presentation 30 oct 08
TRANSCRIPT
MASS MORTALITY AND MASS MORTALITY AND RECRUITMENT OF INTERTIDAL RECRUITMENT OF INTERTIDAL
MARINE INVERTEBRATES IN MARINE INVERTEBRATES IN CHEK JAWA, SINGAPORECHEK JAWA, SINGAPORE
Chek Jawa is lauded for its high Chek Jawa is lauded for its high biodiversity with six distinct ecosystemsbiodiversity with six distinct ecosystems
ObjectivesObjectives
►Attempt a post-event determinationAttempt a post-event determination of the extent of the mass mortality of the extent of the mass mortality event at Chek Jawa of Jan 2007.event at Chek Jawa of Jan 2007.
►Study the contributing factorsStudy the contributing factors leading to the eventleading to the event
► Investigate Investigate the recovery of soft the recovery of soft bodied marine invertebratesbodied marine invertebrates
Figure: Aerial photograph of Chek Jawa (squared in white) and its surrounding. Photo by Google Earth.
Kuala Johore
Salinity decreases
December 06 and January 07 December 06 and January 07 Rainfall eventsRainfall events
►Northeast Northeast monsoon intensified twicemonsoon intensified twice during December 2006 and January during December 2006 and January 2007 2007
►Flooding reportedFlooding reported in many areas in many areas►Freshwater surgeFreshwater surge into Chek Jawa into Chek Jawa
from Johor Riverfrom Johor River►Salinity readings off Eastern Johor Salinity readings off Eastern Johor
Straits were as low as Straits were as low as 4ppt4ppt!!
What contributed to the What contributed to the amplified hyposalinity at Chek amplified hyposalinity at Chek
Jawa? Jawa?
1.1. incidents of low tideincidents of low tide
2.2. amplified river output amplified river output
3.3. prolonged direct rainfall prolonged direct rainfall
Incidence of low tide: Incidence of low tide: 11-14 January 200711-14 January 2007
Jan-07 Hour Hourly Rainfall (mm)Tide level
(m)
11th
10:00 7.8 1.3
11:00 14.1 1.4
21:00 2.1 1.3
22:00 3.3 1.3
23:00 10.9 1.4
0:00 1.4 1.6
12th
11:00 7.4 1.3
12:00 10.7 1.4
13:00 24.1 1.6
14:00 13 1.8
21:00 1.9 1.6
22:00 4.7 1.5
13th12:00 4.6 1.3
13:00 1.1 1.3
14th
12:00 2.4 1.2
13:00 2.3 1.1
14:00 2.3 1.1
15:00 4.4 1.3
16:00 1.6 1.5
Cumulative rainfall data for Cumulative rainfall data for January January 20072007 taken from Changi taken from Changi Meteorological StationMeteorological Station
0
50
100
150
200
250
300
350
400
450
500
.
1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th 12th 13th 14th 15th 16th 17th 18th 19th 20th 21st 22nd 23rd 24th 25th 26th 27th 28th 29th 30th 31st
January 2007
Cu
mu
lati
ve
ra
infa
ll (
mm
)
Prolonged Prolonged direct rainfall for about three days
Mass death first sighted
-1.5
-0.5
0.5
1.5
2.5
3.5
4.5
5.5
6.5
.
1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th 12th 13th 14th 15th 16th 17th 18th 19th 20th 21st
December 2006
Riv
er w
ater
leve
l (m
)
River water-level data taken from River water-level data taken from Johor River, Kota Tinggi.Johor River, Kota Tinggi.
0
5
10
15
20
25
30
35
5-Jul-07
28-Sep-07
23-Dec-07
20-Feb-08
5-Jul-07
28-Sep-07
23-Dec-07
20-Feb-08
5-Jul-07
28-Sep-07
23-Dec-07
20-Feb-08
5-Jul-07
28-Sep-07
23-Dec-07
20-Feb-08
5-Jul-07
28-Sep-07
23-Dec-07
20-Feb-08
5-Jul-07
28-Sep-07
23-Dec-07
20-Feb-08
1 2 3 4 5 6
Transect
Nu
mb
er o
f tu
bew
orm
sNumber of tube worms (Number of tube worms (ChaetopterusChaetopterus sp.) between four sp.) between four
periodsperiods
suggests recovery
Monitoring RecoveryMonitoring Recovery
•Specific fauna targeted
•Once every two months
•Record density
•Study changes
A friend or a foe?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
Comparing December 2007 and Comparing December 2007 and January 2008January 2008
suggests a possibility of mussel beds slowly being replaced away as recovery progresses
DEC 2007 JAN 2008
May 2007
August 2007
October 2007
December 2007
January 2008
August 2008*
* Only mud mounds remain
A
F
B E
D
C
Other fauna surveyedOther fauna surveyed
► Carpet Anemones (Carpet Anemones (Stichodactyla haddoniStichodactyla haddoni))► Sand dollars (Sand dollars (Arachnoides placentaArachnoides placenta))► Sand stars (Sand stars (Astropecten indicusAstropecten indicus) ) ► Common sea stars (Common sea stars (Archaster typicusArchaster typicus))► Button shells (Button shells (Umbonium vestiarumUmbonium vestiarum))► Peacock Anemones (Order Peacock Anemones (Order CerianthariaCeriantharia))
Data of other fauna surveyedData of other fauna surveyed
SpeciesSpecies
Average Average diameter diameter
(cm)(cm)
Average count Average count in one quadrat in one quadrat (corrected to (corrected to
whole number)whole number)Size of Size of
quadratquadratDensity (per Density (per
metre square)metre square)
Sand dollar Sand dollar ((Arachnoides Arachnoides placentaplacenta)) 5.85.8++ 0.1 0.1 3636++1212 (1×1)m(1×1)m22 36 36 ++ 12 12
Sand star Sand star ((AstropectenAstropecten sp.) sp.) 5.55.5++0.10.1 1515++55 (5×5)m(5×5)m22 1515++5 5
Button shell Button shell ((Umbonium Umbonium vestiarumvestiarum)) NilNil 284284++43.243.2 (15×15)cm(15×15)cm22 1262212622++19211921
Common sea star Common sea star ((Archaster typicusArchaster typicus)) 16.1416.14 NilNil NilNil NilNil
Establish baseline
What is the future for Chek What is the future for Chek Jawa?Jawa?
►Appears to be recoveringAppears to be recovering►Recruitment of larvae from nearby Recruitment of larvae from nearby
seeding sitesseeding sites►Designation as protected area Designation as protected area
enhances natural recoveryenhances natural recovery►Marine life is vulnerable Marine life is vulnerable ►better understanding is essential to better understanding is essential to
protect Chek Jawaprotect Chek Jawa