The time scale over which a management plan for a maerl bed is to operate has to be decided. It should be noted that political and biological time spans are irreconcilable. There is at present too little known about the long term effects on the maerl biotopes of many present-day human activities. Maerl is one of the world=s slowest growing plants and, although any identifiable threat may appear to have only limited consequences in the short term (20-50 years), in the life-span of the habitat (6 000 years and more) even apparently small, insignificant present-day perturbations may have a devastating effect on the habitat.

Maerl beds should be managed in order to contribute to the maintenance or restoration of the favourable conservation status of the natural habitat and species composition of the biotope. Each maerl bed, and in some cases each area within a maerl bed, has a different biological composition, which, given the mobile nature of the habitat, is more than likely to be variable over time. Amongst many detailed gaps in our knowledge, are the time scales of the natural variability of the maerl habitat and the extent of temporal variation in species composition.

One important consideration is that scientific investigation and the monitoring process itself do not damage maerl beds. Extensive use of towed vehicles, for example, might have an impact of maerl beds, as might the extensive use of suction samplers which create silt plumes.

The conservation status of the maerl beds must be considered before any activity, plan or project is undertaken that is likely to have a significant effect on the maerl biotope.

Monitoring the marine environment is a time-consuming and very expensive task, requiring high levels of expertise in a wide range of techniques. The maerl biotopes are extraordinary for their species richness and diversity and as such present a challenge with regard to monitoring their status. Monitoring of selected maerl biotopes must be conducted in such a manner that biologically and statistically significant changes can be linked to changes in local conditions, management practices or human activities. Other maerl biotopes could be monitored at a lower level.

This requirement of the Habitats Directive implies that whatever monitoring programme is implemented must be adequate to enable the present status, the optimum status and any changes in the status of the maerl biotopes to be detected. Physical parameters should be checked regularly, such as

• the dimensions of the maerl bed.
• the density of the epiphytic cover.
• the silt content of the background sediment within the bed.
• Water quality, salinity and temperature need to be monitored on a time scale and to a degree of accuracy that is probably (as a statistical statement) able to identify any natural or anthropogenic events which might be detrimental to the maerl biotopes.
• The percentage of living maerl thalli in the surface layer of the biotope should be monitored.
• Species diversity within the maerl biotopes should be monitored; this will include the epiflora and epifauna as well as the endofauna. Meiofauna will be an important category to include.

Despite all the strictures within the Habitats Directive with regard to the conservation of the environment and the species therein, the economic, cultural, social and recreational needs of the local people are to be taken into account.

International experience demonstrates that local co-operation and voluntary systems alone are, in practice, inadequate to protect habitats and the species that they sustain.

Any management scheme will be reliant on the quality of the monitoring programmes to provide adequate scientifically robust data to support any legal cases which may be required in order to defend the maerl biotopes against "local needs" prejudicial to the conservation of the biotopes.

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