atoll research bulletin no* 268 recent history of a fringing reef, bahia

atoll research bulletin no* 268 recent history of a fringing reef, bahia

ATOLL RESEARCH B U L L E T I N
N O * 268
RECENT HISTORY OF A F R I N G I N G REEF, B A H I A S A L I N A DEL SURJ
V I E Q U E S ISLAND, PUERTO R I C O
IAN
6 - MACINTYRE,
BILL
RAYMOND
AND
SEPTEMBER 1 9 8 3
ROBERT STUCKENRATH
RECENT H I S T O R Y OF A F R I N G I N G REEF, B A H I A S A L I N A D E L SURJ
V I E Q U E S I S L A N D , PUERTO R I C O
bY
I a n G. ~ a c i n t ~ rle , B i l l ~ a y m o n d ,
and R o b e r t s t u c k e n r a t h 3
Introduction
The e f f e c t o f U. S. Navy t r a i n i c g a c t i v i t i e s o n t h e s h a l l o w - w a t e r
r e e f s a t t h e e a s t e r n end o f V i e q u e s I s l a n d , P u e r t o R i c o , was
i n v e s t i g a t e d d u r i n g a 1978 e c o l o g i c a l s u r v e y t h a t i n c l u d e d t h e d r i l l i n g
o f t h r e e s h o r t c o r e h o l e s i n t o a n Acropora p a l m a t a (Lamarck) r e e f o f f
t h e e a s t c o a s t o f Bahia S a l i n a d e l S u r ( F i g u r e 1 ) . Radiocarbon d a t e s
o f f i v e c o r e samples y i e l d new i n f o r m a t i o n on t h e a c c u m u l a t i o n r a t e s o f
A . p a l m a t a r e e f s e c t i o n s and p r o v i d e f u r t h e r e v i d e n c e t h a t framework
communities o f many s e a - l e v e l r e e f s a r e m i g r a t i n g l e e w a r d o v e r l o o s e ,
back-reef sediments.
General S e t t i n g
Bahia S a l i n a d e l S u r i s a m a l l , c r e s c e n t - s h a p e d embayment
( a p p r o x i m a t e l y 1 km wide and 1 km l o n g ) on t h e s o u t h c o a s t o f V i e q u e s
I s l a n d and c l o s e t o i t s e a s t e r n end ( F i g u r e 1 ) . The T h a l a s s i a s e a g r a s s and sand and r u b b l e f l o o r i n t h i s a r e a do n o t exceed a d e p t h o f
7m (Raymond, 1 9 7 8 ) . S h a l l o w r e e f s f r i n g e t h e p r o m o n t o r i e s on t h e
e a s t e r n , w e s t e r n , and n o r t h e r n s h o r e s o f t h e bay, and two e x t e n s i v e
s a n d b e a c h e s b o r d e r i t s n o r t h e a s t e r n an? n o r t h w e s t e r n c o m e r s .
The f r i n g i n g r e e f o f f t h e w e s t s i d e o f t h e bay c o n s i s t s o f a w e l l d e v e l o p e d Acropora p a l m a t a c o m u n i t y .
Small c o r a l h e a d s grow b e n e a t h
t h e open framework o f A . p a l m a t a , which e x t e n d s t o a d e p t h o f 5m, where
a h a l o o f sand s e p a r a t e s t h e r e e f from a d j a c e n t broad b e d s of
T h a l a s s i a . T h i s h a l o of sand may be r e l a t e d t o t h e f e e d i n g a c t i v i t y of
f i s h and s e a u r c h i n s (Ogden and Zieman 1 9 7 7 ) .
P cr i t e s p o r i t e s (Fallas)--which resemble t h e
Banks and mounds o f n e a r - s h o r e banks of P o r i t e s off t h e w e s t c o a s t o f Barbados ( M a c i n t y r e
19f8; and c f f t h e s c u t h e a s t c o a s t of S t . C r o i x (Adey 1 9 7 5 ) - - have
d e v e l o p e d around two d i s t i n c t p r o m o n t o r i e s on t h e n o r t h c o a s t of Uahia
S a l i n a ciel S u r , Sreall s c a t t e r e d s t a n d s o f Acropora calrm-ta o c c u r i n
a s s o c i a t i o n w i t h t h e s e Porites b u i l d u p s . During t h e May, 1976 s u r v e y
i t was o b s e r v e d t h a t n a v a l bombardment had d e s t r o y e d t h e e a s t e r n end; of
t h i s n e a r - s h o r e community. During a s u b s e q u e n t s u r v e y f o l l o w i n g
H u r r i c a n e E a v i d , Raymond and Dodge (1980) found t h a t s t o r m waves had
' ~ a t i o n a l Elusem. o f N a t u r a l H i s t o r y , S m i t h s o n i a n I n s t i t u t i o n ,
Washington, D . C . 20560,
2 ~ c e a nR e s e a r c h and S u r v e y , I n c . ,
F o r t L a u d e r d a l e , F l o r i d a 33136.
3 ~ a d i a t i o nBiology L a b o r a t o r y , ~ r n i t h s o n i a n I n s t i t u t i o n , Washington,
D . C . 20560.
Manuscript r e c e i v e d Jan.
1982--Eds.
a l m o s t completely d e s t r o y e d t h e e n t i r e n o r t h - s h o r e P o r i t e s community,
A. palmata on t h e s o u t h c o a s t of Vieques.
a l o n g w i t h most of t h e The r e e f cored d u r i n g t h i s s t u d y ( d e s i g n a t e d S-5 r e e f i n Antonius
and Weiner's 1978 s u r v e y ) j u t s o u t o b l i q u e l y from a b o u t t h e c e n t e r of
t h e e a s t e r n s h o r e of Bahia S a l i n a d e l Sur and i s p r o t e c t e d i n p a r t by
a l a r g e promontory t h a t forms t h e e a s t e r n e n t r a n c e t o t h e hay and by
t h e f r i n g i n g r e e f a d j a c e n t t o t h i s promontory, which c o n s i s t s o f
M o n t a s t r e a , S i d e r a s t r e a , and D i p l o r i a c o r a l heads. A d d i t i o n a l p r o t e c t i o n i s a f f o r d e d by t h e A. palmata r e e f surrounding Roca A l c a t r a z , a n
i s l a n d 1 km s o u t h of S - 5 r e e f ( f i g u r e 1 ) . S-5 r e e f h a s t h e c h a r a c t e r i s t i c z o n a t i o n of shallow-water Caribbean r e e f s dominated by Acropora
palmata i n t h e r e e f c r e s t and s h a l l o w f o r e r e e f ( F i g u r e s 2 , 3D,E,F)
( s e e , f o r example, Dahl e t a l . 1974; Adey 1 9 7 5 ) . A t a d e p t h of 4 m ,
t h e A. palmata community g i v e s way t o a mixed c o r a l - h e a d community t h a t
i n c l u d e s Montastrea a n n u l a r i s ( E l l i s and S o l a n d e r ) , D i p l o r i a s t r i g =
(Dana), and S i d e r a s t r e a s i d e r e a ( E l l i s and S o l a n d e r ) . Small s c a t t e r e d
c o l o n i e s o f b o t h Acropora c e r v i c o r n i s (Lamarck) and Acropora p r o l i f e r a
( L m a r c k ) were found i n t h e s h a l l o w f o r e r e e f d u r i n g t h e 1978 s u r v e y ,
b u t s u b s e q u e n t l y were a l m o s t e n t i r e l y removed by storm s u r g e a s s o c i a t e d
w i t h Hurricane David (Raymond and Dodge 1 9 8 0 ) . The seaward s l o p e of
S-5 r e e f l e v e l s o f f a t a d e p t h of 8 m , where i t g r a d e s i n t o t h e
sediment f l o o r of t h e bay ( F i g u r e 2 ) . The back r e e f shoreward of t h e
r e e f c r e s t i s composed of l a r g e c o l o n i e s o f Montastrea a n n u l a r i s on
r u b b l e and pavement, which grade i n t o sand and r u b b l e ; o n l y a few
c o l o n i e s of M . a n n u l a r i s occur a t t h e i n n e r l i m i t o f t h e d r i l l - s i t e
t r a n s e c t ( ~ i g u r e s2 , 3A, B , C ) .
I t s f a u n a l z o n a t i o n i n d i c a t e s t h a t S-5 r e e f h a s developed under
moderate wave-energy c o n d i t i o n s ( G e i s t e r 1 9 7 7 ) . The a l g a l r i d g e s o r
Palythoa-Millepora r e e f - c r e s t communities c h a r a c t e r i s t i c of h i g h waveenergy r e e f s a r e a b s e n t h e r e , a s a r e Acropora c e r v i c o r n i s o r P o r i t e s
p o r i t e s communities i n low wave-energy r e e f s . Wave a g i t a t i o n does
appear t o be s t r o n g enough t o p r e v e n t any s i g n i f i c a n t accumulation of
t h e f r a g i l e Acropora c e r v i c o r n i s e i t h e r i n t h e d e e p e r f o r e - r e e f s l o p e
o r i n t h e p r o t e c t e d back-reef s a n d f l a t s ,
Core D e s c r i p t i o n s
Three c o r e h o l e s were d r i l l e d a t 50-m i n t e r v a l s a l o n g a t r a n s e c t
c r o s s i n g S-5 r e e f and a d j a c e n t t o t h e e a s t e r n c o a s t of Bahia S a l i n a
d e l Sur ( F i g u r e 1)--two i n t o t h e r e e f c r e s t i n a water depth of a k o u t
0 , 5 rn and one i n t o t h e s h a l l o w f o r e - r e e f s l o p e i n a water d e p t h of 2 m
below mean s e a l e v e l ( F i g u r e 2 )
.
Core h o l e 1, d r i l l e d i n f o u r i n t e r v a l s i n t o t h e r e e f c r e s t t-o a
d e p t h of 6.4 m , y i e l d e d t h e f o l l o w i n g m a t e r i a l :
1.
0-.61 m.--This i n t e r v a l c o n s i s t e d o f f r e s h s e c t i o n s of
Acropora palmata w i t h a comparable amount of fragments
bored and e n c r u s t e d by Bon?otrena rubrum, c o r a l l i n e a l g a e ,
and s e r p u l i d s .
2.
.61-1.83m.--This section was made up of fresh and bored
sections of Acropora palmata and Diploria strigosa, along
with some encrusted (by Eornotrema rubrum and coralline algae)
rubble consisting of A. palmata, Diploria sp., and Porites
porites.
3.
1.83-3.35--Sections of A. palmata and Diploria clivosa were
found throughout and cave-in rubble at the top of this
interval.
4. 3.35-6.40 m.--Only cave-in rubble was collected from this
interval. On-site observations indicated that the drill
had dropped through a section of sand at this point.
Core hole 2 consists of one core interval drilled to a depth of
1.83 m below the surface of the reef. Except for a 6-cm core of bored
and encrusted Diploria striyosa, the material here was mainly A.
~ a l m a t abored to various degrees by sponges, molluscs, and worms and
rubrum,
coralline algae, and serpulids.
encrusted by Eornotrena Core hole 3, dri-lled to a depth of 4.88 m below the surface of the
reef, consists of three core intervals:
1,
0-1.83 me--This interval is characterized by extensive
submarine lithification, so that core sections are
predominently ayglcn-erate lirn~stcne. These cores, which
are identical to those described from the shallow fore
reef off Galeta Point, Fanama (Macintyre 19771, consist
of extensively bored and cemented agglo~erationsof
crustose coralline algae, Millepora sp., Porites sp.,
and Acropora palmata. The multicyclic boring and submarine
lithification have in some places destroyed much of the
original skeletal framework, which has been replaced .by
magnesium calcite cement, Other material collected from
this interval consists of bored, infilled, and cemented
A.
palrata
- and other coral debris,
2,
-1-83-3-35m.--Core
3.
3.35-4.88 m.--Extensive cave-in rcbble occurred in t'r.is
interval. Two cores of bored Acropora palsata vere also
collected here.
sections contaized mainly Acropor~almata-,
both fresh corals and smples & ~ r e dby sponges, w o m s , and
molluscs, Lxtenslve cave-in rratee~alw s present at the
top of this irterval.
Radiocarbon Dates
Five radiocarbon dates were obtained from fresh sarcples of
Acropora palmata, which had been collected from the Gase of core
intervals so as to reduce the error in estimating the depths of
recovery for the dated, sarn~les. Even so, it is not known whether the
l a s t m a t e r i a l t o be cored i s i n p l a c e a t t h e b a s e o f t h e c o r e i n t e r v a l ,
s i n c e a c o r e b a r r e l can punch through a s e c t i o n of t h e r e e f and c a r r y a
The l a c k o f any s i g n i f i c a n t
sample below i t s r e a l d e p t h of recovery.
d i f f e r e n c e i n t h e two d a t e s from c o r e h o l e 3 , t h e poor recovery i n t h e
l a s t c o r e i n t e r v a l , and t h e d r i l l - w o r n c o n d i t i o n o f t h e lower sample
d a t e d s u g g e s t t h a t t h i s c o r e sample was c a r r i e d below i t s t r u e d e p t h o f
r e c o v e r y . Radiocarbon d a t e s and t h e accumulation r a t e s f o r t h e i n t e r vening r e e f s e c t i o n s a r e given i n Table 1.
TABLE 1
RADIOCARBON DATES AND ACCUMULATION RATES,
BAHIA SALINA DEL SUR REEF
Sample
Hole 1:
Core 1
Core Depth
Interval
(m 1
Estimated
Interval
Depth of
of Reef
Recovery
Section
below Reef
Dated
S u r f a c e (m)
(m)
Radiocarbon
Date
Accumulation
Rate
(m/1000 y r s )
--
0-.61
.61
0-0.61
190590
3.21
Core 1
Core 2
Hole 2:
Core L
0-1.83
1.83
0-1.83
860290
2.13
Hole 3:
Core 2
1-83-3.35
3.35
0-3-35
2020+70
1.66
Core 2
1.88-3.35
3.35
2020270
3.35-4.88
Core 3
3.35-4.88
4.88
i<
2020170
* E s t i m a t e s i n . ~ l l i d a t e dowing t o poor r e c o v e r y i n t h i s c o r e
interval.
Summary and Conclusions
Excluding t h e l o w e s t s e c t i o n of c o r e h o l e 3 (where t h e e s t i m a t e s
were d i s c o u n t e d a s i n v a l i d ) we c a l c u l a t e d t h a t t h e Acropora palmata
framework of S-5 r e e f h a s an average accumulation r a t e o f about 2m/1000
y e a r s , which i s lower t h a n t h e average of 3.9m/1000 y e a r s r e p o r t e d f o r
t h e A. palmata f a c i e s o f t h e f r i n g i n g r e e f o f f G a l e t a P o i n t , Panama
(Macintyre and Glynn 1 9 7 6 ) . T h i s d i f f e r e n c e can be a t t r i b u t e d t o t h e
changing r a t e s of s e a - l e v e l r i s e i n t h e l a t e s t a g e s of t h e Eolocene
transgression.
Sea-level curves e s t a b l i s h e d f o r several a r e a s i n t h e
A t l a n t i c and F a c i f i c oceans show a d i s t i n c t d e c r e a s e i n t h e r a t e o f
s e a - l e v e l r i s e , from 3,000 t o 4,000 y e a r s B.P. (Macintyre and Glynn
1 9 7 6 ) . A s p o i n t e d o u t i n t h e study o f G a l e t a Reef, accumulation
r a t e s t h e r e d e c r e a s e d c o n s i d e r a b l y a b o u t t h i s p e r i o d of time because
changing s e a l e v e l s reduced t h e a v a i l a b i l i t y of v e r t i c a l space f o r
r e e f development. Wherever A . palmata communities have experienced
r a p i d changes i n s e a l e v e l , however--for example, a t t h e s h e l f edge o f f
F l o r i d a 7,000 t o 9,500 y e a r s ago (Lighty e t a l . 1978)--the mean
accumulation r a t e s have been e s t i m a t e d a t 6 . 6 m/1000 y e a r s , t h e
maximum r a t e r e p o r t e d being 10.7 m/1000 y e a r s .
The d a t e s from t h e Vieques c o r e s s u g g e s t t h a t hallow-water
Acropora palmata framework t h a t i s l e s s t h a n 2,000 y e a r s o l d can be
expected t o have accumulation r a t e s around 2m/1000 y e a r s .
In addition,
t h e p e n e t r a t i o n of more t h a n 3 m of sand a t t h e b a s e of c o r e h o l e 1
l e n d s s u p p o r t t o S h i n n ' s (1980) o b s e r v a t i o n t h a t some shallow-water
A . palmata framework nay a c c r e t e leeward over back-reef sands "by
c o r a l s e s t a b l i s h i n g themselves on s t o n - d e r i v e d r u b b l e p e r i o d i c a l l y
t r a n s p o r t e d o n t o t h e leeward s i d e of t h e r e e f f l a t " (p. 6 5 1 ) .
O b s e r v a t i o n s of S-5 r e e f b e f o r e and a f t e r Hurricane David i n d i c a t e
t h a t b o t h dead and l i v i n g A . palmata, a l o n g w i t h c o r a l head d e b r i s ,
migrated s e v e r a l m e t e r s o v e r t h e back-reef sands i n t h i s a r e a .
Furthermore, t h e e x t e n s i v e and m u l t i c y c l i c cementation p r e s e n t a t t h e
t o p of t h e shallow f o r e - r e e f c o r e h o l e 3 i s a c h a r a c t e r i s t i c
a s s o c i a t e d w i t h slowly accumulating r e e f f a c i e s (Macintyre, 1 9 7 7 ) .
This combination o f r e l a t i v e l y l i t t l e present-day r e e f growth i n
ow f o r e r e e f and leeward m i g r a t i o n of t h e r e e f f l a t i n d i c a t e s
t h a t S-5 r e e f i s i n a mature s t a g e of r e e f d e v e l o p ~ ~ e n textending
,
l a t e r a l l y i n t o t h e Bahia S a l i n a d e l S u r .
Acknowledgments
Thanks go t o Robin King, Mike Wolfe and Greg McIntosh, a s w e l l
a s t h e Navy E.O.D. d i v e r s of Roosevelt Roads, P.R. f o r a s s i s t i n g w i t h
t h e f i e l d work. Also, t h a n k s t o t h e Navy h e l i c o p t e r p i l o t s who a i r l i f t e d t h e c o r i n g equipment from San Juan t o Vieques.
W. T. Boykin's a s s i s t a n c e w i t h d r a f t i n g i s g r a t e f u l l y
acknowledged.
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IT. S . Dept. o f J u s t i c e , Dec. 1978.
1980. 1979 H u r r i c a n e damage t o c o r a l
Raymond, W . F. and R . E. Dodge.
r e e f s o f V i e q u e s . R e p o r t s u b m i t t e d t o U.S. Kavy.
1980. G e o l o g i c h i s t o r y o f G r e c i a n r o c k s , Key Largo
Shinn, E. A.
C o r a l Reef Marine S a n c t u a r y . B u l l . Mar. S c i . 30:646-656.
F i g u r e 1,
Index map showing l o c a t i o n of Vieques I s l a n d , Bahia S a l i n a d e l
S u r , t h e d i s t r i b u t i o n of f r i n g i n g r e e f s i n t h i s bay, and t h e l o c a t i o n of
t h e three core h o l e s d r i l l e d i n t h i s s t u d y ,
CORE
3
LEGEND
Acroposa cervicornis
r , Acropora palrnata
>f-
--
J
@
Diploriaclivosa
-
@ Diploria strigosa
fl
Montastrea onnuloris
0
Posites asfreaides
@
Siderastrea sp.
#=
Crustose coralline algae
M i l l e p a r a sp.
P--
Porites porites
Octacorai
F i g u r e 2-. Schematic c r o s s - s e c t i o n o f S-5 r e e f a l o n g t h e c o r e - h o l e t r a n s e c t ,
showing ckominant r e e f components on t h e s u r f a c e and t h o s e r e c o v e r e d from
the c o r e holes,
Figure 3.
Bottom p h o t o g r a p h s of S-5 r e e f t a k e n a l o n g t r a n s e c t
shown i n F i g u r e 2 .
A.
-
I s o l a t e d c o l o n i e s of M o n t a s-trea a n n u l a r i s
on sand and r u b b l e bottom, a t 5 m a l o n g t r a n s e c t .
B , and C.
-
r e e f M. a n n u l a r i s c o l o n i e s a t 30 and 5 0 m , r e s p e c t i v e l y .
D,
-
Back-
E,
and F . A. p a l m a t a community on t h e r e e f c r e s t i n t h e v i c i n i t y of
c o r e h o l e 1 and 2 , and on t h e s h a l l o w f o r e - r e e f ,
near core hole 3.