Maerl community in the north-western Iberian Peninsula:: a review of floristic studies and long-term changes

1. A review of floristic studies on the Galician maerl community (north-west Spain) and updated information on the distribution of maerl beds, their associated flora and long-term changes is presented. 2. The Galician maerl community has been poorly studied; most of the previous studies were of short duration and focused on isolated beds. Studies on the associated maerl flora and overall Galician maerl bed distribution are required to put these in context with other Atlantic and Mediterranean European areas. 3. A literature review of all Galician studies produced a list of 198 maerl associated species (204 infraspecific taxa including life history stages) recorded from a total of 111 maerl beds. The current survey (2003-2006) increased the Galician maerl epiflora records to 226 species (232 intraspecific taxa including life history stages: 9 Cyanophyta, 160 Rhodophyta, 36 Heterokontophyta and 27 Chlorophyta), highlighting the occurrence of 10 non-native species. The current Galician catalogue is compared with maerl studies from different Atlantic and Mediterranean regions. 4. In order to assess the long-term changes in Galician maerl beds and their conservation status, 60 maerl beds which have been previously studied by various different workers were resampled to compare their current distribution, area and cover with historical data from the literature. 5. A reduction in the study area of maerl beds and their cover was detected. Most of the lost maerl areas were within or in the vicinity of myticulture areas where burial of maerl by fine sediment has a deleterious effect. Copyright (c) 2007 John Wiley & Sons, Ltd.