Irish waters reflect changing climate

IRELAND is neatly placed to become a research centre into the effects of climate change on the oceans and marine life and the knock-on consequences for the fishing industry.

While over-fishing is a key cause of shortages and the virtual decimation of some species, such as cod, there’s growing evidence many species are increasingly affected by climate change, particularly those in warmer water.

Significant observations in recent years include rises in sea surface temperature, higher waves off our southwest coast and an increase in the number of warm water species in Irish waters, ranging from microscopic plankton to swarms of jellyfish. Ireland is strategically placed to play a key role in monitoring ocean-induced changes in our climate and environment, says Marine Institute chief executive Dr Peter Heffernan.

This is because the warm southern waters of the Atlantic drift come closer to Ireland than any other country in Europe, where they merge with the cooler northern waters off the coasts of Galway and Mayo. It is here the predicted changes in sea life are most likely to occur, making Ireland an ideal laboratory for the study of marine climate change.

What has been described as a milestone report on the effects of climate change – Irish Ocean Climate and Ecosystem Status Report 2009 – was launched last month and is one of three research projects in the area.

The experts say changes will be primarily driven by the Atlantic Ocean, so research is urgently needed to improve our ability to predict marine climate change and deal with the environmental consequences that might follow.

A key finding of the report is that increases of sea surface temperature of 0.6°C per decade have been taking place since 1994, which are unprecedented in the past 150 years. This, in turn, is linked to an increase in microscopic plants and animals, along with species of jellyfish.

Further up the food chain, increased numbers of most warm water fish species have been observed in Irish waters, along with sightings of exotic species such as snake pipefish. Declines in seabird numbers have also been observed and may have a climate link.

The research, under Dr Glenn Nolan of the Marine Institute, examined some information going back five decades and the movements of salmon, trout and eels with the specific aim of identifying any pattern that might be linked to climate change.

Marine scientists and fish experts from around the world recently attended a conference at Queen’s University, Belfast, to discuss the latest situation and share their research.

Their main focus was the warming of fish habitats. Some evidence suggests that parts of the North Sea, for example, may have increased by more than 1°C in the past 30 years. Such a rise in sea temperatures can have a dramatic effect on fish.

Warm water southern fish are becoming increasingly abundant in northern waters, while northern fish more at home in colder water appear to have shifted further north and to deeper water to escape warming.

Scientists have discovered that climate change has also affected the timing of fish migrations, by up to two months in the case of some species. That is enough to have a substantial affect on the survival of young fish and on fisheries capture rates.

The conference organiser, Dr Chris Harrod, a lecturer in fish and aquatic ecology at Queen’s, pointed out that changes in the life pattern of some warm water species, such as the sardine, have been closely related to changing water temperature. As waters heat up and ecosystems change, fish populations are altering in size and distribution and this will lead to big changes for the fishing industry.

Fish that prefer cold water habitats, including trout and char, are already showing signs of the difficulty with climate change, with major declines in both numbers and distribution. Interestingly, a rare char is still found in Killarney Lakes and is believed to be a relic of the Ice Age. However, not enough research has been done to find out if the Killarney char is affected by climate change.

As our waters heat up, cold-adapted fish such as Atlantic salmon, Arctic char and pollan (which is found in no other European country) are under particular threat. Populations that depend on these fish will also have to adapt to change, according to Mr Harrod. Eel and pollan populations in Lough Neagh are already showing signs of decline Hans Portner, of the Alfred Wegner Institute, in Germany, told the conference that a process of “Mediterranisation” was taking place in the southern part of the North Sea, with cold water species like cod moving out and the warm water species moving in instead.

On the other hand, fish living in the coldest waters near the poles will have nowhere to escape to as the water slowly warms and will be trapped. And experts say it could all happen this century.