ABSTRACT1. Maerl beds occur worldwide and are formed by an accumulation of unattached calcareous red algae (Rhodophyta).2. Maerl-forming algae grow in a superficial living layer on sediments within the photic zone. 3. Maerl beds are spatially complex habitats with a high degree of species and trophic group diversity.4. The European Commission's 'Habitats Directive' mandates the conservation management of two of the main European maerl-forming species, Phymatolithon calcareum and Lithothamnion corallioides.5. Mediterranean maerl beds are to be considered for inclusion in national inventories of sites of conservation interest, as required by the SPABIM Protocol of the Barcelona Convention.6. In spite of their importance, and the requirement for their conservation management, European maerl grounds suffer a variety of anthropogenic perturbations including direct exploitation through extraction, fishing impacts and chemical pollution by organic matter and excess nutrients.7. The ecology of northeast Atlantic and Mediterranean maerl beds has received little attention, in contrast to other marine communities (e.g. kelp forests, sea-grass meadows). * Correspondence to: P.G. Moore, University Marine Biological Station Millport, Isle of Cumbrae, KA28 0EG, UK. E-mail: pmoore@udcf.gla.ac.uk y Authorship alphabetical: cite as BIOMAERL team z Coordinator 8. Key conservation and management measures proposed include: the recognition that maerl beds are non-renewable resources and cannot sustain direct exploitation; prohibitions on the use of towed gear on maerl grounds; moratoria on the issue of further permits for the siting of aquaculture units above maerl grounds; monitoring of existing exploited or impacted maerl beds; the designation of 'no-take' reserves; measures to limit the impacts that might affect water quality above maerl beds; a programme of monitoring of the 'health' of European maerl beds; an awareness campaign on the biological importance of maerl beds; a higher conservation status for maerl habitats and maerlforming species in European legislation; and further research on maerl ecosystems.

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Connectivity between ecosystems has been widely recognised as an important issue in ecological studies. Sandy beaches are very dynamic and open ecosystems, mainly supported by allochthonous subsidies of stranded organic matter (mostly macroalgae), also termed wrack supply. The magnitude and composition of algal wrack biomass throughout the annual cycle was assessed for 6 sandy beaches on the Galician coast, NW Spain. The effect of wave action and the topographical features of each beach in the wrack deposition process were investigated. Wrack species composition, biomass and coverage were measured monthly along 6 transects at each beach. Mean dry weight of wrack fluctuated from 14 ± 5.3 to 9189 ± 3594 g m -1 (along transects) between locations. Wrack was predominantly composed of brown algae, which accounted for 70% of the average biomass year round; the dominant species were Cystoseira sp. (30.3 ± 17.4%) and Sargassum muticum (14.2 ± 7.1%). A cyclical pattern in wrack composition, coupled with the life cycle of the predominant macroalgae, was observed. Wrack biomass and species composition were mostly explained by wave height and the ratio of beach length to beach area. Small, wave-sheltered beaches received the largest inputs of wrack, and had the lowest relative contribution of brown algae. These results provide evidence that variability in wrack supply on sandy beaches can be explained through interactions between wave exposure, coastal topography and seasonality.

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