South Africa is facing a water resource management crisis. This is playing out in various forms.

Disruptions to water service delivery are occurring in major metros like eThekwini, Johannesburg and Ekurhuleni; the rapid growth of an invasive species of floating plant on the Vaal River known as water lettuce has triggered public anger; and the Blue Drop reports show the extent to which our wastewater works have broken down, discharging vast quantities of untreated sewage into our rivers.

Read more in Daily Maverick: Official reports reveal massive scale of the waste, pollution and poorly treated water crisis

At the heart of these issues is the rate of change that is simply overwhelming the capacity of the state to respond.

Hartbeespoort Dam is the best example of an aquatic ecosystem that is enriched with nutrients, typically originating from sewage disposal. Technically this is known as eutrophication.

All eutrophic systems are characterised by a large biomass of plants, of which we typically have two types. Floating plants like hyacinth and water lettuce generate media interest as the recreational water-using public becomes angry. Suspended plants, collectively known as blue-green algae, manifest as vividly coloured water, often a luminous green.

Public attention is mostly on the floating plants, but the biggest risk comes from the suspended plants for reasons that will become apparent. In our attempt to “do something”, public support is mostly for the removal of the floating plants. This merely creates the impression that something is being done about the problem, because the biggest risk comes from the suspended algae. These are given a nutrient boost when opposition is removed, which also provides more light for the single-celled plants to multiply.

Cyanobacteria

These single-celled “plants” are bacteria, which are typically animal. Plants photosynthesise whereas animals move around. These primitive organisms are billions of years old and are neither plant nor animal, because they do both.

Technically they are called cyanobacteria, also known as blue-green algae. They photosynthesise and they move around. This unique set of characteristics makes them particularly successful as a species, so there are literally hundreds of different types, many of which produce potent toxins.

This wide range of species is broken down into different genera, of which two are important for South Africa. Anabaena produce anatoxin while Microcystis produces a toxin known as microcystin. Almost all eutrophic dams in South Africa have these two genera, often as dominant residents. These two genera are widely distributed and therefore well known to science.

But ecosystems change, and so does the distribution of cyanobacteria that live there. This is what makes these new discoveries important, so let us look at them in more detail.

Remember that cyanobacteria are primitive toxin-producing life forms, often associated with colour change when they bloom.

New lethal species

In 2008 a new species was reported in a peer-reviewed paper published in the African Journal of Aquatic Sciences. The authors were Dr Sanet Janse van Vuuren and GP Kriel, both from the School of Environmental Sciences at North West University, NWU.

They discovered the presence of Cylindrospermopsis raciborskii, which they described as, “problem-causing cyanobacterium capable of releasing potent toxins, … first detected in the lower Orange River in 2000”.

This new species rapidly multiplied under ideal conditions to levels of a million cells per millilitre of water. The international threshold of concern beyond which human health becomes a risk is a thousand cells per millilitre, so recorded levels were an order of magnitude greater.

The water treatment plant was overwhelmed, and animal deaths were recorded. This new species can assimilate ammonium at low concentration, so it has a comparative advantage over others. It is also more efficient at metabolising phosphate, always abundant in eutrophic water, again giving it an advantage over the normally dominant Anabaena and Microcystis.

Of great importance, this new species is tolerant of high levels of salinity, such as that occurring in the Vaal and the Orange. As salinity increases — the result of evaporation from dams, uncontrolled flow of sewage and acidic mine water — so this new species can multiply faster than the other two dominant genera.

This paper concludes that Cylindrospermopsis raciborskii has already become an invasive species that needs to be monitored closely because little is known about its toxin production.

Second discovery

Which takes us to the second new discovery.

In a more recent peer-reviewed paper, also published in the African Journal of Aquatic Sciences in 2021, the same principal author (Prof Sanet Janse van Vuuren) reported the discovery of another new species identified as Euglena sanguine Ehrenberg, which is one of a “few species of algae known for their ability to turn water red”.

The Latin word for blood is sanguis, so think of a red tide in the ocean, only now it’s in a dam. This paper notes that, “Euglena sanguinea is probably the most common freshwater alga that turn waterbodies red”. It prefers warm water that is high in both phosphate and nitrate, preferably slightly acidic.

This means that it can be associated with pH changes such as that arising from the sustained inflow of acid mine drainage (AMD). This species is known to produce a potent toxin specific to fish, which was named Euglenophycin and was found to be “new to science” in 2010, so its effect on other living organisms is not well documented.

Euglena sanguinea has been recorded in seven African countries (Botswana, Congo, Egypt, Malawi, Nigeria, South Africa and Togo), but deep knowledge of the toxicity is not yet in existence. There are descriptions from East Africa (exact country unnamed so it could be more widely spread than the seven countries reported above), of “regular red water blooms”.

Observed blooms in South Africa are associated with eutrophic water, noting that Euglena sanguinea is an indicator species for polluted water where aerobic conditions (oxygen-rich) are created by photosynthetic aeration, such as might occur when surface floating vegetation is removed, allowing more light to penetrate the water column to stimulate blue-green algae that produce oxygen in the day.

This alters nutrient availability, specifically of proteins, triggering a red bloom. The authors note that this species is problematic because blooms form red scums that can be toxic, creating odour and water treatment problems.

Sign of critical changes

The significance of these two new discoveries cannot be overstated because both suggest a rapidly changing set of conditions in our already distressed aquatic ecosystems.

It is known that our rivers and dams are becoming more saline, while changes in nutrient levels associated with sewage flows, and alteration to pH, caused by inadequate attempts to treat mine water flows, are also being observed.

The known presence of these two species thus becomes relevant because little is known of their risk at a time when our technical capacity is diminishing.

For example, the Department of Water and Sanitation (DWS) used to run a National Eutrophication Programme staffed by highly skilled scientists. This has slowly succumbed to underfunding, staff instability and purges elsewhere in the organisation, so it is now a fraction of what it used to be.

Recently samples that were destined for processing in a lab overseas were removed from the refrigerator and discarded for reasons yet unknown.

We can conclude that our capacity to cope with rapidly changing conditions within our aquatic ecosystems is simply being overwhelmed by the sheer magnitude of change on multiple fronts.

We saw this in the water lettuce crisis that overwhelmed decision-making processes to the point where Glyphosate was used, even though it is not registered for those specific pests, and the public concern about exposure to controversial chemicals was totally ignored.

We are now likely to see it as conditions change on the Vaal and Hartebeestpoort, possibly triggering red algae blooms as Euglena sanguinea gains a foothold.

We need an informed public debate about funding our research institutions as a matter of national priority. DM