Long-term toxicity of zinc to bacteria and algae in periphyton communities from the river Göta Älv, based on a microcosm study

Inhibitory effect of zinc on the remineralisation of dissolved organic matter in the coastal environment

“…Most studies on the effect of Zn on bacteria have been carried out in freshwater environments (Nweke et al 2006, Vega-López et al 2007; the results have shown a strong suppression of bacterial growth at low concentrations (> 0.1 μg Zn l -1 ), which is about an order of magnitude lower than the effective level on phytoplankton (Paulsson et al 2000). Although there have been just a few studies on the effects of Zn on marine bacterial communities (Ku$pilić et al 1989, Caroppo et al 2006, RochelleNewall et al 2008, these studies, too, have suggested that the activity of marine bacteria is also inhibited by the addition of Zn at 1 to 100 μg Zn l -1 .…”

“…Although the role of Zn in DOM remineralisation has been neglected to date, some previous studies have suggested that Zn exerts a strong inhibitory effect on bacterial activity at concentrations ranging from < 5 μg Zn l -1 (Ku$pilić et al 1989, Paulsson et al 2000. In addition, Zn is related to the activities of various kinds of enzyme, such as metalloprotease (Hase & Finkelstein 1993, Ogino et al 1999, Fukuda et al 2000, and dehydrogenase (Choudhury & Srivastava 2001, Vega-López et al 2007), which would be involved in the DOM rem- ineralisation process.…”

“…These findings indicate concentrations of Zn that are several orders of magnitude higher in many coastal environments when compared to other toxic heavy metals such as cadmium, copper and lead (Shitashima & Tsubota 1990, Reddy et al 2005, Cuong et al 2008). As mentioned above, Zn (compared with other heavy metals) is regarded as being a relatively less toxic element for humans and higher organisms, but it exerts a strong inhibitory effect on bacterial activity (Paulsson et al 2000). Most studies on the effect of Zn on bacteria have been carried out in freshwater environments (Nweke et al 2006, Vega-López et al 2007; the results have shown a strong suppression of bacterial growth at low concentrations (> 0.1 μg Zn l -1 ), which is about an order of magnitude lower than the effective level on phytoplankton (Paulsson et al 2000).…”

La méthode PICT (Pollution-Induced Community Tolerance) appliquée aux communautés algales : intérêt comme outil de diagnose et d'évaluation du risque écotoxicologique en milieu aquatique

“…Cependant, il existe certains cas où les mé-thodes classiques de mesure du stress à long terme semblent plus sensibles que celle mise en oeuvre dans l'approche PICT. Par exemple, Paulsson et al (2000) ont constaté une acquisition de tolérance au zinc de communautés périphytiques à des concentrations plus élevées que celles entraînant une différence de structure entre microcosmes témoins et microcosmes contaminés. L'hypothèse proposée est que le zinc interagirait avec le phosphore, provoquant une limitation des algues vis-à-vis du phosphore.…”

Phyto- and zooplankton in fishponds contaminated with heavy metal runoff from a lead-zinc mine

“…Despite numerous studies on the toxicological effects on aquatic microorganisms contaminated with heavy metals, which were based mainly on short-term microcosm experiments (Paulsson et al 2000, Clement et al 2004, studies on the long-term effects of sediment contamination with heavy metals on freshwater species are scarce with only a few studies related to freshwaters affected by lead and zinc mining runoff (Besser et al 2007, Morin et al 2008. With a general lack of documentation of streams and ponds with highly contaminated sediments due to past mining activity, it is difficult to estimate the actual role of the sediments as a contaminant source and predict the long-term potential and real effects on aquatic microorganisms and the functioning of whole communities.…”