Testing a model of zooplankton secondary production in cultures of Daphnia magna

TESTING A MODEL OF ZOOPLANKTON SECONDARY PRODUCTION IN CULTURES OF Daphnia magna M. Gómez* , I. Ma ínez* , I. Mayo*, J.M. Mo ales*& T.T. Packa d* * Labo a o io de Oceanog a ía Biológica, Facul ad de Ciencias del Ma , Uni e sidad de Las Palmas de G an Cana ia, Campus Uni e si a io de Ta i a 35017, Las Palmas de G an Cana ia, Islas Cana ias, España Con ac o: [email protected] Ha es Size measu emen F eeze -20ºC Pa ame e s measu emen s D y mass (Lo eg o e,1966) G ow h a e Condi ion ac o CF = (a · W)/L3 Mo he cul u e (20L) Phy oplank on cul u e (Scenedesmus sp. +Ankis odesmus sp.) Co n lou cul u e (come cial) Yeas cul u e (come cial) Di e en cul u es o D. magna we e g own on phy oplank on, bake ’s yeas , o co n lou a 18-21°C. G ow h a es we e calcula ed om ime cou ses o size (Fig.1) and d y mass (Fig. 2 ). MATERIAL AND METHODS RESULTS Table 1. Cha ac e is ics o he di e en D. magna cul u es Kind o ood Maximum size Lmax(mm) Age o Lmax (days) Maximum weigh Wmax(µg) Age o Wmax (días) Go w h a e (d-1) Condi ion ac o (CF) Tempe a u e (ºC) Phy oplank on mix u e 1.42 ± 0.19 18 153 13 0.203±0.03 ( 2=0.77) 5.78 20.9 ± 1.1 Yeas 2.01 ± 0.14 17 110 12 0.317±0.03 ( 2=0.94) 1.19 20.1 ± 0.5 Co n Flou 1.38 ± 0.07 19 150 19 0.136±0.01 ( 2=0.72) 4.51 19.2 ± 1.2 Table 2. Reg ession analysis o size and d y-mass. W=d y-mass, in µg; L=size, in mm (*) p<0.0001 Kind o ood Equa ion 2 Phy oplank on mix u e Ln W = 1.39 Ln L + 4.51 0.92 (*) Yeas Ln W = 2.68 Ln L + 2.67 0.98 (*) Co n lou Ln W = 1.02 Ln L + 4.46 0.93 (*) CONCLUSIONS  Al hough he highes global g ow h a es we e ob ained wi h yeas (0.317d-1), he highes alues o he condi ion ac o (5.778) and seconda y p oduc ion (508 µg d y mass·d-1) as well as he maximum weigh we e ound in daphnia ed on phy oplank on. This mix u e seems o be he op imal ood o cul u ing Daphnia.  The Hun ley and López (1992) model o e es ima es he seconda y p oduc ion by 174%.  On a u ili a ian basis, because size is such a good index o biomass, i p o ides a simple and mo e eliable measu e o g ow h- a e han d y-mass. BIBLIOGRAPHY: Hun ley, M.E. & M.D.G López, 1992. Tempe a u e-dependenden p oduc ion o ma ine copepods: a global syn hesis. Ame ican Na u alis , 140:201-242 Vij e be g, J., 1989. Cul u e echniques o s udies on he g ow h de elopmen and ep oduc ion o copepods and cladoce ans unde labo a o y and in si u condi ions: a e iew. F eshwa e Biology 21:317-373 Fig. 2 and Fig. 3 .- D. magna g ow h illus a ed by he d y-mass ime-cou se and daily g ow h a e, espec i ely. A: Fed on phy oplank on mix u e; B: Fed on yeas ; C: Fed on co n lou . Dashed lines ep esen he 95% con idence in e als. INTRODUCTION Seconda y p oduc ion is he p oduc o biomass and g ow h a e. The key o i s es ima ion is a good measu emen o g ow h a e. P incipal ac o s con olling his a e in zooplank on a e he amoun , and he quali y o ood (Vij e be g, 1989). He e, we measu e he daily and o e all g ow h a e in he Cladoce an, Daphnia magna, aised unde di e en ood egimes. We hen used he measu emen s as a e e ence s anda d o model zooplank on seconda y p oduc ion in na u al popula ions. Fig.1 .- D. magna g ow h illus a ed by he size ime-cou se. A: Fed on phy oplank on mix u e; B: Fed on yeas ; C: Fed on co n lou . Fig.1 Fig.2 Fig.3 Seconda y p oduc ion alues (pe iod o 12 days) Phy oplank on cul u e (µg d y mass·d-1) Yeas cul u e (µg d y mass·d-1) Co n lou cul u e (µg d y mass·d-1) 508.88 307.46 328.26 Using he exp ession P = B 0.0455 e0.111T (Hun ley and López, 1992) Phy oplank on cul u e (µg d y mass·d-1) Yeas cul u e (µg d y mass·d-1) Co n lou cul u e (µg d y mass·d-1) 1379.32 776.75 943.16 (B = biomass, T = empe a u e) In compa ison, ou measu emen s a e app oxima ely 60% lowe han he Hun ley- López model p edic . I s seems ha hei equa ion may o e es ima e he seconda y p oduc ion in ou cul u e sys em. Yeas Co n lou Mix u e o Scenedesmus sp. Ankis odesmus sp. mix u e Daphnia magna