Traditional research concerning mesozooplankton feeding has focused on adult species-specific estimates. Here, we propose to estimate in situ size-specific feedings of juvenile mesozooplankton. The motivation is based on the metabolic theory, which indicates that size plays an important role in determining predator-prey interactions. Since aquatic food webs are strongly size structured and many marine species will grow in mass by 5 or more orders of magnitude during their life cycle, we investigated size rather than species specific feeding. Moreover, our estimates provide information to evaluate community-level impacts rather than any particular target species. As such, we could investigate how much nutrition is needed for growth for mesozooplankton at the ecosystem level. In this study, mesozooplanktons are sorted into 50-80um and 100-150um size classes, which represent the two size classes that dominate the juvenile (somatic growth) biomass of the mesozooplankton community in subtropical and tropical western Pacific, and in situ incubations are carried out to calculate clearance and ingestion rates. Our experiments suggest some general trends in feeding of juvenile copepods in the subtropical and tropical western Pacific. First, clearance rates increase as food particle size increase in the big animal size fraction but no significant relationship is found in the small animal size fraction. Second, metazoan ingestion is affected more strongly by food abundance than by animal’s food preference. My results suggest that selection of food particles by juvenile copepods may be based on not only particle size but also the basis of shape, motility, taste, and previous feeding.

Introduction……………………………………………………….……………………..1
Materials and Methods………...…………...………………..……………….………… 5
Study sites…………………………………………………………………………..5
Feeding experiments…………………………………………………………….….6
FlowCAM analysis…………………………………………………………………7
Microscopic analysis……………………………………………………………….8
Estimating clearance and ingestion rates…………………………………………..8
Data analysis……………………………………………………………………….9
Results……...…………………………………………………………………….…….11
Discussion………………………………………………………………………………15
Conclusion……………………………………………………………………………...20
References…..………………………………………………………………………….22

Andersen, K.H., and J.E. Beyer. 2006. Asymptotic size determines species abundance in the marine size spectrum. American Naturalist 168:54–61.
Andersen, K.H., and J.E. Beyer, and P. Lundberg. 2008. Trophic and individual efficiencies of size-structured communities. Proceedings of the Royal Society B 276:109–114.
Atkinson, A., Shreeve RS. 1995. Response of the copepod community to a spring bloom in the Bellingshausen Sea. Deep Sea Res 42:1291-1311
Båmstedt, U., Nejstgaard JC, Solberg PT. 1999. Utilisation of small-sized food algae by Calanus finmarchicus (Copepoda, Calanoida) and the significance of feeding history. Sarsia 84:19–38
Båmstedt, U., Gifford D., Atkinson, A., Irigoien, X. and Roman, M. (2000) Feeding. In, Harris, R. (ed.) ICES zooplankton methodology manual. San Diego CA, USA, Academic Press, 297-399.
Banse, K., 1995. Zooplankton: Pivotal role in the control of ocean production. ICES J. Mar. Sci. 52: 265–277.
Batten S.D, Elaine S and Halvorsen E. 2001. The contribution of microzooplankton to the diet of mesozooplankton in an upwelling filament off the north west coast of Spain. Progress In Oceanography 51:385-398
Berggreen, U., Hansen, B, Kiørboe T. 1988. Food size spectra, ingestion and growth of the copepod Acartia tonsa during development: implications for determination of copepod production. Mar Biol 99:341–352
Blanchard, J. L., S. Jennings, R. Law, M. D. Castle, P.McCloghrie, M.-J. Rochet, and E. Benoit. 2008. How does abundance scale with body size in coupled size structured food webs? Journal of Animal Ecology 78:270–280.
Boyle, P.R, Boletzky SV. 1996. Cephalopod populations: definition and dynamics. Philos Trans R Soc Lond B Biol Sci 351:985-1002
Cushing, D.H. 1968. Grazing by herbivorous copepods in the sea. J. Cons., Cons. Perm. Int. Explor. Mer 32: 70-82.
Cushing, D.H. 1975, "The natural mortality of plaice'', J. Cons. Int. Explor. Mer 36: 150-157.
DeMott, W.R. 1998. Utilization of a cyanobacterium and a phosphorus-deficient green alga as complementary resources by daphnids. Ecology 79:2463-2481.
Dickie, L.M., S.R. Kerr, and P.R. Boudreau. 1987. Sizedependent processes underlying regularities in ecosystem structure. Ecological Monographs 57:233–250.
Edwards, C.A., Powell, T.A., Batchelder, H.P., 2000. The stability of an NPZ model subject to realistic levels of vertical mixing. Journal of Marine Research 58: 37–60.
Fernández F. 1979. Nutrition studies in the nauplius larva of Calanus pacificus (Copepoda: Calanoida). Mar Biol 53:131–147
Finlay K, Roff JC. 2004. Radiotracer determination of the diet of calanoid copepod nauplii and copepodites in a temperate estuary. ICES J Mar Sci 61:552–562
Frost, B.W. 1972. Effects of size and concentration of food particles on the feeding behavior of the marine planktonic copepod Calanus pa&us. Limnol. Oceanogr 8: 805-815.
Frost, B.W. 1975. Treshold feeding behavior in Calanus pacificus. Lirnnol. Oceanogr 20: 263-266
Gauld, D.T. 1951. The grazing rate of planktonic copepods. J. mar. biol. Ass. U.K. 29: 695-706.
Gifford, D.J., 1993. Protozoa in the diets of Neocalanus spp. in the oceanic Subarctic Pacific Ocean. Progress in Oceanography 32: 223–237.
Graneli, E., P. Olsson, W. Graneli & C. Nylander, 1993. Weak ''top-down'' control of dinoflagellate growth in the coastal Skagerrak.--J. Plankton Res. 15: 213-237.
Gong, G.-C., Chen, Y.-L., Liu, K.-K., 1996. Summertime hydrography and chlorophyll a distribution in the East China Sea in summer: implications of nutrient dynamics. Continental Shelf Research 16: 1561–1590.
Gong, G.-C., Y.-H. Wen, B.-W. Wang, and G.-J. Liu. 2003. Seasonal variation of chlorophyll a concentration, primary production and environmental conditions in the subtropical East China Sea, Deep Sea Res., Part II, 50: 1219– 1236,
Hansen,B., Koefoed Bjørnsen,P. and Hansen,P.J. 1994. The size ratio between predators and their prey. Limnol. Oceanogr., 39: 395–403.
Ide, K., Takahashi, K., Kuwata, A., Nakamachi, M., Saito, H., 2008. A rapid analysis of copepod feeding using FlowCAM. Journal of Plankton Research 30: 275–281.
Jonsson, P.R. & P. Tiselius, 1990. Feeding behaviour, prey detection and capture efficiency of the copepod Acartia tonsa feeding on planktonic ciliates. Mar. Ecol. Prog. Set., 60: 35-44.
Moloney, C. L., J. G. Field, and M. I. Lucas. 1991. The sizebaseddynamics of plankton food webs. II. Simulations ofthree contrasting southern Benguela food webs. Journal of Plankton Research 13:1039–1092.
Martin, J.H. and S.E. FITZWATER (1988) Iron deficiency limits phytoplankton growth In the north-east Pacific subarctic. Nature, London, 331: 341-343.
Mullin, M. lb., Fuglister Stewart, E., Fuglister, F. J. 1975. Ingestion by planktonic grazers as a function of concentrationof food. Limnol. Oceanogr. 20: 259-262
Omori, M., Ikeda, T. 1984. Methods in marine zooplankton ecology. John Wiley, New York
Paffenhöfer,G.A. 1988. Feeding rates and behavior of zooplankton. Bull. Mar. Sci., 43: 430–445.
Pope, J. G., J. G. Shepherd, and J. Webb. 1994. Successful surf-riding on size spectra: the secret of survival in the sea. Philosophical Transactions of the Royal Society B 343(1303): 41–49.
Paffenhöfer, G. A. 1971. Grazing and ingestion rates of nauplii, copepodids and adults of the marine planktonic copepod Calanus helgolandicus. Mar. Biol. 11: 286-298.
Paffenhöfer, G.A, Lewis KD. 1989. Feeding behavior of nauplii of the genus Eucalanus (Copepoda, Calanoida). Mar Ecol Prog Ser 57:129–136
Reuman, D. C., and J. E. Cohen. 2004. Trophic links’ length and slope in the Tuesday Lake food web with species’ body mass and numerical abundance. Journal of Animal Ecology 73:852–866.
Rice, J.C., J.G. Daan, J.G. Pope, and H.Gislason. 1991. The stability of estimates of suitabilities in MSVPA over four years of data from predator stomachs. ICES Marine Science Symposia 193:34–45.
Roff J.C, Turner JT, Webber MK, Hopcroft RR. 1995. Bacterivory by tropical copepod nauplii: extent and possible significance. Aquat Microb Ecol 9:165–175
Rollwagen Bollens G.C., Landry M.R. 2000. Biological response to iron fertilization in the eastern equatorial Pacific (IronEx II). II. Mesozooplankton abundance, biomass, depth distribution and grazing. Mar Ecol Prog Ser 201: 43–56
Roman, M.R., and P. A. Rublee. 1981. A method to determine in situ zooplankton grazing rates on natural particle assemblages. Mar. Biol. 65: 303-309.
Rublee, P.A., Gallegos, C.L. 1989. Use of fluorescently labelled algae (FLA) to estimate microzooplankton grazing. Mar. Ecol. Prog. Ser. 51: 221-227
Sheldon, R.W., A. Prakash, and W. H. Sutcliffe. 1972. The sizedistribution of particles in the Ocean. Limnology andOceanography 17:327–340.
Sieracki, C.K, Sieracki, ME, Yentsch C.S. 1998. An imaging-inflow system for automated analysis of marine microplankton. Mar Ecol Prog Ser 168:285–296
Silvert, W., and T. Platt. 1980. Dynamic energy-flow model of the particle size distribution in pelagic ecosystems. Evolution and ecology of zooplankton communities, 754–763
Stoecker, JD.K. and Egloff JD.A. 1987. Predation by Acartia tonsa Dana on planktonic ciliates and rotifers. Exp. Mar. Biol. EcoL, 110: 53-68.
Turner, J.T., Tester, P.A. 1992. Zooplankton feeding ecology: bacterivory by metazoan microzooplankton. J Exp Mar Biol Ecol 160:149–167
Turner, J.T., E. Granéli. 1992. Zooplankton feeding ecology: grazing during enclosure studies of phytoplankton blooms from the west coast of Sweden. J. Exp. Mar. Biol. Ecol. 157: 19-31.
Vargas, C.A., and H. E. Gonza´ lez. 2004. Plankton community structure and carbon cycling in a coastal upwelling system. Diet of copepods and appendicularians. Aquat. Microb. Ecol. 34: 151–164.
Waterhouse, T.Y., and Welschmeyer, N.A. 1995. Taxon-specific analysis of mlcrozooplankton grazing rates and phytoplankton growth rates. Limnol Oceanogr 40:827-834