Irish oceans show increased acidity and harmful algae growth

5 May 2023

Image: © Cristi/

A Marine Institute report highlights that 40pc of Ireland’s population live close to coastal regions, making it ‘critical’ to further understand how our waters are being hit by the climate crisis.

A new report has listed the various threats facing Ireland’s oceans, with evidence of rising sea levels, higher surface temperatures, greater acidity and a growth in harmful algae species.

The Irish Ocean Climate and Ecosystem Status Report 2023, published by the Marine Institute, highlights that many climate threats are impacted Ireland’s oceans.

The report was launched yesterday (4 April) by Minister for Agriculture, Food and the Marine Charlie McConalogue, TD.

The findings show Irish sea levels have risen by roughly 2mm to 3mm per year since the 1990s, with a larger sea level rise in Dublin and Cork. Meanwhile, sea surface temperatures are roughly 0.4 degrees Celsius warmer this century compared to the period between the 1960s to 1990s.

Recent years have seen a slight cooling period in Irish waters, but the report suggests this is linked to a slowdown anomaly of the Gulf Stream system.

This system of ocean currents transports warm shallow water north and returns cold deeps water south, and is a “major factor” in Ireland’s mild climate. The report warns that the Gulf Stream system is predicted to decline due to the climate crisis, which could impact Ireland’s future climate.

Due to the oceans absorbing about one third or one quarter of human-made CO2 emissions each year, the report claims that rising emissions levels are altering seawater chemistry.

This process is known as ocean acidification and can result in reduced “calcium carbonate saturation states”, which impacts the ability of organisms to form shells and skeletons.

A growth of harmful algae species has been observed in Irish waters, which impacts the seafood sector and can “potentially”  impact humans.

The report said many of the changes observed in Irish waters mirror those observed at a global scale. Many of the findings are put into context with wider international climate change efforts such as the International Panel on Climate Change’s assessment reports.

A call for action

Speaking about the report, Marine Institute CEO Paul Connolly said changes in the ocean affect seafood, transport and biodiversity and warned of the potential future for Ireland’s waters.

“The oceans provide 50pc of the oxygen we breathe,” Connolly said.  “They are a critical element of the global climate system in their role to regulate atmospheric processes and for distributing heat, salt and organisms.

“This research shows the impact of climate change is already evident in Irish marine waters with patterns of harmful algal blooms changing. The ocean off the southwest coast will likely become warmer and less salty by the year 2035.”

The report lists various recommendations to monitor and address the changes happening in Ireland’s waters. This includes further monitoring of sea level changes and their causes, which the report listed as “crucial for effective climate adaptation”.

Minister McConalogue said it is “critical” that scientists and policymakers have “high-quality evidence in relation to the changing state of our seas”.

“This begins with the collection and observation of essential ocean variables from ships, buoys and robotic platforms in our territorial seas and beyond, measuring ocean temperature, salinity, sea level, ocean carbon, plankton and fish species,” McConalogue said.

“We also need to predict or project what will happen to our oceans in the future using climate models.”

Last year, the Marine Institute’s Dr Caroline Cusack said one of the biggest challenges in ocean observation is the collection of data, as “the ocean is a difficult and at times a hazardous space to work in”.

10 things you need to know direct to your inbox every weekday. Sign up for the Daily Brief, Silicon Republic’s digest of essential sci-tech news.

Leigh Mc Gowran is a journalist with Silicon Republic