Pond management

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

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

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 & summer2009 post-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 Higher chlorophyll concentrations More open water (also independent of ditch) (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 taxaTotal diversity Number of taxaTotal diversity Spring 2007 (pre-dredging) Spring 2008 (pre-dredging) Spring 2009 (post-dredging)  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 CCC D = dredging DD Taxon Richness C = control CC D

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

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 Management - macroinvertebrates

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 years > 25 years Samples taken (83 ponds) - Physical & chemical variables - Morphology - Different organism groups