https://phys.org/news/2018-06-size-energetic-efficiency-lake.html

Available food is utilised less efficiently than expected

The researchers' study involved investigating food webs in two small, shallow and nutrient-rich lakes in Northern Germany, each of which divided into two closed systems for a period of one year by installing a curtain through the middle of each lake. The long period of division meant that the key groups of organisms developed differently in both halves, enabling the scientists to collect data for a total of four different aquatic ecosystems. The researchers determined the biomass and size of all organisms present in the lakes. In addition, the team computed the trophic transfer efficiency for all levels of the food chain in the lake. To achieve this, they compared primary and bacterial production with secondary production (i.e. the increase in biomass at the consumer level).