19724
Total and methyl Hg concentrations and relative trophic position ( using delta ( 15 ) N ) were analyzed in biofilm and invertebrates from 21 streams in New Brunswick , Canada to assess food web biomagnification leading to the common minnow blacknose dace ( Rhinichthys atratulus ) , a species known to have Hg concentrations that are higher in low pH waters .
 methyl, Hg, ( 15 ) N, Hg
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 methyl, Hg, ( 15 ) N, Hg