Zooplankton
There is large interannual variation in the mesozooplankton biomass (mostly copepods). The western Barents Sea has shown a declining trend since the mid-2000s. The mean biomass in the western Barents Sea in 2013 is now the lowest recorded since
the early 1990s. However, the average mesozooplankton biomass in the northeastern Barents Sea is relatively high. Overall there has been a decrease in the biomass of the Arctic hyperiid Themisto libellula.
Changes in the total abundance of krill (euphausiids) within regions show the strongest decline in the east.
In 2014, jellyfish, mostly the Lion’s Mane jellyfish Cyanea capillata, were found across the Barents Sea. The calculated jellyfish biomass in 2014 was close to the record-high biomass of jellyfish (near 5 million tonnes observed in 2001).
