICITY TESTING IN EFFLUENT REGULATION AND CONTROL: A NEW DIMENSION TO ASSESSMENT AND MANAGEMENT OF WATER QUALITY IN SOUTH AFRICA

Summary

Efficient management tools are continually required to cope with increasing demands placed on the quality and quantity of aquatic resources. Recent developments in environmental monitoring indicate the importance of incorporating biological indicators in assessment programmes. Aquatic toxicology has consequently become an important monitoring and regulatory science. Applications of aquatic toxicity testing include: deriving water quality criteria; toxicological evaluations of whole effluents and receiving waters; and the estimation of ecological risk. Toxicity testing can potentially play a significant role in improving water quality in years to come, especially through its application in effluent regulation. Currently however, few environmental laboratories in South Africa have the required expertise and facilities to carry out a representative range of toxicity tests. Training and funding are required to build the capacity for the necessary developmental research, before toxicity testing can routinely be implemented.

The significant problems we face cannot be solved at the same level of thinking we were at when we created them. Albert Einstein.     

Impact of flood events on dolphin occupancy patterns

The aim of this study was to assess potential impacts of water quality changes associated with floods on the occupancy of Indo‐Pacific bottlenose dolphins (Tursiops aduncus) in two subtropical estuaries in Australia. Boat‐based surveys were conducted in the Clarence River estuary (CR) and Richmond River estuaries (RR) over 3 yr. Principal components analysis (PCA) showed that when the dolphins were absent from the estuaries, three water quality components were extracted in the CR and two components in the RR. The PCA¹ component included high loadings for salinity, turbidity, and pH for the CR (46%); and salinity, turbidity, pH, and dissolved oxygen (DO) for the RR (51%). Randomization tests showed that dolphins abandoned both estuaries at times of lower salinity, and during periods of higher turbidity and of lower levels of pH and dissolved oxygen in the RR that were associated with floods. The time until dolphins returned to the estuary postflood depended on the length and severity of the flood, but generally dolphins were observed in waters with salinity levels above 29‰. Their delayed return postflood could be for their physiological health, or because their prey returned to the estuaries under these higher salinity conditions, or more likely a combination of both factors.     

A long‐term study of bottlenose dolphins (Tursiops aduncus) in an Australian industrial estuary: Increased sightings associated with environmental improvements

Delphinids are long‐lived, have delayed maturity and low reproductive rates which necessitate long‐term monitoring programs to detect changes in abundance. Between 1990 and 2013, an observational study of bottlenose dolphins (Tursiops aduncus) was conducted in the Port River estuary (Adelaide, Australia). The estuary has received pollution from industry, sewage plants and storm water. In recent years, pollution entering the system has reduced and the establishment of the Adelaide Dolphin Sanctuary (ADS) increased dolphin protection from harassment and deliberate attacks. Nevertheless, the estuary remains a busy port. Over a 24 yr period, we conducted boat‐based surveys (n = 735) for dolphin groups (n = 3,634) along a predetermined route in the Inner and Outer Estuary of Adelaide's Port River estuary. It is our conjecture that major infrastructure changes and pollution abatement have yielded a more favorable marine environment for dolphins, resulting in an estimated 6% annual increase in sightings, from a near absence of sightings in the 1980s. Increased dolphin numbers were likely the result of improved water quality, augmented by surveillance and education arising from the proclamation of the ADS. This study highlights the importance of long‐term monitoring and has implications for dolphin conservation in heavily impacted urban areas and their protection via protected areas.     

两类水质综合评价方法的特点及其在河流水环境管理中的作用

河流水质恶化已成为严峻的环境问题,针对河流开展水质综合评价对河流水环境管理具有重要意义。依据不同的评价目标,选择合理的综合评价的评估标准成为河流水质评价中重要的问题之一。通过基于期望值和阈值的水质健康综合评估法(ETI)和水质质量指数(WQI)两种水质综合评价方法对"引滦入津"工程重要水源地伊逊河水质进行评价,结果显示:1)伊逊河水质ETI评估结果为良好等级,WQI评估结果为一般等级;2)伊逊河采样点水质在ETI评价中分布于4个等级,WQI仅分布于2个等级;3)伊逊河自上游至下游水质显著降低,特别是ETI评估中由优秀等级转变为差等级;4)ETI和WQI评估结果显示极显著相关性(R=0.951,P0.01);5)通过逐步多元回归,ETI评估结果的主导因子是DO、EC、SS、BOD_5和TP(P0.05),WQI评估结果的主导因子是DO、SS、BOD_5、TP、TN和NH_3-N(P0.05)。进一步分析表明伊逊河水质恶化与其流域内土地利用情况密切相关。在河流水环境管理中,ETI作为一种水质相对值评估方法,能更好体现流域内水质差异的区分度,便于管理者迅速定位流域内亟需治理的河流或河段,同时能够根据河流自身特征制定管理目标,可作为河流管理绩效评估的有效手段;而WQI作为一种水质绝对值评估方法,更适用于河流水质时间变化评估,对河流经长期治理后的管理效果评价起到重要作用。     

An assessment of macroinvertebrate functional feeding groups as water quality indicators in the Buffalo River, eastern Cape Province, South Africa

The aim of this paper was to investigate the potential for using functional feeding groups (FFGs) as indicators of water quality conditions in rivers, using the Buffalo River, South Africa, as a specific example. Multivariate classification and ordination techniques were used to investigate species and FFG distributions in relation to a number of physico-chemical variables at 16 sites from the headwaters to the estuary of the Buffalo River.Two-way indicator species analysis (TWINSPAN) of species composition ranked most of the sites sequentially down the river, irrespective of water quality conditions. Ordination of FFGs from a set of riffle samples collected in mid-late summer showed only weak relationships between FFG distribution and water quality changes, except where variables changed sequentially down the river (e.g. pH and temperature). Individual species responses to water quality gradients were examined for nine riffle-dwelling species representing diverse FFGs. Following correspondence analysis of a matrix of environmental variables and species frequencies, some species showed strong associations with defined ranges of some variables. In particular, Adenophlebia auriculata (Leptophlebiidae, Ephemeroptera) from the headwater sampling site, was associated with low pH and low temperature. Simulium damnosum occurred under conditions of high turbidity, while Afronurus harrisoni was found under high concentrations of potassium, ammonium and nitrite ions.We conclude that although there was a distinct headwaters fauna in the Buffalo River, and sequential downstream changes in species composition, most FFGs (apart from shredders) were represented down the whole length of the river. FFG classifications are therefore unlikely to provide useful indications of water quality conditions in the Buffalo River.Using a categorical approach to classifying water quality variables, and by applying correspondence analysis to the resulting matrix, we recognised nine species that could be used to define water quality. These indicator species can be used to define tolerance ranges of the fauna for water quality conditions in different parts of the Buffalo river.     

Water quality modelling of the western Scheldt estuary

In 1987 the National Institute for Coastal and Marine Management (theNetherlands) initiated the SAWES project (Systems Analysis WEstern Scheldt).The main goals of the project were to acquire knowledge with respect to thepollution problems in the Scheldt estuary and to apply this knowledge tomanagement issues of the Scheldt on an operational level. The main interestwas to understand quantitatively the relation between inputs of pollutingsubstances and effects on the ecosystem. In the framework of the project, awater quality model for the Scheldt estuary was made. In 1995, the modelarea was expanded to include the Belgian coastal region at the mouth of theestuary. The model calculates the fate of discharged substances andestablishes the relation between pollution inputs and the resulting waterquality, including general water quality (oxygen, pH, alkalinity, major ionchemistry and nutrients) as well as pollutant concentrations. The modelincorporates all chemical processes which affect these concentrations,including the precipitation/dissolution of metal sulphides which to a largeextent controls the fate of trace metals. Based on calibration andverification exercises, it has been shown that the model provides a goodrepresentation of the physical and chemical processes taking place withinthe estuary and can therefore be used to support policy development for theestuary. For example, the model can compute how the water and sedimentquality in the estuary will respond to reduced inputs of waste or to suchhuman activities as dredging. This revised version was published online in July 2006 with corrections to the Cover Date.     

AN HOLISTIC APPROACH TO THE MANAGEMENT OF WATER QUALITY IN FALSE BAY,CAPE TOWN,SOUTH AFRICA

Summary

An overview of the water quality status of False Bay identified the bacterial/viral water quality of stormwater and rivers discharging near contact recreation beaches to be the management concern of highest priority. A second water quality concern is the potential impact of nutrients being discharged into False Bay on the surf zone and bay ecosystems. Heavy metals, hydrocarbons and industrial chemical discharges into the Bay are not regarded as a serious water quality threat. Much of the future development planned for Metropolitan Cape Town will impact on the volume and water quality of rivers, groundwater, stormwater and wastewater flowing into False Bay; hence the need for an integrated catchment management approach to the management of the bay.

An assessment of the constraints facing the holistic management of the bay and catchment concludes that the four main concerns are: (1) a lack of key research information on the options for stormwater management, and on the loading and potential impacts of nutrients being discharged into the surf zone and bay ecosystems; (2) jurisdictional fragmentation, and the lack of coordinated policy and planning between different local and government authorities and other users; (3) legislative fragmentation; and (4) a lack of private sector and public consultation by authorities. Preliminary ideas on the structure of a management body for False Bay and its catchment which address the concerns listed above are presented.     

HUMAN ACTIVITIES AND FACTORS AFFECTING THE DISTRIBUTION OF MACROBENTHIC FAUNA IN SALDANHA BAY

Summary

The most recent trends in the economic development of Saldanha Bay are towards the tourist and mariculture industries, both of which are dependent on a high quality of water. Yet this water quality is now under threat. In this study, the extent of human induced changes to the characteristics of the water body are assessed in terms of their effects on the macrobenthic communities of the bay. Such effects are evaluated on the basis of changes in biomass, community structure and species composition using data from recent surveys as well as a limited quantity of historical data.

Whilst gross effects are essentially confined to an area adjacent to the major fish factory outfall, the data do suggest a broader impact. There are substantial differences between the communities of ‘Big Bay’ and ‘Small Bay’, with an apparent increase in deposit feeding species and decline in suspension feeders in the latter. These changes are attributed to the organic loading from the fish factories and mariculture industries together with restrictions imposed on water circulation by harbour constructions. This combination of anthropogenic factors may be leading to significant enrichment of certain areas of the bay.