POPULATION DYNAMICS AND PREDATION IMPACT OF THE INTRODUCED CTENOPHORE 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 Cnidarians Aurelia aurita Cyanea capillata

Many hydromedusae

Ctenophores

Pleurobrachia pileus

Beroe cucumis gracilis

What is dominating has now changed.... Mnemiopsis leidyi - invasive ctenophore

Native along the Eats zooplankton American East Coast (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 2007-2009 Mnemiopsis biomass

90

80 2007 )

-3 70 2008 60 2009

50

40

30

20

10

Biomass (g wet weight m Biomass (g wet 0 08 09 09 09 08 08 09 08 09 10 08 09 07 08 07 08 07 09 07 08 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ Jul Jul Jan Jan ‐ Jun Jun Oct Oct Feb Sep Apr Feb Sep Dec Aug Dec Nov Aug ‐ ‐ Mar ‐ ‐ ‐ May ‐ ‐ 6 ‐ ‐ 3 1 6 9 3 21‐ 6 22‐ 17 14 29 12‐ 22‐ 25‐ 18‐ 25‐ 14‐ 28‐ 17‐ Development

Oral/aboral

Rapoza et al. 2005

Lobate at ca. 3-4 mm - factor 1.4 between total and oral-aboral length Abundances (ind m-3) in 2008

From 450 µm net (ind. larger than 4mm)

10 9 8 )

-3 7 6 5 4 3 2

Abundance (ind m Abundance (ind 1 0 08 08 07 08 08 09 08 08 08 08 08 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ Jul Jan Jun ‐ Apr Feb‐ Sep Dec Dec Aug Nov ‐ ‐ Mar ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 1 2 11 8 27 22 29 18 24 20 13 Size-range - lobates

Lengths measured as oral-aboral

90

80

70

60

50 Length, mm 40

30

20

10

0 08 08 08 08 08 08 08 08 08 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ Jul Oct Oct Sep Dec Dec Aug Aug Nov ‐ ‐ ‐ ‐ ‐ ‐ ‐ 9 8 21‐ 29 19 28‐ 10 30 18 2008 - abundance of larvae (ind m-3)

From 90 um net: ca. 0.4-1 mm From 450 um net: ca. 1 - 3 mm ) -3 400 450 um net 350 90 um net 300 250 200 150 100

50

abundance of larvae (ind m abundance of larvae 0 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ Jul Jan Jan‐ Jun Jun Oct Oct Apr Apr Feb Sep Dec Dec Aug Aug Nov ‐ ‐ Mar ‐ Mar ‐ ‐ May ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 1 9 7 6 8 19‐ 1 21 29 27 10 30 10 17‐ 26 28‐ 16 21‐ 20 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) (ind m3) Zooplankton abund. Zooplankton abund.

8.0 8.0 1600 7.0 average 0‐10 m Primary production 7.0 Chl a 1400 6.0 PP 6.0 1200

) 5.0 -1 a 5.0 1000

4.04.0 800 Chl (µg l 3.03.0 600

2.02.0 400

1.01.0 200

0.00.0 0 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ Jul Jul Jul Jul Oct Oct Oct Sep Sep Sep ‐ ‐ Oct Oct Oct Aug Aug Aug Sep Sep Sep Aug Aug Aug ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 9 9 9

21‐ 31‐

9

31 21

19 29

19‐ 29‐

29 19

10‐ 20‐

30‐

19

29 30

20 10 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

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

How it used to be like……

Cyanea capillata

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