We have seen some dramatic effects of storms and cold water around the UK in the last few months, but at the other end of the spectrum rising sea temperatures are also an issue. We understand the implications of coral bleaching but these two examples with sea grass and starfish provide more evidence of wide ranging impacts of warming implicated with shallow seas species and habitats.

Marine heatwave set off ‘carbon bomb’ in world’s largest seagrass meadow

22% of seagrass in Western Australia’s Shark Bay was lost after 2010-11 heatwave, causing release of up to 9m tonnes of carbon. Over the last century, about 29% of the world’s seagrass has been destroyed and it is estimated it is releasing carbon at a rate similar to the emissions of Australia and the UK combined. A marine heatwave in Western Australia in 2010 set off a massive “carbon bomb”, damaging the world’s largest seagrass meadow, releasing millions of tonnes of carbon that had been collected for thousands of years below the surface. Although Australia doesn’t currently count carbon released from damaged seagrass meadows in its official greenhouse gas emissions, if it did, the results mean those figures might need to be revised upwards by more than 20%. Seagrass is a flowering grass-like plant that grows in shallow waters. It gathers carbon dissolved in the sea and buries it below the surface, often storing similar amounts of carbon in the top metre of sediment as is stored in tropical forests. Recent studies have shown that when the top layer of actively growing seagrass is disturbed – either by local impacts such as boat anchors or climatic impacts like heatwaves – the carbon that has been sequestered over thousands of years can be quickly released.   Click here to read more

Starfish wasting disease – disease and warm water – California & Pacific

It was like something out of a seaside horror movie. Sea stars, once familiar and beautiful and iconic, suddenly had lesions covering their bodies; a sign that something was horribly wrong. Within a day, the stars with lesions started to melt, turning into globs of goo. And, soon after, any sea stars near them suffered the same gruesome fate. In all, from 2013 to 2014, millions of sea stars died, the largest known Sea Star Wasting Syndrome incident on record. The die-off spanned from British Columbia to the shores of Southern California down to Mexico. It was, and is, a mystery. But now, marine scientists are looking in Southern California tidepools and seeing hope — in the form of new, palm-sized sea stars.   The cause – viruses or water temperature – is still a mystery …… In the summer of 2013, an epidemic began sweeping through the intertidal zone off the west coast of North America. The victims were several species of sea star, including Pisaster ochraceus, a species that comes in orange and purple variants. (It’s also notable because it’s the starfish that provided ecology with the fundamental concept of a keystone species.) Affected individuals appeared to “melt,” losing grip with the rocks to which they were attached — and then losing their arms. This sea star wasting disease, as it is known, soon killed sea stars from Baja California to Alaska.

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