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Hunting for lugworms for fishing bait at Brighton beach. Photo: Martin Thomas via Flickr.
Hunting for lugworms for fishing bait at Brighton beach. Photo: Martin Thomas via Flickr.
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Lugworms suffer toxic impact of acidifying oceans

Alex Kirby

30th October 2014

A common marine worm key to the richness of many coastal ecosystems is being damaged by the increasing ocean acidification that was thought to imperil mainly shellfish and coral, writes Alex Kirby. It's an unwelcome sign of more unexpected ecological changes to come.

Lugworms do as important a job as gardeners of our beaches as earthworms do on land, and they bring oxygen down to the underwater sediments.

A common marine worm has alerted scientists to the likelihood that the effects of ocean acidification may be more widespread and severe than they had realised.

The lugworm (Arenicola marina) - common on the coasts of Europe and North America, where it can grow to 30 cms in length and is a bait popular with anglers - is being affected by rising levels of acid in the coastal seas. The acid is also reported to be affecting sea urchins.

This is further confirmation that ocean acidification is affecting species other than those that scientists call calcifying organisms - creatures that rely on calcium carbonate to form shells and similar structures.

The worm is also an important prey species for seabirds and waders that feed on coastal and estuarine mudflats. Any substantial reduction in lugworm numbers could seriously affect the birds that depend on it and wreak havoc on entire ecosystems.

The pH (a measure of acidity - the lower the pH, the more acidic the water) of the planet's oceans is dropping rapidly, largely because the carbon dioxide levels in the atmosphere are increasing. Since carbon dioxide dissolves in water to form carbonic acid, the seas are responding to global change.

Highest rate of ocean acidification since the dinosaurs

Scientists say the oceans are now 30% more acidic than they were at the beginning of the industrial revolution about 250 years ago. The current rate of acidification is thought to be the highest for 65 million years.

Among the sea species most vulnerable to acidification are shellfish, coral and other creatures - including some species of plankton - which suffer because the build-up of acid prevents them from developing their calcium shells.

Animals further up the marine food chain are also at risk when their prey feels the acidity's effects.

Researchers at the University of Exeter's College of Life and Environmental Sciences in the UK have now found that other creatures are also being affected because the growing acidity is increasing their vulnerability to coastal pollutants such as copper.

Writing in the journal Environmental Science and Technology, they explain how they found that the extra copper harms lugworms' sperm, meaning that their young fail to develop properly: "Larval survival was reduced by 24% when exposed to both OA [ocean acidification] and copper combined, compared to single OA or copper exposures."

Rising CO2 increases pollution toxicity

Sperm motility - the ability of the sperm to swim strongly - was damaged by both OA and copper alone, but with added toxic effects when both factors were combined. Individually, both OA and copper also reduced the lugworms' fertilisation success.

One of the report's authors, Dr Ceri Lewis, a marine biologist at Exeter, told BBC News: "It's a bit of a shock, frankly. It means the effects of ocean acidification may be even more serious than we previously thought. We need to look with new eyes at things that we thought were not vulnerable.

"Our work means we are underestimating effects of acidification for coastal invertebrates. We are now realising there are many indirect impacts of ocean acidification on other processes. It could be that we are facing a lot more surprises ahead."

Dr Lewis told the Climate News Network: "Lugworms do as important a job as gardeners of our beaches as earthworms do on land, and they bring oxygen down to the underwater sediments. The discovery that they too are affected means there's a whole new area of concern now, looking at the indirect effect of pollutants and at other species that may be harmed as the acidification increases."

She has also found more evidence that copper pollution is damaging another marine species - sea urchins. They are already affected by the seawater's increasing acidity, which means they have to spend more energy on making their shells and spines.

 


 

Alex Kirby writes for Climate News Network.

 

 

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