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|Eelgrass (Zostera marina L.) in the western Wadden Sea: monitoring, habitat suitability model, transplantations and communication|
Bos, A.R.; Dankers, N.M.J.A.; Groeneweg, A.H.; Hermus, D.C.R.; Jager, Z.; de Jong, D.J.; Smit, T.; de Vlas, J.; van Wieringen, M.; van Katwijk, M.M. (2005). Eelgrass (Zostera marina L.) in the western Wadden Sea: monitoring, habitat suitability model, transplantations and communication, in: Herrier, J.-L. et al. (Ed.) (2005). Proceedings 'Dunes and Estuaries 2005': International Conference on nature restoration practices in European coastal habitats, Koksijde, Belgium 19-23 September 2005. VLIZ Special Publication, 19: pp. 95-109
In: Herrier, J.-L. et al. (Ed.) (2005). Proceedings 'Dunes and Estuaries 2005': International Conference on nature restoration practices in European coastal habitats, Koksijde, Belgium 19-23 September 2005. VLIZ Special Publication, 19. Vlaams Instituut voor de Zee (VLIZ): Oostende. XIV, 685 pp., more
In: VLIZ Special Publication. Vlaams Instituut voor de Zee (VLIZ): Oostende. ISSN 1377-0950, more
|Authors|| || Top |
- Bos, A.R.
- Dankers, N.M.J.A., more
- Groeneweg, A.H.
- Hermus, D.C.R.
- Jager, Z., more
- de Jong, D.J., more
- Smit, T.
- de Vlas, J.
- van Wieringen, M.
- van Katwijk, M.M.
Eelgrass almost completely disappeared in the course of the previous century. Because of this, the Dutch authorities funded a four-year (2002-2005) project “Reintroduction of eelgrass (Zostera marina L.) in the western Wadden Sea”. The objective of this project was to create a stable eelgrass population which would grow into a source for further recovery and expansion. Transplantations were carried out using the expertise from previous research on habitat requirements, donor suitability and transplantation techniques. Furthermore, actual eelgrass beds in the Wadden Sea were monitored, a communication strategy was implemented and a seagrass map (for both Z. marina and Z. noltii) was developed with a Habitat Suitability Model in order to select optimal locations for transplantation and protection. This paper gives an overview of these activities and their results. Transplantation depth, size and density of planting units were varied to optimize the transplantation technique. Some transplantations were carried out in proximity of a mussel bed to test facilitative effects. A chain of unfortunate events caused the transplantation in the year 2002 to fail. The transplantation in 2003 became very successful: high survival rates with abundant development of reproductive shoots, though few seeds were observed. In spring 2004 few seedlings were found, which may have been due to the low seed production observed in 2003 and/or abundant macro-algal development. The transplantations in 2004 resulted in equally high survival rates as in 2003. Fortunately, abundant seed production was measured in September 2004. From the experimental pilot in transplanting we learned that higher density (14 vs. 5 plants·m-2) has a favourable effect on survival, except at the most sheltered locations where density had no effect. Variation in planting unit size (37 vs. 61 plants) had no effect, while variation in depth (+2 vs. +8cm MSL) only had marginal effects. Planting in open spaces within a mussel bed had a positive effect on eelgrass survival during the first growing season, indicating facilitation. At present, natural seagrass beds in the Wadden Sea cover approximately 270ha, but this figure varies from year to year. Habitat suitability was found to be 20-50% in an area of 9,490ha in the Dutch Wadden Sea and 50-80% in an area of 1,747ha. Another 200ha was highly suitable (80-100%) for seagrass growth. This, together with the small scale transplantation successes and the persistence of (dynamic) natural beds, gives hope for future seagrass recovery in the Wadden Sea.