Martin Pusch Leibniz-Institut für Gewässerökologie und Binnenfischerei

2. Functions of hydro-morphological structures in large river-ecosystems with fine sediments, and impacts by shipping and river training structures Martin Pusch Leibniz-Institut für Gewässerökologieund Binnenfischerei Institute of Freshwater Ecology and Inland Fisheries Berlin E-mail: pusch@igb-berlin.de

3. Questions • Which ecosystem functions are going on in rivers? • Why should we care? • What are the governing factors for riverine ecosystem functions? • Relationship between ecosystem function and biodiversity • Impacts by shipping and river training Conclusions / Issues for discussion

4. Case study: The Elbe River in Germany The River Elbe - now one of the best studiedlarge river systems of the world Length: 1091 kmWaterways: 940 kmSlope: 0.021 %Mean discharge: 350 m3/s

5. Total inputs Diffuse inputs Retention of inputsin river system Nitrogen 230 000 t/a 74 % 32 % Phosphorus 12 000 t/a 68 % 56 % Behrendt (2005) EUROCAT WP4 Report Inputs of plant nutrients • Surface waters may retain a significant proportion of nutrient inputs (retention of matter and self purification) • As diffuse inputs can hardly be reduced on the short term, river management should seek to maximize in-stream retention of matter (Grafik: FZ Jülich)

6. Inputs of badly treated sewage water (saprobic contamination) () Phytoplankton Plant nutrients N and P Biologically undegradable organic compounds (Xenobiotics) Pharmaceuticals and hormone-like substances Eutrophication Heavy metals Contaminants River morphology River-floodplain connectivity Morphology Recent human impacts on rivers

7. Human use and modification of riverine functions Transport Retention Habitat Metabolism of matter Dynamic riverine channel structures and their ecological functions…

8. …in rivers used for navigation…

9. …will partially be reduced by shore protection..

10. …or totally disappear

11. Historical river training on the Elbe Overlain maps of Elbe section from 1792 and 1893 (red)

12. Current river morphology of the Elbe • Construction of groynes (and impoundment of upper Elbe section) initiated strong depth erosion in some reaches:max. 1.6 m in 120 a, currently 2 cm/a. • Bedrock ’grows’ out of the river bottom at 2 places, acting as obstacles for navigation. • In erosional reaches groynes are now situated much too high. • Self-acceleration of depth erosion, acceleration of flood peaks. • Currently artificial bedload addition of 80 000 t/a (planned, but not fully implemented because of practical problems). • Depth erosion process is currently still out of control.

13. Riverine morphological structures in the Elbe und Loire rivers 6000 groynes built on the Elbe, mostly in 1880s and 1930s Elbe bei Wittenberge Loire near Bréhémont (Fluss-km 794)

14. Sampling the central river sediments with a diving bell ship

15. Degradation of matter in lowland rivers Percentage of sediments in total riverine metabolism Elbe Spree Winter Summer Winter Summer 96 % 90 % 94% 95% Water column Aquatic plants Sediment Bacterial production Extracellular enzyme activity • Riverine microbial metabolism is mainly related to the river bottom after Wilczek, Fischer, Pusch ( 2005) Microbial Ecology Fischer, Pusch (2001) Freshwater Biology

16. Seasonal dynamics of microbial activities Elbe sediments 2001-2002 May Flood Phosphatase [% of cumulativeenzyme activity in 0-5 cm and15-20 cm depth] 50 Apr Jun 40 Mar Jul 30 Feb 20.0 Aug Algal bloombreakdown Jan Sep Input of terrestrialPOM containing P Dec Nov after Wilczek, Fischer, Pusch ( 2005) Microbial Ecology

17. Bacterial production in Elbe sediments Bacterial production [g C cm-3 h-1] x 10-6 0 0.5 1.0 1.5 2.0 2.5 3.0 0 20 40 Sediment depth [cm] 60 Coswig groyne fields r2 = 0.83 80 Dresden river bottom r2 = 0.93 Dresden river shore r2 = 0.98 100 Coswig river bottom r2 = 0.86 • In river sediments stabilized by groynes microbial activity is restricted to the surface. 120 Fischer, Kloep, Wilczek, Pusch (2005) Biogeochemistry

18. 1 m 30 m Lee side Luff side Plateau Hydrodynamics and microbial activity in a subaqueous dune • Infiltration of water and FPOM • High microbial activity • Exfiltration • Low input and activities • Trapping of POM • High microbial activity MeasuredVariable Hierarchical control Hydro- dynamics and morpho- dynamics Flow velocity VHG O2 O2DO Input of labile microbialsubstrates FPOM input O2 O2 POM pool O2 POM quality Bacterial density Microbial activity Comm. respiration Extracellular enzyme activity • Hydrodynamic coupling of water column and sediments is crucial for significant microbial activity Wilczek, Fischer, Brunke, Pusch (2004) Aquatic Microbial Ecology

19. Central channel sediments – the ‚river‘s liver‘ Bottom sediments swiftly overflown by river waterform a hot spot of microbial activity Fischer, Kloep, Wilczek, Pusch (2005) Biogeochemistry

20. Distribution of sedimentary metabolism Stable discharge conditions Laterale Konnektivität Central channel sediments Permanent vertical connectivity by advective transport

21. Distribution of sedimentary metabolism Discharge and water level fluctuations Laterale Konnektivität Parafluvialsediments Parafluvialsediments Temporary lateral connectivityby advectivetransport Temporarylateral connectivity by advective transport Central channel sediments Permanent vertical connectivity by advective transport

22. Balance of suspended solids load between the two stations Wittenberge (Elbe-km 455) and Hitzacker (Elbe-km 523) (Schwartz et al. 2004) Isolines of water residence timein a groyne field (Sukhodolov et al. 2004) Intensive particle sedimentation in groyne fields

23. Intensive particle sedimentation in groyne fields 1889 1990 • Groyne fields are sites of intensive sedimentation processes • This results in the disappearance of shore habitat diversity • and in huge accumulations of contaminants (e.g. 50kg Pb in 1 groyne field)

24. Retention of matter – balances and regulation • Sedimentation of suspended solids in groyne fields: c. 2,5 t per river kilometer and day in winter • In summer c. 1,4 % of OC load is degraded per river km • Denitrification rate c. 10-20 t NO3-N per river km and year • Aerobic and anaerobic microbial metabolism is governed by hydrological connectivity of sediments with the water column. • Hydrological connectivity is governed by channel morphology and dynamics • Reduction in functionality due to river training cannot be estimated to date because of lack of reference reaches in the Elbe

25. River Quality Model QSIM • Human impacts on rivers can be modelled / predicted concerning hydrodynamics, sediment transport, water quality,as well as habitat availability for fish and invertebrates. Bundesanstalt für Gewässerkunde(Federal Agency of Hydrology)Koblenz, Germany

26. Aquatic organisms as indicators of ecosystem health Benthic invertebrates Fish

27. Habitat quality of several shore protection types Standard groyne field

28. Shore without groynes Parallel groyne Nearshore pool at low flow Parallel groyne at low flow Habitat quality of several shore protection types Pool phase  

29. Shore without groynes Parallel groyne Nearshore pool at low flow Parallel groyne at low flow Habitat quality of several shore protection types • In sand-bed rivers, ecosystem metabolism reaches its maximum in constantly mobile central sediments,while invertebrate diversity reaches its maximum in temporally stable nearshore areas. • Hot spots of ecosystem functions and biodiversitydo not necessarily coincide spatially in river systems. • Both ecosystem functions and biodiversity depend on typical riverine dynamics (floods, sediment transport, morphological dynamics.

30. Effects of ship-induced waves on river margins Passage of cruise ship „Victor Hugo“ on the Elbe near Coswig  Increase of zoobenthos drift by 3x – 30x Brunke, Sukhodolov, Fischer, Wilczek, Engelhardt, Pusch (2002): Verh. Int. Verein. Limnol.

31. ? Parallel groyne ? Modified groyne with central opening Unaltered shore morphology Is an ecological optmization of river training measures feasable and effective? Modelling of habitats before and after planned alterations necessary

32. Synopsis of groyne effects • River training by the construction of groynes is expensive both in installation and maintenance. • The construction of groynes may result in uncontrollable depth erosion, and in higher subaqueous dunes (due to faster flow), thus potentially reducing navigational depths at low flow. • In large rivers, aquatic invertebrates and fish mostly live near the river margins. Modification of these margins strongly affects these organisms. • The construction of groynes fosters storage processes (incl. contaminants) and reduces microbial metabolism.

33. Issues influencing Danube management strategy • Navigation in unstable river channels is largely facilitated by the Radarpilot device, which integrates Radar observa-tions of other ships, GPS and a digital river map.

34. Radar pilot

35. Issues influencing Danube management strategy • Navigation in unstable river channels is largely facilitated by the Radarpilot device, which integrates Radar observa-tions of other ships, GPS and a digital river map. • The Black Sea is a highly sensitive ecosystem which needs strong reduction of inputs especially in plant nutrients. • The European Water Framework Directive does not allow impedement of the ecological status of a river. • The European Commission could possibly require ecological mitigation of planned river training measures.

36. What is needed European R&D projects aiming to integrate objectives for the development of the Danube concerning- Navigation in rivers with limited depth- Hydropower generation- Flood control- Water Framework Directive- EU Habitat Directive- Socio-economic development of regions bordering the Danube • Co-ordinated implementation of river training measures Goodecological status Moderate ecological status Bad ecological status

37. Restorationof secondary channels in the lower River Rhine / Waal (NL) Reconstruction of typical riverine structures from a highly altered state is very expensive, if possible at all.

38. For those who want to read even more on the ecology of the Elbe River I recommend this book (in German) … Vol. 5 of book series on the Elbe Weissensee-Verlag, Berlin ISBN 3-89998-011-5 Maßnahmenvorschläge Thank you for your attention !