Development in plankton community: the Barents Sea. E. Eriksen SEAPOP, April 2017

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1 Development in plankton community: the Barents Sea E. Eriksen SEAPOP, April 2017

2 Arctic ocean The Barents Sea short description The Barents Sea is a shelf sea (~ 1.6 million km 2 ) and a transition zone between Atlantic and Arctic conditions Inflowing Atlantic Water is relatively warm and gives boreal conditions in the western and southern areas, while Arctic Water is cold and gives sub-arctic and arctic conditions in the northern area The atmospheric pressure and winds influence inflow, and air temperature influence water temperature Vilnus A productive area, with more than 200 species of fish, thousands of benthic invertebrate species and diverse communities of plankton, seabirds and marine mammals inhabiting or visiting the area.

3 Oceanography: long term changes Air temperature anomaly, С SST anomaly, С Ice coverage anomaly, % Western Eastern Western Eastern Air temperature Sea surface temperature Ice coverage Positive air temperature anomalies prevailed during the last 15 years in the Barents Sea The was a cold period from the 1960s into the 1980s. Since then there has been a warming trend with highest temperature observed in Reduction in the winter sea ice (typically in April), with a loss of about half the area of winter sea ice during the warming period ICES WGIBAR 2017, The Barents Sea ecosystem survey report 2016

4 Net Primary Production: long term changes Increase ice-free area and warmer conditions provides improved habitat for phytoplankton growth as the growing season has increased Spatially integrated production (NPP) has increased over the years in most polygon regions, especially in the eastern areas. ICES WGIBAR 2017

5 Mesoplankton: long term changes For the smallest size-fraction, the 2016 biomass was similar to the average for the last 20 years For the intermediate size-fraction, the 2016 biomass was above the average for the last 20 years For the largest size-fraction, the biomass shows a decreasing trend during the ca. 10 last years Time-series of mean zooplankton biomass from bottom 0m (dryweight, g m-2) for the western and central Barents Sea for the Norwegian part of the autumn ecosystem-survey, Data are shown for the three size-fractions ( μm, μm and >2000μm) based on wet sieving. ICES WGIBAR 2017

6 Mesoplankton: long term changes The biomass has declined during the last 10 years, and there are few signs of recovery of the zooplankton biomass associated with the capelin collapse in Time series of total zooplankton biomass for the Central Bank and Great Bank based on combined IMR-PINRO data, Mean zooplankton biomass (total, g dw m -2 ) from vertical nets (WP-2 and Juday) by IMR and PINRO, ICES WGIBAR 2017

7 Macroplankton: long term changes Krill (as a group) Relative low biomass during s, and increased during 2000s It seems that the recent warming conditions have favourable impacts on krill populations Krill biomass, MT Jellyfish (Cyanea capillata) The biomasses were low during 1980s, increased during 1990s, and were highest in early 2000s with a subsequent decline It seems that the ongoing warming trend may be favourable for Barents Sea jellyfish medusae, which distributed mostly in the AW (in waters of 4>T <7) Jellyfish biomass, MT Eriksen, E. and Dalpadado, P Polar Biology Eriksen et al PLoS ONE

8 Ecological significance of 0-group fish The total biomass of the four most abundant 0- group fish species can be up to 3.3 million tonnes, with an average of 1.3 million tonnes ( ). A new time series: 0-group fish Distribution the central area seems to be the most important, accounting for approximately 50-80% of the annual biomass 0-group fish is a fifth important pelagic stock in the ecosystem Eriksen E., Bogstad B., Nakken O Ecological significance of 0-group fish in the Barents Sea ecosystem. Polar Biology

9 0-group fish: long term changes 0-group fish biomass Zero group fish are important consumers on plankton and prey of other predators During last 10 years several strong year classes occurred (capelin (6) and cod (6), haddock (3), herring 82) and redfish(2) Fish length, cm Length of 0-gr fish larger than long term mean in Length anomaly of 0-gr fish Large area covered by Atlantic water masses, rich of plankton, provided good feeding condition for 0-group fish in 2016 ICES WGIBAR 2017 Eriksen et al ICES Journal of Marine Science, 69(5)

10 Changes in the pelagic compartment: stratigraphically clustering of years oceanographic (flux, temperatures and areas of water masses) biological (biomass of krill and jellyfish, fish recruitment) cold conditions with low T C and a large area of AcW slightly increased volume transport and T C and area of AW increased area of ArW and MW, varied T C and stronger Atlantic water transport low biomass of macroplankton and good recruitment for wide distributed species low biomass of macroplankton and generally low fish recruitment record high biomass of jellyfish, generally recruitment warmest recorded with record high T C and largest areas of warm waters (AW and MW) high biomass of macroplankton and good recruitment of boreal species and capelin

11 Changes in the pelagic compartment: spatial biomass fluctuation A- Total biomass for all components of the pelagic compartment B- Biomass of pelagic fishes C- Biomass of 0-group fishes D- biomass of macrozooplankton, mostly krill The mean biomass values are for the period with the range of annual estimates for the subareas shown in parentheses Paper Eriksen, E., Skjoldal, H.R and Gjøsæter, H. Spatial and temporal changes in the Barents Sea pelagic compartment during the recent warming. Progress in Oceanography:

12 Changes in the pelagic compartment: temporal biomass fluctuation Figure shows estimated biomass (million tonnes wet weight) of the pelagic compartment in the Barents Sea from 1993 to Figure shows the temporal development of biomass (in million tonnes) of pelagic fish species (above) and 0- group fish (below) in the Barents Sea from 1993 to 2013 Paper VIII. Eriksen, E., Skjoldal, H.R and Gjøsæter, H. Spatial and temporal changes in the Barents Sea pelagic compartment during the recent warming. Progress in Oceanography:

13 Development in plankton community: summary The sub-arctic Barents Sea is warming (larger area of warm water) and the sea ice is retracting This is followed by higher primary production Larger biomasses of mesoplankton distributed in the western and northern areas. Decreasing long term trend in mesoplankton biomass observed in the central area Marcoplankton (krill and jellyfish) showed an increased trend in recent years The recent warming conditions have had favorable impacts on 0-group fish and several strong year classes occurred Thus, it should have been more food for sea birds!!!

14 Thank you for your attention