The shortsightedness of using grass carp as a lake management tool

4 September 2014

Pondweeds are a vital part of healthy aquatic environments (Photo: Bill Harding)

Pondweeds are a vital part of healthy aquatic environments (Photo: Bill Harding)

In nearly thirty years of working in the field of aquatic ecosystems, I have yet to see a single example of using grass carp as a means to ‘control’ aquatic plants actually being successful.  I was asked about this again this week and thought it best to lay out a few facts here:

For some reason or other, people who live around lakes and ornamental ponds don’t want to see any plants in the water.  Now, I am not talking about noxious floating species such as Kariba weed or water hyacinth or red water fern, rather the rooted, filamentous pond weeds that are characteristic of many local waters.  Pondweeds, belonging to the genus Potamogeton, together with many smaller sub-canopy types such as Chara and Nitella, provide essential functions and ecosystem stabilisation which, once lost through irresponsible management, are almost impossible to replace. Read more »

South Africa’s eutrophication challenges under discussion in Italy

3 September 2014


Eutrophication remains the major threat to stored water supplies

This week sees the hosting of the 15th World Lakes Conference (WLC15) in Perugia, Italy.  One of the discussion themes is that of Wicked Problems, those complex, ever-changing societal and organisational planning problems that evade successful remedial intervention.  The problem of eutrophication is one such problem, for which a group of researchers is now invoking the tool of Morphological Analysis to illustrate their ‘wicked’ nature and, hopefully, underpin a better understanding of what eutrophication management is really all about.

The abstract for one of the three South African papers to be presented on this topic is provided here: Read more »

Another South African dam joins the polluted list

29 August 2014

Its green but you can drink it (?).  Conditions in a well-known South African dam.

Its green but you can drink it (?). Conditions in a well-known South African dam.

A report this week has added KwaZulu Natal’s well-known Midmar Dam to the growing list of South African reservoirs that are grossly-polluted (eutrophic and hypertrophic).  Research funded by the Water Research Commission (WRC) has shown that approximately 50% of the total water stored in South African dams is eutrophic.  In most of these cases reducing the problem pollutant loads would require massive interventionsRead more »

Algal Toxins in Water Supplies: It won’t happen here… or… will it?

19 August 2014

A couple of posts ago I mentioned the incident in Toledo (Ohio) that caused many to padlock (figuratively) their taps and take to their computers about the topic of algal toxins.  An article of a couple of days ago speculates whether water supplies in the Philadelphia area are even likely to produce toxic blue-green algal blooms. Based on experience I would hesitate to make such a sweeping statement.  Here are just three examples of why I say this: Read more »

Toxic algae in Ohio leaves thousands without water

4 August 2014

Sales of bottled water have soared in Toledo (Ohio) USA as algal toxins persist in the drinking water supply.

Ohio Gov. John Kasich declared a state of emergency for Lucas, Wood and Fulton counties and deployed the National Guard to make water available to the area.

Water from this area comes from the massive Lake Erie, long infamous for algal blooms and toxins.  A couple of years ago Droplets reported on an article entitled Lake Erie on Death Watch!  Lake Erie, once a lake management success story, has regressed in recent years, with an increasing incidence of toxic algal blooms threatening millions of water users. Read more »

Perfection is reality for 126 sewage treatment plants

26 June 2014

Don’t you wish that this was the heading for an article about wastewater treatment in South Africa?  Wish again. It comes from the State of Washington in the US:

There were 126 wastewater treatment plants across the state with perfect performance in 2013, a jump from 107 the year before. There are approximately 330 wastewater treatment plants in Washington. When the award program began in 1995, only 14 treatment plants had perfect compliance. Read more »

Algae tests result in higher [water] bills

26 June 2014

The quality of drinking water supplies is becoming increasingly threatened by pollution (Photo: Bill Harding)

The quality of drinking water supplies is becoming increasingly threatened by pollution (Photo: Bill Harding)

PORT CLINTON — Ottawa County water customers are paying 4.5 percent more for their water this year, partly because of the cost of removing toxins caused by harmful algae. Blue-green algae that grows on Lake Erie in late summer and early fall can produce a toxin, called microcystin, that can cause gastrointestinal illness and skin irritations.  Normal water treatment processes don’t always remove the toxin from the finished drinking water, causing plants like Ottawa County’s to use additional chemicals, methods and testing to make sure the water coming from the tap is safe.

Read more »

Clean Water: Getting the message across

26 June 2014

The US state of Colorado encompasses a catchment area known as the Barr-Milton Watershed (BMW) – a catchment area that benefits from the attentions of the non-profit Barr Lake – Milton Reservoir Watershed Association. The catchment serves as a water source for both agriculture and urban use, i.e. need to accommodate often-conflicting uses in a state that is home to 50% of Colorado citizens. Read more »

Shining new light on South African rivers, estuaries and rocky shores

18 June 2014


The NMMU research team on the coast near Port Elizabeth.  Dr Miranda (left), holding the BenthoTorch, Prof Perissinotto (centre) and Jacqueline Raw (right)

A portable scientific instrument, known as the BenthoTorch (manufactured by bbe Moldaenke, Germany)  is providing a diverse group of South African aquatic scientists with the means to measure algal growth off living cells in their natural habitat.  Various algal species have adapted their nutrient uptake systems enabling them to survive in shallow water close to the shoreline, where sunlight still penetrates to the sea or river bed. This habitat is home to benthic algae, ranging from the microscopic to the enormous. Such flora play an essential role in primary production.   The ability to measure the level of algal growth, in situ, as well as the dominant groups present (the BenthoTorch can distinguish the pigment signatures of green, blue-green and diatom algae), is of enormous importance for assessing the condition and ecosystem health of streams, rivers, estuaries and coastal shorelines. Read more »

Concern grows about the impacts of hormones on aquatic ecosystems

12 June 2014

For quite  a few years now the threat of hormones and oestrogen mimicking compounds (EDCs) – entering our rivers, lakes and dams in sewage effluents – has been growing.  The topic is generally swept under some or other carpet as the implications for wastewater treatment needs (read “increased rates and taxes”) rendered it unpopular.  The scientific evidence suggests that there is cause for concern, especially in water-stressed countries.  The frightening concept of “feminized fish populations”, whispered about more frequently that many will realise – first appeared in the 1990s (see report about English sole).

These so-called “feminized” fish, first found in the late 1990s, are thought to be victims of human hormones and hormone-mimicking chemicals — flushed into the water from sewage-treatment plants, factories, storm-water drains and runoff from roads — that had made their reproductive systems go haywire. Now a King County study has found that those chemicals, which come from sources as varied as birth-control pills and plastic bottles, detergent and makeup, are more widespread in the region’s water than previously known.  The chemicals were found at very low levels, but some scientists worry that even in tiny amounts, they could mess with the sensitive reproductive systems of animals that already have plenty of challenges.

Back in 2007, impacts on lobsters were found to be somewhat different, affecting their moulting process and making them more susceptible to disease.  The controversial video entitled “The Disappearing Male” initiated a debate that was a small version of those nowadays typical of climate change.  The Bottom-Line here is that less-sophisticated wastewater treatment increases the risk of EDC build-up in our water resources.

Read more »