We attempted to characterize zooplankton community response following spills of the unconventional crude oil, diluted bitumen (dilbit), into 10-m diameter, ~ 100 m 3 , ~ 1.5-m deep boreal lake limnocorrals, including two controls and seven dilbit treatments ranging from 1.5 to 180 L (1:100,000 to 1:1,000 v/v, dilbit:water). Community composition and abundances were monitored weekly to bi-weekly over three months. Total zooplankton biomass and abundance seemingly collapsed in all limnocorrals, regardless of treatment, though some rotifer species persisted. As a result, it was not possible to determine the impacts of dilbit. We theorize several potential non-oil-related reasons for the sudden community collapse – including elevated zinc levels, fish grazing pressures, and sampling biases – and provide guidance for future work using in-lake enclosures.