1 / 18

North Sea

The Barents Sea, physical features:. Large 1.6 mill km 2 High latitude ~70°-80°N Shelf sea Mean depth 230m. Barents Sea. Russia. Norwegian Sea. Norway. North Sea. The Barents Sea, main species:. HADDOCK. POLAR COD. SHRIMP. PHYTOPLANKTON. COPEPODS. OTHER BENTHOS.

sheba
Download Presentation

North Sea

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. The Barents Sea, physical features: • Large • 1.6 mill km2 • High latitude • ~70°-80°N • Shelf sea • Mean depth 230m BarentsSea Russia Norwegian Sea Norway North Sea

  2. The Barents Sea, main species: HADDOCK POLAR COD SHRIMP PHYTOPLANKTON COPEPODS OTHER BENTHOS

  3. External driving forces: Climate: Fishing: Inflow, ice cover, atmospheric conditions => determine the extent and characteristics of main water masses • Arctic water • Mixed/Frontal water Atlantic water Coastal water • Mainly by Russia and Norway • Demersal fishery • -Mainly cod/haddock • -Shrimp, other demersal fish • Capelin • Harp seals/minke whales

  4. Barents Sea dynamics Pro Mare 1984-1989 : National Research programme Early 1980’s: IMR project ”Lodde på sommerbeite” Skjoldal et al 1992 Blindheim and Skjoldal 1992 Skjoldal et al 1987

  5. How does the climate influence ? • Inflow influences ice distribution, pressure system influence fluxes. • area and volum of water masses • On average atlantic water resides 4 years in the BS, • current condition integrates inflow over several years • Seasonal aspects of inflow? More inflow in winter vs summer? • Climate/inflow influences some important ecosystem components: • Bloom dynamics, match-mismatch copepods and phytoplantkon • Advection of copepods (Calanus finmarchicus) • Strong Recruitement variability (e.g, cod, herring) => Influenced by advective currents

  6. Phytoplankton ~four zones • Coastal current along the coast but goes also quite far into the BS Seasonal dynamics=> always stratification, stable/predictable spring bloom determined by day light • Atlantic water/inflow formation of termocline and stratification: strong internanual variation, timing vary by 6 weeks, can have 2 generations of copepods feeding on the spring bloom during the same season, similar to the Norwegian sea • Seasonally ice covered zone: Shallow melt water, leads to fast but short lived spring bloom, large buid up of phytplankton, copepods unable to reduce it by grazing • Permanently ice covered area (almost disappeared in recent years), partly melted, and has melt water, but light penetration reduced by ice and limits production

  7. Pro mare Phytoplankton Nutrients: Bloom of diatoms reduces silicate and nitrates Bloom of other phytoplankton reduces only nitrates Phaeocystis pouchetii flagelate, geletionous , may form colonies Diatoms better food for copepods, ratio nitrate/silikate at the end of bloom => indicative of grazing pressure from and biomass of copepods

  8. Phytoplankton pelagic bloom • low grazing pressure from copepods • more sedimentation • Indications that Calanus biomass influences the proportion of productions that sinks • Old Russian literature, fast bloom, less grazing, more sedimenation • => Higher organic content in sediments in northern areas • => Still valid?

  9. Zooplankton: Atlantic inflow => fills up the amount of Calanus finmarchicus (BS sink area for Calanus) But a lot of the inflow does not contain Calanus finmarichus and dilutes it. Calanus glacialis shelf species, most important herbivore in arctic BS, l arge and more fexible than C. finmarchicus C. Hyberboreus dominates in the Greenland sea Themisto libelulla; arctic, carnivor amphipods, not as shelf species, transported southwards T. Libellula both prey and competitior of capelin (both feeds on copepods)

  10. Barents Sea dynamics Pro Mare 1984-1989 : National Research programme Early 1980’s: IMR project ”Lodde på sommerbeite” end ofcoldperiod (1970’s), afterthisperiod, large fluctuations and warming trend Dynamics in capelingrowthdeterminecapelinstockdynamics Foodavailability large influenceoncapelingrowth and a strongfeed back ofcapelinonitsprey

  11. Capelin

  12. 1983: strong recruitement of herring and cod • herring predation on capelin larvae • Winter 82-83: large Atlantic inflow during winter, filled the BS with Atlantic water with very low abundance of copepods in central BS • induced reduced growth of capelin • 84/85 capelin stock collapse => increase in krill and amphipods • 1987 year class of capelin had fast growth and matured as 2 year olds due to high abundance of krill and amphipods, fast recovery of capelin

  13. Development in external driving forces: Fishing: 1970’s: High / increasing 1980’s: High on demersal fish High on capelin fishing until collapse 1990’s: Demersals: reduction followed by increase 2000-2009: Decreased on cod => New harvest control rule From Johannesen et al (2012)

  14. Fishing: • Herring: • Collapse of herring in the late 1960’s • Lack of juvenile herring in the BS in the 1970’s • linked to collapse of herring • Cod and haddock: • High fishing pressure: Low levels of cod and haddock in the 1980’s • Altered size/age structure (younger/smaller fish) • ”bottle neck” effect on cod, loss of genetic variability=>Mature younger and smaller ? • Capelin • First capelin collapse, prolonged by fishing? • Shrimp: • Effect on redfish recruitment?

  15. Development in main species: • Demersal fish: • 1970’s: High levels • 1980’s: Historic low levels • 1990’s: Variable • 2000’s: Increasing=>cod comparable to 1950’s • Pelagic fish: • 1970’s: Abundant capelin/Polar cod • No herring • 1980’s: 1. capelin collapse and recovery • Return of herring • 1990’s: 2. capelin collapse and recovery • 2000’s: 3. capelin collapse /recovery • Other pelagics abundant • Zooplankton /Shrimp: • Strong variability, • especially in 1980’s and 1990’s • 2000’s: Shrimp/Krill increasing trend

  16. ”Ecosystem state”

  17. Chronological clustering

  18. Results has not been related to drivers

More Related