Use of radiocarbon dating to interpret past environments of maerl beds

Beds of nongeniculate coralline algae, known as rhodolith beds or maerl, occur throughout the world. They are protected under European legislation due to their high conservation value; however, within Europe there are significant areas of dead maerl deposits and the causes of the demise of these past habitats is not always clear. In this study we utilize radiocarbon dating techniques to constrain the time of the maerl bed deaths from a number of historical or pre-historical possibilities. We highlight the threat from burial to these precious habitats, which has implications for contemporary conservation. We found that a maerl bed in Strangford Lough, Northern Ireland, was killed around 4200 C-14 BP (before present, AD 1950), which is the same as a previously reported maerl bed death in Marseille, France. This also coincides with evidence of a significant period of climatic change. The case study of Belfast Lough highlights the modem threat to maerl bed by sedimentation caused by channel dredging, which complements previous experimental work.