28168
To this end we monitored : ( i ) changes in the proportion of the diatoms in relation to other algal groups at the biofilm community level ; ( ii ) shifts in species composition at the diatom - assemblage level ; ( iii ) projected changes in the densities of the most representative species at the population level through comparison of relative growth rates and generation times ; and ( iv ) the cytological changes at the cellular and subcellular levels as indicated by the appearance of teratological effects on individuals and nuclear alterations .
 None
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None