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

Chek Jawa is lauded for its high Chek Jawa is lauded for its high biodiversity with six distinct ecosystemsbiodiversity with six distinct ecosystems

Mass mortality Mass mortality occurredoccurred

on January on January 20072007

Dying Carpet Anemones, Dying Carpet Anemones, Sponges, echinodermsSponges, echinoderms

Soft bodied invertebrates Soft bodied invertebrates affectedaffected

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

Results and Results and DiscussionDiscussion

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.

Six transect linesSix transect linesT1

T2

T3

T4

T5

T6

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

Monitoring Mussel BedsMonitoring Mussel Beds

A closer lookA closer look

reaching densities of up to 26,000 + 2738.6 per m2

MusculistaMusculista senhousiasenhousia

An invasive species

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

August 2008?August 2008?

May 2007

August 2007

October 2007

December 2007

January 2008

August 2008*

* Only mud mounds remain

A

F

B E

D

C

October 2008?October 2008?

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

Thank youThank you