INDIAN J. MAR. seL, VOL. 5, JUNE 1976

show no change in metabolic rate during the experi­mental period. The energy expenditure is calculat­ed from the oxy-calorific coefficient. While thecontrol animals spend only 5·56 cal in i! hr, theanimals 'exposed for 6 and 12 hr need 7·4lJ and 8·4cal resp~tively. The post-exposure energy demandof 1·93 cal for 6 hr exposed mus~els and 2·84 calfor 12 hr exposed mussels show clearly the strainon the animal in relation to the duration of exposure.

The author expresses his gratitude to Dr S. Z.Qasim, former Director of CMFRI, Cochin, for techni­cal gu.idances. Thanks are due to Dr K. V. Sekharan,Senior Fishery Scientist, CMFRI, for his continuedinterest and guidance, to Dr M. N. Rutty, Reader,Madurai University, Madurai, for useful sugges­tions in setting up the experiments, to Mr T. Thola­silingam, Officer-in-Charge, CMFR Substation,Madras, Ifor offering laboratory facilities and toMr D. C. V. Easterson for useful suggestions. Thiswork waiS carried out with financial assistance inpart fro:t;n Ministry of Education, Government ofIndia, by offering a Research Training Scholarship.References

1. PROSSER, C. L. & BROWN, F. A., Comparative animalphysiology (Saunders, Philadelphia), 1961.

2. KINNE, 0., Marine ecology, Vol. 1 (Wiley Interscience),1972.

3. GHIRE;rT, F., in Physiology of mollusca, edited by K. M.Wilb.ur & c. M. Yonge (Academic Press, New York),1966, 175.

4. NEWELL. R. C.• Biology of intertidal animals (LogosPress Ltd, London), 1970.

5. BRUCEI J. N., Biochem. J., 20 (1926), 829.6. BAYNE, B. L., Physiol. Zool., 40 (1967), 307.7. THOMIlSON, R. J. & BAYNE, B. L., j. expo mar. Biol.

Ecol., 9 (1972), 111.8. BROWN, B. E. & NEWELL, R. C., Mar. Biol., 16 (1972). 108.9. WIDDOWS, J., Mar. Bioi., 20 (1973), 269.

10. SHAFEE, M. S. & SUNDARAM, K. S., in Third All India

symjJ.osium on estuarine biology (in press), 1975.11. WEIGERT, E. G., Am. Zool., 8 (1968), 71.12. MATHEW, C. V. & SUMITHRA, V., Indian J. Fish., 20

(1973), 658.13. STRICKLAND, J. D. H. & PARSONS, T. R., A practical

hand book of sea water analysis, Bull. No. 167 (Fish.Res. fBd, Canada). 1968.

14. IVELE\(, V. S., Zool. Zh., 18 (1939), 303.15. BOHLE( BJORN., J. expo mar. Biol. Ecol., 10 (1972), 41.16. ZEUTHEN, E., Quart. Rev. Biol., 28 (1953), 1.17. HEMMINGSEN, A. M., Rep. Steno. Meml Hosp., 9 (1960), 1.18. SUNDARAM, K. S. & SHAFEE, M. S., in Third all India

symposium am estuarine biology (in press), 1975.

Effect of Urea on Growth of MarinePhytoplankters

X. N. VERLENCAR

National. Institute of Oceanography, Dona Paula 403004

Received 21 July 1975; revised received 9 December 1975

Growth rates of 3 phytoplankters - Asterionellajaponica, Synechocystis sp. and Chlorella sp.- werestudied asa function of urea by enrichin~ the nutrient·depleted water with varyin~ concentrations (0 to 50JI~­at N/litre) of urea; ~rowth rate was calculated from theincrease in chlorophyll a content of the or~anisms.Maximum growth of these phytoplankters was ob.served between concentrations 1 and 2 JI~-at urea·N/litre.

132

UREA in sea water is probably similar to ammo-nium ions, produced as a result of excretion of

animals, and plants cotsume it during photosynthesis.Phytoplankters of estuaries and coastal waters useurea as a nitrogen source at times of nitratedeficiency!. It may al~o form a source of nitrogenin oligotrophic waters, where it is found in sufficientlyhigh quantities, but within the biological limitsduring certain seasons2•

In the present study, growth experiments havebeen conducted with different concentrations ofurea using phytoplankton species, Asterionella japo­nica, Synechocystis sp. and Chlorella sp., isolatedfrom the Goa waters and maintained as unialgalcultures. Increase in chlorophyll a (chI. a) contenthas been used as an index of growth rate. Earlierstudies on growth and uptake experiments areconfined mostly to ammonia, nitrate and phos­phate3,4. The importance of urea as a source ofnitrogen for the phytoplankton growth has beenemphasized only recently, after the standardmethods of urea determination have been workedout5•6.

For each set of experiments, 2 1 of sea water,filtered through GFjC pads, were taken in a seriesof flasks. Urea was added in different concentra­tions (0 to 50 (1.g-at Njlitre). All the flasks werethen inoculated with equal quantities of healthy(but not bacteria free) algal cells. The flasks werekept under alternating periods of light (Shr offluorescent illumination) and darkness. The initiallevel of nitrate present in the sea water was O'S&p.g-at/N litre.

Aliquots of 300 ml were drawn frem each flaskat intervals of 1 or 2 days, filtered through GFjCpads, and chI a from the filters was extracted with90% acetone and measured on a spectrophotometer.Samples for nitrate and chI a were analysed bystandard methods7. Growth rate of each organismwas calculated from:

(.I; = In ChI.~ (_1_)Chl.ao t In2

where chI. at and chI. ao were chI. a concentrationsat times t and 0 respectively4.

Urea was estimated using diacetyl spectrophotc­metric method of Newell et al.6•

Growth rate in A. japonica was low initially atalmost all concentrations of urea. It increasedsteadily and reached the peak from 6th to 10thday and decreased thereafter. However, in thecontrol experiment with no urea, the growth remain­ed more or less steady (Fig. 1). In Synechocystissp. also the growth for the first few days was lowin 2.11 urea concentrations. Peak growth reachedfrom 3rd to 9th day and then decreased (Fig. 1).Chlorella sp. abo showed a slow rate of growth atall urea concentrations in the beginning. It in­creased from 10th day till the last day of the experi­ment. At higher concentrtion of (50 p.g-at urea­Njlitre) the growth remained low throughout (Fig. 1).

Maximum growth rate (p.)values of phytoplanktoncells recorded under different urea concentrationsare given in Table 1 for different species. Maximumgrowth rate for A. japonica, Synechocystis sp. andCMorella sp. was respectively at concentrations 1, 2

I ~

SHORT COMMUNICATIONS

d18'-

c18

b

2,(

o5 7 9 11 13 15 1 3

,.III..5 7

9 11 13 151351 9 11 13 15I 35-;9 11 13 151 3579 11 Q 15

f 26[e!~ ASTERION ELLAJAPONICA221-22-- SYNECHOCYSTl5 51>.

I

I tA---<:l. CHLORELLA 51"

lat

18

14

14

lot

J/:6·

2

o1 3

10

a

6

6

18

10

14

22

2,

o5 7 9 11 13 15 1 3 5 7 9 11 13 15

DAYS

Fig. 1 - Ratio of chI. at/chI. aoas an index of growth for 3 phytoplankton species at different urea concentrations[Urea concentrations ([Jog-at N/litre): ,a. 2; b, 10; c, 20;' d, 50; e, 1; f, 0,5; and g, 0 (control)]

2 ..

••• 0 0

~l~1 3:s:::..r:.

c.> u

9

TABLE 1 - MAXIMUMGROWTHRATE ([Jo)FOR A. japonica,Synechocystis sp. AND Chlorella sp. IN DIFFERENT UREA

CONCENTRATIONS

and 1 [Lg-a.t urea-Njlitre. There was a gradualdecrease in the growth rate with increasing concen­trations of urea.

Carpenter et al.1 have shown the importance ofurea as a nitrogen source for estuarine and neritic

0'579 0·741 0-377 0·617 0,635

o 0,5(Control)

species of phytoplankters. Hulbert8 has observedthat the Chlarella sp. was a more predominantspecies of phytoplankton in the surface waters ofNew York Bight, where variable amounts of ureawere present. Dayis et al.9 have also shown thatmost Chlarella sp. are able to use urea as a nitrogensource. These observations agree well with thepresent findings that Chlarella grows well in lowconcentrations of urea. McCarthylO has indicatedthat Skeletanema castatum can utilize urea at concen­trations less than 1 [Lg-at Njlitre. He has alsoobserved that not all phytoplankters can use ureaas a chief source of nitrogen. For fxample, P. Micansha.s failed to grow in the laboratory with urea asa main source of nitrogen.

In the coastal waters of Goa, urea concentrationvaries from 1·5 to 7·5 [Lg-atNjlitre, but in the Vel~aoBay (Goal, the variation in the urea concentration.is from 10 to 120 [Lg-atNjlitre. Such high concen­trations of urea are due to the effluent discharge·from a fertilizer factory located in the vicinity ofVelsao Bay.

Several authors have reported different ureaconcentrations from the surface waters in the ~ea.Newelln and Ram~en12 have found values ranging

SO

0'283

0,83

2010

0,605 0,54

1·003 0,86

2

0'58

A. japonica

Chlorella sp.

Synechocystis sp.

0,76

0,605 1·14

Conc. [Jog-aturea-N/litre

0,72

('351

0'22

0-45

133

INDIAN J. MAR. 8eL, VOL. 5, JUNE 1976

from 0·51 to 5 {Jog-aturea-Njlitre, using diacetylmethod of urea estimation6; whereas McCarthy5has reported values from 0 to 0·67 [log-aturea-Nflitre using urease technique6• '

The ur~a concentration, therefore, present in theenvironment can be a significant source of availablenitrogen for the phytoplankton in coastal watersof the tropics, perhaps when nitrate and ammonialevels in the euphotic layer are low. These findingsalso suggest that abnormally high concentrationsof urea in any locality, like the Velsao Gay (Goa),may prote to be harmful to the algae.

The author is grateful to Dr S. Z. Qasim, Director,for his interest and encouragement. He is thankfulto Dr M. G. Gogate, Professor of Physiology, GoaMedical College, Panaji, Shri P. M. A. Bhattathiriand Shd V. P. Devassy for their guidance andhelp.References

1. CARPENTER, E. J., REMSON, C. C. & WATSON, S. W.,Limnol. Oceanogr., 17 (1972), 265.

2. MCCAR'fHY, J. J. & KAMYKOWSKI, D., Fish. Bull., 70(1970), 1261.

3. EpPLEY, R. W., ROJERS, J. N. & MCCARTHY, J. J.,Limnol. Oceanogr., 14 (1969), 912.

4. QASIM, S. Z., BHATTATHIRI. P. M. A. & DEVASSY, V. P.,Mar. !Biol., 21 (1973), 299.

5. MCCARTHY, J. J., Limnol. Oceanogj'., 15 (1970), 309.6. NEWELL, B. S., MORGAN, B. & CUNDY, J., J. mar. Res.,

25 (1967), 201.7. STRICKLAND, J. D. H. & PARSONS, T. R., A manual of

sea water analysis, Bull. No. 167 (Fish. Res. Bd, Canada),1968 .

.8. HULBERT, E. M., cited by C. C. Remson, Limnol. Oceanogr.,16 (1971), 732.

9. DAVIS, E. A., DEDRIC, J., FRENCH, C. S., MILNER, H. W.,MYERS, J., SMITH, J. H. C. & SPOEHR, H. A., in Algalcultures from laboratory to pilot plant, edited by H. S.Burlew (Carnegie Institution, Washington, Pub!. 600),1953, 105.

10. MCCARTHY, J. J., Limnol. Oceanogr., 17 (1972), 738.11. NEWELL, B. S., J. mar. biol. Ass. U.K., 47 (1967), 271.12. RAMSON, C. C., Limnol. Oceanogr., 16 (1971), 732.

Mass Mortality of Fish in the VisakhapatnamHarbour

P. N. GANAPATI & A. V. RAMAN

Departmen~ of Zoology, Andhra University, Waltair 530003

Received 11 March 1976

Mass mortality of fish was observed in the Visakha­patnam Hhrbour, which receives both industrial anddomestic effluents from installations located in itsenvirons, on 4 di fferent occasions which was precededby sudden climatic and hydrographical changes in theenvironment. Mortality was localizild in one arm ofthe harbour which receives the effluents from an oilrefinery and a fertilizer factory. Mortality might havebeen caused by the sudden discharge of large quantitiesof acids and sulphur dioxide which brought out con­ditions favourable for emanation offree CO. in abnormal-quantities. The mortality was also believed to havebeen caused by asphyxiatIon due to lowered oxygentension and presence of abnormal quantities of freeCO., whichrwas supported by the data collected on one<lccasion (21)Sept. 75).

134

MASS mortality of fish has been reported hemtime to time, from different parts of the world,

owing to some abnormal event in the aquaticenvironment. An appraisal of the extensive litera­ture cited by Brongersma-Sanders1 and more recentlythat of Korringa 2 indicates that fish mortalitiesresult from a variety of causes, ~ome of naturalorigin and some man-induced. Those from naturalcauses may result from such phenomena as tectonicearth or sea quakes, storms, salinity and temperaturechanges, noxious plankton blooms, decompositionof natural organic materials, bacterial or parasiticepidemics, etc. Man-induced fish-kills result fromindiscriminate discharge of industrial and domesticwastes or to such other water manipulations aschannel dredging, etc., that significantly alter thenearshore waters.

The vresent account is documentation of 4 suchevents ~f fish mortality, on a large scale, in the north­western arm of the Visakhapatnam Harbour whichreceives the industrial effluents from a fertilizerfactory and an oil refinery through a monsoon-fedstream, the Mehadrigedda. The mortalities occurredin November 1974 and in May, September andOctober 1975, in the early hours of the morning,during low tide, and the reports were received afew -hours later. Ganapati and Raman 3 havealready reported that the Mehadrigedda is the majorsource through which industrial effluents enter theharbour through the north-western arm from thefertilizer factory and the oil refinery. The indus­trial waste water, besides being acidic, containsappreciable amounts of toxic substances such asammonia, fluorides, phenols and heavy metallicions such as copper and lead.

The principal species of teleostean fish thatsuccumbed were identified as Megalops cyprinoides,Nematalosa sp. and M ugil cePhlaus of which Nema­talosa sp. formed the bulk of the casualties. Duringthe last 2 occasions of mortality (29.9.75 and20.10.75) Nematalosa sp. alone was affected. Post­mortem examination on this and the other affectedspecies of fish showed no signs of any parasiticinfection and their general appearance was foundto be normal. Considering the number of fisheswashed ashore during each event (average of about350 individuals/100 m stretch of the canal), thefish-kills observed may be classified as 'Major Kills'involving more than a few thousands of fish. Themortalities were also found to be of an acute typeoccurring within a period of 6 hr, usually duringthe pre-dawn hours. In general, the size rangeof the fishes affected varied from about 5 to15 cm.

While it was not possible to collect and analysethe water samples at the time when the mortalityoccurred, on all the 4 dates, some observationshave been made on the weather conditions and thewater quality collected at 0830 hr on 29.9.75 whenthe 3rd mortality was reported. There Was fairlyheavy rain (8·4 mm) and cloudy weather with littlesunshine (1·3 hr) during the preceding 24 hI. Thew:ate.r temperature was 29°C, pH 5'5, free carbondIOXIde 77 ppm and dissolved oxygen 1·2 mljlitre(29'0%). Extreme weather conditions of hot sum­mer, with atmospheric temperature of 36°C and

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