Lifetable demography of four cladoceran species in relation to algal food (Chlorella vulgaris) density

Algal food density is known to influence life history variables of cladocer an species. It is not, however, well established whether both littoral and planktonic cladocerans show similar trends when exposed to increasing food concentrations. In the present work, we studied the life table demography o f four cladoceran species (Ceriodaphnia cornuta, Moina macrocopa, Pleuroxus aduncus and Simocephalus vetulus) in relation to three algal food concentr ations (low: 0.5 x 10(6), medium: 1.5 x 10(6) and high: 4.5 x 10(6) cells m l(-1) of Chlorella vulgaris) (in terms of carbon content, these were equiva lent to 0.15, 0.45 and 1.35 mug ml(-1), respectively) at 25 degreesC. In ge neral, for all the tested cladoceran species, values of average lifespan, g ross reproductive rate, net reproductive rate, generation time and the rate of population growth were higher at lower food concentrations. Furthermore , high food concentration resulted in a negative population growth rate (me an +/- standard error: -0.091 +/- 0.026) for P. aduncus. The highest popula tion growth rate (0.602 +/- 0.014) was recorded for M. macrocopa at low foo d density. S. vetulus had the longest average lifespan (40 +/- 1 d) while M . macrocopa had the lowest (5 +/- 1 d). C. cornuta showed better performanc e at medium food concentration. We conclude that among the algal concentrat ions used here, 0.5 x 10(6) - 1.5 x 10(6) was beneficial not only to the pl anktonic species but also to the littoral P. aduncus and S. vetulus while 4 .5 x 10(6) cells ml(-1) was unsuitable for all the cladocerans tested.