Here We Go Again….

Thursday 6th August, 2021

The lower Wye was hit with another severe algal bloom this week. Although not yet as bad as the bloom of June 2020, the river was reported as turning a putrid green from around the Hoarwithy area down to below Monmouth. Visibility through the water in this section is currently around 40cm. At this time of year, it should be clear.

This is not the first severe bloom of the year. The first was witnessed in the Ithon at the end of May and there have been numerous days since where they have been reported from various parts of the river.

Interestingly, the upper Wye, Irfon and Ithon have been running clear this week. What might have triggered this latest bloom were the thunderstorms over Herefordshire last week that allowed a fresh release of nutrients to enter the Lugg system from combined sewage outlets and from farm yards, fields and tracks.

Above right: The Wye just below Monmouth yesterday showing the severe algal bloom. The title photo is of the river near Ross-on-Wye on Tuesday (photo: Adam Fisher).

Above: The Ithon algal bloom at Llandrindod Wells on 31st May, a day when the upper Wye and Irfon were running clear.

The effects

Whatever the source or cause, this is bad news for the Wye’s ecology. The ranunculus, a highly protected keystone plant species that only a few years ago was abundant in the river, is now severely depleted. Damaged originally by the record floods of two winters ago, its recovery has been stifled by the algal blooms that now appear during the peak growing period. It has been estimated that the main stem of the Wye has between 90 to 95% less ranunculus compared with just 3 years ago.

The loss of this plant actually makes the algal blooms worse. Previously, the filter feeders that live in the ranunculus beds consumed much of the algae and dampened the blooms. With their numbers restricted, the blooms are exacerbated. If the ranunculus cannot regrow as a result, the ecology of the Wye will change fundamentally.

It is estimated that around 90-95% of the ranunculus on the main stem of the Wye has been lost. The algal blooms will hamper and maybe even prevent the recovery of this highly protected plant species that is so important to the river’s ecology.

Invertebrates and fish are obvious victims of this change but there are others too. There have been plenty of reports of less swans on the river, a species that eats ranunculus and also helps in its recolonisation by creating a trail of fronds drifting downstream as they feed. It would be understandable if any bird enthusiasts felt the need to ask other specialist organisations if they are aware of this issue and what they are doing about it.

It is possible that there could be an impact on humans too. The Foundation, working with Fish Legal and Cardiff University, has been organising eDNA sampling of the Wye’s algae so that we can identify the species that make up the blooms and get a better understanding of the cause.

There is much more work to be done but we have found that cyanobacteria (blue-green algae) is present in the river. Levels of this algae in the June samples may not have been dangerous to human health but we are still awaiting the July and August results. In the meantime, those enjoying any form of water-based recreation will need to be aware of this, as will the area’s tourism businesses.

In partnership with Fish Legal, the Foundation has been organising eDNA testing of the Wye’s algae this year. We hope that this information will inform us what species are present and what types of phosphorus might be influencing the blooms.

The photo above is of water samples taken from the Wye today and on their way to Cardiff University for eDNA analysis. The far left hand sample was taken at Monmouth with the rest taken progressively upstream.

A complex issue

Algal blooms are a very complex puzzle, but one that we are starting to find more pieces for. Part of the issue is that most testing in rivers is for one type of phosphorus: soluble reactive phosphorus or SRP. This is what most statutory authorities and citizen science testing kits record and is the type of phosphorus that all algae use first to proliferate. It might make sense then that river targets are set to SRP by the national Governments.

However, it also means that much of the phosphorus within animal manures and attached to soil particles is not therefore picked up by standard sampling. These other types, together with SRP, make up what is called “total phosphorus”. Crucially, once SRP is depleted in the water, some types of algae are able to switch to using these other forms of phosphorus. Blue-green algae are one such species.

Our monitoring equipment (sonde) in the lower Ithon has been giving us some interesting results. We have found that there is a strong correlation between rises in the Ithon’s water levels and increases in both total phosphorus and SRP. In other words, it appears that every time it rains, the Ithon not only receives a fresh dose of SRP but one of total phosphorus too.

The May and June results from our river Ithon sonde showing a strong relationship between rises in river levels with rises in total phosphorus.

More data and analysis is required before firm conclusions can be made of course but one reason for the eDNA sampling is to confirm whether the algae species making up the Wye blooms are able to use other forms of phosphorus. If so, total phosphorus levels may be more relevant than SRP in their generation.

There were the signs of an algal bloom forming in the Usk this July too. This photo was taken from Talybont Bridge on the 14th.Leaving the Wye for a moment, there were also signs of an algal bloom forming on the Usk last month (photo right: The Usk from Talybont Bridge on 14th July). Although it was nowhere near as severe, this is the worst performing SAC river in Wales for phosphorus according to Natural Resources Wales. The problem with the Usk is the dearth of data. Much more monitoring is required before it can be established what the true levels and sources of this phosphorus are. Thanks to the generosity of a landowner in the Usk Valley, the Foundation will be installing its first sonde in the river later this year.

Hope on the horizon

There has been a huge amount of publicity recently surrounding the subject of phosphorus and algae in rivers across all types of media. The ire is understandable. Watching rivers suffer and their ecology change before our eyes is extremely distressing to anyone with affection for nature. But there is hope. Foundation staff have been working hard to understand algal blooms and develop the solutions. We think the answer lies in determining exactly how the problem arises and then getting the actors to accept that they are the cause. We must then work with them to develop solutions that are meaningful, effective and long-lasting.

On Tuesday night Kate Speke-Adams, the Foundation’s Head of Land Use, hosted a meeting for a group of 50 Herefordshire farmers and associated businesses to discuss what they could do to help. It is important to stress that this meeting was instigated by farmers concerned with the health of the Wye. While the sector has been widely vilified over the Wye algae issue, it must be remembered that many farmers also retain a deep affection for the rivers and streams passing through their land and the wildlife within.

Also attending were representatives from the Environment Agency and Lancaster University’s Rephokus project, who explained the proportion of phosphorus attributed to agriculture, the ways it is finding its way into the river and the Wye catchment’s “mass balance” of phosphorus that clearly shows how this situation has developed over time to where we are now. Presented with all the data and modelling, the consensus in the room was of shared responsibility. There was an agreement that the industry needed to be a proactive and make significant changes to reduce its phosphorus contribution.

This was very rewarding for us to hear. The challenge now is drawing together this determination and enable changes to be made in day-to-day farming practices. Concepts that were put forward by attendees at the meeting and in the conversations that have taken place since include:

  •  Adding technology to strip phosphorus from manures and digestate.
  • A scheme whereby farmers commit to making no phosphorus applications to soils that have already reached a critical threshold, and work to run down those reserves within the soil.
  • Supply chain level schemes to process or treat manures so that the phosphorus can be exported from the catchment to areas of the country whose soils are currently in deficit.
  • Expanding research to improve understanding of how our soils and nutrients are behaving, including monitoring the impact of subsequent changes to land management that attempts to influence this behaviour.

The Foundation is exploring these and other measures with food producers and their buyers, along with the water companies, to help solve the Wye’s elevated phosphorus levels. All of the proposals above could deliver reductions but it is imperative that they are also underpinned by regulation against bad practice. The Environment Agency has been allocated an additional two enforcement officers for the English Wye and we look forward to seeing the impact this has on compliance. However, for the health of the whole river to improve, it is also vital that such positive moves are replicated on the western side of the Wales/England border too.

We also need to continue to gather data and improve our understanding of the make-up of the algal blooms. The huge expansion in citizen scientists offering to help with monitoring is helping enormously and the Foundation is also installing more monitoring sondes in both rivers. While citizen scientists can monitor SRP levels, complex and expensive sondes are the only real way of sampling total phosphorus. Both, however, will be crucial in determining how successful the solutions described above will be in solving the problem. We will need everyone’s support to install more sondes, maintain them, to analyse and disseminate the results and to devise and deliver the solutions.

Tackling the algae issue will take time. There is no quick, easy solution. Even if we stop all the phosphorus entering the river tomorrow, the high levels already within the catchment’s soils will take decades to run down. But despite everything else that is going on, the health of the UK’s rivers are firmly in the limelight at present and that gives us the opportunity to enable the changes required.


Ithon Sonde Data

Fish Legal

Rephokus Project, Lancaster University

Farmers Weekly: “Wye catchment farmers vow to limit phosphate losses”

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