Basic Management Guidance
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.
Maintenance and restoration
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
Integrity of sites of maerl beds
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.
Avoidance of habitat deterioration
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
- 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
Local human needs
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