Limitations and solutions to the exchange of macrobenthos community data

1. RIKZ Limitations and solutions to the exchange of macrobenthos community data between scientists and CZM managers in the frame of human impact monitoring studies in SW Netherlands Herman Hummel, Bart Schaub, Wil Sistermans, Mieke Rietveld, Rinus Markusse, Ko Verschuure, Olaf van Hoesel, Tom Ysebaert, Dick van Oevelen, Peter Bot & Peter Herman NIOO, Netherlands Institute of Ecology, Centre for Estuarine and Marine Ecology Korringaweg 7, P.O. Box 140, 4400 AC Yerseke, The Netherlands RIKZ, the Dutch Governmental Institute of Coasts and Sea, Den Haag, the Netherlands

2. Presentation content: 1. Why monitoring of macrobenthos 2.Present-day problems regarding monitoring 3. Problem 1: Data stored but not analysed 4. Solution to problem 1: Analyses of data - time series, ordination Example: Grevelingen - major changes, not observed before 5. Problem 2: Causal relationships Mismatch of data-series 6. Solution to problem 2: Correspondence analyses Adjustment of sampling strategy Example: Grevelingen - impact abiotic factors

3. 1. Why monitoring of macrobenthos Benthic organisms are suitable indicators for changes in environmental quality, because of : - their sessile character - relatively long life-span Thereby, benthic organisms - integrate environmental fluctuations and influences - at a particular place over a relatively long time span

4. 1. Why monitoring of macrobenthos The aim of the long-term studies on benthosis to obtaininsight in: - natural development of estuarine and coastal areas - the anthropogenic influences in those areas Such in order to help coastal managers: - saveguard natural resources - allow optimal use of a system’s potentials

5. 1. Why monitoring of macrobenthos As most monitoring programma’s this kind of continuous long-term assessment (= many data) is perfect to detect: - small deviations from a standard or norm - over a long-term - in a large area Year-to-year changes may not be significant, but longer series of data may reveal trends

6. 2.Present-day problems regarding monitoring In the Netherlands TWO major PROBLEMS arise in the present-day evaluation and use of the monitoring data (mainly because of restricted funding).

7. 3. Problem 1: data storage and analysis The first problem is: Basic data are stored by funding governmental agencies often without any further processing and analyses. By that the benefit of monitoring-programmes is debated: - projects were costly - yet did not yield a proper end-product for the end-users (managers and the public in large)

8. 4. Solution to problem 1: data storage and analysis Solution to problem 1: data storage and analysis Use new techniques which allow us to analyse and visualise monitoring data in a limited time and at (relatively) limited costs: - advanced databases - statistical analyses (e.g. ordination, correspondence analyses) - internet communication (web-pages)

9. 4. Grevelingen example 1: data storage and analysis The Grevelingen example Visualisation of a long-term (10-year) data-set showed for the brackish lake Grevelingen dramatic changes in macrobenthos species composition -

10. 4. Grevelingen example 1: data storage and analysis - dramatic changes in macrobenthos species composition - without having been noticed before by managers.

11. 4. Grevelingen example 1: data storage and analysis In case of “ so what ?! “ remarks it may be helpful to communicate on changes in commercial species

12. 4. Grevelingen example 1: data storage and analysis Next step is a statistical analysis of the data by means of correspondence analyses Spring 6-45 m 0-2 m Showed influence of : - depth - season - year Autumn

13. 4. Grevelingen example 1: data storage and analysis Next step is a statistical analysis of the data by means of correspondence analyses 5 4 Showed influence of : 6 3 2 - depth 7 1 - season 8 - year (independent of depth and season) 1990 1999

14. 4. Grevelingen example 1: data storage and analysis Thus a strong temporal evolution

15. 5. Problem 2: Causal relationships The question arises: What are the causes of the changes ? Our second problem therefore is: - coastal managers nowadays ask for causal relationships - relations to (changes in) environmental quality Whereas we have only information on large-scale long-term processes

16. 6. Solution to problem 2: causal relationships Solution to problem 2: causal relationships More detailed information is needed on: - temporal and spatial dynamics in distribution of benthic populations (short-term / small scale) - environmental variables

17. 6. Grevelingen example 2: causal relationships Possible relationships, i.e. causes for the changes in Grevelingen ? - sedimentation of organic matter and silt (esp. in the deeper parts) more sediment surface feeders, more worms - higher salinity, disappearance of seagrass-beds disappearance associated fauna - lower light penetration change of primary production decrease of suspension feeders or grazers - high concentration of pollutants decrease in numbers / biomass of sensitive species

18. 1990-2002 West 1990-2002 East 1982-2002 Dreischor 1972-1985 data 6. Grevelingen example 2: causal relationships Benthos environmental variables Mismatch between benthos and environmental data

19. Hydrobia ulvae Nereis succinea 6. Grevelingen example 2: causal relationships

20. 6. Grevelingen example 2: causal relationships Relation with light penetration and freshwater inflow from polders More freshwater from polders > Lower light penetration > Lower benthic primary production > Decrease of epiphytic grazers

21. 6. Grevelingen example 2: causal relationships Relation with TBT Decrease TBT Still high TBT levels > imposex in molluscs > decrease in numbers All these relationships need further examination and verification

22. Conclusion: In addition to a better use and co-ordination between existing long-term large-scale monitoring programmes a different type of integrated monitoring, at short-term and small-scale is desirable

23. Thank you