The physical characteristics of the Baltic Sea might act as a bottleneck for the Mnemiopsis leidyi population expansion in this newly invaded area

Transcription

1 The physical characteristics of the might act as a bottleneck for the Mnemiopsis leidyi population expansion in this newly invaded area Cornelia Jaspers, Thomas Kiørboe, Kajsa Tönnesson & Matilda Haraldsson 5th International Zooplankton Production Symposium Pucón, Chile

2 Introduction Invasion history of Mnemiopsis Mnemiopsis leidyi First observed 25 in northern European waters (Oliveira 27)

3 Introduction Mnemiopsis invasion route Reusch et al. 21 (Mol. Ecol.)

4 Introduction Fecundity Egg production is high and maximum rates are reported 14 eggs day 1 US (Kremer, 1976) 12 eggs day 1 Black Sea (Zaika & Revkov, 1994) 12 eggs day 1 Kattegat (Jaspers p.obs.) Furthermore Hermaphrodites hours from fertilisation to hatching Disoogenie (larval reproduction) (Chung 1892, Martindale 1987)

5 Introduction Egg production Egg production in Mnemiopsis has been shown to vary with (Kremer,1976; Reeve et al., 1989; Purcell et al. 21) Size Food availability Temperature Production is regarded as highly sensitive to food environment 2-4 days of starvation leads to a cessation of egg production (Båmstedt in Purcell et al. 21)

6 Aim What does this mean for the?

7 Aim What does this mean for the? Objectives: Understand the in situ reproduction rates of Mnemiopsis in the

8 Hydrography Investigation area 1 Kattegat 6 Depth (m) 2 3 Depth (m) Salinity Southern Baltic Salinity Salinity 1 Kattegat km Exp. temperature: 12.5 ± 1 C Salinity

9 6 Results Size dependent egg production Eggs Mnemiopsis -1 24h Kattegat Size (oral-aboral, mm) Egg production in the Kattegat at 12 ± 1.5 C in October 29 (R 2 =.48, p<.1)

10 6 Results Size dependent egg production Eggs Mnemiopsis -1 24h Kattegat Eggs Mnemiopsis -1 d -1 =.64 x L Size (oral-aboral, mm) Egg production in the Kattegat at 12 ± 1.5 C in October 29 (R 2 =.48, p<.1)

11 6 Results Size dependent egg production Central & Southern Baltic Eggs Mnemiopsis -1 24h Size (oral-aboral, mm) Egg production in the Southern Baltic at 12 ± 1.5 C

12 6 Results Size dependent egg production Eggs Mnemiopsis -1 24h Central & Southern Baltic Eggs Mnemiopsis -1 d -1 =.2 x L Size (oral-aboral, mm) Egg production in the Southern Baltic at 12 ± 1.5 C (R 2 =.27, p=.2)

13 6 Results Egg production rates Kattegat vs. Southern Baltic log (eggs [Mnemiopsis -1 d -1 ] +1) Kattegat S. Baltic log (size[mm]+1) Slopes of Kattegat versus Southern Baltic egg production rates differ significantly (p=.7, F 1,95 =12.28)

14 Results Volume specific egg production Eggs ml Mnemiopsis -1 d Kattegat Southern Baltic n=17 n=2 n=15 n=25 n=14 n=8 Slaggoe Anholt 24h Anholt T1+T2 Hanoebugten Bornholm BY1

15 6 Results Volume specific egg production Eggs ml Ctenophore -1 d n=52 n=47 Kattegat Southern Baltic Egg production varies significantly between high saline Kattegat 2±17 and low saline S. Baltic 3.±2.5 (t=6.77, DF=97, p<.1).

16 Summary I In situ egg production rates Mnemiopsis leidyi Similar temperatures Salinity differs (Kattegat) 7-9 (Baltic) Egg production rates are significantly higher in the higher saline Kattegat How does the community composition look like in both areas?

17 6 Results Mnemiopsis leidyi abundance m Abundance (m -3 ) upper 2m Station Depth distribution: Accumulation in the surface (2 m)

18 6 Results Mnemiopsis leidyi abundance m Abundance (m -3 ) upper 2m Abundance 1 fold higher in Kattegat Station Depth distribution: Accumulation in the surface (2 m)

19 6 Results Mnemiopsis leidyi population size distribution M.leidyi average size (mm) Station

20 6 Results Mnemiopsis leidyi population size distribution M.leidyi average size (mm) Station

21 6 Results Mnemiopsis leidyi population size distribution M.leidyi average size (mm) Av. 4% reproductive active Station

22 6 Results Mnemiopsis leidyi population size distribution M.leidyi average size (mm) Av. 4% reproductive active Av. 9% reproductive active Station

23 6 Results Mnemiopsis leidyi population size distribution M.leidyi average size (mm) Av. 4% reproductive active Av. 9% reproductive active Station Higher active recruitment in the Kattegat

24 6 Biomass Potential egg production Mnemiopsis leidyi Potential egg production (eggs m -2 d -1 ) Station

25 6 Biomass Potential egg production Mnemiopsis leidyi Potential egg production (eggs m -2 d -1 ) Station Potential population egg production higher in the high saline Kattegat

26 6 Biomass Potential egg production Mnemiopsis leidyi Potential egg production (eggs m -2 d -1 ) x higher in Kattegat than S. Baltic Station Potential population egg production higher in the high saline Kattegat

27 Summary II Population structure Mnemiopsis leidyi Factor 1 higher abundances in Kattegat Higher fraction of small sized animals in the Kattegat => recruitment Higher potential population reproduction in the Kattegat How does the food composition compare?

28 6 Biomass Zooplankton standing stock: 5 fold difference Zooplankton biomass (mgc m -3 ) Kattegat Baltic Total zooplankton carbon from lengths (9µm samples), averaged

29 6 Biomass Zooplankton standing stock: 5 fold difference Zooplankton biomass (mgc m -3 ) x higher food availability for Mnemiopsis in the Baltic Kattegat Baltic Total zooplankton carbon from lengths (9µm samples), averaged

30 6 Biomass Zooplankton production: 5.5 fold difference Zooplankton biomass (mgc m -3 ) Production: 17 % d -1 Kattegat Baltic 3 % d -1 Higher copepod production rates in the Kattegat

31 6 Biomass Zooplankton mortality: due to Mnemiopsis Zooplankton biomass (mgc m -3 ) Zooplankton mortality: 3.5 % d -1 Kattegat Baltic.2 % d -1

32 6 Biomass Zooplankton Chl a concentrations Zooplankton biomass (mgc m -3 ) Chl.a: 2.2±.7 µg L -1 Chl.a: 3.3±.8 µg L -1 Kattegat Baltic

33 Summary III Zooplankton standing stock Mnemiopsis leidyi Zooplankton standing stock 5 times higher in the Baltic, but Mnemiopsis reproduction rates are much lower

34 Summary III Zooplankton standing stock Mnemiopsis leidyi Zooplankton standing stock 5 times higher in the Baltic, but Mnemiopsis reproduction rates are much lower Conclusion: Salinity acts on the reproductive output of Mnemiopsis in the

35 Mortality Egg morality rates Back of the envelope calculation (assuming steady state): µ(d -1 )= (egg prod.m -2 d -1 /egg obs.m -2 ) - 1/egg hatching time d -1 High mortality rates in both areas, but 3 times higher in the Kattegat than Southern Baltic. Abundance and size distribution suggest that the recruitment success is higher in the Kattegat even though eggs face higher mortality rates.

36 Outlook Can M. leidyi sustain a population in the Baltic? Salinity might constrain population expansion under current situation in the central M. leidyi population in the Baltic is probably sourced from Kattegat Mnemiopsis population in the Baltic depends on drift of animals from high reproduction area - Kattegat Temporal and spatial M. leidyi abundance in the Kattegat & Baltic: Poster Haraldsson et al. GP: 71

37 Collaborators & Funding Acknowledgements BAZOOCA Team (Baltic ZOOplankton Cascades) BAZOOCA