Water Quality in Slovenia - Agencija RS za okolje

2.4.4
Quality of Shellfish Waters
S U R F A C E W A T E R S
Shellfish are molluscs living in hard shells. Their shells can be of various shapes and they protect their
soft bodies from threatening dangers. Many shellfish live in the sand or mud at the sea bottom, some
can be found attached to a hard surface (rock), and some move around by swimming. They feed on tiny
particles of food floating in the water - they open their shells and filter the water through their gills.
Shellfish are popular as food as well. If they are grown for the market, special floats are made in
shellfish farms, thus providing them with conditions similar to those of their natural environment.
Because of filtering the water, they improve water quality, but at the same time hazardous substances
accumulate in their bodies. It is therefore essential that the shellfish intended for human consumption
live in a clean environment. In the 1980’s the European Union adopted the Directive on the quality
required for shellfish waters (59). Directive requires that the Member States protect and/or improve
the quality of coastal and brackish water bodies in which shellfish live, in order to contribute to the
quality of edible shellfish products.
The above-mentioned Directive was entirely translated into the Slovenian legislation with the
Decree on the quality required of water supporting marine bivalves and gastropods (60), Rules for
the monitoring of the quality of waters supporting marine bivalves and gastropods (61) and Rules on
the determining marine areas where the quality of water is suitable to support marine bivalves and
gastropods (62).
Monitoring according to these regulations has been carried out since 2003 (63). Three monitoring
sites have been chosen in the shellfish growing areas, i.e. in the Piran Bay, Strunjan Bay (monitoring
sites 0035 and 0024) and at Debeli rtič (monitoring site 00DB).
The basic physico-chemical parameters, organic halogens, metals in water, and cadmium and mercury
in both sediment and molluscs flesh are monitored, as part of the programme, with the frequency of
twice to 12 times a year. In the period from June to October, analyses of toxic phytoplankton are also
included in the programme.
Map 10: Shellfish growing areas, and monitoring sites
49