The Barents Sea food-web has changed over the years, with different types of fish and zooplankton becoming dominant at different times. Scientists used a model to study possible food-web configurations and found that the actual data matched one of the main configurations. However, the way energy flows through the food-web changed over time, with fluctuations between bottom-up and top-down control. This shows that the Barents Sea food-web is not always controlled in the same way, and there are more possible configurations than what has been observed.