Cyanobacterial Monitoring 1990-2000: Evaluation of SA Data
Report No. 1288/1/04
Concerns about the extent of eutrophication processes and the associated phytoplankton related problems, particularly toxic cyanobacteria, have been voiced for decades. Toxic, and taste and odour producing blooms during summer months in South Africa have frequently been reported and have been associated predominantly with the genera Anabaena and Microcystis. In recent years there appears to have been an increase in the frequency of reports of problem events. Recent reports also include problem organisms such as Cylindrospermopsis raciborski, a species not previously associated with problems in South Africa. In several cases death of livestock and fish have been reported, although whether the cause of the fish kills was toxicosis, or as a result of oxygen depletion in the eutrophied waters remains unknown. Much of the available literature on the subject cites only events where severe blooms or livestock or fish kills occurred. The question of whether there is an increase in the frequency and/or severity of cyanobacterial nuisance events, and particularly toxic blooms, is therefore widely debated, with anecdotal evidence suggesting an increase.
This report is therefore aimed at identifying and, where possible, rectifying the gaps in our current knowledge in these areas and in determining the need for guidelines for monitoring and managing water resources applicable to local conditions, and the need for continued research in this field. It is not the aim of this report to assess causes, evaluate or produce models for bloom events, or compile data on eutrophication status or trends. In order to accomplish the aforementioned aims, all available data pertaining to phytoplankton levels and selected associated parameters, were obtained from the DWAF database. In addition to this data, several water management bodies (municipal and other treatment works, and water boards) in various parts of the country were visited and where possible information and data from these visits were included in this report.
Available data for use in this study were found to be unsuitable for detailed statistical analysis. The major problems in this regard were variation in sampling method and sampling frequency both spatially and temporally. Results of this study therefore reflect trends only in as much as the data allowed for this, and correlations in variables obtained reflect generalizations based on monthly averages. Raw data used for this study are available from the Institute of Water Quality Studies.
Results of this study show that cyanobacterial problem events are widespread, frequent, prevalent and typically seasonal. Water resources subject to eutrophication commonly experience problems. There exists a geographical variation in the frequency, duration and severity of the problems primarily due to the condition of the catchment, but also the nature of the water source, abstraction points, and regional climatic conditions. Insufficient data is available to establish the nature of this variation. Microcystis is the dominant problem cyanobacterial genus, with Anabaena also being common. The most common problem associated with cyanobacterial bloom events or increased cyanobacterial biomass, is taste and odour. No national trend in frequency of bloom events, toxin, or taste and odour, could be established with the available data, although an apparent decrease was observed in the catchments for which data was available. Toxin and geosmin/MIB data is extremely limited due to the limited resources for the analysis and the cost of such analysis. Suggestions from water management bodies include subsidisation of such analyses. The apparent trend in frequency and severity of cyanobacterial events in certain catchments/impoundments is presumably related to climatic conditions, and is therefore probably part of a cycle of increasing and decreasing severity and frequency. An analysis of climatic data and correlation to available cyanobacterial data was unfortunately beyond the scope of this report. Without significant improvement in eutrophication status of South Africa's fresh water resources, increasingly severe problems with longer duration of events can be expected in future.
Water management and treatment bodies identified the following information and resource needs:
In order to facilitate (1) through (3) above, it is recommended that appropriate administrative structures be developed for regional management of monitoring procedures. Such structures would also facilitate all data analysis according to a national model, and be subject to national control. This would allow current and cumulative information on national incidence and trends. Items (4) through (7) above can be addressed by a series of workshops run nationally and at a regional level with representation from all stakeholders. These should be introduced as a function of a coordinated national monitoring and assessment program.
In order to address the identified research needs, the following areas (as prioritised by water management bodies) need to be addressed:
Analysis of the available data suggests the need for the following research:
The following areas should also receive attention:
Limited information is available on these water sources. There is some information on problems in canalised water, and cyanobacterial and algal problems in drip irrigation systems have been reported. Data collected by the University of Port Elizabeth Department of Biochemistry and Microbiology suggest that farm dams are highly susceptible to cyanobacterial blooms. Informal water sources are typically in rural areas where the water serves not only as drinking water for humans but also livestock. In addition to this the waters often become eutrophic due to human and animal waste. Research in other countries suggests that substantial human health risks associated with cyanobacteria exist due to the use of untreated water.
In conclusion, substantial research and coordinated monitoring are still required to understand the dynamics of cyanobacterial bloom events and associated problems, and thus facilitate the improved management of fresh water resources.
Addendum of Figures
A CD providing data concerning the levels and occurrence of cyanobacteria according impoundments, and catchments, is included with Report 1288/1/04.