All metals are potentially toxic, yet many metals are essential for organisms. In recent years, some heavy metals, such as Ba, Se, Sr and Ti, have also gained special interest by conservationists for their adverse effects on the ecosystem and human health. Light metals, such as Na, K and Ca, which generally play important biological roles, could also cause toxic effects when their concentrations beyond a certain threshold.  

The rapid pace of human civilization has caused serious metal pollutions in lakes in addition to notorious eutrophication and the presence of harmful algal blooms. Our freshwater ecosystems are not only being polluted to varying degrees from general nutrient enrichment, but are also condemned to fairly long-term pollution due to metals deposited in sediments from past human activities. Therefore, metal pollutions in eutrophic lakes may be very serious, especially in developing countries. 

In order to determine bioconcentration pot ential of ten metals (Al, Ba, Ca, K, Li, Mg, Na, Se, Sr and Ti) in submerged macrophytes and to discuss influences of environmental factors on the metal accumulation potential of submerged macrophytes in eutrophic lakes at the watershed scale, Dr. XING Wei under the supervision of Prof. LIU Guihua from Wuhan Botanical Garden studied metal concentrations (Al, Ba, C a, K, Li, Mg, Na, Se, Sr an d Ti) in submerged macrophytes and corresponding water and sediments in 24 eutrophic lakes along the middle and lower reaches of the Yangtze River (China).  

Results showed that these eutrophic lakes had high metal concentrations in both water and sediments because of human activities. Average concentrations of Al and Na in tissues of submerged macrophytes were very high in sampled eutrophic lakes. By comparison, Ceratophyllum demersum and Najas marina accumulated more metals (e.g. Ba, Ca, K, Mg, Na, Sr and Ti). Strong positive correlationswere found between metal concentrations in tissues of submerged macrophytes, probably because of co-accumulation of metals. The concentrations of Li, Mg, Na and Sr in tissues of submerged macrophytes significantly correlated with their corresponding water values, but not sediment values. This research helps the metal pollution treatment in eutrophic lakes at the watershed scale. 

This study was supported by National Natural Science Foundation of China, the National S & T Major Project and Youth Innovation Promotion Association of CAS. Results were published in Environmental Science and Pollution Research online entitled “Metal accumulation by submerged macrophytes in eutrophiclakes at the watershed scale”. 

 Metal concentrations (in milligram per kilogram dry weight) in tissues of submerged macrophytes at site-species scale (Image by Dr. XING Wei)