1. Baltic Sea food web dynamics and response to environmental change PhD plan Susa Niiranen 28th July 09, Bornholm Photographs: Hirvonen, A. and Lastumäki, I.

2. Aim to Study the past food web mechanisms of the open Baltic Sea ecosystem and their response to external forcing Study the food web changes induced by changes in future climate, fishery and nutrient input. Address management from an ecosystem point of view Place the study results into a more global perspective

3. Questions in food web studies What are the roles of external forces and direction of trophic cascades? Combined effects of control most likely: e.g. “bottom-up” control creates basis for food web structure (e.g. TLs) and production potential  platform for ”top-down” control (Carpenter and Kitchell, 1984; Oksanen, 1988) What influences what? what are the thresholds?  Relevance to management (fishery, nutrient inputs and change in climate)

4. Baltic Sea food web A relatively simple and species-poor food web Ecosystem heavily exposed to human-impact e.g. intensive fishing and eutrophication  ”management matters”. Ecosystem has gone through major transitions in state The most recent shift (late 1980s) when cod and sprat due to: overfishing and spawning habitat deterioration (cod) Change in winter climate  T  ZP (sprat)

5. Ecopath with Ecosim-approach (www.ecopath.org): - Ecopath (mass-balance) P = M p + F + M other + BA + migration C = P + Unass. food + R - Ecosim (simulation) Input parameters: B, P/B, C/B, diet In the Baltic e.g. Harvey et al., 2003; Sandberg et al. 2007 and 2008; Hansson et al., 2007 Food-web modelling approach

6. Spring phytoplankton Bacteria Microzoopl. Mysids Meiobenthos Seals Detritus sed Age 0 Eggs/larvae Pseudocalanus Acartia Temora Other... Macrozoobenthos Cyanob.Other... Age 1 Herring Age 2 etc.. Age 2, etc Age 1 Cod Age 2, etc... Age 1 Sprat DOM Spr_fleet Cod_fleet Her_fleet Temp/Climate /Salinity SAL RV O2O2 ? N, P

7. Planned studies 1. model robustness 2. past dynamics 3. alternative trophic mechanisms 6. spatial dimension 5. future climate effects 4. ensemble modelling

8. 2. Disentangling the effects of multiple drivers influencing Baltic Proper food web Aim to understand the mechanisms behind past food web dynamics Future food web effects cannot be projected and appropriate management options selected without understanding the past Different combinations of external forcing (fishing, T, sal etc.) will be applied on the food web model  What factors and combinations could reproduce the observed model dynamics (incl. late 1980s shift)?

9. Acartia spp.herring spring T F

10. 3. Identifying critical knowledge gaps for our understanding of the Baltic Sea food web dynamics Central fw mechanisms unknown  Aim: What management effect will alternative fw assumptions have? Possible mechanisms to study: ZP feeding on cyanobacteria spatial sprat/cod overlap Invasive species Potential future fw changes tested? Photo: FIMR

11. 4. Ensemble food web and multi-species models Aim to identify knowledge gaps in our understanding of the Baltic Sea system dynamics Comparing the results of different multi-species and fw models A common set of scenarios with varying environmental forcing (cc) and fishing pressure Study is part of the work of ICES WGIAB. ICES WGIAB report 2009

12. 5. How can the future climate affect the Baltic Sea ecosystem and does this create new needs for policy-making? Aim to describe the potential food web effects of future changes in climate and nutrient load Does management need to adapt to cc e.g. for sustainable fishery or “de-eutrophication”? Knowledge on comparative ecosystems is reflected in the analyses of the modelling results. Scenario output from the ECOSUPPORT project is used  Multi-model ensemble simulations

13. ECOSUPPORT model hierarchy www.baltex-research.eu/ecosupport

14. Timetable 2009/102010/112011/122012/13 PhD essay: literature study Papers 1 and 4 Papers 2 and 3Paper 5Paper 6 PhD thesis Papers 2 and 3 Licenciate thesis PhD thesis PhD defence

15. e-mail: susa.niiranen@mbox.su.se Hirvonen, A. and Lastumäki, I. BONUS project ECOSUPPORT is acknowledged for financing this PhD study (www.baltex-research.eu/ecosupport)www.baltex-research.eu/ecosupport Collaboration: Alf Norkko (benthic-pelagic coupling) Maiju Lehtiniemi (mysid and Mnemiopsis dynamics) Brian MacKenzie, John Havenhand (ECOSUPPORT) ICES WGIAB (Integrated assessment) Fiskeriverket – Anna Gårdmark et al. (fish dynamics) Georgi Daskalov (Black Sea) SMHI – Markus Meier et al. (climate scenarios)