Ocean acidification changing key organisms which form the basis of the marine food chain, say Swansea University researchers

OCEANS and marine life face a more uncertain future because ocean acidification, caused by climate change, is altering the growth of the organisms which are the basis of the entire food chain at sea. That is the finding of a Swansea University-led research team.

Ocean acidification has been described as “the other CO2 problem”, and is also caused by rising levels of carbon dioxide in the atmosphere. This carbon dioxide dissolves into the ocean, making it more acidic. Ocean acidification is already happening yet, say scientists, we still know little about its impacts and implications.

The research team also looked at the combined effects of acidification together with a process called eutrophication, which is when the sea becomes enriched with nutrients such as fertiliser and which can in turn encourage the spread of harmful algae.

They studied how three types of phytoplankton, the tiny organisms at the bottom of the food chain, responded to different levels of acidity in seawater: existing levels, a more acidic level likely in future with ocean acidification, and a more alkaline level.

The researchers found that the growth of phytoplankton was most predictable at the existing level of seawater acidity.

The growth was most variable – and thus least predictable – at the more acidic level likely in the future due to ocean acidification.

The researchers said we were more likely to see more frequent instances of “harmful and ecosystem disruptive algal blooms, and increases in hypoxic and anoxic zones (deprived of oxygen), affecting fisheries and thence food security”.

The team included researchers from Swansea University’s Centre for Sustainable Aquatic Research, with colleagues from Plymouth, Denmark and the USA. Their research has been published in the Proceedings of the Royal Society B.

Dr Aditee Mitra of the Centre for Sustainable Aquatic Research, and one of the authors of the paper, said: “Ocean acidification is unquestionably due to carbon dioxide released by human activity. Microalgae (phytoplankton) and indeed all life in the oceans are facing more acidic conditions. This is affecting the competition between different species and thus changing patterns of growth.”

Professor Kevin Flynn, head of the centre and lead author of the paper, said: “The implications of our results for shifting plankton successions in shelf seas are numerous and far-reaching. They indicate patterns of change that will affect fisheries and the health of coastal waters.

“Life in the oceans is driven by the growth of plant-like microalgae like phytoplankton. Our work shows that changes to phytoplankton will impact on the very base of the food chain, affecting marine life through to fish and whales, and thence also us.”

South Wales Evening Post, 26 February 2015. Article.

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