13352
The objective of this study was to evaluate the single and combined effects of waterborne copper and experimental infestation of eels with the nematode Anguillicoloides crassus after a salinity challenge from nearly isotonic ( 18ppt ) to hypo - ( 5ppt ) and hypertonic ( 29ppt ) conditions , in order to investigate the osmoregulatory capacity of eels exposed to these stressors .
 Chemical: copper
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: copper 
Answer:
 Chemical: copper