Mortality and growth responses of Daphnia carinata to increases in temperature and salinity

Abstract

1. Daphnia carinata King, a freshwater cladoceran, occurs in Lake Waihola, a tidal lake with seasonal fluctuations in temperature (4–21 °C), and salinity (30–2000 mg L–1 Cl). We hypothesise that these fluctuations influence the seasonal changes in D. carinata abundance. 2. To test this hypothesis, adults and juveniles were exposed to combinations of temperature and salinity. We measured mortality of adults and juveniles, growth of juveniles over 20 days, and their age at first reproduction. 3. The salinity tolerance of adult D. carinata was temperature‐dependent. Juveniles were more sensitive to salinity, but more tolerant of temperature increases. 4. Growth rates were higher at elevated temperatures, but reduced by elevated salinities. The onset of reproduction was earlier at elevated temperatures. 5. We conclude that seasonal changes in temperature and salinity contribute to seasonal population changes of D. carinata.

Responses of crustacean zooplankton to seasonal and tidal salinity changes in the coastal Lake Waihola, New Zealand

“…The presence of D. carinata only at low salinities, and negative correlations with higher salinities, are supported by the low salinity tolerance threshold of <750 mg litre L Cl of D. carinata from Lake Waihola (Hall & Burns 2002a). At salinities below this lethal threshold, increases in salinity also depressed growth rates (Hall & Burns 2002a).…”

“…The presence of D. carinata only at low salinities, and negative correlations with higher salinities, are supported by the low salinity tolerance threshold of <750 mg litre L Cl of D. carinata from Lake Waihola (Hall & Burns 2002a). At salinities below this lethal threshold, increases in salinity also depressed growth rates (Hall & Burns 2002a). In contrast, however, D. carinata has been recorded in Australian environments with salinities from 250 mg litre-1 Cl (Timms 1997) to as high as 3850 mg litre-1 Cl (Williams et al 1990).…”

“…In laboratory studies, the tolerance limits of B. hamata andD. carinata were <1000 mg litre L Cl and <750 mg litre-1 Cl, respectively (Hall & Burns 2001a, 2002a, whereas G. pectinatus demonstrated a salinity tolerance of >1000 mg litre L Cl (Hall & Burns 2002b). Owing to differences in the species' salinity tolerance thresholds, we hypothesised that, in Lake Waihola, salinity is the most important water quality variable determining the seasonal abundance and taxonomic composition of the crustacean zooplankton community, whereas water movement would strongly influence the distribution of the community.…”

Temperature reaction norms ofDaphnia carinatafitness: the effects of food concentration, population density, and photoperiod

“…Increasing temperature usually enhances zooplankton feeding, growth, and reproduction (Burns 1969;Korpelainen 1986;Achenbach and Lampert 1997;Kee and Ebert 1996). Increasing temperature also exacerbates the inhibitory effects of toxic cyanobacteria on population growth rates (Claska and Gilbert 1998) and decreases salinity tolerance (Hall and Burns 2002) in daphniids. Recently, the possibility of a 4 C increase in average temperatures accompanied by occasional brief extreme events by the end of the twenty-first century due to climate change has reignited interest in temperature effects (Thuiller 2007).…”

“…In an effort to separate the effects of four variables and their interactions on zooplankton fitness, we investigated D. carinata fitness using a full factorial design of temperature, food concentration, population density, and photoperiod. D. carinata is a dominant herbivore in ponds, reservoirs, and lakes of subtropical regions (Hall and Burns 2002;Deng et al 2008;Jiang et al 2013a) and is used extensively as a model zooplankton species in toxicological, ecological, and evolutionary studies (Grant and Bayly 1981;C aceres et al 2007;Jiang et al 2013b). The results may contribute to our knowledge of zooplankton responses under global warming scenarios.…”