The Rivers Trust Conference 2025: A Bloomin’ Disaster — The causes and costs of blue-green algae

The Rivers Trust’s Annual Conference in 2025 will examine the vast impacts of blue-green algal blooms on waterbodies whilst uncovering the root causes of how and why they occur, and the integral roles played by our rivers and catchments.

Blue-green algae are more and more present in news headlines, not least in relation to Lough Neagh, the UK’s largest lake. But this ecological disaster is anything but new and is increasing in frequency and severity. They are not actually algae, but a group of photosynthesising bacteria called cyanobacteria - microscopic organisms that naturally occur in freshwater bodies. When conditions are favourable, cyanobacteria proliferate to form the blooms that appear like algae, causing a range of subsequent problems that will only worsen in the future. Pollution from catchments and rivers can have significant impacts on waterbodies such as lakes, creating the perfect storm of conditions for blue-green algae to thrive.

The impacts of these blooms go well beyond them being an eye sore to our waterbodies; they affect tourism, recreation, fisheries, agriculture, and property values, all of which are essential components of sustainable social and economic development. This blanket of blue-green algae suffocates our water bodies by reducing oxygen and sunlight and releases harmful toxins, posing health risks to not just wildlife, but people too.

Whilst environmental and climatic factors like warmer temperatures, excess nutrients, and low rainfall are typically known as the key drivers for triggering algal blooms, ongoing scientific research highlights how the causes are much more varied and have been compounded over time. In fact, algal blooms are largely a symptom of systemic failures of land and sewage management, exacerbated by the increasing pressures of climate change. Unravelling the myriad causes of blue-green algae will help us to restore balance in our catchments and improve environmental health in the round.

This online conference will delve deeper into the features, causes and impacts of blue-green algal blooms on water bodies, communities, and the economy, as we try to mitigate their effects and find ways to reverse the factors causing their proliferation. Addressing the causes of blue-green algal blooms is no easy feat, and will require multi-disciplinary and multi-sectoral solutions at a whole catchment scale, but further understanding this is a step in the right direction.