NO. 193.
A PHQT~GMAPHIC SURVEY IIBBWW THE SEAWARD REEF-FRONT OF ALDABRA ATOLL
by Ed~c~artl A.
DrewIsslletl by
TIElti, SMI1'IISONIA;B' INTd'lTlia'lQPN Washington, D.C., 1j.S.A.
Summary
I n t r o d u c t i o n Methods
1 3 s t a b l i s h m e n t of t h e t r a n s e c t P h o t o g r a p h y
A n a l y s i s of p h o t o g r a p h s l i e s u l t s
O t h e r t r a n s e c - t s D i s c u s s i o n
A c h ~ o w l e d g e m e n t s R e f e r e n c e s
F i g u r e s ( f o l l o w i n g p .
7 )
1 A l d a b r a Atol.l., s h o w i n g l o c a - t j ~ o n of a1.l t r a n s e c t s a n d i m p l i e d s u b m a r i n e c o n t o u r s ( m o d i f i e d f r o m B e l l a m y e t a l , 1 9 7 0 )
2 Camera o r i e n t a t i o n o n p l i o t o g r a p h i c t r a n s e c t
3
T r a n s e c - t t o p o g r a p h y a n d p e r d e n t a g e Il.:ivircf; c o v e r I+ D e p t h d i . s t r i b u t i o n . of v a r i . o u s g r o w t h t y p e s5
H o r i z o n t a l d i s t r i b u t i o n o f g r o w t h t y p e s away f r o m s u r f z o n e6
S u b m a r i n e l i g l i t i n - l e n s i - t y a n d p e r c e n t a g e 1.i.vi.ng c o v e rP l a t e s
1 P h o t o t r a n s e c t f r a m e s i l l u s - l r a t i 1 7 g g r o w t h t y p e s d i s c u s s e d
a . M i l l e p o r e
b . B r a n c h i n g c o r a l c . Col.umnar c o r a l d . B r a i n c o r a l
2 P h o t o - t r a n s e c t f r a m e s i l l u s t r a t in(: (.;rowtli - t y p e s d i - s c u s s e d
a . F o l i a c e o u s c o r a l
b . A:Lcyo:nacean s o f t c o r a l c
.
1-Ial.i.meda a l g a ed . U s l c o l o n i s e d b a r e a r e a s
3
R e p r e s e n - l a - t i v e s t r i p s f r o m v a r i o u s i ~ n p o r t a n t z o n e s a . M i l l e p o r e c o r a l z o n eb . Urav~cliisig c o r a l z o n e c . C o l u ~ n n a r c o r a l z o n e d . B r a i n c o r a l z o n e
e . F o l i a c e o u s c o r a l z o n e
A PHOTOGRAPHIC SURVEY DOWN THE SEAWARD REEF.FRONT OF ALDABRA ATOLL
1
/
by Edward A. Drew- SUMMARY
A simple photographic transect method, using aqualung diving techniques, is described, together with an assessment of its limitations and possible improvements.
Data obtained from analysis of a 250 metre long transect
(0- 40 metres depth) photographed o n the seaward reef-front of Aldabra Atoll are presented. Results are discussed in the con-
text of previous reef zonat.ion data and the possible environ- mental factors controlling such zonation.
INTRODUCTION
The upper 20 metres of the seaward reef-front of any barrier, fringing or atoll coral reef has until recen-Lly been impossible to investigate thoroughly due to prevailing sea conditions so close to the reef ridge.
However, in recent years the introduction of self-contained diving equipment, and care in selection of the season for field work to coincide with moderately calm conditions, have allowed a ccnsiderable amount of direct observational data to be acquirec in this environment.
Nevertheless, such investi.gations tend to use a variety o:E ecological methods, mostly qualitative, and still "much of the difficul-ty in comparing reefs stems from the lack of unif0rmj.t~
i n surveying methods" (stoddart, 1969a).
In this paper a simple method of photographic recording down a reef transect is described and the results from i-ts use on the most luxuriant section of the Aldabra reef-front are presented. The field work can easily be carried out by divers with no training i n coral taxonomy and could be applied to any reef system, giving a standard basis for valid comparisons.
l / ~ a t t y Marine Laboratory, St. Andrews, Fife, Scotland.
( ~ a n u s c r i ~ t received May, 1970--Ed.)
E s t a b l i s h m e n t of t h e t r a n s e c t
-- -
T h i s was marked by a s t r i n g , k n o t t e d w i t h a l o o p a t one m e t r e i n t e r v a l s . It was l a i d down i n 50 m e t r e s e c t i o n s from t h e r e e f r i d g e (mean low w a t e r s p r i n g s
-
MLI~S) t o t h e b e g i n n i n g of t h e b a s a l s a n d p l a i n a t 40 m e t r e s d e p t h . The s t r i n g t o t a l l e d 253 m e t r e s i n l e n g t h and was o r i e n t a t e d a p p r o x i m a t e l y p e r p e n d i - c u l a r t o t h e s h o r e - l i n e a l t h o u g h some meandering o c c u r r e d i n t h e e x t e n s i v e s h a l l o w p a r t s . Each end was marked w i t h a s m a l l buoy a n d t h e s e were t r i a n g u l a t e d from t h e s h o r e ; b e a r i n g s a r e shown on t h e i n s e t of t h e map i n F i g u r e 1 .Depth was r e c o r d e d a t 1 0 m e t r e i n t e r v a l s u s i n g an 'SOS' t o t a l l y e n c l o s e d bourdon t u b e g a u g e , and c o r r e c t e d t o d e p t h below MLWS a c c o r d i n g t o t h e s t a t e o f t h e t i d e .
An a t t e m p t t o a s s i s t d i v e r o r i e n t a t i o n on t h e v e r y l o n g t r a n s e c t by p l a c i n g numbered p o l y s t y r e n e f l o a t s on s h o r t s t r i n g s a t 10 m e t r e i n t e r v a l s p r o v e d u n s u c c e s s f u l . The f i l m of a l g a e
( d i a t o m s ? ) which r a p i d l y d e v e l o p e d on t h e s e f l o a t s was a t t r a c t i v e t o t h e b r o w s i n g f i s h p o p u l a t i o n which r a p i d l y consumed most of t h e f l o a t s c o m p l e t e l y .
Photography
S t a n d a r d ' C a l y p s o p h o t ' and ' N i k o n o s ' u n d e r w a t e r cameras w i t h 35mm wide a n g l e l e n s e s were used t o p h o t o g r a p h t h e . t r a n s e c t
e v e r y m e t r e from a d i s t a n c e of a p p r o x i m a t e l y 2 m e t r e s from t h e b o t t o m . The open frame v i e w f i n d e r of t h e cameras was u s e d t o a l i g n t h e camera a s shown i n F ' i g u r e 2. C o n s i d e r a b l e o v e r l a p was a c h i e v e d i n a l l f r a m e s .
Monochro~ne 35mm f i l m was u s e d
-
Kodak P l u s X ( 1 2 5 ASA) f o r most of t h e t r a n s e c t p h o t o g r a p h s , r e p l a c e d by I l f o r d HP3 (400 ASA) i n t h e d e e p e r s e c t i o n s . No a r t i f i c i a l l i g h t i n g w a s u s e d . The wide a p e r t u r e s e t t i n g r e q u i r e d i n t h e 30-
40 m e t r e s e c t i o n r e s u l t e d i n c o n s i d e r a b l e l o s s of r e s o l u t i o n i n many of t h o s e f r a m e s.
F i l m s were d e v e l o p e d i n t h e f i e l d , u s i n g a d a y l i g h t - l o a d i n g d e v e l o p i n g t a n k and c o o l i n g s o l u t i o n s i n t h e r e f r i g e r a t o r t o a b o u t 20°C b e f o r e u s e . Tn t h i s way i t was p o s s i b l e t o e n s u r e c o m p l e t e c o v e r a g e of t h e t r a n s e c t w i t h u s a b l e n e g a t i v e s .
Although s e v e r a l p h o t o g r a p h i c d i v e s were c a r r i e d o u t on t h e t r a n s e c t , a l a r g e p r o p o r t i o n of t h e u s a b l e e x p o s u r e s were made on a s i n g l e d i v e o f two h o u r s d u r a t i o n . Three cameras were u s e d , and e a c h was r e l o a d e d t w i c e i n t h e b o a t , g i v i n g a t o t a l of o v e r 300 f r a m e s .
The b e s t n e g a t i v e f o r e a c h m e t r e s e c t i o n was p r i n t e d t o 1 2 . 5 x 20 cm
( 5 "
x 8 " ) i n t h e l a b o r a t o r y i n t h e U n i t e d Kingdom, u s i n g ' I l f o p r i n t ' m a t e r i a l s f o l l o w e d by hypo f i x a t i o n and h i g h g l o s s f i n i s h i n g .A n a l y s i s of p h o t o g r a p h s
-
S e q u e n t i a l p r i n t s were o r i e n t e d and c u t t o produce complete b u t u n d u p l i c a t e d c o v e r a g e down t h e t r a n s e c t ; s t r i p s of f i v e p r i n t s were e a c h a n a l y s e d a s f o l l o w s .
Code numbers were a l l o c a t e d t o a t o t a l of
26
d i f f e r e n t c o r a l growth forms and o t h e r r e c o g n i s a b l e o r g a n i s m s . Some of t h e s e were l a t e r lumped t o g e t h e r and f i n a l a n a l y s i s i n v o l v e d t h e f o l l o w i n g g r o u p s :Cymodocea ( m a r i n e angiosperm) Alcyonacean ( s o f t c o r a l )
B r a n c h i n g c o r a l Gorgonian
Columnar c o r a l Halimeda a l g a e
( +
t r a c e s C a u l e r p a )B r a i n c o r a l Sponges
F o l i a c e o u s / e n c r u s t i n g c o r a l T r i d a c n a clams
' P i o n e e r ' c o r a l Anemones
F u n g i a c o r a l U n c o l o n i s e d b a r e a r e a s
E n c r u s t i n g c a l c a r e o u s r e d a l g a e c o u l d n o t be d i s t i n g u i s h e d on t h e p h o t o g r a p h s a l t h o u g h t h e y r e p r e s e n t e d a s i g n i f i c a n t p a r t of t h e l i v i n g c o v e r i n some s e c t i o n s . The organisms and c o r a l t y p e s i n v o l v e d a r e i l l u s t r a t e d i n a r e p r e s e n t a - t i v e s e l e c t i o n of f r a m e s i n P l a t e s 1 and 2 .
The o u t l i n e s of t h e v a r i o u s c o l o n i e s i n e a c h s e t of f i v e c o n t i g u o u s p r i n t s were t r a c e d on-to h i g h q u a l i t y t r a c i n g p a p e r ( u n i f o r m d e n s i t y ) and t h e a p p r o p r i a t e s h a p e s were c u t o u t and weighed. I n t h i s way t h e a r e a of e a c h 5 m e t r e t r a n s e c t s e c t i o n
c o v e r e d by a p a r t i c . u l a r g r o w t h t y p e was d e t e r m i n e d . No a t t e m p t was made t o a l l o w f o r d i f f e r i n g c o l o n y morphology and t h e r e f o r e
a c t u a l s u r f a c e a r e a of l i v i n g c o r a l which i n some i n s t a n c e s would b e s e v e r a l t i m e s g r e a t e r t h a n t h e a r e a p h o t o g r a p h e d .
I n
view of t h e g r e a t i m p o r t a n c e of t h e s y m b i o t i c a l g a e p r e s e n t i n t h e c o r a l o r g a n i s m s , i t seems p r o b a b l e t h a t t h e a r e a exposed t o d i r e c t s o l a r i l l u m i n a t i o n w i l l b e of major i m p o r t a n c e i n t h e i r g r o w t h .
RESULTS
The t o p o g r a p h y of t h e t r a n s e c t s t u d i e d i s sllown i n F i g u r e
3 ,
t o g e t h e r w i t h a n a n a l y s i s o f t h e p e r c e n t a g e c o v e r of l i v i n g o r g a n i s m s on b o t h a h o r i z o n t a l and a v e r t i c a l b a s i s .
T h i s p a r t i c u l a r - t r a n s e c t , t h e l o n g e s t of a t o t a l of 1 2 a c c u r a t e l y s u r v e y e d around t h e a t o l l ( s e e F i g u r e 1
) ,
p r o v i d e d two c o n t r a s t i n g e n v i r o n m e n t s . F i r s t l y t h e r e was a n e x t e n s i v e s h a l l o w r e g i o n where. t h e major v a r i a b l e f a c t o r a p p e a r e d t o b eproximity to the reef ridge surf zone, followed by a region of moderately rapid increase i n depth until the growth of lierma-
typic corals ceased at the start o f the basal sand plain. This last appeared to slope away indefinitely at a n angle of about 20° from horizontal.
Analysis according to depth has been carried out by
averaging the various series of prints included i n each 2 metre increment of depth. Percentage living cover remains remarkably constant until below 30 metres, when it drops rapidly to a much lower value.
The regular alternation between high and low cover values shown in the horizontal analysis is due mainly to a series of completely bare areas, on a scale several times greater than the size of a photographic frame. These were either bare coral rock or depressions filled with coral debris (mainly branching types) i n shallow water but sandy in deeper parts.
The distribution of the various growth types with depth is illustrated i n Figure 4, again averaged for the series of 5
metre strips included in each 2 metre depth increment. Uncolo- nised bare areas have been disregarded in this analysis which shows the percentage of the living cover represented by each type. There is a marked zonation, with the branched and less massive types i n shallow water and the massive brains much deeper. Alcyonacean soft corals were intermediate in distri- bution whilst only the foliaceous and encrusting types occurred in the deepest parts. The significance of this zonation will be discussed later; representative strips from the major zones are shown in Plate 3.
Additional information about the response of the shallow water types to surf action has been obtained by analysis of the first 60 metres of the transect horizontally, this being restric- ted to the upper 2 metres of the depth range. Heavy surf is un- likely -to occur far seaward of low water mark. Figure 5 shows such a horizontal analysis which indicates restriction of the millipore corals to the maximum surf zone whereas branching corals formed a small part of the total cover until some 25 metres from MLWS. Columnar corals were relatively unimportant andshowed little correlation with distance from MLVS, but the restriction of the Alcyonaceans to the most distant part
suggests that they are relatively sensitive to severe water movement.
OTHER TRANSECTS
In order to put this transect into perspective compared
with other areas of the Aldabra reef-front, the 1 4 transects
surveyed around the atoll are shown in Figure
1 .Only transect
topography and the approximate coral cover were determined o n
all but transect 1 , the photographic transect. The submarine
c o n t o u r s shown a r e g r e a t l y e x a g g e r a t e d compared wi-th -the s c a l e of t h e a t o l l o u t l i n e . Also shown i s t h e v e r t i c a l e x t e n t of r e e f - f r o n t r o c k y s u b s t r a t e b e f o r e t h e b e g i n n i n g of t h e basal.
s a n d p l a i n . .
The n o r t h - w e s t p a r t of t h e r e e f - f r o n t was t h e o n l y regi.on.
w i t h l u x u r i a n t c o r a l g r o w t h , t h a t a l o n g t h e n o r - t h s l i o r e was g e n e r a l l y p o o r , and t h a t on t h e s o u t h had a p p a r e n t l y r e c e n t l y s u f f e r e d a major c a t a s t r o p h e w i t h t h e d e a d r e m a i n s of a p p a r e n t l y good grow-th. e v i ~ d e n - t i n s e v e r a l p l a c e s . The e a s t e r n end of t h e a t o l l had no c o r a l r e e f f r o n l , b u t r a t h e r a v e r y g e n t l y s l o p i n g s a n d p l a i n from MISS.
DISCUSSION
I n i t i a l s t r u c t u r a l c o n s i d e r a t i . o n s would s u g g e s t t h a t b r a n c h i n g c o r a l s of t h e m i . l l e p o r e and a c r o p o r e t y p e s a r e l e s s w e l l s u i . t e d t o -the r i g o u r s of s h a l l o w w a t e r r e e f - f r o n t enviroli- ments t h a n a r e t h e more m a s s i v e b r a i n c o r a l s . I n d e e d , S t o d d a r t
( 1 9 6 9 a ) c i t e s nuloerous r e f e r e n c e s t o t h e o c c u r r e n c e of f r a g i l e - b r a n c h i n g t y p e s on 1.agoon r e e f s and i n . s h e l t e r e d p o o l s , w h i l s t s t o u t - b r a n c h i n g a n d more m a s s i v e t y p e s a r e c o n c e n t r a t e d on r e e f f l a t s and u p p e r seaward s l o p e s .
The d a t a p r e s e n t e d i n t h i s p a p e r s u g g e s - t t h e o p p o s i t e f o r t h e 1uxuri.ant s e c t i o n of A l d a b r a r e e f - f r o n t , a s i t u a t i o n a l s o n o t e d by S t o d d a r - t (1966, l 9 6 9 b ) i.n t b e M a l d i v e s and t h e Solomouis where " r e e f s c o n s i s t 1argel.y of f o l i a c e o u s and f i n e b r a n c h i n g forms even i.11 exposed. s i t u a t i o . n s " . T h i s f e a t u r e of r e e f zonatiol?.
may be due t o t h e r a r j . - t y of s e v e r e s t o r m s i n t h e s e t h r e e r e g i o n s .
?'he n o r t h - w e s t t i p of A l d a b r a i s n e v e t h e l e s s c o m p l e t e l y e x p o s e d ' t o o c e a n i c s w e l l and r e c e i . v e s a c o n s i d e r a b l e pounding by n a v e s f o r much of t h e y e a r . T a y l o r (1968) a l s o r e p o r t s dominaace of m i l l e p o r e / a c r o p o r e t y p e s i n exposed s i t u a t i o n s on S e y c h e l l e s r e e f s , bu-t w i t h massive s p e c i e s dominant i n s1ielt;ered a r e a s .
The r e s t r i c t i o i i o r m i l l e p o r e c o r a l s t o t h e heavy s u r f
r e g i o n of t h e r e e f - f r o n t may be a s s o c i a t e d w i t h t h e same f a c t o r which a l l o w s t h e i r predomi.nance i n t h e f a s t - f l o w i n g chalin.els
l e a d i n t < i i l t o A l d a l s r a ' s e x t e n s i v e b u t v e r y s h a l l o w l a g o o n , p e r h a p s a r e q u i r e m e n t f o r c o n s t a n t l y moving w a t e r o r an a 1 s i . l i . t ~ t o wi.t:~- s t a n d t h e r e l a t i v e l y warm wa-ter which f l o w s b o t h o f f t h e r e e f f l a t and o u t of tire l a g o o n . T a y l o r ( 1 9 6 8 ) s u g g e s t s t h a t t h e v e r - t i c a l ill-t:cr-connected p l a t e s which c o m p r i s e tile s u r f - z o n e m i l l e p o r e colosi:i.es a r e w e l l a d a p t e d t o a b s o r b t h e e n e r g y of b r e a k i n g waves, b u t i t i s a l s o n e c e s s a r y -to expl-ain t h e i r v i r t u a l a b s e n c e i n s - t i l l - e r w a t e r .
Folj.aceous forms of c o r a l a r e w e l l s u i t e d t o i l l - t e r c e p t a maxi.mal amount of a v a i . l a b l e l i g h t w i t h a minimum volume of c o l o n y , and a r e t h u s we1.l s u i t e d t o t h e d e e p dim w a t e r s w%ere t h e y p r e d o m i n a t e d on t h i s t r a n s e c - t . It i s llowever s u r p r i s i n g t h a t t h e - t o - t a l l i v i n g c o v e r o:F t h e r e e f remained r e a s o n a b l y
c o n s t a n t w ~ t i l t h e v e r y r a p i d r o d u c - t i o n bel.ow 3 0 m e t r e s . T h e r e w a s e v e n a n o t i c e a b l e i n c r e a s e b e t w e e n '1
5
a n d 25 m e t r e s . T h u s , l i v i n g c o v e r d o e s n o t a p p e a r -Co b e c o r r e l a t e d d i r e c t l y wi.thambi.en-t :L.igl'~S enerf,T
-
t h e two a r e c o ~ ~ ~ p a r c d i n F j ~ g u r e6 -
a l t h o u , ~ l l - t h e i n t e r r e l a - t i . o n s be-tween g r o r i t h - t y p e , e f f i . c i e n . c y o f l i g h tu t i l i s a - t i o n , r a - t e o:? p r i m a r y o r g a n i c p r o d u c t i o n a n d r a t e o:f c a l - c i . f i c a t i o n a r e as y e t o.nly known i n t h e b a r e s t outl:i..l1e. I m p o r t a n t -too may b e t h e p r e f e r e n c e s o f c o r a l b r o w s e r s s u c h as p a r r o t f i . s l ~ , a n d i ; l ? e i r a b i l i t y -to f e e d i n t u r b u l e l l t s h a l 3 . o ~ w a t e r .
The si.mp:Le p l ? o i ; o g r a p h i c t r a r l s e c t method d e s c r i b e d h e r e c o u l d p r o v i ~ d e a b a s i s f o r r a p j . d a c c u r a - t e a s s e s s l ~ ~ e n ~ t o:f v a r j . o u s t y p e s o f r e e f arid a l ~ l o w v a l i d qua11-ti la - t i ~ v e cornparj.sons
.
Them e t h o d h a s c c r t a 5 . n i . i r n i t , a t i o n s i.11 a c c u r a c y , s u c i l as t l r e e d g e d i s t o r t i o n p r o d u c e d by u i ~ c o r r e c t e d rii.de ang3.e l e n s e s , a l t h o u g l l m o s t of t h i s i s el.:i.mii~atecl b y c u t t i n g of:f t h e e x - t r e 1 n i . t i . e ~ o:f e a c h p r i . n t f o r o v e r 1 a : p . Tile e x p e n s e o f u s i n g t h e 28mm c o r r e c t e d u n d e r - w a t e r l e n s a v a i l a b l e f o r t h e Ni.konos c a m e r a i s p r o b a b l y u n w a r r a n - t e d , e s p e c : i . a l l . y as s e v e r a l s e p a r a t e c a m e r a s a r e r e q u i r e d f o r l o n g t r a n s e c t s ( s e e l a t e r ) .
R e c o g n i . - t i o n of v a r i o u s g r o w t h . :forms p r o v e d r n o d e r a t e l y e a s y w i t h - t h e monoclrrome pri.ulLs u s e d , a l t h o u g h a r t i f i c i a l i l l u n l i n a t i o n rioultl h a v e al.:l.oxied i n c r e a s e d d e f i n i - L i o n i.n d e c p s e c t i o n s w h i l s t t h e u s e of c o l . o u r p r i r l - t f i l m s h o u l ~ d j h : f u t i . r e a l l o w p o s j . t i . v e i d e r 1 t i : f i c a t i o n o:f n o s t s p e c i e s
,
i . r i c l u d i n g t h e en.crus t i n g c a l c a - r e o u s r e d a l g a e , as w e l ~ l a s a f u r t h e r i n c r e a s e i n d e : f i n i t i . o i i . U n f o r - t u n a t e l y - t h e : p r i n t s fro111 c o l o u r t r a n s p a r e n c i . e s u s u a l l y l a c k - t h e s h a r p n e s s requfired. f o r t h i s w o r k .P h o t o t r a n s e c t m e t h o d s c o u l d a l s o b e u s e d i n t h e r a p i d t o p o - ,grap:L?ic s u r v e y inetllod u s e d 011. t h e ~ n a j o r i l y o f t r a n s e c t s s t u d i e d i.11 A l d a b r a . T h i s i n v o l - v e d two d i v e r s , s e p a r a t e d b y a 1 0 m e t r e l e n g t h o f s t r i n g , l e a p - f r o g g i n g e a c h o t h e r i n a s t r a j - g h t l i n e down - t h e r e e f and. r e c o r d i n g d e p - t b e v e r y 1 0 m e - t r e s . A t h i r d d i v e r c o u l d p h o t o g r a p h t h e t e n m e t r e s t r i p i n 1 m e t r e s e c t i o n s -rih:i.lst -th.e s u r v e y o r s r e c o r d e d % h e i r ow1~ da-ka. T h i s would r e q u i r e s i x c a m e r a s f o r a l o n g t r a n s e c t
-
s a y 200 m e t r e s-
a n d may d o u b l e - t h e s u r v e y Lime. :Towever, tI1.e v a s ~ t i n c r e a s e i n d a t a o b t a i n e d , a n d t h e s a v i n g i.11 t i m e r e q u i r e d t o estab:Lisl:i serni-permanent t r a n s e c t s a n d r e l o c a t e the111 o n e a c h d i v e , wou1.d c e r - t a i . r r l y j u . s t i . f y t h i . s .F i - n a l l y , a n o t e 011 d i v e r s a f e - t y . C o r a l : r e e f s a r e : f r e q u e n t l y i n h a h i . t c d b y p o - t e n t i a l l y a g g r e s s i v e a n i m a l s , nra.i.111y s h a r k s .
F o r t u n a t e l y t h e s e w e r e v i r - t u a l l y a b s e n t :Prom t h c A l d a b r a r e e f - : f r o n t a t t h e 1;i.r;le t l l i s s u r v e y w a s c a r r i e d o u t ( ~ e c c r n b e r ,
1968
t o F e b r u a r y , 1 9 6 9 ) , s o t : l ~ a t d i v e r s c o u l d c o n c e n t r a t e o n t h e i r s c i e n - t i f j ~ c - t a s k s . :it woul.6, h o w e v e r , h e e s s e n t i a l : f o r a s u r v e y t e a m w o r k i n g i n more d a n g e r o u s w a t e r s t o b e acconipariied by'
l o o k - o u - t s' ,
p e r h a p s i.11vol.ved i k more random p h o t o g r a p h y o r c o l l . e c t % o n o f r e e f f l o r a and : f a u n a , b u t p r i 1 n a r i . 1 ~ t i l e r e t o a l l o w t l e t e a m - t o colicen-
% : r a t e oil t h e i r complex t;aslss kuowi11.g t h e y w i l l . b e warned o:f i r n p e n d i ~ n g d a n g e r .
'I'hi.s rvorlc f o r m e d a si~!al.l. p a r - t o:? t h e ci:i.vi.i~f.: programme of P h a s e
VI:
o:f t h e Royal. Soc:i.ety lCx:pe<ii.ti.on i;o A..Lilal>ra, asid w a s made p o s s i ~ l ? l f : b y tl?e org'amisati.oi-I a n d 1 o y ; i s l : i c s u p p o r t p r o v i d e d by - t h e A l d a b r a R e s e a r c h . Cornmitttee and t h e o v e r a l l cxpediti.013~l e a d e r ,
Dr.
D .R.
S t o d d a r t .3: would a l s o l i l c e t o thasi1.c a l l -ti?.(? o t h e r nrenll?ers o:f t h a - t p h a s e of t h e l:xped:i..tios~, and. especia1:l.y i):r. J
.
Lytl-if:-oe,
M r . D. J o n e s a n d M r . J . U a r n e s roho accompnni~ccl. me oil m o s t of - t h e p b o t o , g r a p i i i c and s u r v e y d i v e s , f o r t1-iei.r h e l p i n t h e r i e l - d .
Tlie C o u r t o f S t . Andrews U n i v e r s i t y gen.erous3.y g r a n t e d me 3.eave of a b s e n c e f o r t h i s ex.pcdi.l.ion..
Del.larny, l'i., Drew, I < . , J o n e s , 1). and I,yt;h.f;oe,
J.
1970. i l l d a b r a-
a p r e l j ~ m i n a r y r e p o r t o:L' -the w o f k o f P h a s e V7: of t h e Iioyal.
S o c i . c t y 11:xpetli-tion. Unrlcrx?atcr A s s . Reporl;
1')68-69.
S t : o d d a r t
,
I). R . ( l o r )6 .
Ree:E s t u d i r i s a t Add11 A t o l l , Malclivc I : s l a r i d s . iitol1. Res.
1'11111. 116
: i ..-,I 2 % .S t o d d a r - t , 13.R. 1 9 6 9 a . 1Ccolof;y and rnorphol.ogy of Rcceni: c o r a l r e c : ? s , A r ~ o l . R e v . , 1111.:
41-498.
T a y l o r , 3. 1 9 6 8 . Coral. r e e : ? asid a s s o c j a l : e d j . ~ ? v e r t e ' b r a t e communi.-ties aroulid Mah.6, S e y c l i e 7 ~ l . c : ~ . I'hj.1.. 'l'rans
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