The Town Council has tried and continues to try to alleviate the problem of blue-green algae in Diss Mere:

  1. The fountain works on a timer coming on at 8.30am – 10.30pm every day from 1st April to 30th October. This reduces in the Winter months. (Did you know?  It costs approx. £4k per year in electricity alone & an additional £3k to maintain the fountain)
  2. We measure oxygen levels in the Mere daily. If they drop beneath a certain level, the fountain is switched on 24/7
  1. Duck pellets are available to purchase from the Break charity shop on Mere Street opposite the Mere at 50p per 100g bag. This was a Town Council initiative to dissuade visitors from feeding bread to the ducks as it’s not food for them or the water
  1. In November 2017, a water quality management plan was undertaken by AGA Group. They concluded that there are a number of problems associated with the Mere that are contributing to its overall relatively poor condition as a sustainable aquatic habitat. These include run off from the surrounding catchment, the large waterfowl population, erosion and insufficient infrastructure. To overcome these problems, they recommended that we take a holistic approach and treat the cause instead of the symptom and identified possible recommendations to improve the health of the Mere. Given that half of the banks are owned privately, the degree of success will be impacted by our ability to gain the involvement of other stakeholders.
  1. If you’d like to find out more, please find the full plan here.   We have so far actioned the urgent / immediate recommendations. The other recommendations relating to tree management, lake infrastructure, silt, erosion & waterfowl will be considered as per the plan schedule (see page 56)
  1. One of the urgent recommendations is to purchase and install an ultrasonic unit to control the blue-green algae. This will be installed next week on the boardwalk. AGA Group recommended this as the best and most cost-effective method for the size of the Mere. Its ultrasonic technology has the ability to eliminate a significant proportion of existing algae and prevent new algae growth by transmitting ultrasound through the water body, which disrupts the cell vacuole of blue/green and filamentous algae. This kills the cell but the cell wall remains intact preventing the release of toxins from the algae into the water. The ultrasound used by the ultrasonic units is safe for fish, zooplankton and invertebrates because the voltage is low.
  1. We are budgeting to find a long-term solution to the Mere drain, which will enable a better flow of water from the Mere when levels rise
  1. We have a good relationship with the Diss & District Angling Club who own the fish stock and are a key stakeholder. We are meeting regularly with them to discuss the Mere.

Background info

  1. Diss Mere is owned by the Town Council but there are a number of key stakeholders also responsible for its proper management including surrounding landowners, the Diss & District Angling Club and everyone who visits it. If visitors can play their part in either not feeding the waterfowl or buying pellets instead of bread, put litter in the bins and report any issues directly to us, it will help us to maintain the Mere for everyone’s benefit.
  1. Diss Mere, as a 6-acre body of mostly still water, has suffered with blue-green algae outbreaks during summer months for hundreds of years so this is not a new phenomenon. Algae plays a fundamental role in the health of any body of water, but problems arise when blooms grow out of control or the wrong types of algae begin to grow. When dissolved oxygen (DO) levels drop to low levels, it can cause fish to die.  It can be fatal to dogs although most blue-green blooms are not toxic to humans and the signage around the Mere highlights this.
  1. Managing algal growth in water is complicated, in part, because there’s no definitive answer as to the cause of algae in ponds or lakes. Several factors come into play. Water nutrient levels, exposure to light, temperature, turbidity and the general conditions found in a body of water such as movement all contribute — and they’re all different from site to site.
  1. Humans have had a considerable impact. The most prevalent algae on the planet today is blue-green algae, which feeds on a steady diet of phosphorus and nitrogen. While supplies of these nutrients are found in water naturally — especially in areas where the water has a low oxygen content — it’s also introduced through chemical runoff and erosion. Fertilizers and other products as well as poor sewage management have contributed to excess nutrients for many years. Practices and products are changing, but in most circumstances the damage has been done.

Source –

  1. The Mere is home to a large population of wildfowl including Mallard ducks and Canadian Geese due to a constant supply of food, which has encouraged the Mallard population to become increasingly sedentary. This in turn increases the build-up of droppings, which encourages the growth of algae and smothers aquatic plants and depletes the oxygen levels.
  1. The fish stock of Diss Mere belongs to the Diss and District Angling Club and consists of roach, perch, carp, bream, and pike. Despite a view that the Mere is overstocked with fish, an acoustic survey completed by the Environment Agency several years ago determined that the fish stock of the Mere wasn’t in excess.

There is always more that could be done & by implementing some of the recommendations in the plan, the support of the public and consideration for alternative ideas, we should be able to celebrate Diss Mere as the town’s most unique asset and certainly one of the reasons I moved to the area. – Sarah Richards, Town Clerk.



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