Effects of naturally acidified seawater on seagrass calcerous epibionts -

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How oceans are changing

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INTRODUCTION

The ocean plays a crucial role in sustaining life on Earth and is a key element in climate change. But, says Dr Gunnar Kullenberg, Executive Secretary of UNESCO's Intergovernmental Oceanographic Commission (IOC), "Ocean issues are not receiving the attention they ought to be given." The ocean is a resource that is less well known than some distant planets and undoubtedly contains a resource potential that remains partly untapped. But this resource is limited, both in capacity and in its ability to absorb effects of reckless development and pollution. Signs of stress are already visible, especially in low-lying coastal areas and small islands. The picture of the ocean that is emerging from shared observations all over the world is not very comforting. The catalogue of symptoms of disease include: pollution, exhausted fishing stocks, disappearing coastlines, rising sea level, increasing surface temperatures that threaten the deep ocean currents, more frequent storms, melting ice caps... When we understand the ocean system better, we will be able to predict some of the changes expected in the next century and, hopefully, offset them through intelligent, co-operative action. In the shorter term, better and more systematic observations of the ocean will enable us to forecast imminent disasters from storms, floods and drought and mitigate their effects, by warning the populations at risk.
Text courtesy of UNESCO

Photo title: The world's oceans

Photo credit: Geostationary Operational Environmental Satellites (GOES), NOAA

Flooding of the Bering Land Bridge, A Geospatial Animation

Sea level rise between Siberia and Alaska

During the Last Glacial Maximum, about 21,000 years ago, global sea level was approximately 120 m (400 ft) lower than today. The Bering Land Bridge existed as a vast tundra plain connecting Asia and North America. As the world's glaciers and ice sheets melted over the following millenia, rising sea level flooded the land bridge - blocking migration routes for animals and humans.

<-- The reduced-resolution animation at left shows sea level rising across the land bridge between Siberia (left) and Alaska (right). Movement is in 3,000 year steps. Refresh or reload the page to see the animation again.

Full-resolution QuickTime movies are available for analysis, education, and outreach at The Institute of Arctic and Alpine Research (INSTAAR).
Text provided courtesy of INSTAAR.

Photo title: Sea level rise between Siberia and Alaska

Photo credit: Institute of Arctic and Alpine Research (INSTAAR)

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Institutional Contact (1)

Title

Effects of naturally acidified seawater on seagrass calcerous epibionts ( DOCUMENT )

Author(s) / Editor(s)

Sophie Martin, Riccardo Rodolfo-Metalpa, Emma Ransome, Sonia Rowley,and Jason Hall-Spencer

Description

Surface ocean pH is likely to decrease by up to 0.4 units by 2100 due to the uptake of anthropogenic CO2 from the atmosphere. Short-term experiments have revealed that this degree of seawater acidification can alter calcification rates in certain planktonic and benthic organisms, although the effects recorded may be shock responses and the long-term ecological effects are unknown. Here, we show the response of calcareous seagrass epibionts to elevated CO2 partial pressure in aquaria and at a volcanic vent area where seagrass habitat has been exposed to high CO2 levels for decades. Coralline algae were the dominant contributors to calcium carbonate mass on seagrass blades at normal pH but were absent from the system at mean pH 7.7 and were dissolved in aquaria enriched with CO2. In the field, bryozoans were the only calcifiers present on seagrass blades at mean pH 7.7 where the total mass of epiphytic calcium carbonate was 90 per cent lower than that at pH 8.2. These findings suggest that ocean acidification may have dramatic effects on the diversity of seagrass habitats and lead to a shift in the biogeochemical cycling of both carbon and carbonate in coastal ecosystems dominated by seagrass beds.

Keywords

ACIDIFCATION;

CO2;

CARBONATE PRODUCTION;

CALCEROUS EPIBIONTS;

CAROLLINE ALGAE

Geography Keywords

EUROPE

Content Language(s)

English

File Location

1237198530353_Martin_etal2008.pdf