Pond management Pond management Data Natuurpunt last 15

Pond management

Pond management Data Natuurpunt (last 15 years): Management of > 200 ponds in Flanders (preliminary results) 2% 1% 9% 33% 34% 21%

Pond management Data Natuurpunt (last 15 years): Creation of 1049 new ponds in Flanders Regionaal Landschap Provinciale domeinen Natuurpunt Agentschap Natuur & Bos Provinces & Municipalities Private persons …

Pond management Dredging (sludge removal): often used management technique Dredging needed silting up What is the effect of dredging? Tommelen pond complex: Case study

Management - dredging Ponds in Tommelen dredged in October 2008 MOVIE (see website Pondscape: www. pondscape. be)

Case study: management

Case study: management Physical & chemical variables (nutrients, turbidity, oxygen, . . . ) Morphology (depth, surface area, …) Different organism groups * Bacteria * Macroinvertebrates * Diatomea * Amphibians * Phytoplankton * Vegetation * Zooplankton Sampling: - Spring & summer 2007 & 2008 pre-dredging - Spring & summer 2009 post-dredging Dredging in 2008 effect in 2009?

Management - dredging Effect dredging on environmental factors? After dredging: Higher suspended matter Higher chlorophyll concentrations More open water (also independent of ditch) Could affect communities Effect of ditch on environmental factors? Before dredging: Less vegetation and higher conductivity After dredging: No effect of ditch So effect of ditch is partly ‘filtered’ out due to dredging

Management - dredging Effect dredging on macroinvertebrates? Number of taxa Total diversity Spring 2007 (pre-dredging) 21. 5 +- 6. 8 54 Spring 2008 (pre-dredging) 20. 1 +- 4. 4 54 Spring 2009 (post-dredging) 9. 4 +- 3. 3 34 Less taxa after management (also independent of ditch) Mostly rare taxa disappear after management Ditch no effect on taxon richness

Management - dredging Effect dredging on macroinvertebrates? DREDGING Taxon Richness 20 10 C = control D = dredging C D 2007 C D 2008 C D 2009

Management - dredging Ponds dredged in the mid-90’s: difference with other ponds? Current macroinvertebrate communities: no significant effect Current environmental features: no significant effect No proof for longterm negative effect on macroinvertebrate communities

Management - macroinvertebrates Reduction of macroinvertebrate richness right after dredging Reduction of richness probably recovers after a few years Before management Year after management

Management - macroinvertebrates High beta diversity in Tommelen: Conserving only a few ponds is not sufficient Rare species seem mostly affected immediatly after dredging: Do not dredge all ponds in an area at the same time Spread management over several years

Other sampling campaigns - Multiscale survey - Age experiment

Multiscale survey 125 ponds in Belgium & Luxembourg Hierarchical design Reveal spatial scales of pond biodiversity Samples taken & being analysed - Physical & chemical variables - Morphology - Different organism groups

Age effect Effect age on communities Important information for creation of new ponds Age classes: 0 -5 years 5 -10 years 10 -25 years > 25 years Samples taken (83 ponds) - Physical & chemical variables - Morphology - Different organism groups