In the presence of different types of environmental stressors diatoms can produce frustules that are deformed in different ways (anomalies mainly in symmetry, striation, and raphe course and structure; e.g., Falasco et al. 2009). Heavy metals are one of the most common causes of these malformations (e.g., Morin et al. 2008, Falasco et al. 2009). The Achnanthidium minutissimum species group (in particular not-very-elongated, capitate phenoecodemes, e.g. Round 1993) are reported to be amongst the most tolerant diatoms with respect to metals (Falasco et al. 2009). In low alkalinity, high-elevation springs and streams, acid precipitation can interact with bedrock geology determining increases in the concentrations of heavy metals, indicated by diatom deformities (Furey et al. 2009). In samples taken from a spring in an old pyrite mine in the south-eastern Alps, from a spring in a monastery in Kraków (Poland), and from a stream in the Liguria Region (Italy), teratological forms of the widespread benthic diatom Achnanthidium minutissimum were noted. These were characterized mainly by possessing one (sometimes even two) more or less bent off endings, conferring to the specimens a cymbelloid ("cymbelliclinum"-like in the case of one single end; compare Reichardt 1999) outline. Detailed hydrochemical analyses, including heavy metals and trace elements, were carried out, and enrichment factors (relative to average crustal composition using barium as a crustal reference) were calculated (EFs are significant when >10). In one site fresh material was sampled to document living cell morphology, in particular chromoplast shape and arrangement. The three study sites differ very much in their characteristics: the south-eastern Alps spring is a low-alkalinity, oligotrophic spring in the Adamello-Brenta Nature Park; the Kraków study site is a mineral spring (fountain) in the Pauline monks monastery supplied by a Miocene aquifer from a depth of 67 m; the Gromolo is an Apenninic stream in Liguria (the sampling site is located only 5 km far from the sea). In the old pyrite mine, together with copper, also cadmium and zinc have enrichment factors comprised between 100 and 500; in the Krakow spring, copper concentrations are relatively low (EF = 8) while bismuth and antimony are particularly high (EFs > 500); in the Gromolo, copper is the only contaminant with EFs > 500 (around 1850) but zinc, nickel, and cadmium present EFs comprised between 100 and 500. In spite of the expected marked differences in hydrochemical composition, the only heavy metal / trace element with significant EFs (almost significant in the case of the Kraków fountain) in all sites is copper. Our first observations at the SEM on the teratological forms are in agreement with Falasco et al. (2009) who report in their review that copper contamination appears to change valve outline leaving the ultrastructure of striae and raphe unaffected. Moreover, in the spring in the old pyrite mine, the cyanobacterium Chamaesiphon fuscus (Rostafi?ski) Hansgirg, known to develop massively in Cu-polluted streams in Norway (Lindstrøm 1996), was found to occur with high cover values. In collaboration with Colleagues from the ISE-CNR of Pallanza (Lago Maggiore) observations are underway to check if similar teratological forms of Achnanthidium minutissimum might be present in the sediments of Lake Orta that was affected by severe copper pollution and in which A. minutissimum was one of the dominating diatom taxa (Ruggiu et al. 1998).
Achnanthidium minutissimum (Bacillariophyta) teratological forms as indicators of heavy metal (Cu) enrichment / pollution in different freshwater environments
2011
Abstract
In the presence of different types of environmental stressors diatoms can produce frustules that are deformed in different ways (anomalies mainly in symmetry, striation, and raphe course and structure; e.g., Falasco et al. 2009). Heavy metals are one of the most common causes of these malformations (e.g., Morin et al. 2008, Falasco et al. 2009). The Achnanthidium minutissimum species group (in particular not-very-elongated, capitate phenoecodemes, e.g. Round 1993) are reported to be amongst the most tolerant diatoms with respect to metals (Falasco et al. 2009). In low alkalinity, high-elevation springs and streams, acid precipitation can interact with bedrock geology determining increases in the concentrations of heavy metals, indicated by diatom deformities (Furey et al. 2009). In samples taken from a spring in an old pyrite mine in the south-eastern Alps, from a spring in a monastery in Kraków (Poland), and from a stream in the Liguria Region (Italy), teratological forms of the widespread benthic diatom Achnanthidium minutissimum were noted. These were characterized mainly by possessing one (sometimes even two) more or less bent off endings, conferring to the specimens a cymbelloid ("cymbelliclinum"-like in the case of one single end; compare Reichardt 1999) outline. Detailed hydrochemical analyses, including heavy metals and trace elements, were carried out, and enrichment factors (relative to average crustal composition using barium as a crustal reference) were calculated (EFs are significant when >10). In one site fresh material was sampled to document living cell morphology, in particular chromoplast shape and arrangement. The three study sites differ very much in their characteristics: the south-eastern Alps spring is a low-alkalinity, oligotrophic spring in the Adamello-Brenta Nature Park; the Kraków study site is a mineral spring (fountain) in the Pauline monks monastery supplied by a Miocene aquifer from a depth of 67 m; the Gromolo is an Apenninic stream in Liguria (the sampling site is located only 5 km far from the sea). In the old pyrite mine, together with copper, also cadmium and zinc have enrichment factors comprised between 100 and 500; in the Krakow spring, copper concentrations are relatively low (EF = 8) while bismuth and antimony are particularly high (EFs > 500); in the Gromolo, copper is the only contaminant with EFs > 500 (around 1850) but zinc, nickel, and cadmium present EFs comprised between 100 and 500. In spite of the expected marked differences in hydrochemical composition, the only heavy metal / trace element with significant EFs (almost significant in the case of the Kraków fountain) in all sites is copper. Our first observations at the SEM on the teratological forms are in agreement with Falasco et al. (2009) who report in their review that copper contamination appears to change valve outline leaving the ultrastructure of striae and raphe unaffected. Moreover, in the spring in the old pyrite mine, the cyanobacterium Chamaesiphon fuscus (Rostafi?ski) Hansgirg, known to develop massively in Cu-polluted streams in Norway (Lindstrøm 1996), was found to occur with high cover values. In collaboration with Colleagues from the ISE-CNR of Pallanza (Lago Maggiore) observations are underway to check if similar teratological forms of Achnanthidium minutissimum might be present in the sediments of Lake Orta that was affected by severe copper pollution and in which A. minutissimum was one of the dominating diatom taxa (Ruggiu et al. 1998).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
