MONITORING THE MONITORING THE RECOVERY OFRECOVERY OF BLEACHEDBLEACHED

CORALS IN SINGAPORE CORALS IN SINGAPORE FROM THE 1998 GLOBAL FROM THE 1998 GLOBAL MASS BLEACHING EVENMASS BLEACHING EVEN T

Karenne TunChou Loke Ming

Jeffrey LowBeverly Goh

Marine Biology Laboratory, Department of Biological SciencesNUS

What are Corals and Coral Reefs?

CORALS

• Invertebrate

• Either hard or soft

• Each individual coral is called a polyp• Solitary or colony forming

• Two basic types : hermatypic (harboring symbiotic algae)ahermatypic (with no symbiotic algae)

• Built entirely by reef-building corals (and other reef building organisms)

ahermatypic (with no symbiotic algae)

CORAL REEFS

• Massive 3D geological entities, whose framework of limestone (calciumcarbonate) is made up of layers upon layers of coral skeleton

What is coral bleaching?

• Coral “bleaching” is defined as an unusual response of corals to moststresses that are short of lethal.

• Corals turn pale or white!!!

Why do Corals Bleach?

• Corals thrive under very narrow tolerance ranges

• These include : temperatures too high or too lowsalinity too high and too lowirradiance too high or too lowsediment loads too high

• Bleached corals may die if stress is sustained or worsened, butcan recover if stress is removed or lessenedcan recover if stress is removed or lessened

• This can take a few days to over a year

1998 - A Bleak Year for Coral Reefs

• Coral bleaching has been reported for nearly a century

• Prior to the 1980’s, all known cases were very limited in extent and duration

• In the 1980’s, bleaching spread dramatically from very small areas to huge areas of oceans

• 1998 also saw one of the largest El Niño’s in 150 years

• In 1998, a global mass bleaching of corals were reported in manytropical countries

• NOAA scientists (and many others too) have attributed mass bleaching events over the past 1 1/2 decades to the rise in sea surface temperature brought about by El Niño

1998 - A Bleak Year for Coral Reefs

Coral Bleaching in Singapore

• Subsequent surveys to other reefs confirmed that the bleachingwas widespread, affecting all coral reefs in the Southern Islands of Singapore

• First ever observation of mass bleaching of corals in Singapore was on 15nd June 1998 at the fringing reef along Pulau Hantu West

• Visual observations put the bleaching at between 50% to 90% at all reefs surveyedreefs surveyed

• Reports from colleagues working in the region confirmed that thebleaching was also widespread regionally

• Sea temperature readings have been observed to be increasing since the second half of 1997, and unusually high sea temperatures were observed in the coastal waters of Singapore since March 1998

Monitor the Bleaching

• Initiated a monitoring programme to assess the recovery (if any) of thebleached corals

• 3 permanent 10m line transects were established

• 35 coral colonies of various genera and growthforms were selected and tagged

• Chlorophyll analysis were conducted • Chlorophyll analysis were conducted

• Currently data is being analysed and results synthesized

• Water temperature readings were taken during each survey

Some Results

LINE INTERCENT TRANSECTBenthos T1-1 T1-2 T1-3 T1-4 T1-5 T1-6 T1-7 T1-8

7/31/98 8/4/98 8/11/98 8/17/98 8/24/98 8/31/98 9/17/98 12/14/98CBCE 20-40 0-20 0-20 0-20 0-20CF 80-100 60-80 60-80 80-100 0-20 0-20 0-20 0-20CM 60-80 60-80 60-80 40-60 60-80 60-80 60-80 0-20

CMRCS 20-40 20-40 0-20 0-20 0-20 0-20 0-20 0-20

Benthos T2-1 T2-2 T2-3 T2-4 T2-5 T2-6 T2-7 T2-87/31/98 8/4/98 8/11/98 8/17/98 8/24/98 8/31/98 9/17/98 12/14/98

CBCBCE 80-100 80-100 80-100 80-100 80-100 0-20CF 60-80 60-80 60-80 60-80 80-100 60-80 40-60 0-20CM 20-40 20-40 40-60 20-40 20-40 20-40 20-40 0-20

CMR 80-100 80-100 20-40 0-20 0-20 0-20 0-20CS 80-100 80-100 80-100 60-80 60-80 60-80 0-20

Benthos T3-1 T3-2 T3-3 T3-4 T3-5 T3-6 T3-7 T3-87/31/98 8/4/98 8/11/98 8/17/98 8/24/98 8/31/98 9/17/98 12/14/98

CB 40-60 20-40CE 40-60 40-60 40-60 40-60 40-60 0-20 0-20 0-20CF 60-80 60-80 60-80 20-40 20-40 0-20 0-20 0-20CM 20-40 0-20 0-20 0-20 0-20 0-20 0-20 0-20

CMR 60-80 60-80 60-80 60-80 60-80 40-60 20-40 0-20CS 40-60 40-60 40-60 40-60 40-60 20-40 0-20 0-20

Some Results

INDIVIDUAL COLONY MONITORING

• Outlines of the 35 colonies were digitally drawn from scannedslides of the corals

• The percent bleaching of the corals and proportion of bleaching weredrawn onto the outlines, and a series of these outlines spanning the 10surveys were produced

• Recovery was observed, but variable within and among coral genera

CHLOROPHYLL

• Chlorophyll concentrations at various wavelengths increased over 3samplings

Some Results

• Colony status on 15 July 1998 (1st survey) and 14 Dec1998 (last survey) :

15 July 1998 14 Dec 19981,1 Pectinia 80-100% 0%1,2 Pectinia 100% 0%1,3 Pectinia 100% 0%1,4 Pectinia 100% Colony dead1,5 Pectinia 80% Colony dead

2,1 Goniopora 30-80% 0%2,2 Goniopora 30-70% 0%2,3 Goniopora 30-70% 0%2,4 Goniopora 40-90% 0%2,5 Goniopora 40-80% 0%

4,1 Euphylia 100% Colony dead 4,2 Euphylia 100% Colony dead 4,3 Euphylia 100% 0%, Part of colony dead4,4 Euphylia 100% Almost entire colony dead 4,5 Euphylia 100% 0%

Some Results

• Recovery of the coral Pectinia sp. (Code 1,1) over several surveys

170898

171098310898

240898

Some Results

• Some corals that didn’t survive :

• And some that did :

Date 24 hr Average

Average DaytimeTemp

Average Night-time Temp

DaytimeMax/Min

Night-timeMax/Min

27 Nov 1997 30.28 30.28 30.15 31.00-29.75 30.35-29.75

2 Dec 1997 30.49 30.58 30.40 32.40-30.20 30.60-30.00

9 Dec 1997 30.33 30.47 30.19 32.60-30.10 30.50-29.90

21 Jan 1998 30.04 30.44 30.10 31.70-30.00 30.50-29.70

5 Mar 1998 31.01 31.19 30.76 31.90-30.50 30.90-30.40

Some Results

TEMPERATURE• 24 hour temperature data:

5 Mar 1998 31.01 31.19 30.76 31.90-30.50 30.90-30.40

6 Mar 1998 33.89 33.98 33.77 34.55-26.55 34.30-32.95

13 Mar 1998 31.08 31.20 30.91 31.50-30.75 31.05-30.60

15 Mar 1998 31.04 31.13 30.91 31.55-30.65 31.05-30.65

16 Mar 1998 31.43 31.51 31.31 31.95-31.05 31.50-31.05

18 Mar 1998 31.33 31.43 31.22 31.85-30.95 31.40-30.60

3 June 1998 34.25 34.35 34.12 36.15-32.15 35.70-31.85

•Instantaneous sea surface temperature (SST) recordings :

Date (1998) 31 July 4 Aug 17 Aug 24 AugSST range 30.0-30.5 30.2-30.5 30.1-30.4 29.8-19.9

So What’s Next?

• It is important to study coral bleaching and their causes

• A relatively new science

• Numerous of organisations have already started focusing on the studyof bleaching and its causes

• Better access to SST in the coastal waters of Singapore

• More conscious of “natural” signals• More conscious of “natural” signals