Impact of harbor seals on the Wadden Sea food web A ... fileLoligo sp. Shrimps Impact of seals % 1-...
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Impact of harbor seals on the Wadden Sea food web A modelling approach Camille de la Vega Harald Asmus, Benoit Lebreton, Ursula Siebert, Ragnhild Asmus ©Camille de la Vega
Transcript of Impact of harbor seals on the Wadden Sea food web A ... fileLoligo sp. Shrimps Impact of seals % 1-...
Impact of harbor seals on the Wadden Sea food web A modelling approach
Camille de la Vega
Harald Asmus, Benoit Lebreton, Ursula Siebert, Ragnhild Asmus
©Camille de la Vega
1- The ENA Model 2- SI principle 3- Seal´s diet 4- Impact of seals 5- Perspectives
Sylt Rømø Bight
Ecological Network Analyses
Susp. POC
Sed. POC
DOC Asmus 2012
Fish (12)
Bird (17)
Zoopl.
Meiof.
Macrof. (28)
Free living Bact.
Sed. Bact.
MPB Phytopl.
Macroalg.
1- The ENA Model 2- SI principle 3- Seal´s diet 4- Impact of seals 5- Perspectives
Sylt Rømø Bight
Ecological Network Analyses
Susp. POC
Sed. POC
DOC
Seal
Asmus 2012
Fish (12)
Bird (17)
Zoopl.
Meiof.
Macrof. (28)
Free living Bact.
Sed. Bact.
MPB Phytopl.
Macroalg.
≈ 470 individuals ( Phoca vitulina )
© Chloée de la Vega
1- The ENA Model 2- SI principle 3- Seal´s diet 4- Impact of seals 5- Perspectives
Sylt Rømø Bight
Biomass
≈ 470 individuals ( Phoca vitulina )
© Chloée de la Vega
Export
Prod.
Respiration Egestion
Biomass
Export
Prod.
Respi.
Fish
? ?
?
?
?
?
Egestion
? Diet
Where do the seals feed ?
1- The ENA Model 2- SI principle 3- Seal´s diet 4- Impact of seals 5- Perspectives
Benthic – Sea floor
Pelagic – water column
δ13C
-
+
Trophic markers : Stable Isotope
1- The ENA Model 2- SI principle 3- Seal´s diet 4- Impact of seals 5- Perspectives
Benthic – Sea floor
Pelagic – water column
Coast Offshore
δ13C
-
-
+
+
Trophic markers : Stable Isotope
1- The ENA Model 2- SI principle 3- Seal´s diet 4- Impact of seals 5- Perspectives
Benthic – Sea floor
Pelagic – water column
Coast Offshore
δ13C
-
-
+
+
%
%
%
% %
%
%
%
?
Trophic markers : Stable Isotope
1- The ENA Model 2- SI principle 3- Seal´s diet 4- Impact of seals 5- Perspectives
δ13C
δ15N
δ1
5N
δ13C
Seal : summer, fall, winter Seal : spring
Prey from the Sylt Rømø Bight
Prey from the North Sea
Harbor seals feed in the Wadden Sea
Coast Offshore
PREY ITEMS Sylt-Rømø bight Benthic fish Bentho-pelagic fish Pelagic fish
North Sea Benthic fish Bentho-pelagic fish Pelagic fish
SEALS Spring Summer Fall Winter
1- The ENA Model 2- SI principle 3- Seal´s diet 4- Impact of seals 5- Perspectives
Benthic
Pelagic
Benthic
Pelagic
Analses of the vibrissae
Food Web Model Ecological Network Analysis
Fish sp. Loligo sp. Shrimps
Impact of seals
%
1- The ENA Model 2- SI principle 3- Seal´s diet 4- Impact of seals 5- Perspectives
0.0
-0.1
Zooplankton Macrofauna
Zooplankton Macrofauna
Impact of seals
Impact of fish and loligo sp.
Top Down Cascading effect
Fish
Macrofauna Zooplankton
1- The ENA Model 2- SI principle 3- Seal´s diet 4- Impact of seals 5- Perspectives
Impact of seals
Impact of fish and loligo sp. 0.0
-0.1
Birds
Birds
Impact Birds
Zoopl.
1- The ENA Model 2- SI principle 3- Seal´s diet 4- Impact of seals 5- Perspectives
Impact of seals
Top Down Cascading effect
Fish Birds
Macrofauna Zooplankton
Bivalves
Competition
1- The ENA Model 2- SI principle 3- Seal´s diet 4- Impact of seals 5- Perspectives
Conclusions
Cascading effect of seals This effect is very low Several competitors of fish
Perspectives
Seasonal variation of fish biomass Seasonal variation of seal´s diet Seasonal variation of bird biomass
© Chloée de la Vega
Competition and impact of seals might be different depending on the season
1- The ENA Model 2- SI principle 3- Seal´s diet 4- Impact of seals 5- Perspectives
Thank you for attention !
Questions ?
©Camille de la Vega
Camille de la Vega
Harald Asmus - Benoit Lebreton - Ursula Siebert - Ragnhild Asmus
