The contribution of the nannoplankton to the total productivity

was studied for nine months in coastal waters of Cochin. On an average,

- nannoplankton accounted for 66.40% of the observed productivity. The

mean assimiIation ratios between the total algal and nannoplankton fraction

were very low (1.29 and 0.94 respectively)

Balachandran, V K

Joseph, K J

Vijayaraghavan, Sumitra

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lj3J) PRELIMINARY STUDIES ON NANNOPI,ANKTON PRODUCTIVITY ABSTRACT The contribution of the nannoplankton to the total productivity was studied for nine months in coastal waters of Cochin. On an average, - nannoplankton accounted for 66.40% of the observed productivity. The mean assimiIation ratios between the total algal and nannoplankton fraction were very low (1.29 and 0.94 respectively). The importance of the nannoplankton to the total phytoplankton in marine environments has been well documented by the works of Teixeira (1963), Gil-martin (1964), Malone ( 1971 a & b ) and McCarthY e/ a/ (1974). Except for the recent studies on the contri-bution of microplankton and nanno-plankton III the Cochin Backwater (Qasim e/ aI., 1974), no other data pertam mg to nannoplankton produc-tivity of the inshore or offshore waters in this area arc available. The present communication gives the con-tribution of nannoplankton in the total algal production of the coastal waters of Cochin. Water .amples from the surface were collected at monthly intervals fr0m September 1972 to June 1973 from a fixed station (Mannacherry). About five litres of water were filtered through No . 25 bolting silk. The water that passed through No. 25 bolting net (representing the nannoplankton fra-ction) was taken for the measurem ent of P:lOtosynthesis. chlorophyl! -a content and cell numbers. In addition , un-filtered water sample (representing the total algae) was also taken for the above three measurements. of photosynthesis of the The rate total and nannoplankton fraction was measured by 14C technique. For the measure· ment of chlorophyll and phytoplankton counts, techniques used earlier were employed (Qas im e/ al., 1974). Values of photosynthesis, chloro-phyll -a and cell counts for both total and nannoplankton have been shown in Figure 1. It is seen that during the first few months of the year (January to Marchl, the contribution of the netplankton photosynthesis was greater, while during the rest of the year (April to December), the contribution of nan-noplankton photosynthesis was more than 60% of the total. This indicates that there is seasonal variation in the photosynthesis of nannoplankton. Sea-sonal variation in the contribution of nannoplankton to the total photosyn-thesis in an eutrophic temperate lake has been reported by Kalff (1972). , Mahasagar , Vol. 7, Nos. 1 & 2, March-June 1974 • , 90 "0 "0 , ., f\ CELL COUNTS ~. " 0 " ... PRODUCTIVITY - t OTAL SAJoIPl ( • • - NANNO Pl ANIOOH 'OL..:,~l......,--:-:J---:-~::::~..J M.6.M J'iO N O MONTHS Fig. 1 Seasonal variation in photosynthesis, chloropbylI-a content and cell counts, However, Anderson (1965), Subra-manyan and Sharma (1965), Gilmartin (1964), Malone (1971 a) and McCarthy e/ aJ (1974) reported no seasonal cycle in the contribution of nannoplankton to the total photosynthesis. The trends in the two sets of values of photosynthesis were more or less similar (Fig. I). The rate of photosyn-thesis of total algae ranged from 0.93 mgC m- s d- 1 in March to 167.62 mbe m- s d- 1 in April and that of nanno-plankton fraction was from 0.35 mgC m- ' d- 1 to 107.23 mgC m- s d- 1 • The maximum value obtained appears to be nearer (100 mgC m- s d- 1 ) to that reported by Ramachandran Nair e/ aJ (1973) for the coast.1 waters . High values of chlorophyll -a wete obtained during March, May and Sep-tember W:l ich were rather independant of similar rises in the rate of photo-synthesis. The peak values of photo-synthesis both for the total algae and nannoplankton were recorded during the month of April, which was asso-ciated with very low levels of chloro-phyll. This may probably be due to the presence of detri tal or degraded chlorophyll which was physiologically inactive. Such a situation has been reported by Yentsch and Ryther (1959) in Vineyard sound and Qasim et aJ (1974) from Cochin Backwater. In the present study , the cell counts of the nannoplankton fraction was lower than that of the net fraction in most of the months . This is in agreement with the findings of Digby (1953) and Sub-ramanyan .nd Sharma (1965). Table I gives the range in photo-synthesis, chlorophyll·a and cell counts of both net and nannofractions to the total. The annual percentage contri-bution of the nannoplankton to the total photosynthesis was about 66·40%. This is close to the value 7-t.47 % reported for the Cochin Backwater (Qasim et aI. , 1974). Steemann-Nielsen and Jensen (1957), Holmes (1958), Malone (1971 a & b) have she wn that 80 to 100% of the total ph ytoplankton 126 Sumitra Vijayaraghavan et al. : Studies on nannoplanktDn productivity TABLE Photosynthesis, chlorophyll-a and cell numbers of net and nannoplankton expressed as percent of the two combined. Netplankton Nannoplankton Photosyn-thesis 5.88-64.42 35.58-94.12 productivity is contrihuted by nanno-plankton. The assimilation ratio of the total sample ranged from 0.11 to 7.85 (1.29 mean) and that of the nannoplankton 0.01 to 5.35 (0.94 mean). Malone (1971 aJ obtained a mean nannoplankton assi .. milation ratio of 9.4 for the inshore waters and 8.3 for the offshore waters_ Anderson (1964) reported a range from 1.6 to 9.8. As compared with these values, the assimilation ratio obtained in the present study seems to be very low. According to Curl and Small (1965) a ratio below 3 is indicative of nutrient deficiency, while those above 5 indicates abundance of nutrients. In the present case, while calculating the assimilation ratios, light saturation intensity was not taken into account. This may partly be responsible for the low assimilation values. However, the mean nannoplankton assimilation Cenlral Marine Fis !leries Research Ins titute. Coch;" - 18 Chloro-phyll - a 6.18-50.00 50.00-93.82 Cell counts 42_19-96.02 3.98-57.8\ ratio was almost thrice as great as that of the netplankton ratio. Malone (1971 a ) reported a mean assimilation ratio of the nannoplankton which was nearly double than that of the net-plankton. The importance of nannoplankton as food for the fish larvae along the West coast of India has been pointed out by Subramanyan and Sharma (1965). Detailed investigations on these lines would provide useful information re-garding the possibilities of exploitation of commercially important fishes. The authors wish to express their thanks to Dr. S. Z. Qasim then Director, Central Marine Fisheries Research Institute, Cochin for his keen interest in this work and to Mr. P. M. A. Bhattathiri of National Institute of Oceanography, Goa for his useful suggestions. SUMITRA VIJAYARAGHAVAN * K. J. JOSEPH V. K. BALACHANDRAN • Present Address: National Tnstitute of Oceanography. Dona Paula (Goa.) 127 , REFERE NC ES Anderson, G . C., 1965 . Fractionation of phytoplankton commUnItIes off the Washington and Oregon Coasts. Limnol. Oceanogr., 10 : 477-480. Curl, H. and L. F. Small , 1965. Variations in photosynthetic assimilation ratios in natural marine phytoplankton communities. Limnol. Oceanogr" 10 (SUpp. ) : R67-R73. Digby, P. S. B., 1953. J. Anim. Ecol., Plankton production in Scoresby Sound East Greenland. 22 : 289-322. Gilmartin. M. 1964. The primary production of a British Columbia Fjord. J. Fish. Res . Bd. Canada , 21: 505-538. Holmes, R. W. , 1958. Size fractionation of photosynthesizing phytoplankton. In: Physical. chemical and biological oceanographic observations obtained on expedition SLOPE In the Eastern Tropical Pacific. November-December , 1956. p. 69- 71. U. S. Fish. widl. serv., Spec. Sci . Rep. Fish. 279. Kalff, J., 1972. Netplankton and nannoplankton production and biomass in the North temperate zone Lake. Limnol. Oceanogr. , 17: 712-720. McCarthY, J. J., W. R. · Taylor and M. E. Loftus., 1974. Si;;nificdnce of nannoplankton in the Chesa~cakc Bay Estuary and problems asso· cia ted with the measurement of nannoplankton productivity. Mar . Bioi., 24: 7-16. Malone, T. C., 1971 a. The relative importance of nannopl ankton and nct. plankton as primary producus in the California current system. Fish . Bull. U. S., 69: 799 -802. Malone, T. C., 1971 b. The relative importance of netplankton and nanne-plankton as primary producers in neritic and oceanic tropical waters. Limnol. Oceanogr., 16 : 633-639. Ramachandran Nair, P. V. R, Sydeny Samuel, K . J. Joseph and V. K. Bala· chandran, 1973. Primar y production and potential fish ery resources in the seas around India. Proceedings of the symposiuru on the living resources of the seas ar8und India. pp. 184-198. Steemann-Nielsen, E and E. A. Jensen, 1957. Primary oceanic prod uetion. The autotrophic production of organic m,ltter in th e ocean. Galathea . Rap. , 1: 49-139. Subramanyan, R. and A. H. V. Sarma , 1965. Studies on the phytoplankton of the West coast of India . Part I V. Magnitude of the stand ing ' crop for 1958-1962 with observations on nannoplankton and its s igllifi "a nc~ to fish eries. J . mar. bioi. Ass . India ., 7: 4C6-419. Qasim, S. Z., Sumitra Vijayaraghavan , K . J. Joseph and V. K . Balachandran, 1974. Contribution of m i;.;ropldnkton and nannoplank ton in the waters of a tropical estuar y. Ind. J . mar . Sci. , 3: 146- 149. 128 -Sumitra Vijayaraghal'an et. a!. : Studies on nannoplankton productivity Teixeira , C. 1963. Relative rates of photosynthesis and standing stock of the net phytoplankton and nannoplankton. Bol. Inst. Oceanogr. Uni· vtrsidade de sao Paulo., 13: 53-60. Yentsch, C. S. and J. H. Ryther, 1959. Relative significance of tbe net and nannoplankton in the waters of Vineyard Sound. J. cons. perno Int. Explor. mer., 24: 231- 238. 129 

Preliminary studies on nannoplankton productivity

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Preliminary studies on nannoplankton productivity

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