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CARIBBEAN RESEARCH INSTIrUT"t
W ,ATR POLLUTION REPORT NO. 9
TILL STATUS OF WATER QUALITY IN CRUZ MAY
AUND CH COLATL lIOLL, ST. JOHN
David I. Grigg and Robert P. vanEepoel
January, 1971
(2nd Printing June, 1971)
GOVERNMENT OF THE VIRGIN ISLANDS
DEPARTMENT OF HEALTH, DIVISION OF ENVIRONMENTAL HEALTH
WATER POLLUTION REPORT
Contracted By
CARIBBEAN RESEARCH INSTITUTE
COLLEGE OF THE VIRGIN ISLANDS
REPORT ON
THE STATUS OF WATER QUALITY IN CUZI BAY
ANDCHOCOLATE HOLE, ST. JOHN
David 1. Grlgg and Robert P. vanEepoel
January, 1971
(2nd Printlig June 1971)
CONTENTS
Pag
I. INTRODUCTION I
II CRUZ BAY 2
m. CHOCOLATE HOLE 5
IV. APPENDIX 6
I. INTRODUCTION
This reports a follow-up evaluatona of two bays previously studied.1 It should
be interpreted In that contest and with reference to the original report. The present
evaluation ti based on quantutaUve data collected in November and December of 1970,
and on aerial photographs and snorkella investigations of both bays. We wish to thank
Mr. Fred Nicholson, Director of the Bureau of Public Health laboratorleo for once ag&in
performing th. bacteriological analyes.
1
Brody. R. W., D. I. Grigg, D. M. Haup and R. P. valEepool,
Report on Estuarine Envirnament at Cruz Bay. St. John, Goverment of the
Virgin Islands, Department of Health. Division of Enviroonmeital Health:
"Phase T Report. A Study of the Effects of Pollutants o the Waters and Sediments
of COru Bay", October, 1969; "Phase I Report, A 8 udy of the Waters, Sediments,
and Blots of Chocolate Hole, St. John, with Copa on to Cruz Bay, St. John",
January, 1970.
11. CRU7 BAY
Water quality data were gathered in Cruz Bay on November 20, 1970 and again on
December 1, 1970 and are summarized in Table 1. Between these times rough seas had
stirred up the bottom of the bay considerably. Tits was evident by increased turbidity
and large amounts of benthic grasses, algae, bivalve mollusks and sponges washed up on
the beach. This very high energy situation must have occurred shortly before our inspection
on December 1, 1970 because all f the stranded organisms were still alive at that lime.
Other effects of this surge action were apparent and are evident in Table I.
The temperature was lowered at all stations, reflecting the intrusion of colder
water from Pillabury Saund. Salinity was made more uniform throughout the bay; the
range was compressed from 35. ppt 37.5 ppt measured on November 20, 1970 to
35. 0 ppt 36.4 ppt. At all stations except #38 (deepest in the creek), pH was higher on
the second occasion. There was no change at Station #38. At all but one staton (027)
there was an increase In suspended solids and Secchi depth was reduced at several stations.
Visibility was obviously reduced it the northeast portion of the harbor around Government
House Point and the ferry dock. In fact, the reduction (compared to summer, 1969) at
Station 027 off the tip of the deck was very striking: from 4.2 meters (bottom) to 2.5
meters. Color was normal around the channel light and along the reef south to Golge Point
and in a arro- bnsd east of the reef. Elsewhere colnr was noticeably affected by the
milky cast ol suspended sand fines. Snorkeling investigation showed that there was indeed
suspended sand and organic particulates In the water. Much scouring has occurred In the
back reef area and this area was also the source of the large number ol benthic organisms
found washed up on the beach.
It is apparent that seasonal changes in sea and weather signlficantly affect the
water In Crus Bay (Table 2). For this reason, it is more likely that reliable indications
of algnlficant or permanent changes in water quality would be gained by comparing the
data from winter, 1969 and winter, 1970. When this is done, the most striking difference
Is that dissolved oxygen in both areas was higher this December than a year ngo: 6.2
mg/] as compared with 5.7 mg/I in the harbor and 5.G mg/I versus 4.3 mg/l in the
creek. A definite redaction in aquatic visibility is apparent, especially at Stations
h14, 21, 23, 27. This ita the area around Govsenmet LHouse Point. The average Seche
dLac visibility in the harbor (2.7 meters) is apparently reduced compared to 3.2 lneters
(average bottom depth) last year. Visibility is very much reduced compared to summer
and fall of 1969. Now the bottom is visible only in that section north and west of
Stations #4, 5. 6, 1I, 18 and in water less than 1.6 2 meters along the bench. Along
the north shore the bottom can be seen only in less than I meter. On the other hand,
most stations checked in the ureek aea showed an increase in water clarity. The
improvement here is also evident from a boat and from aerial photos.
There are now many boats anchored in the bay than n year ago, and a small
floating dock has leen placed off the beach to service ferry boats. Boat traffic In
and oat of the bay is noticeable heavier. In the creek the water color is still very
bld and in the area of Stations '34 and 236, there was a great deal of oil. The sept
od or of enage was very bad here on November 20, 1970 and It was noted that where
the sewer lice comes out of the bulkhead near Otation .;30 the elbow was broken loose
and sewage was being discharged upward out of the breaook to the water surfnee. Of
six samples evaluated for fecl coliforms and streptorocci this was the only positive
sample, with 2 fecal colform per 1oo ml,
-3-
In summary, Crus Bay water quality on the whole is worse now than it was a
year ago. Accompanying this reduction of quality, however, has been a relative Improve-
meat in the quality of the oreak water. Presently, it seem likely that most of the change
la due to seasaMl wave action in Crau Bay. This has di1turbed bottom Benmenta In the
outer bay and promoted uumiual nixing between the waters of the harbor aend te creek.
This mbidK has resulted, because of the uaual nequIty ina these water masses, In a
relative Improvement of creek water quality at the expense of a simultaneous reduotlon
In harbor water quality. It is therefore difflaut to determine if Crui Bay has eastalaed
say permanent, log-tert cuhbge in water quality.
-4-
m. CHOCOLATE HOLE
Data collected in Chocolate Hole in November are given In Table 3. The bay
hbows very few changes alnoe our survey a year ago. Water color, visibility and
bottom organisms seem to be nla as good condition now as then and the bottom can still
be Been throughout the bay. The only quantitative observation of note s a sip cantly
lower salnity at Statio #7, where the pood conecta to the bay. This saljntty depression
is undoubtedly caused by outflowing pond water which, considering the aumseul amoonta
of rainfall during the past year, most now be quite brackleb. Monthly averages for water
quality data are gives In Table 4.
There are now 4-5 boats anchored in the bay and littering of the se bottom
is Increasing: several cans aad other items were noted. Except for these, no adverse
ohabges were noted.
-5-
2001
CRUZ 8
L4;-
CRUZ BAY, 37. JOHN
uz AY/
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200 FT
TABLE 1
CRUZ BAY, ST. JOHN
WATER QUAIJTY DATA, NOV.-DEC., 1970
Fecal Fecal
SecOhi Suspended Colitfor Strep
Temp. Sal. D. O. Depth Solids per per
Staton Date C. . pH MG/L C Sat. M- MG/L I00 ML 10A Ml
4 11/20/70 28.0 37.5 8.1 6.4 102 B 27.2 0 0
12/1/70 27.1 36.0 8.3 6.3 97 B 32.2 -- -
14 11/20/70 27.9 37.5 8.1 6.9 H4 3.0 17.6 --
12/1/70 27.0 36.2 8.3 6.3 97 2.8 20.6
18 11/20/70 28.0 37. 86.1 6.8 108 B 8.6 0 0
12/1/70 27,1 36.0 8.3 6.2 95 B 16.1
21 12/1/70 27.2 35. D 8.2 6.2 95 2.8 13.0
23 12/1/70 27.1 36.0 8.3 G.3 97 2.3 23.7
27 11/20/70 2B.0 35.6 5.1 0.3 99 3.0 10.1
12/1/70 27.2 36.2 B.3 6.1 94 2.5 13.9 0 0
A VeRAr E 27.5 3.r. 8. e. 2.7-B 1a.9 G 0
30 11/20/70 28.0 37.5 8.1 5.8 92 2.0 0.0 2 0
12/1/70 26.8 36.0 8.2 6.1 94 2.3 18.0
34 12/1/70 24.6 36.4 8.2 5.5 85 -- 16.2
36 11/20/70 28.0 36.7 8. L 5.4 86 0.8 14.1 0 0
12/1/70 26.6 36.2 8.2 5.4 82 -- 19.1
38 11/20/70 28.2 35.7 8.0 5.3 83 1.25 13.7 0 0
12/1/70 26.6 36.4 8.0 5.3 80 -- 21.3
AVERAGE 27.3 36.4 8.1 5.6 86 1.6 14.6 I1 0
CRUZ BAY, ST. JOHN
?MONTHLY AVERAGES FOR SIX WATER QUALITY PARAMETERS
SECCHI FzCAL COLIFORM
TEMP. SAL. D. 0. DEPTH AND STREP
STATION DATE O C. .. pl_ G/L METERS c.LS/100 ML
4 AUG/69 29.5 36.2 -
SEP/69 29.2 36.5 8.3 6.0 3.8 8
DEC/69 27.2 36.5 8.3 6.1 3.8 0
NOV/70 28.0 37.5 8.1 6.4 3.8B 0
DEC/70 27.1 36.0 8.3 6.3 3.8B -
14 AUG/69 29.5 36.3 -
SEP/69 29.3 36.6 6.3 5.2 3.5B 31
DEC/69 27.2 36.5 8.4 5.9 3.5 -
NOV/70 27.9 37.5 8.1 5.9 3.0
DEC/70 27.0 36.2 8.3 6.3 2.8 -
18 AUG/69 29.5 36.4 -
SEP/69 29.5 37.5 8.3 5.7 1.88 4
DEC/69 27.0 36.5 8.4 5.8 1.88 7
NOV/70 28.0 37.5 8.1 6.8 1.88 0
DEC/70 27.1 35.0 8,3 6.2 1.88
21 AUG/69 29.5 36.3 -
SEP/69 29.4 37.0 8.3 5.6 3.2B 48
DBC/69 27.1 36.5 8.4 5.7 3.2B
NOV/70 -
DEC/70 27.2 36.0 8.2 6.2 2.8
23 AOG/69 30.0 36.0 -
SEP/69 29.6 36.6 8.3 4.7 2.78 15
DEC/69 27.3 36.5 8.3 4.7 2.7B 11
NOV/70 -
DEC/70 27.1 36.0 8.3 6.3 2.3
27 AUG/69 30.0 35.6 -
SEP/69 28.5 36.6 8.3 5.5 4.2B 7
DEC/69 27.2 36.5 8.4 5.9 3.9 0
NOV/70 28.0 35.6 8.1 6.3 3.0 0
DEC/70 27.2 36.2 8.3 6.1 2.5
30 AUG/69 30.0 28.2 -
SEP/69 29.8 36.2 8.2 4.3 1.9 12
DEC/69 26.9 36.5 8.3 5.3 2.2 -
Nov/70 28.0 37.5 0.1 5.8 2.0 2
DEC/70 26.8 36.0 B.2 6.1 2.3 -
34 AUG/69 30.0 35.9 -
S SEP/69 29.7 36.6 8.2 4.3 1.1 79
D.C/69 27.3 36.5 8.3 3.8 1.:
NOV/70 -
DEC/70 26.6 36.4 8.2 5.6
36 AUG/69 30.0 36.0 -
SEP/69 29.8 36.0 8.2 4.3 1.1 80
DEC/69 27.3 36.5 8.3 4.4 1.5
NOV/70 20.0 36.7 8.1 5.4 0.8 0
DBC/70 26.6 36.2 8.2 5.4
38 AUG/69 29.5 36.8 -
SEP/69 29.6 37.1 8.1 4.0 0.8 20
DBC/69 27.4 36.6 8.3 3.7 1.8 3
NOV/70 28.2 35.7 8.0 5.3 1.3 0
DEC/70 26.6 36.4 8.0 5.3 -
TABLE .
CHOCOLATE HOLE, ST. JOHN
WATER QUALITY DATA, NOV. 13, 19T7
Recthi Light Extinction
Temp. Sal. Depth (Ft-CaDdleA i
saUti- C. %. pH /MlM % 9Rt. M. Too Meter To Bottom
7 28.5 34.8 8.2 5.1 80 B -- -
16 2895 -- 8.2 6.0 94 B 2,600 705
18 28.1 36.0 8.2 6.3 98 B 3,.20 745
20 28.1 -- 8.1 6.2 98 B 330 655
22 28.0 36.0 8.1 6.0 95 B 3.000 61,640
AVTRAGE 28.2 35.6 8.2 5.9 93 B 2.275 936
TABLE 4
CHOCOLATE HOLE. ST. JOIN
MONTHLY AVERAGES FOR SIX WATER (WALITY PARAMETERS
Sal.
Station Date i Temp. %ct
Oct./69 30.0 36.7
2 Nov./69 26.5 36.1
Dec./69 27.6 36.4
Nov./70 -
Oct./69 29.5 -
5 Nov./69 28.4 36.2
Dec./69 27.8 36.4
Nov./70
Oct./69 -
7 Nov./69 28.7 36.0
Dec./69 28.2 36.4
Nov./70 28.5 34.8
Oct./69 30.0 36.3
18 Nov./69 28.6 36.2
Oec./69 27.4 36.4
Nov./70 28.1 36.0
Oct./69 29.6 36.7
20 Nov./69 28.8 36.2
Oec./69 27.7 36.
Nov..70 28.1 -
Oct./69 29.6 36.7
22 NOV./69 26.5 36.2
Dec./69 27.8 36.3
Nov./70 28.0 36.1
Oct./69 30.0 36.7
26 Nov./69 28.5 36.1
Dec.169 27.8 36.4
Nov./70 -
Oct./69 29.4 36.7
30 Nov./69 28.4 36.2
IHc./69 27.8 36.4
Nov./69
Oct./69 30.0 36.7
PI Nov./69 28.7 35.4
Occ./69 30.8 37.8
Oct./69 30.5
P2 Nov./69 28.0 35-7
Dec./69 30.6 38.3
m ...
Fecal Strep
Scchi Depth s Coliform
Meters Cell /100ol
8 48
8 3
B0
S 0
B 0
0o
B 0
B 8
B 6
B 6
B 0
& 0
D 0
B 14
8 8
N 82
B 20
o 0
3
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