Zooplankton community structure and size spectra linked to phytoplankton and hydrographic features on the Faroe Shelf in spring

Transcription

1 Zooplankton community structure and size spectra linked to phytoplankton and hydrographic features on the Faroe Shelf in spring Sólvá Jacobsen, Eilif Gaard, Karin M. H. Larsen, Sólvá K. Eliasen

2 Faroe Islands Background

3 Sea surface temperature 8. April 3 Inner shelf Outer shelf Temperature ( o C) Courtesy of P. Miller Plymouth Marine Lab

4 Sea surface temperature 8. April 3 Inner shelf Cold Outer shelf Warm Temperature ( o C) Courtesy of P. Miller Plymouth Marine Lab

5 Sea surface temperature 8. April 3 Inner shelf Cold Outer shelf Warm Front Temperature ( o C) Courtesy of P. Miller Plymouth Marine Lab

6 Sea surface temperature 8. April 3 Inner shelf Cold Mixed water Outer shelf Warm Front Temperature ( o C) Courtesy of P. Miller Plymouth Marine Lab

7 Sea surface temperature 8. April 3 Inner shelf Cold Mixed water Outer shelf Warm Front Temperature ( o C) Courtesy of P. Miller Plymouth Marine Lab

8 Inner shelf in late April Inner Faroe shelf ecosystem is bottom-up controlled First-feeding fish larvae feed on zooplankton

9 Aim What controls the zooplankton community and size structure on the inner Faroe shelf in late April?

10 Sampling Annual cruise in late April (except and ) Temperature and salinity (CTD) Phytoplankton (fluorometer) Zooplankton (Bongo µm) Total: 58 hydrographic stations and 38 zooplankton stations

11 Image analysis - Taxonomic classification - Community size spectra

12 Average -5 m Temperature April Outer shelf Inner shelf Results

13 Chlorophyll a April Average chlorophyll a -5 m average Outer shelf Inner shelf Results

14 Abundance (number m -3 ) Zooplankton April Inner shelf Neritic copepods Meroplankton C. finmarchicus CIV-CVI C. finmarchicus CI-CIII Other Copepod nauplii Copepod eggs Outer shelf Results

15 Zooplankton groups on inner shelf plotted by size April C. finmarchicus CIV-CVI Neritic copepods C. finmarchicus CI-CIII Other Meroplankton Copepod nauplii Copepod eggs

16 Zooplankton groups on inner shelf plotted by size April C. finmarchicus CIV-CVI Neritic copepods C. finmarchicus CI-CIII Other Meroplankton Copepod nauplii Copepod eggs

17 Abundance (number m -3 ) Abundance (number m -3 ) Inner shelf Outer shelf C. finmarchicus CI-CIII C. finmarchicus CIV-CVI Year Year Results

18 Relative abundance (%) Relative abundance (%) Abundance (number m -3 ) Abundance (number m -3 ) Inner shelf Outer shelf C. finmarchicus CI-CIII C. finmarchicus CIV-CVI

19 Relative abundance (%) Relative abundance (%) Abundance (number m -3 ) Abundance (number m -3 ) Inner shelf Outer shelf C. finmarchicus CI-CIII C. finmarchicus CIV-CVI

20 Relative abundance (%) Relative abundance (%) Abundance (number m -3 ) Abundance (number m -3 ) Inner shelf Outer shelf C. finmarchicus CI-CIII C. finmarchicus CIV-CVI C. finmarchicus phenology shift

21 Relationship between PP-index and modelled exchange rate between the inner and outer shelf water masses Eliasen et al

22 Temperature difference ( o C) Relationship between chl. a and temperature difference between the inner and outer shelf water masses temperature difference Chlorophyll a a.5 R² =.367 P = Year.5.5 Temperature difference ( o C) Results

23 Temperature difference ( o C) Relationship between chl. a and temperature difference between the inner and outer shelf water masses temperature difference Chlorophyll a a Year.5.5 R² =.367 P =.65.5 Temperature difference ( o C) Positive relationship between chl. a concentration and temperature difference between inner and outer shelf

24 Zooplankton (number m -3 ) Relationship between local zooplankton groups and chlorophyll a on inner shelf a a Results

25 Zooplankton (number m -3 ) Relationship between local zooplankton groups and chlorophyll a on inner shelf Zooplankton (number m -3 ) a a?

26 Zooplankton (number m -3 ) Relationship between local zooplankton groups and chlorophyll a on inner shelf Zooplankton (number m -3 ) a High positive correlation between neritic copepod species and chlorophyll a concentration and between a meroplankton and chlorophyll a concentration?

27 Zooplankton (number m -3 ) Relationship between C. finmarchicus and chlorophyll a on inner shelf C. finm. CI-CIII Chlorophyll a C. finm. CIV-CVI Chlorophyll a Year Results

28 Zooplankton (number m -3 ) Zooplankton (number m -3 ) Relationship between C. finmarchicus and chlorophyll a on inner shelf C. finm. CI-CIII Chlorophyll a C. finm. CIV-CVI Chlorophyll a Year

29 Zooplankton (number m -3 ) Zooplankton (number m -3 ) Relationship between C. finmarchicus and chlorophyll a on inner shelf C. finm. CI-CIII Chlorophyll a C. finm. CIV-CVI Chlorophyll a Year No correlation 3

30 Zooplankton (number m -3 ) Relationship between eggs and nauplii and chlorophyll a on inner shelf Copepod eggs Chlorophyll a Copepod nauplii Chlorphyll a Year Results

31 Zooplankton (number m -3 ) Zooplankton (number m -3 ) Relationship between eggs and nauplii and chlorophyll a on inner shelf Copepod eggs Chlorophyll a Copepod nauplii Chlorphyll a Year

32 Zooplankton (number m -3 ) Zooplankton (number m -3 ) Relationship between eggs and nauplii and chlorophyll a on inner shelf Copepod eggs Chlorophyll a Copepod nauplii Chlorphyll a Year No correlation 3

33 Conclusions Phytoplankton concentration strongly affects the abundance of neritic copepod species (and meroplankton) in the inner shelf ecosystem during spring C. finmarchicus phenology shift in outer shelf since 7

34 Inner Faroe shelf ecosystem Suggested mechanism: water exchange rate between the inner and outer Faroe shelf Low exchange Phytoplankton biomass High exchange Phytoplankton biomass Neritic copepod species and meroplankton (small to medium sized zooplankton) Neritic copepod species and meroplankton (small to medium sized zooplankton)

35 Acknowledgements