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 known. The Hoylandet region in central Norway experiences relatively low levels of atmospheric pollution and its surface waters, although acid, are not significantly acidified. Hence lakes and streams in this region were selected to study the influence of water chemistry on diatom algae. Relationships between the two were explored using the multivariate technique of canonical correspondence analysis (CCA). The principal water chemistry variables influencing species composition of periphytic diatoms were found to be pH and water colour. Furthermore, the relationship between species abundance and pH was sufficiently strong to enable reconstruction of water acidity from diatom data. Establishing the nature of aquatic communities in atmospherically clean but geologically sensitive regions is an important means of identifying control systems 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 required to follow up and extend the results of this preliminary study.