Ka. Work et M. Gophen, Factors which affect the abundance of an invasive cladoceran, Daphnia lumholtzi, in US reservoirs, FRESHW BIOL, 42(1), 1999, pp. 1-10
1. Daphnia lumholtzi is a subtropical, Old World species which is rapidly s
preading throughout reservoirs in the southern U.S.A. It was first recorded
in Lake Texoma (Oklahoma-Texas) in September 1991.
2. Southern U.S. reservoirs typically have strong spatial and temporal grad
ients in temperature, conductivity, turbidity and in the distribution of or
ganisms. Therefore, the present experiments examined the reproductive and m
oulting rates, and survival of D. lumholtzi in relation to extremes of food
concentration, temperature, conductivity and turbidity.
3. Increases in temperature (range 15-29 degrees C) and decreases in turbid
ity (range = 0.6-470 NTU) increased reproductive and moulting rates, wherea
s food concentration only affected the rate of reproduction, while conducti
vity had no effects. Survival was affected only by temperature.
4. Daphnia lumholtzi tolerates high temperatures (27-30 degrees C) at which
other cladocerans in Lake Texoma disappear. Therefore, D. lumholtzi may ex
ploit resources in midsummer, when there are few potential competitors.