Zooplankton variability on the Faroe Shelf and in the surrounding oceanic area

in relation to phytoplankton and physical conditions

E. Gaard, H. Debes, B. Hansen, H. Hátún, K. M. H. LarsenFaroe Marine Research Institute

ICES/NAFO Symposium on the Variability of the North Atlantic and its Marine Ecosystems during 2000-2009.

Santander, Spain, 10-12 May 2011

Nordic Seas

Content

• Variability:

– North of the Faroes • Warm Atlantic • Cold East Icelandic current water

– Outside the shelf front

– On the Faroe shelf

North of the Faroes

Copepod life cycle

Calanus life cycle

Calanus finmarchicusMay 1993-2009

Chlorophyll aMay 1993-2009

TemperatureAnnual mean

N1

N14

The Faroe Shelf Ecosystem

• Separate water mass

• Distinct ecosystem

• Largely neritic zooplankton.

• Mixed with variable abundances of oceanic zooplankton

Copepods on and around the Faroe shelf19-27 June 2009

Copepods

Calanus finmarchicus

Zooplankton monitoringLate June

< 100 m bottom depthZooplankton biomass

> 150 m bottom depthZooplankton biomass

M icroscopic examinations (Shelf)

M icroscopic examinations (Outside she lf)

Zooplankton dry weight (g/m2)Outside the shelf, late June

Outside the shelf front, late June

Zooplankton biomass

Calanus finmarchicusStage composition

Calanus finmarchicusRelative stage composition

Faroe Self copepodsSeasonal development, 2004

Zooplankton dry weight (g/m2)Shelf and Outside the shelf, late June

Faroe shelfLate June, 1992-2009

Copepods Calanus finmarchicus

Temora: 10 X increase

Shelf temperature and chl. a

Chl. a: 15 April - 30 June

Temperature Mean, 15 April – 30 June

Calanus finmarchicusStage duration

5°C

8°C

7°C

Summary

• Atlantic and shelf water:– 10x increase in Temora (shelf), 1995-2009– Zooplankton biomass increase (C. finmarchicus) during the 2000s– Phenology changes.– No relationship with chlorophyll a.– Shorter stage duration induced by higher temperature (~1°C) only

shortherns the generation time ~1 weak.

• East-Icelandic current water:– Large phenology shift in 2003-2004. Earlier reproduction.– No relationship with chlorophyll a– Most like caused by temperature increase and/or changes in

currents