Long term trends and prospects for the Wadden Sea

Transcription

1 CWE Symposium: Back to the future, the ecological reshaping of Dutch waters Long term trends and prospects for the Wadden Sea Franciscus Colijn, Helmholtz Zentrum Geesthacht, Institut für Küstenforschung KNAW, 5 February 2015 With support from: Jan Bakker, Justus van Beusekom, Rob Dekker, Jan Drent, Stefan Garthe, Ingrid Kröncke, Remi Laane, Ursula Siebert, Ingrid Tulp, CWSS

2 Source for information 2

3 Phytoplankton in the North- and Wadden Sea 3

4 Marsdiep annual chlorophyll a concentrations, ,00 chl 14,00 12,00 10,00 8,00 chl 6,00 4,00 2,00 0, Data: Cadee, Philippart, NIOZ 4

5 Annual TN Load main rivers, after Van Beusekom Annual TN Load Southern and Central Rivers Total Nitrogen Load (Tonnes/year) Elbe, Weser Rhine, Maas, Noordzeekanaal, IJsselmeer, Ems Year 5

6 Specific loads of TN corrected for river flow (JvB) 6

7 TN Load and mean summer chlorophyll Acknowledgements to Justus van Beusekom 7

8 Data: Justus van Beusekom 14 Annual mean of chlorophyll at Sylt (AWI) very cold winters Chl a (µg/l) Year 8

9 Dense seagrass bed at Sylt, courtesy Anja Schanz 9

10 Seegras return in the North Frisian Wadden Sea (right) slow return in southern Wadden Sea Explanations, causes Latitude ( N) North Sea Summer-Chlorophyll a (µg/l) Wadden Sea (Mean ) Weser Ems Elbe Seagrass area (>20% coverage, km²) Seagrass area (km²) Rhine NO 3 - (Dutch-German border) Rhine NO 3 - (µm) Rhine / Maas Longitude ( E) Year Dolch, Buschbaum, Reises (2013) Dolch, Buschbaum, van Beusekom, Reise, unpubl. 0 10

11 Total macrozoobenthic biomass 150 Balgzand Subtidal Wwad Biomass (g AFDM. m -2 ) year Courtesy: Rob Dekker, NIOZ 11

12 Drent, in prep. Comparison of chlorophyll a concentrations and benthos biomass at 6 locations in the Wadden Sea: Ho Bugt and Romo in DK, Norderney in Germany, and GW, Piet Scheveplaat and Balgzand in the Dutch part. 12

13 Comparison between spatial distribution of the intertidal macrofauna communities in the 1970s and 2009 Nephtys hombergii Cerastoderma edule Corophium volutator Scoloplos armiger- Urothoe poseidonis Heteromastus filiformis Tharyx marioni Cerastoderma edule Mya arenaria Peringia ulvae Caulleriella killariensis-pygospio elegans Scoloplos armiger Caulleriella killariensis Peringia ulvae Tubificoides benedii 13

14 Pacific oyster bank, from QSR 10 cm 14

15 High biomass of Pacific oyster beds in the Jade source: QSR,

16 Total fish Wadden Sea Courtesy of Ingrid Tulp, IMARES, IJmuiden 16

17 Migratory birds: population developments Oystercatcher Spotted redshank Source: Laursen et al Wadden Sea Ecoystem No

18 Greenshank Great cormorant Source: Laursen et al Wadden Sea Ecoystem No. 30 Source: Laursen et al Wadden Sea Ecoystem No

19 Migratory birds: developments of all species Reasons for the declines are still widely unclear Source: Blew et al Wadden Sea Ecoystem No

20 Trends in breeding birds (German Wadden Sea) Kentish Plover Photo: Martin Stock Courtesy: Stefan Garthe 20

21 Trends in breeding birds (German Wadden Sea) Kentish Plover Ruff Photo: Martin Stock Courtesy: Stefan Garthe 21

22 Trends in breeding birds (German Wadden Sea) Kentish Plover Ruff Spoonbill Photo: Martin Stock Courtesy: Stefan Garthe 22

23 Trends in breeding birds (German Wadden Sea) Kentish Plover Ruff Spoonbill Oystercatcher Photo: Martin Stock Courtesy: Stefan Garthe 23

24 Possible causes for declines in breeding birds Succession in conservation polders (shrubs and high vegetation missing natural dynamic in embanked areas) Predation by mammals at mainland sites strong increase in numbers of foxes and raccoon dogs 25, Number of hunted foxes 20,000 15,000 10,000 5,000 Number of hunted raccoon dogs Year Year Data taken from: MLUR (2008) Drowning: Frequency of summer storm surges increased Courtesy: Stefan Garthe 24

25 Back barrier island of Schiermonnikoog Van der Wal

26 Back-barrier marsh (> 100 yr) of Schiermonnikoog Bakker

27 courtesy: CWSS, W haven, Germany 27

28 Return to the Wadden Sea by grey seals, first birth in DK in 2015! Courtesy of: CWSS, W haven, Germany 28

29 Distribution Harbor Porpoises in North- and Baltic Sea based on air surveys Gilles, A., Scheidat, M. and Siebert, U Marine Ecology Progress Series 383: ; Herr, H., Fock, H. and Siebert, U Biological Conservation 142, ; Scheidat M., Kock K.H. and Siebert U Journal of Cetacean Research and Management 6(3), ; Scheidat, M., Gilles, A. and Siebert, U Endangered Species Research 5, ; Siebert U., et al Journal of Sea Research 56,

30 Temporal Trend of PFCs in Harbor Seals Declining PFC contamination in harbor seals from the German Bight, Germany, Ahrens, L.; Siebert, U.;Ebinghaus, R. Chemosphere,

31 PAKs in Dutch coastal sediments from: Laane et al.,

32 AMOEBA: Description and Assessment of ecosystems Comparison between present (1988) and reference situation for ca. 30 species ten Brink, Hosper and Colijn, Mar. Poll. Bull.23: