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ATOLL RESEARCH BULLETIN
No. 151
BACTERIAL COUNTS IN SURFACE OPEN WATERS OF ENIWETOK ATOLL,
MARSHALL ISLANDS
by Louis H. DiSalvo
Issued by
THE SMITHSONIAN INSTITUTION
Washington, D. C., U. S. A.
BACTERIAL COUNTS IN SURFACE OPEN WATERS OF ENIWETOK ATOLL,
MARSHALL ISLANDS
by Louis H. DiSalvo'
INTRODUCTION AND METHODS
During my investigations of c o r a l reef microbiology at Eniwetok Atoll, Marshall Islands in
1968, l a r g e numbers of bacteria were found inhabiting c o r a l reef internal sediments (lo7-lo8
colonies/g; DiSalvo, 1969). With the high level of metazoan activity on r e e f s i t was expected
that sediment processing and disturbance might cause the r e l e a s e of bacteria, contributing to
the organic particulate enrichment of lagoon w a t e r s (Marshall, 1965; Johannes, 1967). T o my
knowledge, no bacteriological data were available which compared oceanic counts to lagoonal
counts n e a r a n atoll, and therefore the following m e a s u r e m e n t s were made both in r e f e r e n c e
to the work a t hand and a s a general contribution to atoll ecology.
Open w a t e r sampling f o r aerobic h e t e r o t r o p h i c bacteria was c a r r i e d out on s i x bi-weekly
d a t e s in June and July 1968. A total of 24 s a m p l e s of s u r f a c e seawater w e r e obtained a t
oceanic and lagoonal stations. In addition, a total of 14 s a m p l e s were obtained downstream
f r o m the Japtan r e e f a t the s u r f a c e and a t 2 m e t e r s depth. Sample locations a r e shown in
Figure 1. Surface (top 5 cm) water s a m p l e s w e r e obtained in s t e r i l e 200 m l prescription
bottles f r o m a boat. Skin diving was employed to obtain the 2 m samples. Samples w e r e kept
on i c e f o r r e t u r n to the laboratory, and plated f o r b a c t e r i a l counts within five hours of collecThe plating medium was ZoBell 2216e (Oppenheimer and ZoBell, 1952) solidified with
tion.
1.5% (w/v) a g a r .
Duplicate pour p l a t e s w e r e made using 0.1 m l r a w Seawater inocula and
10 m l medium which had been cooled to 40-45OC. P l a t e s w e r e incubated a t ambient temperat u r e (30°C) f o r 48 h o u r s and then counted f o r total colonies.
RESULTS AND DISCUSSION
Bacterial counts f o r numbered sam.3les located by Figure 1 a r e listed in Table 1. T h e s e
counts a r e within o r d e r of magnitude limits established by other investigators using s i m i l a r
methods on w a t e r s n e a r non-atoll r e e f s (Table 3). Table 2 l i s t s counts for two depths immediately behind the Japtan Reef. Summarized r e s u l t s in Table 3 suggest there was no significant
difference between oceanic and back-reef counts.
Conclusions f r o m these data a r e tentative and preliminary. Comparisons with plate counts
of other w o r k e r s in Table 3 have been made f o r convenience, although they may be invalidated
by slight differences in methodology and materials. The limitations of the plate count technique
in obtaining "true counts" a r e well known (ZoBell, 1946; J o n e s and Jannasch, 1959) and p r e s e n t
r e s u l t s can only be considered a s a m e a s u r e of relative microbial activity. The counts a r e
' p r e s e n t a d d r e s s : Naval Biomi?dical Laboratory, NavalSupply Center, Oakland, Calif. 94625.
(Manuscript r e c e i v e d J u l y 1970--Eds.)
within higher r a n g e s expected f o r c l e a r tropical pelagic waters, and it may t h e r e f o r e be hypothesized that the w a t e r s surrounding the atoll a r e enriched in some way, perhaps by local upwelling o r organic enrichment f r o m the reefs.
The s m a l l numbers of sample platings preclude rigorous statistical interpretations of the
data.
M o r e seriously, I w a s unable to s a m p l e t h e s a m a water m a s s flowing f r o m ocean to
lagoon o v e r the Japtan Reef f o r the before-after measuremsnts. Both t h e s e f a c t o r s were the
r e s u l t of logistical problems, helping to explain why t h e r e a r e essentially no microbiological
data available f o r atoll waters. Since i t h a s previously been suggested that the Japtan Reef was
i n a steady s t a t e with r e g a r d to the i m p o r t and export of m a t t e r and energy (Odum and Odum,
19651, i t i s not unreasonable to deduce f r o m :he available data that this reef is i n equilibrium
with r e g a r d t o input and output of heterotrophic bacteria.
Future studies should attem2t to confirm p r e s e n t r e s u l t s under various seasonal and tidal
r e g i m e s , and extend the m-.asuremsnts to representative depths within and outside the atoll.
Such m e a s u r e m e n t s might be useful i n studies of o u t e r slope upwelling and local enrichment
due to the c o r a l reefs.
ACKNOWLEDGEMENT
The author wishes to thank the Eniwetok Marine Biological Laboratory and the University
of Hawaii f o r support and facilities u s e d to accomplish this research.
LITERATURE CITED
DiSalvo, L.H. 1969. Regenerativefunctionsandmicrobialecologyofcoral r e e f s . Ph.D. Thesis.
Univ. of N. Carolina, Chapel Hill. 289 p.
Gee, A.H. 1932. Lims? deposition and the bacteria. I. Estimate of b a c t e r i a l activity in the
F l o r i d a Keys. Pap. Tortugas Lab., Carnegie Inst., Washington, D.C. 28: 67-82.
Gundersen, K.R. and D.B. Stroupe. 1967. Bacterial pollution of Kaneohe Bay, Oahu. Univ.
Hawaii Water Resources Res. Ctr., Tech. Rpt. 12. 24 p.
Johannes, R.E. 1967. Ecology of organic a g g r e g a t e s in the vicinity of a c o r a l reef. Limnol.
Oceanogr. 12: 89-195.
Jannasch, H. and G.E. Jones. 1959. Bacterial population inseawater a s determined by s e v e r a l
methods of enumzration. Limnol. Oceanogr. 4: 128-139.
Marshall, N. 1965. Detritus o v e r the reef and i t s potential contribution to adjacent w a t e r s of
Eniwetok Atoll. Ecology. 46: 343-344.
- - - - - - - - - - 1968.
Observatious on organic aggregates in the vicinity of c o r a l reefs. Mar.
Biol. 2: 50-53.
Odum: H.T. and E.P. Odum. 1955. Trophic s t r u c t u r e and productivity of a windward c o r a l
reef community a t Eniwetok Atoll. Ecol. Monogr. 23: 291-320.
Oppenheimer, C.H. and C.E. ZoBell. 1952. The growth and viability of sixty-three s p e c i e s of
m a r i n e bacteria a s influenced by hydrostatic p r e s s u r e . J. Mar. Res. 11: 10-18.
Sisler, F.D. 1962. Microbiology and biochemistry of sediments and overlying water, p. 64-69,
in, P.E. Cloud, Jr., Environment of calcium carbonate deposition west of Andros I.,
Bahamas. Geol. Surv. Prof. Pap. 350. US. Govt. Printing Off., Washington, D.C. 138 p.
Marine microbiology. Chronica Botanica Pub., Waltham, Mass. 240 p.
ZoBell, C.E. 1946.
Table 1. BACTERIAL COUNTS FOR ENIWETOX ATOLL OPEN WATERS
Date
19fiR
Sam.?le*
Colonies/ml**
1:
-
Date
1968
Sample
it
Colonies/ml
6/23
13
16
18
21
24
12
14
17
19
20
22
23
70
140
50
80
160
180
100
500
50
100
150
30
6/30
* F o r sample location, s e e Fig. 1.
**Colonies/ 0.1 m l plated x 10.
Table 2.
BACTERIAL COLONY COUNTS FOR JAP'TAN I. BACKR E E F WATERS*
Date
1968
Surface~samples
~ ~ ~ .
~~
Sample ;I
Samples. . .from
~ ~ -~
~ ~....
2m
~ . . depth**
. .
~
Colonies/ml
Sample !i
7/15
7/17
7/19
Mean values
3
4
5
6
-
~
Colonies/ml
-
Id
2d
3d
4d
5d
250
500
350
160
150
6d
7d
8d
300
330
250
550
-
-
--
* W a t e r depth approximately 4 meters.
**Obtained by diving.
-
C3
235
= 285
I
Table 3.
SUMMARY OF COLONY COUNTS FOR ENIWETOK
ATOLL OPEN WATERS
Stations
Number of samples
Ocean
(nos. 1-5, 7-11
10
Lagoon
(all Japtan*, nos.
20-24)
19
Colonies/ml
Previous data, near reefs
Gee (1932)'
Sisler (1962)'
Gundersen and Stroupe
(196'7)~
Sieburth ( ~ n p u b . ) ~
3
nd
(a) 5
(b) 3
4
100,150,700**
< 10-lo3
50,60,1360,12,42**
13,2,5**
215,235,250,700**
*See table 2.
**Individual results.
1
Open water near Florida reef t r a c t (Gulf Stream, BirdKey Harbor,
Marquesas lagoon).
2
Water over Great Bahama Bank west of Andros I.
3
(a) immediately outside northern Kaneohe Bay, Hawaii.
(b) Kauai I., Hawaii, 1.5-2.5 mjles offshore.
4
unpolluted lagoon stations, Majuro Atoll, Marshall Is., Feb-Apr.
1970. Unpub. data of J.McN.Sieburth, U.Rhode I.
Narragansett Marine Laboratory, Kingston,
Figure I .
S o u t h e a s t q u a d r a n t o f Eniwetok A t o l l , M a r s h a l l I s .
( 1 1 ° 3 0 ' ~ , 165'15'W),
t o show sampling- s t a t i o n s .
Approximate c u r r e n t p a t t e r n i s d e s i g n a t e d by small
a r r o w s . Contour i n t e r v a l 10 m e t e r s .