Growth Dilution of Metals in Microalgal Biofilms

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• 作者：Walter. R. Hill and Ingvar L. Larsen
• 刊名：Environmental Science & Technology
• 出版年：2005
• 出版时间：March 15, 2005
• 年：2005
• 卷：39
• 期：6
• 页码：1513 - 1518
• 全文大小：217K
• 年卷期：v.39,no.6(March 15, 2005)
• ISSN：1520-5851

文摘

Despite the key role microalgae play in introducingtoxicants into aquatic food webs, little is known about theeffects of environmental factors on metal accumulationby these primary producers. Environmental factors such aslight and nutrients alter growth rates and may consequentlyinfluence metal concentrations in microalgae throughgrowth dilution. Laboratory experiments suggested thatmetal uptake and elimination by microalgal biofilms weregradual enough to enable dilution of metals within the biofilmsby photosynthetically accrued carbon, and a simplekinetic model of metal accumulation predicted significantvariation in metal content due to growth dilution overthe natural range of microalgal growth rates. The ratio ofmetal uptake to carbon uptake by microalgal biofilmsdecreased exponentially with increasing light in short-term laboratory experiments because photosynthesis wasmuch more sensitive to a light gradient than was metaluptake. The effect of light on biofilm metal concentrationswas confirmed in situ with a long-term experiment inwhich experimental shading of biofilms in a metal-contaminated stream decreased biofilm growth rates andcaused a 3× increase in biofilm concentrations oftwelve metals, including methylmercury. Slow growth atthe primary producer level is a likely contributor to higherbiotic metal concentrations in shaded, oligotrophic, orcold ecosystems.