An analysis of seasonal dynamics of a mixed population of Daphnia, and the associated cladoceran community

SUMMARY. The dynamics of a mixed population of Daphnia (D. ambigua and D. parvula) are analysed over 9 months in a small eutrophic lake. A spring peak of D. ambigua occurred shortly after ice break-up. Decline of D. ambigua coincided with a high occurrence of sexual reproduction, the appearance of D. parvula which did not become abundant, and a substantial increase in Ceriodaphnia quadrangula . A third cladoceran, Bosmina longirostris , was abundant before and after the period of numerical dominance by D. ambigua , but declined to very low numbers coincident with the increase in D. ambigua.
Estimates of egg hatching rate at various temperatures demonstrate that these three cladocerans have different rate responses to temperature, and that seasonal succession of species is predictable from temperature alone. The importance of temperature versus species interactions in controlling species succession is discussed.