Environmental campaigner and teacher, Brian Murray looks the damaging effects of algal blooms and the reasons we’re not stopping outbreaks.
IN 2023, IRELAND’S ongoing struggle with biodiversity loss took centre stage when satellite imagery captured a disturbing phenomenon. #Lough_Neagh, the largest freshwater lake on the island of Ireland, was blanketed by an algal bloom so severe it was visible from space. This event was a stark visual representation of the nationwide environmental crisis affecting Irish waters.
The Lough Neagh outbreak was found to be the dangerous result of bacteria from livestock waste and human effluent, and caused major public health concerns at a site that provides more than 40% of Northern Ireland’s drinking water. A study of the area found that the presence of the algae toxins may have also contributed to the death of animals such as dogs that entered the water at the time.
Algal blooms, the rapid proliferation of algae populations in freshwater and marine environments, are primarily driven by excess nutrients, specifically nitrogen (N) and phosphorus (P), entering these delicate ecosystems.
This process, known as eutrophication, creates an environment ripe for explosive algae growth when combined with other favourable environmental conditions such as warmth, still water and sunlight.
According to the Environmental Protection Agency (EPA), agricultural practices are by far the most significant contributors to nutrient pollution in rural waters in Ireland.
Intensive farming, including slurry spreading and the widespread application of chemical fertilisers rich in nitrogen and phosphorus, introduces excessive nutrients into waterways. Rainfall washes these nutrients from fields into rivers and lakes, setting the stage for algal blooms.
The same EPA report notes that urban wastewater treatment also plays a critical role in polluting Ireland’s water. Ireland’s ageing infrastructure struggles to adequately treat sewage before discharging it into rivers and coastal waters, allowing nutrient-rich wastewater to enter sensitive aquatic ecosystems regularly.
Despite numerous reports highlighting the issue, substantial investment and improvements in wastewater treatment infrastructure remain slow. I recently discovered an algal bloom (pictured) in the pond I manage as part of the microWild biodiversity project in Wicklow.
Weeks earlier, heavy rainfall had followed slurry spreading very quickly, and the inevitable happened. These unwelcome nitrates had been washed off the land before fixing and polluted the pond’s water source.
The damage caused by blooms
Algal blooms have devastating impacts on the environment, wildlife and human communities. Firstly, many species of algae involved in blooms, such as cyanobacteria (blue-green algae), release toxins harmful to aquatic life.
Fish and invertebrates can be killed outright, while prolonged exposure severely disrupts reproductive cycles and immune systems, causing long-term damage to biodiversity.
The toxins also pose significant risks to human health. People swimming in contaminated waters may experience skin rashes, respiratory distress and gastrointestinal illnesses. Each year, numerous pets tragically die after ingesting water contaminated by toxic algae.
Furthermore, algae reduce water clarity, blocking sunlight from penetrating deeper water column layers. This lack of sunlight severely impacts underwater plant life, crucial feeding, breeding and sheltering habitats for aquatic fauna. Without these plants, ecosystems collapse, triggering cascades of biodiversity loss.
Additionally, algal blooms dramatically reduce oxygen levels in the water. When algae die, their decomposition consumes vast amounts of oxygen, creating hypoxic conditions. These “dead zones” cannot sustain life, sometimes causing mass fish die-offs and often bringing long-term disruptions to ecosystem balance.
The victims
In algal bloom scenarios, there are no winners except perhaps the algae. The victims, however, are numerous and varied. Aquatic ecosystems suffer immediate and often catastrophic damage, with repercussions that echo through food chains for months or even years.
Sensitive species, including certain fish, amphibians and invertebrates, can face local extinction events.
Communities reliant on these waters for recreation, tourism, or drinking supplies also suffer economically. In towns around Lough Neagh and elsewhere, the impacts of algal blooms ripple through local economies, affecting businesses dependent on tourism and recreation.
The Vartry Reservoir in Wicklow has suffered many algal blooms, which clog up the sand filtration capabilities, and has seen its output drop from 75 million litres of drinking water per day to just 40 million litres per day.
The perpetrators
Identifying those responsible is complex. On the surface, it is easy to blame intensive agriculture or inadequate wastewater management. Indeed, these sectors bear the lion’s share of acute responsibility, as they tend to be the direct perpetrators of the environmental insults.
Farmers struggling to maintain profitability often rely on chemical fertiliser and slurry practices that encourage algal blooms, which are well known to damage waterways. Similarly, local authorities tasked with managing sewage treatment infrastructure face budgetary and logistical constraints that slow progress toward necessary upgrades.
However, responsibility also lies with policymakers and regulators who fail to enforce existing environmental laws adequately or to prioritise environmental protection in decision-making processes. Years of inadequate action, insufficient enforcement and underfunded infrastructure investments have created conditions ripe for recurring crises.
The Government’s stance
The Irish government declared a biodiversity emergency in 2019 and has historically acknowledged the severity of nutrient pollution and eutrophication in Ireland’s waterways. Still, it has consistently fallen short of effectively addressing it. Although national regulations exist, enforcement and compliance have been inconsistent and insufficient.
Critics argue that agricultural and business interests frequently outweigh environmental priorities, delaying necessary reforms and investments. The Nitrates Derogation is a perfect example of this. Irish farmers can apply to use higher volumes of nitrates per hectare than the EU recommends.
The opening line of that document speaks volumes. “Derogation for Ireland pursuant to EU Council Directive 91/676/EEC concerning the Protection of Waters against Pollution caused by Nitrates from agricultural sources.” It is nothing short of an acknowledgement that the derogation will cause nitrate pollution of our waters.
Moving forward
Addressing Ireland’s algal bloom crisis requires a multi-faceted approach. Immediate steps include stricter enforcement of agricultural regulations, increased investment in wastewater treatment infrastructure, and widespread adoption of sustainable farming practices.
Public awareness campaigns are crucial to fostering understanding and action among communities and stakeholders. Education about nutrient pollution, its impacts and practical mitigation steps can drive collective action.
Right now, Ireland faces a pivotal moment in its environmental history. Confronting the algal bloom crisis is not merely a conservation imperative, but a moral and social responsibility. By acknowledging the interconnected roles played by agriculture, urban infrastructure and governance, Ireland can embark on a path toward restoring its freshwater ecosystems and safeguarding biodiversity for future generations. But is anyone brave enough to take it on?
It’s hard to hold out hope when Minister Michael Healy-Rae of the Department of Agriculture, Food, Fisheries and the Marine was recently touting the idea of planting trees on peatland as a means of reaching Ireland’s reforestation goals.
With the game of business-as-usual being played by successive governments, I don’t think it will be too long before the Blessington Lakes (Poulophouca Reservoir), the area in which I live, suffers the same fate as Lough Neagh. It supplies roughly half of Dublin’s water. Then we can cue the hand-wringing, laments and echoes of “if only we had known”.
