POPULATION DYNAMICS AND PREDATION IMPACT OF THE INTRODUCED CTENOPHORE MNEMIOPSIS LEIDYI IN THE GULLMARS FJORD, WEST COAST OF SWEDEN Lene Friis Møller & Peter Tiselius Dep. Of Marine Ecology Kristineberg University of Gothenburg
The Gullmar Fjord Always stratified Well-documented Rich and diverse fauna Kristineberg
Also many jellies Aurelia aurita Cnidarians Cyanea capillata Many hydromedusae Ctenophores Pleurobrachia pileus Bolinopsis infundibulum Beroe cucumis Beroe gracilis What is dominating has now changed...
Mnemiopsis leidyi - invasive ctenophore Native species along the American East Coast Eats zooplankton (and fish eggs) Invaded northern Europe in 2005/2006 High reproduction Most famous for its invasion into the Black Sea in the 80 s
Given the rapid growth and high reproductive output of the Mnemiopsis, severe effects on its prey populations may be expected It is impossible to predict the outcome of the introduction into Swedish waters based on observations from other areas both potential prey and predators differ It is therefore necessary to investigate the development and impact of Mnemiopsis locally
Mnemiopsis studies in the Gullmar Fjord In the current project we study the development of the Mnemiopsis population in the Gullmar fjord by regular sampling from March 2007 to present (for long periods every week) (+ zooplankton, chl a, primary production, CTD) x
90 80 70 60 50 40 30 20 10 0 17 Jun 07 6 Aug 07 25 Sep 07 14 Nov 07 3 Jan 08 22 Feb 08 12 Apr 08 1 Jun 08 21 Jul 08 9 Sep 08 29 Oct 08 18 Dec 08 6 Feb 09 28 Mar 09 17 May 09 6 Jul 09 25 Aug 09 14 Oct 09 3 Dec 09 22 Jan 10 2007 2008 2009 2007-2009 Mnemiopsis biomass Biomass (g wet weight m -3 )
Development Oral/aboral Rapoza et al. 2005 Lobate at ca. 3-4 mm - factor 1.4 between total and oral-aboral length
24 Dec 07 2 Feb 08 13 Mar 08 22 Apr 08 1 Jun 08 11 Jul 08 20 Aug 08 29 Sep 08 8 Nov 08 18 Dec 08 27 Jan 09 10 9 8 7 6 5 4 3 2 1 0 Abundances (ind m -3 ) in 2008 From 450 µm net (ind. larger than 4mm) Abundance (ind m -3 )
21 Jul 08 10 Aug 08 30 Aug 08 19 Sep 08 9 Oct 08 29 Oct 08 18 Nov 08 8 Dec 08 28 Dec 08 Length, mm 90 80 70 60 50 40 30 20 10 0 Size-range - lobates Lengths measured as oral-aboral
400 350 300 250 200 150 100 50 0 2008 - abundance of larvae (ind m -3 ) From 90 um net: ca. 0.4-1 mm From 450 um net: ca. 1-3 mm 1 Jan 08 21 Jan 08 10 Feb 08 1 Mar 08 21 Mar 08 10 Apr 08 30 Apr 08 20 May 08 9 Jun 08 29 Jun 08 19 Jul 08 8 Aug 08 28 Aug 08 17 Sep 08 7 Oct 08 27 Oct 08 16 Nov 08 6 Dec 08 26 Dec 08 450 um net 90 um net abundance of larvae (ind m -3 )
The potential predation impact of Mnemiopsis has been estimated by multiplying abundances with specific feeding rates measurements to obtain % removal of zooplankton per day Feeding rates have been obtained from both controlled laboratory experiments with different prey species and from gut content analysis on individuals from the fjord Granhag et al. (in press), Møller & Tiselius (in prep.) Here representative rates have been used Predation impact is minimum values since averages for 20 m is used and larvae have been excluded for now
2008 Predation impact (% removal per day) Zooplankton abund. (ind m -3 )
1600 Primary production 8.0 8.0 7.0 7.0 6.0 6.0 5.0 5.0 4.0 4.0 3.0 2.0 1.0 0.0 1400 21 Jul 08 31 Jul 08 10 Aug 08 20 Aug 08 30 Aug 08 9 Sep 08 19 Sep 08 29 Sep 08 9 Oct 08 29 Oct 08 19 Oct 08 average 0 10 m Chl a 1200 PP 1000 800 600 400 200 0 Chl a (µg l -1 ) Zooplankton abund. (ind m3)
2009 Zooplankton concentration Ind. m-3
A severe reduction in zooplankton is observed potentially caused by Mnemiopsis Zooplankton fluctuations are of course also affected by other parameters However it deserves further investigations! 1) Continue analyze data already obtained 2) Apply Mnemiopsis carbon budgets 3) Analyze microzooplankton samples 4) Continue monitoring!!
The monitoring was continued during 2010 and is still ongoing Many additional intensive investigations during 2010 Still much to analyze e.g. all zooplankton However Mnemiopsis came later (beginning of September) -probably due to a very long and cold winter
Back in 2007 we asked our selves: Would Mnemiopsis become a problem at the West Coast? Most concern was regarding the Baltic because of eutrophication, the cod, the simple and sensitive food web and no potential Mnemiopsis enemies On the West Coast there are several potential enemies e.g. the jellyfish Cyanea capillata and the ctenophores Beroe gracilis and Beroe cucumis
Parasites Edwardsiella sp. (sea anemone) Erik Selander, Lene Friis Møller, Per Sundberg, Peter Tiselius (Biol Inv 2010)
BAZOOCA (BAltic ZOOplankton CAscades) A 3 year EU project (Bonus + program) with 11 partners from the Nordic countries - co-ordinated by Peter Tiselius University of Gothenburg By use of models, experiments and field studies, BAZOOCA will quantify ecosystem consequences of the occurrence of the comb jelly Mnemiopsis leidyi in the pelagic food web from microbes to gelatinous top predators in the Baltic Sea Kick-off at Kristineberg Dec 2008
Process cruise October 2009 R/V Skagerak University of Gothenburg
Highest abundances of Mnemiopsis are found on the West coast However lots of Aurelia aurita in the Baltic What is interesting is the total impact of jellies on the ecosystem
S2-7150 (Presenters: Lene Friis Møller/ Aino Hosia) Mnemiopsis vs. Aurelia: The role of gelatinous top predators in the northern Baltic Sea food web GP-7157 Matilda Haraldsson, Cornelia Jaspers, Josefin Titelman, Dag L. Aksnes and Peter Tiselius A place for Mnemiopsis: Spatio-temporal habitat characterization in Scandinavian waters
Jelly community has changed in the Gullmar Fjord Aurelia aurita used to dominate during summer in 2010 there was none Cyanea capillata How it used to be like Aurelia aurita J F M A M J J A S O N D
To find out what is going on with the jellyfish and in turn the effect on the rest of the ecosystem more monitoring is needed!!
Acknowledgement: Baltic Organisations Network for funding Science EEIG, BONUS & The Swedish Research Council FORMAS All photos of Mnemiopsis and parasites by Erik Selander