An extensive study of the hydrobiology of the Colombo Lake was initiated by the authors in May 1969 as a contribution to the International Biological Program (Productivity of freshwater communities) by the Department of Zoology, Vidyalankara University of Ceylon, Kelaniya. The Colombo Lake often referred to as the Beira Lake covers an area of approximately 160 acres. The water is usually very turbid with a greenish blue appearance due to the presence of large quantities of blue green algae

Costa, H.H.

De Silva, S.S.

Aquatic Commons

Ru7l. ]i'-ish. Res. Stn., Oey7on. Vol. 20, No.2, ]J]J 141-149, Decembe1', 1.96.9 
II ydrohiology of Colombo (Beira) Lake, I. Diurnal Variations 
In Ten1-perature, Hydrochemical Factors and Zooplankton 
By 
H. H. CosTA1 AND S. S. DE SrLvA1 
AN extensive study of the hydrobiology of the Colombo lake was initiated by the authors in May 
1H69 as a contribution to the International Biological Program (Productivity of freshwater communi~ 
ties) by the Department of Zoology, Vidyalankara University of Ceylon, 1\elaniya. 
The Colombo lake often referred to as the Beira lake covers an area of approximately 16()-
acres. The water is usually very turbid with a greenish blue appearence due to the presence of large 
quantities of blue green algae. The bottom of the lake is almost completely muddy. The most 
recent morphometric data for the lake has been given by Menclis (1964). 
Area of the lake .. 
Volume of water in the lake 
lVIaximmn. depth 
Mean depth 
Shore line 
Shore development 
64.8 hectares (160 acres) 
1872 x 103cu.m. 
8.5m. 
2.8m. 
ll,315m. 
2.1. 
The area of the lake has tended to change very slightly as small areas are being continuously 
reclaimed for building purposes. Recently, due to dredging the depth has increased. 
As described by Mendis (1964), the lake has two main parts; East La.ke and South \~Test Lake. 
'These two are connected together by the narrower vVest Lake. The Lake has two mah1 outlets to 
the sea; one at the Galle Face Spill and the other at the Colombo harbour (Fig. 1). The connection 
to the harbour is through a canal provided ·with lock gates which are opened only to allow the 
passage of boats and barges. 
The depth of the lake is not uniform ; deepest being the area closer to the harbour in the East 
Lake and the shallowest being the South \iVest Lake. Most of the sides of the East Lake and West 
Lake are built up in cement. 
The lake receives the outlets of several surface drains and also the waste matter of several engi-
neering and commercial concerns bordering the lake ·which tend to pollute the water at several points. 
Portions of \Vest Lake and South West Lake also receive the domestic waste from a large number of 
tenements situated bordering the lake. Large areas of South vVest Lake and Vaxuhall street area of 
E. Lake sometimes tend to be covered by a thin layer of oil. 
Several ·workers earlier have studied varying aspects of the biology of Colombo Lake. The 
earliest work recorded \Vas done by Daday (1898) who described several new animal species. Subse-
quently work has been clone by Gurney (1906), Apstein (1907) Lemmermann (1907), Crow (1923), 
Bar (1924), Holsinger (1955), Arudpragasam and Costa (1961) and Mendis (1964). Apstein (1907) 
·worked on the succession of Rotifera and Cladocera populations while Holsinger (1955) studied the 
distribution and periodicity of phytoplankton. Investigations of Menclis (1964) was on the plankton, 
benthos and the fish fauna mostly in relation to fish potential. 
1 Department of Zoology, Vidyalankara University of Ce,ylon, Kelaniya, Ceylon. 
8-J 94-15 (12/69) 
142 HYDROBIOLOGY OF COLOMBO LAKN 
-.._,_ ...... 
---' 
+ 
0 
Fig. 1.-lVIap of Colombo (Beira) lake. 
8 5AMPLIH" STATIONS 
150 
RECENTLY 
R.liC:I.I\IMIEI> OR 
I'ILLB,I) UP 
300 
•• SC:AI.E 
450 6'00M 
ii:W =:=:::::1 
COS'l'A AND DE SILVA 143 
The first paper in this study deals with diurnal variations in temperature, hydrochemical 
fatlltors and zooplankton of the Colombo lake. This investigation was undertaken because of the 
complete absence of information on diurnal variations in freshwater bodies in Ceylon; and this study 
is therefore the first of its kind in Ceylon.. Some infmmation is however available on diurnal variations 
in other tropical fresh waters; the notable contribu '·ions being those of Carter and Beadle (1930), 
Hutchinson (1957), George (1961) Sreenivasan (1964), and Verma (1967). 
MATERIALS AND METHODS 
The investigations reported in this paper were carried out on the 15th of September 1969. 
The day on which the observations were made was bright and sunny, though a few patches 
of dark clouds were seen in the early hours of the morning and in the evening. Meteorological 
department temperature recordings for this day were 31 oc maximum and 27°C minimum. 
Collections were made at three sampling stations I, IV, and VI (See Fig. I) from 6 a.m. to 10 p.m. 
at two hourly intervals. At station VI, the deepest area of the lake collections and determinations. 
were made at three different depths; at the surfce, at a depth of about 6m. and at the bottom (depth 
12m). At stations I and IV determinations were done on samples taken just below the surface of 
the water. At station VI water samples were colleeted from various depths using a Ruttner sampler. 
Samples were collected as far as possible when the water was undisturbed by passing boats. Plankton 
samples were taken only at station IV and at 3 hour intervals. Analysis reported in this paper were 
done immediately after collections were made. Determinations were done according to methods 
described by Mackereth (1963). Surface water temperature was measured by a mercury thermometer 
graduated upto ll0°C, 
RESULTS 
Temperature 
The data indicate (Fig. 2 A) that at all the sampling stations the highest temperature of the 
day occured between 1300 and 1500 hr. The variation within a day appears to be less than 6°C. At 
station VI where the temperature was measured with depth (Fig. 2 B), slight thermal stratification 
was noted with a very thin upper warmer layer. This stratification of temperature occurs just before 
evening. 
34° :~., 
I \, 
iR \. // \ ~ ! I \ \ 
IJ \ \ 
STATION I--
STATION IV-·-· 
STATION VI ---
i! \ "· if \ ~-.... 
i I \ 
·; \ \ 
......... ~ \ \ 
. / ~ . 
;/ ---"'0.; \ 
I. / ' \ 
• G) '\, \ 
/ r '' i I "'--;' I Ill'·----<~> 
,. I 
l/ 
/ v 
i 
/ '/ I '/ 
l/· 
A 
2~-=~--~~~~--~--~~~~~~~ 6o.m. Bo.m. IOo.m. 12noon 2p.m. 4p,m. 6p.m. Sp.m. IOp.m. 
Fig. 2 A.-Diurnal variation of surface 
temperature 
9--J' 9445 (12/69) 
33·6 
52·.5 
SURFACE -~ 
6 METERS-·-
12 METERS - - -
27·5 ."---:::-'---:-1:----:-t----::"---:-<--,........--:-"'-"":':"_ 6a.m. a a.m. IOo.m. 12noon 2p.m. 4p.m. 6 p.m. 8 p m IOp.m 
Fig. 2' B . .......:.Diurna,l variation of t~mJ?erature at 
Rt-a.tion VII wi'tll depth 
144 HYDROBIOLOGY OF COLOMBO LAKE 
Oxygen 
The highest surface oxygen content of the day occured between 1300 and 1700 hr. From the 
dissolved oxygen figures for the three sampling stations (Fig. 3 A) it was very apparent that at 
the stations I and IV the water was less than saturated during the early part of the day and more 
than saturated in the later part. It is also to be concluded that the maximum photosynthetic rate 
occurred between llOO and 1400 hrs. and subsequently declined. At station VI the oxygen pro-
duction in the surface water was higher in the early hours of the day (Fig. 3 B). The oxygen curves 
at station VI show that even in mid-day the dissolved oxygen content was low, although still super 
saturated, when compared with the other two stations showing that the photosynthetic rate here 
is lower. Conspicuous stratification of oxygen with depth was not apparent; the super saturation 
was also noticed below lm. However, a very slight stratification was observed in the very early 
hours of the day. 
20 
18 
. 16 
14 
.12 
5:i 8 
C> 
>-X 
0 6 
4 
STATION I--
STATION IV-·-·-
STATION VI---
.---·~\ 
\ 
\ 
)lr----o--_\ 
i /. '\?\ 
? / Gj\ 
/ / \ \ 
/ ~/ \ \ 
/.--"' \ \ \ ~----.;~ 
\ 
\ 
\ 
·k.. 
................. €' 
A 
IOo~m 12noon 2p,m. 4 p.m. 6p.m. 6p.m.. IOp.m. 
Fig. 3 A.-Diurnal variation of surface plankton. 
12 
II 
10-
9 
e 
~ 8 
z 
w 
SURFACE 
6 METERS 
12 METERS 
~ 7 
X 
0 
6 B 
5 
~~--~--~--~~--~--~--~--~~--~ 6o.m. 6a.m. IOa.m. 12noon 2p,m. 4p.m. 6p.m. 8p.m .. IOp.m. 
Fig. 3 B.-Diurnal variation of dissolved oxygen 
at station VI with depth. 
Table 1 Showing % oxygen saturation values at the three sampling stations 
~,........_ 
Time Station I Station IV Station VI 
6 a.m. 6 12 -
8 a.m. 7 30 82 
. . 
10 a.m. 116 95 96 
12 noon 198 138 116 
2 p.m . 215 225 154 
. . 
4 p.m. 276 229 156 
I 
.. 
6 p.m. 245 136 149 
ti p.m. 157 
I 
50 98 
Carbon..Dloxide. 
Free carbon dioxide was. con:tpletely absent at all three stations sampled, probably because 
of -H& ui':Wzaitic)I~ in :Jjhdt:>synthesis. 
COSTA AND DE SILVA 145 
Salinity 
The three t.tations sampled show distinct differences (Fig. 4 A) in salinity, the least amount 
of dissolved solids was at station I which also showed the least amount of diurnal fluctuations. At 
station IV the salinity was low but some slight diurnal fluctuation was seen in the salinity content. 
At station VI the salinity was rather high and a noticeable vertical distribution of salinity (Fig. 
4 B) was seen, the deeper waters were slightly more saline than the surface waters. 
A 
STATION I 
STATION IV 
STATION VI 
~ 
0 Ga.m. 1\om. IOo.m. •2no011 otp.m. 4p.m. 6p .• ~. Bp.m. IOp_m 
Fig 4 A.-Diurnal variat.ion in surface salinity. 
Alkalinity 
2·9 
\ 
\ 
\ 
\ 
\ 
\ 
\ 
B 
SURFACE -
8 ME'fEit6 -·-·-
Ill MI!TE'F'IS - -~ _ 
2·0 t-::---;;7':--;;;!-:::-7-:-:-::--.:-''---:-'--::'----:-l--~ 6o.m. Bo.m. IOa.m. 12nc>on 2p.m. 4p.m. Gp.m. Sp.m. tOp,m. 
Fig. 4 B.-Diurnal variation of salinity with depth. 
The range of variation in total alkalinity in the appreciably waters was not surface conspicuous 
(Table II). Maximum 99 ppm. at station I was at 1800 hr.; at station IV the maximum 108 ppm. 
was at 1400 hr. and at station VI the maximum 114 ppm. was also at 1400 hr. At station Vl the 
alkalinity va.lue.3 of the bottom water was not very different to those of the smface water. 
Table II showing diurnal variation of alkalinity in p.p.m 
Time Station I I Station IV Station VI 
6.00 a.m. 87.0 87.0 112.0 
8.00 a.m. 90.0 104.0 113.0 
10.00 a.m. 88.0 104.0 109.0 
12.00 noon 83.0 105.0 109.0 
2.00 p.m. 84.0 108.00 114.0 
4.00 p.m. 81.0 110.00 109.00 
6.00 p.m. 99.0 100.00 113.00 
8.00 p.m. 92.0 100.00 113.00 
Hydrogen Ion Concentration 
The pH of the surface water fluctuated from 7.4 to 9.0 at station I; 7.2 to 8.4 at station IV ; 
and from 7.5 to 8.6 at station VI (Table III). The data for station VI, where the pH of the water 
was measured at different depths, indicates that like alkalinity there was no discernible pH stratifi-
cation from surface to bottom. 
146 HYDROBIOLOGY OF COLOMBO LAKE 
Table III showing diurnal variation of pH 
) Station VI Station VI Station VI Time Station I Station IV Surface 6m. 12m. 
6.00 a.m. 7.4 7.2 7.5 7.5 7.5 
8.00 a.m. 8 1 7.0 8.1 8.0 8.0 
10.00 a.m. 8.1 8.2 8.3 8.2 8.2 
12.00 noon 8.2 8.1 8.6 8.6 8.7 
2.00 a.m. 8.6 8.4 8.9 8.6 8.9 
4.00p.m. 9.0 8.1 8.5 8.3 8.5 
-----
6.00p.m. 8.0 8.1 8.1 8.1 8.1 
--------
8.00 p.m. 8.5 8.0 8.1 8.1 8.1 
Zooplankton 
Samples were collected with a cone shaped net made up of no. 21 bolting silk and attached 
to a ring which was 12 inches in diameter. The method of sampling was to tow the net at an average 
speed of that of a hand oared boat. The net was usually fishing just below the surface. All tows of 
the series were of the same duration ( 1 t minutes). 
The samples were immediately preserved in 4 % formalin. The sample was later concentrated 
to 100ml volume. Three subsamples each of 1 ml volume was taken to a rafter cell and all the speci-
mens were counted fully in each subsample. The relative numbers are expressed in Fig 5. 
Diurnal variations in the zooplankton was studied from 6 a.m. to 9 p.m. at 3 hr. intervals 
from a predetermined spot at sampling station No. IV. Bmchionus sp., Kemtella sp., Diaphanosoma 
sp., Diaptomus sp. Cyclops sp., and crustacean nauplii were the most notable of the zooplankton, 
with copepoda cyclopoidea constituting the bulk of the zooplankton. The trend in the variation of 
the different groups at different times of the day is given in Fij. 5. 
3200 
3000 
280 
2600 \ 
2400 
e2200 
0 
22000 
z 
- 1800 
VI 
;t 1600 
liE 
~ 1400 
... 
0 1200 
ffi 1000 
m 
liE 
::::> 800 
z 
..J 600 
~ 
:: 
200 
\ 
COPEOPODA ·- ·- • 
ROTIFERA 
1 NAUPLII I 
\ CLADOCERA ---- I 
\ (f)-·-·-·-~· 
\ \ i 
\ i 
I 
i 
l 
/ 
I 
\ I 
\ i 
I / 
I I ~ . . . . 
\ / \ I ....... !3· 
®....... .·er·" ·~:-~<~-@· 
'•, 
'•, 
~-
------0s~o-.m-.--~9~o=.;=~--~--~-;~2n~oo-n--~3~p-.m-.--~6~p~.m~.--~9~m 
- ____ -l(--
Fig. 5.-Diurnal variation of relative numbers of dominant plankton. 
COSTA AND DE SILVA 147 
Cyclops which was the dominant zooplankton was maximum at 2100 hr. and least at 1200 hr. 
Brachionus was also maximum at 2100 hr. and minimum at 1200 hr. Diaphanosoma ·was maximum 
at 2100 hr. and minimum at 9.00 hr. Nauplii showed the highest peak at 1800 hr. 
DISCUSSION 
In tropical freshwater bodies temperature is of great importance in determining the production 
of oxygen. A relationship in the increase of temperature and the increase of dissolved oxygen 
content was seen in the waters of Colombo lake; the highest temperature recorded for the day was 
at about 2 p.m. while the highest concentration of dissolved oxygen was noted at about 4 p.m. 
Increase in temperature brings about an increase in the rate of photosynthetic activity of the phyto-
plankton (Hutchinson 1957) and this account for the increase in the oxygen content in the illuminated 
hours. 
The absence of free Carbon dioxide in the samples examined is probably due to the presence 
of large amounts of phytoplankton and because of its utilization in photosynthesis. 
On the basis of pH ranges, Colombo lake could be considered highly alkaline inspite of the 
very slight diurnal variations. 
tz 
4 
(). 
TI<MPtRATURE >E-----k 
OXYGEN ~ 
pH 
SALINITY 
1\LI<ALINITY 
STATION. Vi 
]J.5 
0 1.00 
i so 
0 5TATION.1 
Fig. 6.-Diurnal variation of temperature, oxygen, pH, salinity and alkalinity. 
148 HYDROBIOLOGY OF COLOMBO LAkE 
On examination of diurnal records of surface temperature and oxygen for the different stations 
(Fig. 6) it is apparent that there are slight variations. The maximum surfac3 temperature and 
maximum dissolved oxygen content was noted at station I while the minimum surface temperature 
and minimum dissolved oxygen content was recorded as station VI. Station I is rather shallow 
(1-2m.) while station. VI is comparatively deep (12m.). This could account for the slight differences 
noted in the temperature. Light and heat stimuli affect the movement of plankton (Worthington--
1931) and this probably accounts for the increase in oxygen content. Station VI is the closest to the 
lockgate and station I is the farthest a.nd this accounts for the differences in the salinity recorded 
in our study. 
The present study indicate that the rotiferan Brachionus was more abundunt in the collections 
of the night hours than in those of the day hours. This is in agreement 1vith the observation of 
Vaas & Sachlan (1953) and contrary to those of Verma (1967). Oyclops was found in large numbers 
both by day and night. The nauplii however showed a tendency for migration to the surface in the 
evening. Since the diurnal variation in plankton was studied in a, very shallovv area, of the lake 
more work will have to be done to confirm these results. 
ACKNOWLEDGEMENTS 
This study would not have been possible if not for the kind assistance of Mr. H. A. Indrasena, 
Superintendent of Freshwater Fisheries, Dept. of Fisheries, who helped us in very many ways and to 
whom we are grateful. We wish to express our thanks to the Ministry of Scientific Research and 
Housing for giving us a grant in aiel for purchase of essential equipment and to the Vidyalankara 
University for giving us a working grant. We wish specially to thank Mr. W. F. Abeykoon, Group 
Scout Master, lst Port of Colombo, Sea, Scouts, providing us with a boat and also for providing 
working fadlities at the premises of the Boy Scout Headquarters. Our thanks are also to 
Dr. K. D. Arudpragasam for critically reading the manuscript. 
SUMMARY 
The diurnal variation of temperature, wa,ter chemistry and zooplankton was studied at two 
hourly intervals for a period of 16 hours. The highest temperatures were attained at about 2 p.m. 
Oxygen content reached a maximum bet-ween 2 and 4 p.m. No free carbon dioxide was found. The 
diurnal variations in pH, salinity and alkalinity were not very marked. The variations in plankton 
were similar to those fo1._md in other tropical fresh waters. The results are discussed and compared 
with results of other workers. 
REFERENCES 
A:PsTEIN, C {1907) : Das Plankton in Colombo Sea aus Ceylon. Zool Jb. (Ab,. syst) 25, .201-224. 
AiRUDPRAGASAM, K. D. & CosTA, H. H. 1961 :The atyidae of Ceylon. Orustaceana 4, 1-24. 
CARTER, G. S. & BEADLE, L. ~· 1930 : The fauna of the swamps of the Paraguyan Chacko in relation to its environ-
ment. J. L~nn Soc. (Zool) 37, 205-258. 
BAR, G. 1924: Uber cladoceron Von der insel Ceylon (Fauna et anatomicaCeylonica 14) Gena, Z. Nattww. 60, 83-126. 
CRow, W. B. 1923: Notes on Entomostraca collected by Mr. Haly in Ceylon. J. Linn. Soc. (Zool) 19, 293. 
DADAY, E. VoN 1898: Microskopische susswasserthiere aus Ceylon. Termeszetr. Fuz. 21, 1-123. 
GANAPATI, S. V. 1955: Diurnal variations in dissolved gases, Hydrogen ion concentration and some of the important 
dissolved substances of Biological significance in three temporary rock pools in stream bed at 
Mettur Dam. Hydrobiologia 7, 285-303. 
GEORGE, M. G. 1961 :Diurnal variation in two shallow ponds in Delhi, India, Hydrobiologia 18, 265-273. 
GuRNEY, R. 1906: On two new entomostraca from Ceylon. Spolia, zelycm. 4, 126-134. 
HoLSINGER, E. C. T. 1955a: The plankton algae of three Ceylon lakes. Hyd1·obiologia 7, 8-24. 
1955b: The distribution and periodicity of phytoplankton of three Ceylon Lakes. Hydt·ob-iologia 
7, 25-35. 
HuTCH.JNSON, G. E. 1957: A l1'eC!tise on Limnology 1 Geography, Physics ancl Ohe1m:stry. John -Willy and Sons. 
New York. 
COS'l'A AND DE SILVA 
LEM111ERi\IANN, E. 1907-Protophyten plankton von Ceylon. Zool Jah1'. 25, 263. 
lVIACKERETH, J. H. (1963): Wate1' analysisjo1' Limnolog·ists F. B. A. Publication No. 21. 
149 
MENDIS, A. S. 1964: A Contribution to the Limnology of Colombo Lake. Bull. F1:sh. Res. Stn. Ceylon. 17, 213-220. 
SREENIVASAN, A. 1964: The Limnology, primary production and fish production in a tropical poncl. Limnology and 
Oceanogmphy 9, 391-396. 
VAAS, K. F. and SACHLAN, M-1953 : Limnological studies on diurnal fluctuations in shallow ponds in Indonesia. 
Ver. int. Ver Limnol12, 309-319. 
VERMA, ::M. N.-1967 :Diurnal variation in a fish pond in Seoni, India. Hydrobiologia 30, 129-137. 
\VoRTHINGTON E. B. (1931) Vertical movements in freslnvater macroplankton. Int. Rev. d. ges. Hydrogr. 25, 
394-436. 
M.S. Received 26.10.69. 


Hydrobiology of Colombo (Beira) Lake, 1. Diurnal variations in temperature, hydrochemical factors and zooplankton

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Hydrobiology of Colombo (Beira) Lake, 1. Diurnal variations in temperature, hydrochemical factors and zooplankton

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