20966
A strong spatial variation of metals in the oyster Saccostrea cucullata was found in the estuary , confirming that oysters can be used as a good biomonitor of metal contamination in the studied area .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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