Different types of methodology are required for the monitoring of different target groups. The key to biological montoring is the identification of indicators, indicator species or indicator communities. However, at present we have very little information on maerl bed species that may function as "sentinel organisms", i.e. those indicator species which, for example, accumulate pollutants in their tissues and can therefore be used as bioindicators (Phillips & Rainbow, 1993). The first potential sentinel species has been identified by the BIOMAERL team (P.G. Moore, pers. comm.). The diversity of the polychaete Hesione pantherina is much reduced at eutrophicated sites in Brittany compared to non-impacted sites; this species may be especially sensitive to eutrophication. Until sentinel species are identified, all species and their abundances should be monitored regularly, as far as possible, using appropriate methodology for each life-form.

The Biomaerl team, while developing a comprehensive inventory of the biota at the study sites, have likewise concluded that it is necessary: a) to utilize as many methods of sampling as possible; and b) for sampling to take place over all seasons of the year. Not every organism present on the ground is captured in any one type of gear, and there are strong seasonal influences at work both in terms of species occurrences (migrations), and/or population fluctuations. The methodology they have used for biological sampling of the maerl biota, to obtain detailed data on population structure, biomass and population density for the commonest and/or structurally most important key species from each ground, is a combination of:

  • sampling directly by divers using quadrats and/or cores in situ,
  • deployment of a variety of indirect sampling gears from ships (grabs, box corers).
  • Infaunal samples being sieved through a 1 mm screen as standard; comparison of megafauna and macrofauna.
  • The use of towed dredges and trawls and direct diver observation to obtain additional, semi-quantitative and qualitative faunistic/ floristic data.

Next Section                     References