Decrease in Daphnia egg viability at elevated pH

Abstract

The effect of high pH on the reproduction of two Daphnia galeata clones was experimentally investigated in the laboratory. We observed that the mortality of juveniles and adults did not increase with increasing pH in the range pH 9.0–10.5, which agrees with what is generally reported in the literature for cladoceran zooplankton and suggests that the threshold value for mortality is between pH 10.5 and 11.5. However, both egg mortality and the proportion of stillborn neonates increased at pH 10.0 and above, and the two clones differed in their sensitivities to pH. Consequently, pH already affects population growth rate markedly from pH 10.0 onward. Because pH values ≥ 10.0 are common during spring and summer in many eutrophic and hypertrophic lakes due to intense photosynthetic activity, we expect that high pH has a much larger effect on the population structure of Daphnia and the community composition of microcrustacean zooplankton in such water bodies than was assumed previously.

Invited Review - Fight on Plankton! or, Phytoplankton Shape and Size as Adaptive Tools to Get Ahead in the Struggle for Life

“…At that time (after 2.5 weeks), both chlorophyll-a and seston already were decreasing. High pH values were observed, indicative of low CO 2 concentrations and potentially harmful to zooplankton (Vijverberg et al, 1996). Light limitation (or co-limitation with carbon) may also have been responsible for the phytoplankton decline, but we can neither proof nor exclude this.…”

Fluctuations of the population of Daphnia laevis Birge 1878: a six-year study in a tropical lake

“…Environmental conditions (such as temperature, dissolved oxygen, pH, and others) are important factors that act directly on the structure of the zooplankton community, changing the spatial and temporal distribution of the species (Bottrell, 1975;Vijverberg et al, 1996;Gyllström et al, 2004). Furthermore, biotic factors, such as predation (Brooks and Dodson, 1965;Rocha et al, 1990), competition (Smith and Cooper, 1982), food availability and quality, within others, have an enormous pressure on the populations.…”

Effect of pH on survival, reproduction, egg viability and growth rate of five closely related rotifer species

“…Among these, results of field experiments and laboratory bioassays verified the lethal or sublethal effects of pH values of above 9 or below 6 on zooplankton species (O'Brien and deNoyelles 1972;Potts and Fryer 1979;Alibone and Fair 1981;Mitchell and Joubert 1986;Mitchell 1992;Vijverberg et al 1996;Wang et al 1997;Locke and Sprules 2000). In natural water bodies, due to the photosynthetic activity by algae and the respiration of aquatic animals, the pH usually fluctuates between 6 and 9.…”

“…The mean and variation of r m were based on 500 Jackknife samples of individual survivorship and fecundity schedules (Meyer et al 1986). Since the egg viability of freshwater organism is greatly affected by pH (see Vijverberg et al 1996), we computed the r m 0 , assuming all eggs are viable and will result in living neonates, with the method described above. During the experiments all individuals of B. angularis died without producing offspring in the first few days at pH 5.…”

“…Sublethal influences of hydrogen or hydroxyl ion have been noted as impairing survival, growth, reproduction and feeding of zooplankton species (reviewed in Locke 1991;Mitchell 1992;Vijverberg et al 1996). Considering the differential responses of zooplankton species to pH, the sublethal effects of pH indirectly alter the species interactions (e.g., competition, predator-prey) (Hessen et al 1995;Fischer and Frost 1997;Locke and Sprules 2000), and result in changes of distribution and abundance of populations and species, which ultimately influence the community structure (Kiesecker 1996).…”