UNIVERSITI PUTRA MALAYSIA

SOME EFFECTS OF SUBSEA WATER PIPELINE CONSTRUCTION ON SESSILE BENTHIC COMMUNITY STRUCTURE OF REDANG ISLAND,

MALAYSIA

HAMID REZAI-MARNANI

FSAS 1998 9

SOME EFFECTS OF SUBSEA WATER

PIPELINE CONSTRUCTION ON SESSILE BENTHIC

COMMUNITY STRUCTURE OF REDANG ISLAND,

MALAYSIA

By

HAl\1ID REZAI-MARNANI

Thesis Submitted in F u lfilment of the Requirements for the Degree of Master of Science in the Faculty of Science and Environmenta l Studies

Universiti Putra Malaysia

December, 1998

He let forth the two seas that meet together.

Between them a barrier they do not overpass.

o which of your Lord's bounties you and you deny?

From them come forth the pearl and the coral...

o which of your Lord's bounties you and you deny?

Lovely as rubies, beautiful as coral-

The Quran Chapter 55, Verses 19 ... 58

Dedicated to the memory of my father who no longer accompany us on these rocky shores.

ACKNOWLEDGEMENTS

I would l ike to take this opprtun ity to express my sincere grat itude to the

members of the supervisory comm ittee, Professor Dr. Mohd. I brah im Hj. Mohd.,

Dr. I dris B in Abd. Ghani. Dr.Hishamudd in Bin Omar, and Dr. Mohd. Kushain ,

Mohd. Raj uddin tor the ir advice, guidance, encouragement and kind understand ing

throughout the project. I am most grateful to Professor Dr. Chou L .M . , and Dr

Ridzwan, A .R. for the ir guidance on coral reef studies.

This study was funded partly by Babena Send i rian Berhad, SEAFDEC

Terengganu, Marine Park Authorit ies, and Universit i Putra Malaysia. Spec ial

thanks are expressed to Mrs Zaleha Kassim and Miss A ida Abd. Rahman for the

identification of meiobenthos. [ would l i ke to thank Mr Hamid Salsal i and Mr Sujak

Samad for their extensive assistance during the field sampl ings. Last but not least.

thanks are also due to Mr Paymon Roustaian for the critical rev iew of the paper and

Mr Farshad Schishechian for the painful computer operat ions.

lV

TABL E OF CONTENTS

P age

ACKNOWLEDGEMENTS . . . .......... . . . . . . . ........... . . . . . . ..... . . . . . . . . . . ...... . . . . . . . iv

LIST OF TABLES .... ....... . . . . . . . . . . . . . . . . ......... . .. . . . . . . . . . . .. . . . . . . . . . . .... . . . ... . . . . . . . . . v i i i

LIST OF FI GURES .... . . . . . . .. . . ..... . . . . . . . . . . . . . . . . . . . . .. . . . .. . . .... . . . . . . . . . . . . . . . ........ . . . x

L IST OF PLATES . . . . . ..... . . . ..... . ................ ....... . . . . . . . . . . . . ......... . . . .......... . . . . xi

L IST OF ABBREVIATIONS . . . . . . . . . . ............ . . . . . . . . . . . . . ........ . . . . . ............ . . xii

ABSTRACT . . . . . . . . . . . . . . . . . . . . . . ........... . . . . . . . . . ... . . . . . . . .............. . . . . . . ...... . . . . . . .. . . . . xi i i

ABSTRAK . . . . ........ . . . . . . . . . . . . . . . . . . .......... . .. . . . . . . . . . ....... . . . . ........ . . . ....... . . . . . . . . . . . . xv

CHAPTER

. I INTRODUCTION . . . ...................... . . ........ . . . . . ............. . . ..... . .. . . . . I Background of the Study ..... . . ........ . . . . .............. . . . . . .................... 2 I mportance of the Study ..... ............................ ............... . . . . . . ...... 3 Benthic I nvertebrates as Monitoring Tools .... . . . .. ..... .... . ... ....... .4

Objectives .................. ....... . . . . . ........... . . . . . . ........ . . . ..................... . . 5

I I L ITERATURE REVIEW ... . ... . .... . . . . . . . ......... ....................... 6 Lay ing of Submarine Pipe l ines ..... ............................................ 7

Pipe l i nes B urial ........................... . . .... . . ...... ........ ...... . . . ............... 8

Characteristics of H igh Density Polyethlene Pipel ine . . . ........... 1 9

Pipe laying Hazards .................................. . .. . . ............................ 10 Natural Hazards ..... ..... . .. . ..... . . .................... ......... ................. 12 Man-Made Hazards ........................ ....... . .. . . . .......... . ...... . .. . . . . . 15

Fish ing Activ ities ....... . . . .. . ............................................. 15 Sedimentation . ................................ . . . .......... . . . ........... . ...... . .. . . . . . 1 6

Turbidity ............. ....... . ...... . . ... . . . ............ . ........ . . . . .................. 17 Effects on Coral Reefs ............... . . . . . .. . . ...... . . . . . ....... . ........ . ..... 1 7

Measuring B iological Effects .. . .. . . . ............. ......... ........ . . . . . ........ 1 9

Biological Evaluation of Risk ... . .. . . . . . . ......... . . .............. ......... 20 Environmental Monitoring ......... . . ..... . . . . . . . . . . .. . ..... . . . .. . .. . . . . . . . . 21 Effects on Diversity and other Faunal Parameters .. . . . . . . . ..... 21 Effects of Disturbance on Benthos . . ............ . . . . . . . . . ............... 23 Effects of Disturbance on Corals . . . . .. . . . . .. . .. . . . ....... . . . . . . . . . . . . . . . . 25 Colon isation ..... . . . . . . . . . . . . . . . ..... . . . . . ........... . . ......... ... . ........ . . . . ..... 26

I I I MATERIALS A N D M ETHODS . . .... . ... . ..... . . . ....... . . . . . . . . . . ... 30 Study Area and Field Sur vey ..... . . . . . . . . . . . . . .. . . . . . . . . . . . . ...... . . ........ 30 Sampl ing Program . . . . . . . . . . . . . ..... . . . ......... . . . . . . . . . .......... . . .... . . . . . . . . . 30

v

Macroinvertebrates ............................................................ . . . 30 Coral Reefs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Meiobenthos ............. .............. . . . . . ........... . . . ............... ............. 35 Colonisation .......... ..................... ........... . . . . .............. .............. 35 Total Suspended Solids (TSS) .................... . ............. . . .......... 36

Turbidity ............... ...................... . . .............. . . ................ ........ 37 Particle S ize Analysis ... . . . . . . .......... . ................................... .... 37 Statistical Analysis of Data . ........ . . ......... . . . . ......... . .... . . . . ... .. . . . . 38

Macroinvertcbrates ....... . . . . . .. . . ...... ...... . . ...... . . . . . . . ......... ...... 3 8

Coral Reefs ................. . . ............... ............ ....... ................. 40

Condition I ndex . . . ..... .......... . . . . ................................. . . .40

Development I ndex . ......... ... ....................... . ........... . . .. .41 Succession I ndex ................. .............. . . . ........... . . . . ........ 4 1

Meiobenthos .................................................... . . . . ......... . . . . 42 Species Diversity and Coeffic ient of S im i larity . . . . .... .42 The C luster Analysis (CA) . ..................................... . . .4 3

Colon isation ............................................. . . ..... .......... . . ..... 43

Total Suspended Sol ids and Turbid i ty ....... ....... . ........... . . . 43

IV RESULTS ............. . ................ . . . . .......................................... 44

Macroinvertebrates ...................... . . . ............ .............. .... . ....... 44

Coral Reefs .................................................................. . . . . . .... 52 Percentage Cover .............................. . .............................. 52 The Results F rom I nd ices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Relationships Between I ndices ....... . . . . . . . . . . . . ... . .... . . . ..... . . . 56

Meiobenthos .......................................................................... 57

Meiofauna ........ ................................................................ 57 Benthic Diatoms .......................... ........ ................... . . . ...... 64

TSS and Turbidity Measurements ....................... ................ 66

Physical Characteristics of the Substratum .......................... 68

Pre-construction Period .............................................. 68

Post-construction Period ........ ....... ............................. 69

Colon isation ................................. ........................ . .............. . 72 Observation .... . ................... . ............. . ................................... 75

V D ISCUSSION ........................................................... . ...... ..... 80

Macrofauna ........................... . . .. . . . ...... .................. . . ...... . ..... . . . 80 Coral Reefs ............. . . . .. . . . .. . . . . ......... . . . . . . . . . . .. . . . . ........... .... . . . . . . . . 84

Meiofauna ...... . . .. . . ....................... ....... ..................... ..... . .. . .. . . . 88

Colonisation ........... . . . .. . . . ................................. . ...... . . . . ....... .... 89

Sed iment Characteristics . . ............................ . .............. . . . . . . .. . 92

vi

Total Suspended Sol ids ........ ........... .......................... . . . . . . . . .. . . 93

VI CONCLUSiON ..................................................................... 95

REFERE NC ES ..................................................................................... 98

API >E NDICES ............... .. . . ..... .......... .......... . . . ...... . . . . . . . .... ....... . . . . . . . ......... 1 10

ViTA . . .. . . .... . . ............ . . . . . ..... ....... . . ....... . . . . . ..... . . . . . ..... . . .. . . . . . . . . ...... . . . . . . . . ...... 112

vi i

T able

4

5

6

7

8

9

10

1 1

12

L IST O F T AB L E S

P age

Dates of reef survey, benthos and water quality sampling at Redang Island . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Semi-qualitative scale for an assessment of index quality in

log-transformed index scale form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

The effects of pipeline crossing and related pipeline construction

activities on the standing crop (No./m2) of the macro invertebrates

in the vicinity of Redang Island . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45

The etfects of pipeline crossing on the benthic macro­invertebrate communities of Redang Island. Sites L 2, 3, and 4 were 18 m, 8 m, 7 m, and 2 m, respectively . . . . . . . . . . . . . . . . . . . . .48

The effects of pipeline crossing on the benthic macro­

invertebrate communities of Redang Island. Sites L 2, 3. 4 and 5 were 1 8 m, 8 m, 7 m, 2 m, and 7 m, respectively . . . . . . . . . . . . .48

Species Diversity (H') recorded for the mollusc community

associated with Redang Island's subsea pipeline during pre and post-construction periods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49

Pearson's correlation coefficients for macrofauna associated with the pipeline sediment at Redang Island . . . . . . . . . . . . . . . 50

Pearson's correlation coefficients for Annelids associated

with the pipeline sediment at Redang Island . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Pearson's correlation coefficients for Arthropods associated with the pipeline sediment at Redang Island . . . . . . . . . . . . . . . 51

Pearson's correlation coefficients for Mollusc community associated

with the pipeline sediment at Redang Island . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

The percentage area cover of tive major benthic lifeforms on coral reef along with their condition, succession and development indices during pre and post-construction periods at Redang Island . . . . . . . . . . . 56

Semi-qualitative results for an assessment of index quality

based on results obtained from Table 2 and index scale (log (Xiy» in selected sites during pre and post-construction periods . . . . . . . . . . . . 57

vii i

13 The abundance o f meiofauna in the sediments along Redang Island's subsea water pipeline during the post-construction period . . . . . . . . . . . . 5X

I..J. Species DIversity (H'), Evenness ( J') , and the Number of SpecIes (S) recorded tor the mciofauna community associated with the

sediments along the pipeline at Redang Island during post-construction period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

15 Pearson's correlation coefficients for meio fauna associated

with the pipeline sediments at Redang [sland . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

16 The density of macro-and meiofauna expressed as numbers of indiVIduals per m2 during post-construction period . . . . . . . . . . . . . . . . . . . . . () 1

17 The composition of benthic diatom species (in 1 0 cm2) associated

with sediment at the study sites along the Redang Island's subsea pipeline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

18 Species Diversity (H'), Evenness (J ' ), and Number of Species (S) recorded for the benthic diatom species associated with the

sediment along the subsea pipeline at Redang Island during post-construction period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

1 9 Total suspended solids (TSS, mg L,I) in seawater samples collected at the sampling locations at Redang Island coastal waters . . . . . . . . . . . . . . 66

20 Attenuation of light (f-Lmol S,I m,2 per f-L A) in the water at the

study sites . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . , . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

2 1 Some physical characteristics of sediments during pre-construction period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

22 Some physical characteristics of sediments during post-construction period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

23 Checklist of meiobenthos detached from the pipeline six months after the construction . . . . . . . . . . . . . . . . . . . . ' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7..J.

24 Checklist of the observed macro invertebrates associated with the pipeline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 7

ix

LIST OF FIGURES

Figure

Erosion of coastal sands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14

Seabed pipeline stabil ity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 .., j L ocation of sites visited for coral survey, and benthos sampling . . . 3 1

4 Water depth-pro ti le at the study sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

5 Abundance of macro invertebrates at the study sites (pre-const.) .. .46

6 Abundance of macroinvertebrates at the study sites (post-const. ) . . 46

7 Abundance and standing crop of macro invertebrates (pre-const. ) . .4 7

8 Abundance and standing crop of macro invertebrates (post - const. )4 7

9 Per centage cover of benthic l if ef orms (pre-onstruction) . . . . . . . . . . . . . 53

10 Percentage cover of benthic l if ef orms (post-construction) . . . . . . . . . 53

11 The development, condition, and succession indices . . . . . . . . . . . . . . . . 55

12 Meiof auna groups according to their abundance . . . . . . . . . . . . . . . . . . . . . 60

13 Meiof aunal homogeneity based on Jaccard' s coef ficient of similarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

14 Dendrogram f or cluster analysis of meiof auna abundance data . . . . 62

15 A comparison between density of meiof auna and benthic diatoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

16 Distribution of sediment particles at the study sites (pre- const . ) . 71

17 Distribution of sediment particles at the study sites (post-const . ) . 71

x

Plate

1

4

5

6

LIST OF PLATES

Page

General location of the study area . . . ..... . .. . . . . . . . . . . . . . . . 32

Subsea pipeline laying on the seafloor. .. . . . . . . . . . . . . . . . . . 32

Broken concrete collars of the pipeline" . . . . . . . . . . . . . . .. . . . 78

Heavy weight mattresses laid on the pipeline . .... . . . . . . . 78

A sea cucumber creeping on the pipeline .. . . . . . . . . . . . . . . . . 79

An unidentified reef fish sheltering on the pipeline . . .... 79

xi

LIST OF ABBREVIATIONS

A

AB

AL

CI

Cs

S

DC

01 HC

HOPE

H'

LC

Md

NS

OF

SCUBA

So SC

SI

TSS

Abundance

Abiotics

Algae

Condition Index Jaccard's Coefficient of Similarity

Number of Species

Dead Corals

Development Index

Hard Corals

High Density Polyethylene

Shannon Diversity Index

Live Corals

Median

Not Significant

Other Fauna

Self Contained Underwater Breathing

Apparatus

Sorting Coefficient

Soft Corals

Succession Index

Total Suspended Solids

xii

Abstract of the thesis submitted to the Senate of Universiti Putra Malaysia in fulfilment of the requirements tor the Degree of Master of Science.

SOME EFFECTS OF SUBSEA WATER PIPELINE CONSTRUCTION

ON SESSILE BENTHIC COMMUNITY STRUCTURE OF REDANG

ISLAND, MALAYSIA

By

HAMID REZAI-MARNANI

December 1 998

Chairman: Professor Mohd.Ibrahim Hj.Mohamed., Ph.D.

Faculty: Faculty of Science and Environmental Studies

A pipeline system, constructed in 1997- 1 998, to provide water to Redang

Island, traverses an area covered with coral reefs. Biological studies were

conducted before and following the construction to monitor changes in habitat and

biota at selected sites. Pre-construction studies consisted of conducting inventories

of predominant marine life, and evaluating sites for their sensitivity to construction,

whilst, post-construction studies involved assessment of d isturbed areas and

monitoring the pattern of re-colonization by marine life. Marine environmental

impact associated with the pipeline-crossing was monitored in the vicinity of the

Island for one year. Evidence of the pipeline impact was assessed mainly by values

concerning the abundance of zoo benthic community (including corals) and species

diversity indices. Annelids and Arthropods were the most dominant phyla

xiii

numerical ly during both study periods, be ing greater in pre-construct ion period.

Student t-test and One-way ANOV A analyses revealed that there was no significant

di fferences bctwcen total abundance of scssi Ie macroinvertebrates during pre and

post-construct ion periods. Student t-test revealed a significant difference bctween

the means of l ive coral coverage during pre and post-construction periods. There

was no apparent change in total number of macro-invertebrates as a result of

p ipe l ine construct ion. Results indicated that impacts aris ing from marine-crossing

were short-term and non-residual .

xi v

Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia bagi memenuhi syarat untuk mendapat ijazah Master Sains

BEBERAPA KESAN PEMBINAAN SALURAN PAIP DASAR LAUT

KEATAS STRUKTUR KOMUNITI SESIL BENTIK DI PULAU

REDANG, MALAYSIA

OLEH

HAMID REZAI-MARNANI

Disember 1998

Pengerusi: Prof.Mohd.Ibrahim Hj.Mohamed., Ph.D.

Fakulti: Fakulti Sains dan Pengajian Alam Sekitar

Satu sistem saluran paip telah dibina pada 1997-1998, untuk membekalkan

air ke Pulau Redang, merentangi satu kawasan yang diliputi oleh terumbu karang.

Kajian biologi telah dijalankan sebelum dan selepas pembinaan untuk memerhati

perubahan di dalam habitat dan biota pada lokasi yang dipilih. Kajian pra-

pembinaan merangkumi penentuan inventori hidupan marin yang paling dominan

dan menilai sensitiviti tapak-tapak kepada pembinaan, sementara. kajian selepas

pembinaan melibatkan penilaian kawasan tapak yang terganggu dan pemerhatian

corak pengkolonisasi semula hidupan marin. Kesan persekitaran marin berhubung

saluran paip telah diperhatikan di sekitar pulau terscbut selama setahun. Bukti

kesan saluran paip tersebut telah dinilai terutamanya dengan nilai-tapak yang

melibatkan kehadiran komuniti zoobcntik dcngan banyaknya (tcrmasuk karang)

dan indeks kepelbagaian spesis. Annelida dan Arthropoda adalah filum yang paling

xv

banyak pada masa scbc lum pcmbinaan . Ujian 'studcnt-t' dan anal isis ANOV A

schab mcnunjukan bahawa tidak tcrdapat perbczaan yang bcrmakna di antara

jumlah kehadiran scs i l makroinvcrtcbrat sebelum dan sclcpas masa pcmbinaan.

Uj ian 'studcnt-t' menunjukkan bahawa tcrdapatnya pcrbczaan yang kuat d i antara

purata karang h idup pada masa scbelum dan sclepas pcmbinaan . Tidak tcrdapat

perubahan yang je las dalam jumlah kcseluruhan makroinvcrtcbrat akibat daripada

pcmbinaan saluran paip . Kcputusan mcnunjukkan bahawa kcsan daripada lalLlan

paip marin bersifat jangka pendek dan t idak bcrpanjangan.

xvi

C HAPTER I

INTROD UCTION

The construction or Redang I s land' s subsea water pipe l ine from Penarik to

Redang I s land, Terengganu, offered an opportunity to monitor and determ ine the

effects of p ipe l ine construction on benthic macroinvertebrate commun ities of

Redang I s land.

The Redang submarine water pipel ine project w i l l supply water from

Penarik in Setiu to Redang I sland, a d istance of about 28 km. The project. wou ld

enable residents as wel l as Is land's hospitality industry at Redang I s land to receive

fresh water supply from the mainland via the high density polyethylene submarine

p ipe l ine. It can supply one mi llion g::!l lor.s of fresh "vater per c::.y (Anon, 1 997). But

based on the current need, only 400,000 gal lons w i l l be suppl ied.

Coral reefs and thei r associated marine l ife are one of the greatest natural

treasure of Redang Is land. Both their qual ity and quantity are impressive. Coral

reefs form the core of the l ivel ihood for hundreds of Redang subsistence tishermen.

Redang I s land is known for its crystal c lear b lue water and rich diversity of

beautifu l corals and associated ecosystem that fringe the smal ler peripheral is lands.

Not only are the coral reefs a source of food, but also provide a natural

barrier against wave erosion, thereby protecting coastal dwel l ings, and tourism

beaches. They are a potential source of fore ign exchange from d ivers and other

1

marine tourists. [n addition, because of their unique biodiversity, they are of great

interest to scientists, students, pharmaceutical compan ies, and others. These and

many other functions give coral reef an important and growing value (Erdman and

Pet-Soede, 1996). The pathway in which the p ipeline system traverses is an area

covered with coral reefs and poss ibly undu lations along ridges result ing in widely

varying water depths. !-knce, the corals are vulnerable to physical destruct ion

caused by the p ipel ine construction.

The gazetting of Redang [sland as a Fisheries Protected Area in 1988 as a

precursor to its subsequent gazetting as a Marine Park in 1 994 has brought about

tremendous development for th is is land famous for her crystal clear waters and

beautiful illlexplo ited coral reef g,udens.

Background of the Study

Previously, several studies have been undertaken on Redang Island . These

include a general survey carried out (Green, 1 978: Green et al., 1 979) under the

auspices of W W F Malays ia. Coral mapping with the aide of remotely sensed

imagery was completed by Schwamborn ( 1 993). The area was briefly investigated

by White ( 1 986) and De S ilva ( 1 979) reported the destruction some reefs by the

Crown-of-Thorn sea star, Acanthaster planci. Othman et al. ( 1 990) studied the soft

bottom communities of Redang Is land and gave a detai led account of the benthos

in the area.

3

Those studies by Ibrahim el al. (1992.1993). and more recently Japar el al. ( 19(7)

wen.: concerned primari ly on mon itoring the coastal environment related to the

development of Redang Is land . The latter authors reported that the decrease in l i ve coral

c()ver in some of their s ites may have been attributed to several factors result ing from

human activ i t ies inc luding land ti l l ing, dredging. boating, shipp ing. anchor damage. di ver­

re lated damage and natural phenomena such as crown-of-thorns attack and invasion of

macroalgae growth. These studies brought about some l ight to the po l l ution etkcts due to

the development of the Is land.

There have been few publ ications on the effects of subsea p ipe l ine to the benth ic

communi ties. Such examples were those of the North Sea. Most of these studies

concentrated on the effects of oi l/g::l� p ipe l ine on marine communit ies . These include

studies by Oe Groot (1982), Haldane (1992), Pranesh and Kumar (1993), T i l l i nghast el al.

(1987), and the work of Tsu i and McCart (1981) . These studies had revealed short term and

long-term damages to the marine benth ic communities, and consequently to the fisheries .

Importance of the Study

The construction of a freshwater p ipe l ine made from HOPE (high dens ity

polyethylene) and its impact on benthic community is one of its kind in Malaysia. However.

benthic communities may respond differently to the d isturbances i n tropical waters where

there are far more hard coral assemblages than in the temperate reg ions. The study of the

effects of subsea pipe l ine construction is important because at present there is no record on

the phys ical and mechan ical d isturbances to the benthic community in Redang Is land.

4

Some habitat d isturbances due to the construction was anticipated but whether these

disturbances could affect the corals in the short and long term, and their impacts on other

benthic l i feforms remains to be seen . This study high l ights the importance of benth ic

commun ities as too l to mon itor the effects of p ipe l ine construct ion.

Benthic Invertebrates as Monitoring Tool

Benthic i nvertebrate community structure is an important tool for eval uatlllg

ecosystem stress induced by anthropogenic perturbations. The benthic invertebrates were

chosen due to their important ro le in the food chain and rap id responses to changes in

physical and chemical env ironments, such as the potential impact of pipel ine construction

and operation on the Is land. The benthos may serve as food for some fish, which agalll

attract larger fishes.

I n terms of output, percentage cover of l ive and dead coral cannot

provide more than a s ign ificant out look of reef status. From an economic point of v iew,

the data col lection i n th is study takes a significant amount of t ime and money, but only

a smal l part of th is information is used for management. Therefore, a more efficient way

is to use what are requ i red, or try to maxim ize the use of the present i nformation at its

fu l l potent ial.

The status of a reef does not only depend on how much coral or the amount of l ive

and dead coral but needs to include the other components of the reef. In fact, sand and other

components can contribute to the status of the reef. The use of l ive and dead coral data may

be l imi ted or could mis lead the management dec is ion (Manthachitra, 1 994) .

Objectives

Since the laying of a pipel ine can induce a sign ificant impact upon its surrounding.

environment, the purpose of th is study was to determine the effect of water p ipel ine

construction on:

(i) the changes in benthic macroinvertebrate community structure fol lowing construction

(ii) the effects of construction on coral community

(iii) the colonization of the p ipe l ine by the benthos after the construction.

The a im of reef moni toring was to determi ne the health of reef and to monitor

changes in these reefs after the p ipel ine construction. Healthy reefs are general ly able to

survive natural stress, whi le unhealthy reefs are more l i kely to suffer cumulative

degradation and a poss ib le reduction in species diversity and density.

C HAPTER I I

LITE RATURE REVI E W

Prom the beginning of the o i l and gas exploration in the North Sea, the

impact o f o ffshore insta l lat ion, especial ly p ipe l ines, on the tishery has been

thoroughly d iscllssed and invest igated (Mac Lennan and Stro'1ge,! 979: Moshagen

and Kjeldsen, 1980: Lange, 1995). De Groot ( 1982) gives a comprehens ive review

of the impact of laying of otfshore p ipe l ines on the marine environment and the

North Sea Fisheries.

Submarine pipel ines are used for the marine transportation of o i l , water and

gas from offshore places to the main land or v isa versa. These p ipe l ines are laid on

the seabed w ith soi l support on the route selected after surveying. The uneven

surface areas such as rocky outcrops are covered by the sediments, which are

transported from one place to another.

These p ipel ines are placed e ither to rest directly on the seabed or in a trench

or on saddles depending on the bottom topography of the seabed along their routes.

When placed in a hosti le environment such as the oceans, the pipelines are

subjected to various environmental loads due to waves, c urrents, etc . It has been

estab l ished by many researchers in the area of wave-pipe l ine i nteract ion prob lem

that the effect of the gap between the p ipe l ine and ocean bottom wou ld p lay a

dominant ro le in the evaluation of the hydrodynamic forces on marine pipel ines

( Subbiah et a/. , 1 990).

6

7

Laying of Submarine Pipelines

Variolls methods are avai lable to lay p ipe l ines at sea. The fo l lOWIng

methods are the most llsed, the bottom-pu l l method, the lay-barge method and the

reel-barge method (LOllS, 1 978) . [n Redang [s land, the lay-barge method was

llsed . The lay-barge or semi-submers ible acts as a pipe l ine factory where the pipe

sections are we lded together at weld ing stations, X-rayed and the joint:, (oated.

Each time a section of pipe is complete[y added to the pipel ine, the anchored barge

pu l ls itself ahead with its anchor winches. Wi th this method pipel ines can be laid

at depths to about 200 m (De Groot, [982). If the p ipe is proper ly laid, i t wi II rest

on a flat bottom without residual curvature due to yielding. Carstens ( 1 980) and

Richardson ( 1 980) reviewed experiences from the contractor's point of vie\.\- with

the navigaliull Mid �ositiuning of iay-barges (semi-submersibles) in the northern

North Sea from 1 975 to 1979.

In due course the corrosion or scour ing of the sea floor which supports the

pipel ine w i l l take p lace leading to the loss of support and thereby some parts of

pipel i ne are made to rest on the elevated obstructions. This causes additional stresses

in the p ipe l ine depending on site condit ions such as height of obstruction, pi pel ine

span, the unsupported span, and the soil properties (Pranesh and Johnson, 19931.

Pipeline Burial

Submar ine p ipe l ines are general ly buried to provide greater assurance of

protection against the forces in the surf zone, the hazards of ship anchors and

8

general sea bottom envi ronment. However, this procedure is not always feasible

particularly on a moveable seabed (Ozturk el al., 1 994). Pipe l i nes laid in trenches

should be backfi l led with suitable materials, rather than re lying on natural

processes to prov ide sed iment cover (Herbich, 1 98 1 ) . When a pipe l ine trench is

formed by a plough, soi I spoi Is arc formed on e ither s ide of the trench. Backti I I

blades are attached to the plough, which when redeployed and towed along the

trench, guide the spoi l back into the pre-cut trench and covers the p ipel ine (Haldane

et al., 1992). The actual depth of burial depends on several factors, including storm

frequency, sediment erosion, and environmental consequences of pipel ine fai l ures.

I n depths of less than 6 1 m, the p ipe l i ne is usual ly laid in a trench of 0.9

in jeep unless i t is i n area congested with p ipe l i nes, or the bottom is rocky and th�

disturbance due to trenching is expected to be greater than laying the p ipe on the

surface with some rip rap cover (Boesch and Rob i l l iard, 1 990) . Trenching is

accompl ished by hydraul ic jetting or cutt ing a trench under the p ipe after it has

been laid on the seafloor. Typically the trench is not backfi l led by the operators,

but w i l l usual ly fi l l up with sediment due to wave and sediment action. As water

depth increases. natural backfi l l ing may not occur as fast because of the decrease

in the i nfluence of surface waves and bottom current veloc ity (Anon, 1 983)

I f shore approaches are coral or sol id rock, a trench can be blasted through

the wave breaking zone to provide lateral stabi l ity and protection from floating