The term "up surged" refers to a sudden increase or rise in something, but there are several antonyms that indicate the opposite. The first antonym could be "decline" which reflects a reduction or decrease in something. Another opposite for "up surged" is "plunge" or "drop," which refers to a sudden or sharp fall. "Decrease," "diminish" or "dwindle" are some other antonyms that can be used in such cases. Conversely, "downfall" is a similar term that suggests a sudden and unexpected decline or failure. Other antonyms that appropriately contrast with "up surged" include "slump," "fall," "plummet," and "descend.