Maerl is a term used for loose-lying calcified algae that can accumulate over thousands of years. They develop into a dense and valuable habitat with rich biodiversity and are also considered valuable as a mineral deposit. In the past environments of Strangford Lough, Belfast Lough (Northern Ireland) and Milford Haven (Wales) there were larger live beds of maerl than are present today. We have investigated the possible causes for the demise of these deposits by utilising radiocarbon dating. The study included radiocarbon dating of mollusc shells of known collection age from the Ulster Museum, obtained prior to industrial input of 14C into the marine environment. The main aim of this study was to examine specific examples of extinct maerl beds in the United Kingdom and Ireland, and use the evidence gathered to evaluate potential threats to present day maerl habitats. If the anthropogenic causes of historical maerl bed extinctions can be determined then justified advice for conservation management of present day maerl beds can be provided. In both Belfast Lough and Milford Haven radiocarbon dating has eliminated recent 20th century construction work as a cause of maerl bed extinction.
This work is supported by EU Framework 6-HIPPOCRATES (NMP3-CT-2003-505758), NERC (radiocarbon grant 15.47) and the Department of Education and Learning for Northern Ireland.
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