THE RELATIONSHIP BETWEEN DIATOMS AND SURFACE-WATER QUALITY IN THE HOYLANDET AREA OF NORD-TRONDELAG, NORWAY

Although the ecological effects of surface water acidification are now well researched, factors controlling the abundance and occurrence of aquatic organisms in unpolluted acid-sensitive systems are poorly know n. The Hoylandet region in central Norway experiences relatively low l evels of atmospheric pollution and its surface waters, although acid, are not significantly acidified. Hence lakes and streams in this regio n were selected to study the influence of water chemistry on diatom al gae. Relationships between the two were explored using the multivariat e technique of canonical correspondence analysis (CCA). The principal water chemistry variables influencing species composition of periphyti c diatoms were found to be pH and water colour. Furthermore, the relat ionship between species abundance and pH was sufficiently strong to en able reconstruction of water acidity from diatom data. Establishing th e nature of aquatic communities in atmospherically clean but geologica lly sensitive regions is an important means of identifying control sys tems against which the recovery of acidified lakes in polluted regions can be assessed. The Hoylandet region has the potential to provide a Europe-wide control system of this nature but much further work is req uired to follow up and extend the results of this preliminary study.