Introduction, sites, selection criteria and site operators

Unlike the AL:PE project, that established the extent of lake acidification and air pollution across the remote regions of Europe, the four work packages of the MOLAR project concentrate on a select number of key sites (Figure 1). Although many of the activities within each package are specific to that package, some activities (e.g. fieldwork, basic water chemistry), are common to two or more packages.

The project is undertaken by a consortium of laboratories from EU and non-EU countries. Participation of non-EU partners strengthens and extends the geographical transect of sites across the continent of Europe (see Figure 1) and brings specific expertise (e.g. zooplankton and microbial analyses from FSCU and HBI-ASCR, access to pan-European climate history datasets from EAWAG).

The AL:PE project has established an excellent network of study sites (Figure 1) throughout Europe from which to choose the most suitable sites for each work package. Three new EU sites, however, are included. These are:

- Limgambergtjern - this arctic site in Northern Norway is more accessible than the AL:PE site Arresjoen in Svalbard and therefore is a more suitable site for the frequent seasonal sampling required by this project. The region is contaminated by air pollution from the Kola Peninsula and the site is therefore included in work packages 1 and 2.

- Saanajarvi - this site in northern Finland has been selected as a very clean site in the arctic to be included in work package 3. It also increases the number of arctic sites in the programme and extends the collaboration to include Finland as a new member state.

- Gossenkollesee - this site in the Austrian Alps has been selected because of the major investment in on-site infrastructure (research station, weather station, mains electricity etc.) by a national research programme that is not available at the AL:PE site Schwarzsee Ob Solden.

Sites in Slovakia, Poland and Russia are taken from the AL:PE network. However, Zgornje Krisko Jezero in Slovenia is substituted by Jezero Ledvicah, located in the same region but with a faster sediment accumulation. Hagelsee and Jorisee in Switzerland are new sites and represent the inclusion of Swiss scientists in the project. The relationship between individual sites, the AL:PE network and the MOLAR project is shown in Figure 1.

All sites strictly adhere to the characteristics established for AL:PE, namely that they should be above or beyond the regional timberline and have no evidence of human disturbance in the lake or catchment area. In other words any changes in their ecology can only be due to air pollution, climate change and natural variability.

Figure 1

In contrast to AL:PE where sites were sampled only once per year, MOLAR sites will be sampled intensively throughout a period of 18-24 months to provide data for dynamic modelling. For this reason site selection is based on a combination of site quality, site accessibility, and availability of prior chemical and biological data. Data from four less-intensively sampled secondary sites (Figure 1) and from other AL:PE sites not included for specific study within MOLAR will be used to enhance model validation.

In addition to these requirements, criteria for site selection for work package 1 also includes sensitivity to acidification, and for work package 3, minimal pollution. Three sites are common to all themes: Ovre Neadalsvatn in Norway, Estany Redo in the Spanish Pyrenees and Gossenkollesee in the Austrian Alps (Figure 1). Four sites are used for two strands and 10 for one only.

Because many sites are included in more than one work package and because of the sampling frequency and the need to maintain on-site equipment, each site has a designated "site operator" responsible for the field sampling across the scientific strands undertaken at that site. Site operators are therefore a unifying component of the overall work programme.