Presentation 30 Oct 08

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  • Presentation 30 Oct 08

    1. 1. MASS MORTALITY AND RECRUITMENT OF INTERTIDAL MARINE INVERTEBRATES IN CHEK JAWA, SINGAPORE
    2. 2. Chek Jawa
    3. 3. Chek Jawa is lauded for its high biodiversity with six distinct ecosystems
    4. 4. Mass mortality occurred on January 2007
    5. 5. Dying Carpet Anemones, Sponges, echinoderms
    6. 6. Soft bodied invertebrates affected
    7. 7. Objectives <ul><li>Attempt a post-event determination of the extent of the mass mortality event at Chek Jawa of Jan 2007. </li></ul><ul><li>Study the contributing factors leading to the event </li></ul><ul><li>Investigate the recovery of soft bodied marine invertebrates </li></ul>
    8. 8. Results and Discussion
    9. 9. Figure: Aerial photograph of Chek Jawa (squared in white) and its surrounding. Photo by Google Earth. Kuala Johore Salinity decreases
    10. 10. December 06 and January 07 Rainfall events <ul><li>Northeast monsoon intensified twice during December 2006 and January 2007 </li></ul><ul><li>Flooding reported in many areas </li></ul><ul><li>Freshwater surge into Chek Jawa from Johor River </li></ul><ul><li>Salinity readings off Eastern Johor Straits were as low as 4ppt ! </li></ul>
    11. 11. What contributed to the amplified hyposalinity at Chek Jawa? <ul><li>incidents of low tide </li></ul><ul><li>amplified river output </li></ul><ul><li>prolonged direct rainfall </li></ul>
    12. 12. Incidence of low tide: 11-14 January 2007 1.5 1.6 16:00 1.3 4.4 15:00 1.1 2.3 14:00 1.1 2.3 13:00 1.2 2.4 12:00 14th 1.3 1.1 13:00 1.3 4.6 12:00 13th 1.5 4.7 22:00 1.6 1.9 21:00 1.8 13 14:00 1.6 24.1 13:00 1.4 10.7 12:00 1.3 7.4 11:00 12th 1.6 1.4 0:00 1.4 10.9 23:00 1.3 3.3 22:00 1.3 2.1 21:00 1.4 14.1 11:00 1.3 7.8 10:00 11th Tide level (m) Hourly Rainfall (mm) Hour Jan-07
    13. 13. Cumulative rainfall data for January 2007 taken from Changi Meteorological Station Prolonged Prolonged direct rainfall for about three days Mass death first sighted
    14. 14. River water-level data taken from Johor River, Kota Tinggi.
    15. 15. Six transect lines T1 T2 T3 T4 T5 T6
    16. 16. Number of tube worms ( Chaetopterus sp.) between four periods suggests recovery
    17. 17. Monitoring Recovery <ul><li>Specific fauna targeted </li></ul><ul><li>Once every two months </li></ul><ul><li>Record density </li></ul><ul><li>Study changes </li></ul>
    18. 18. Monitoring Mussel Beds
    19. 19. A closer look reaching densities of up to 26,000 + 2738.6 per m 2
    20. 20. Musculista senhousia An invasive species
    21. 21. A friend or a foe? can dominate and exclude native species by settling in aggregations to reach high densities may restrict growth of some seagrass species provide additional habitat
    22. 22. Comparing December 2007 and January 2008 suggests a possibility of mussel beds slowly being replaced away as recovery progresses DEC 2007 JAN 2008
    23. 23. August 2008?
    24. 24. May 2007 August 2007 October 2007 December 2007 January 2008 August 2008 * * Only mud mounds remain A F B E D C
    25. 25. October 2008?
    26. 26. Other fauna surveyed <ul><li>Carpet Anemones ( Stichodactyla haddoni ) </li></ul><ul><li>Sand dollars ( Arachnoides placenta ) </li></ul><ul><li>Sand stars ( Astropecten indicus )  </li></ul><ul><li>Common sea stars ( Archaster typicus ) </li></ul><ul><li>Button shells ( Umbonium vestiarum ) </li></ul><ul><li>Peacock Anemones (Order Ceriantharia ) </li></ul>
    27. 28. Data of other fauna surveyed Establish baseline Nil Nil Nil 16.14 Common sea star ( Archaster typicus ) 12622 + 1921 (15×15)cm 2 284 + 43.2 Nil Button shell ( Umbonium vestiarum ) 15 + 5 (5×5)m 2 15 + 5 5.5 + 0.1 Sand star ( Astropecten sp.) 36 + 12 (1×1)m 2 36 + 12 5.8 + 0.1 Sand dollar ( Arachnoides placenta ) Density (per metre square) Size of quadrat Average count in one quadrat (corrected to whole number) Average diameter (cm) Species
    28. 29. What is the future for Chek Jawa? <ul><li>Appears to be recovering </li></ul><ul><li>Recruitment of larvae from nearby seeding sites </li></ul><ul><li>Designation as protected area enhances natural recovery </li></ul><ul><li>Marine life is vulnerable </li></ul><ul><li>better understanding is essential to protect Chek Jawa </li></ul>
    29. 30. Thank you

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