16307
The mean metal concentrations in the Ulva tissue from the river and the lake decreased in the following order : Mn > Zn > Cr > Cu > Co and Mn > Cr > Zn > Cu > Co , respectively .
 Mn, Zn, Cr, Cu, Co, Mn, Cr, Zn, Cu, Co
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Mn, Zn, Cr, Cu, Co, Mn, Cr, Zn, Cu, Co