We reared mixotrophic (Ochromonas tuberculata and Cryptomonas sp.) and photoautotrophic specialist algae (Scenedesmus obliquus) at different light : phosphorus supplies and compared their effects as food for zooplankton (Daphnia magna). According to the light : nutrient hypothesis (LNH), biomass and nutrient stoichiometry of phototrophic specialists depend strongly on light : phosphorus supplies. If this is true, herbivore growth and fecundity should be limited by food quantity at low light intensities and by stoichiometric food quality at high light intensities. In turn, phosphorus fertilization should cause a transition from limitation by food quality to limitation by food quantity. In contrast to the LNH, biomass and nutrient stoichiometry of mixotrophs were almost unaffected by alterations in the supply of light and dissolved nutrients. Bacterial counts indicate that mixotrophs compensated for light or phosphorus deficiency by heterotrophic nutrition. Compared to phototrophic specialists, a diet of Cryptomonas sp. therefore enabled a similar or higher and more stable secondary production at most light : nutrient supplies. O. tuberculata, however, appeared to be toxic. Our results indicate that mixotrophs might have a balancing effect on variations in transfer efficiency caused by perturbations to light and nutrient supplies.

This study applies stated-preference methods to estimate the public good values of preservation and restoration of a local historic landmark in a medium-sized US city. The survey device centres on a referendum-style dichotomous-choice question regarding city participation in a restoration partnership. Use of a double-split sample allows analysis of the effect on valuation of both heritage information and willingness-to-pay versus willingness-to-accept constructs, where the latter is approached by the method of paired comparison, allowing a non-substitutability effect to be separated from any endowment effect. Econometric analysis using a standard binary logit model indicates the existence of a strong non-substitutability effect and a significant information effect that further suggests the importance of non-substitutability in valuation.

No abstract

No abstract

No abstract