AbstractsBiology & Animal Science

Temporal and spatial turnover of freshwater diatoms : Implications for bioassessment

by Laura Virtanen




Institution: University of Helsinki
Department: Department of Environmental Sciences
Year: 2015
Keywords: ympäristötieteet
Record ID: 1134533
Full text PDF: http://hdl.handle.net/10138/154780


Abstract

Water quality in streams usually changes fast, and sensitive biological indicators are essential for monitoring these changes. Diatoms are widely used in biological stream quality assessments. However, there are temporal and spatial variations in diatom communities that may result in unreliable quality assessments. Under different kinds of environmental stressors, diatoms can produce deformed frustules. Heavy metals are among the most common causes of these teratological forms. In addition to eutrophication and organic pollution, diatoms could potentially be used for indicators of heavy metal enrichment. The aim here was to examine the interannual and intra-annual turnover of stream diatom communities. The focus of this study was on whether specific species traits and species local abundance and regional distribution affected temporal occurrence of diatom species. The study also included an examination of how stable diatom inferred stream classifications are in time and if pure spatial variation in diatoms should be considered when assessing stream water quality based on diatoms. The final aspect of the study was to determine which heavy metals, and to what extent, trigger the occurrence of deformations in diatom Achnanthidium minutissimum. Our results imply that abundant and widely distributed species with larger niches and the ability to attach to the substratum sustain persistent populations in varying environmental conditions typical for streams. The most persistent species are thus perhaps the most reliable species to be used as indicators of water quality. The stream classification based on diatoms resulted in temporally stable and statistically distinct community types. Thus, the results suggest that sampling of diatoms in every three years seems to be a reliable procedure to assess biological water quality. The investigation also revealed that study regions differ in their diatom species composition more than in their environmental features indicating that diatoms are structured not only by the local environment but also by large-scale processes, possibly related to climate, dispersal and history. As diatom species composition varies between regions, future bioassessments would benefit from regional stratification. Finally, study results indicated that two metals, copper and zinc, and a metalloid, antimony, were the most likely triggers of A. minutissimum deformations. The definition of their morphological and quantitative characteristics, along with a better taxonomic circumscription of the affected species, should allow the use of deformations as a reliable indicator of heavy metal enrichment in freshwater habitats. Veden laatu joissa vaihtelee jatkuvasti, ja herkät bioindikaattorit ovat tärkeitä näiden muutoksien havaitsemiseksi. Piileviä käytetään laajalti veden laadun biologisissa seurannoissa. Ajallinen ja paikallinen vaihtelu piileväyhteisöissä voi kuitenkin hankaloittaa veden laadun arviointia. Erilaiset ympäristötekijät voivat myös aiheuttaa epämuodostumia piilevien kuorissa.…