Doerthe C. Müller-Navarra

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The factors that regulate energy transfer between primary producers and consumers in aquatic ecosystems have been investigated for more than 50 years. Among all levels of the food web (plants, herbivores, carnivores), the plant-animal interface is the most variable and least predictable link. In hypereutrophic lakes, for example, biomass and energy transfer(More)
Determining the factors that control food web interactions is a key issue in ecology. The empirical relationship between nutrient loading (total phosphorus) and phytoplankton standing stock (chlorophyll a) in lakes was described about 30 years ago and is central for managing surface water quality. The efficiency with which biomass and energy are transferred(More)
Herbivorous zooplankton production is often constrained by algal food quality, and variation in algal food quality has been attributed to its phosphorus (P) content. To test the hypothesis that mineral P limitation is an important constraint on freshwater herbivorous zooplankton production, we conducted a quantitative analysis of published data on lake(More)
We conducted a series of experiments feeding Daphnia pulex nine different phytoplankton monocultures with widely varying fatty acid composition and nutritional values to test the extent to which Daphnia fatty acid composition was affected by diet. In general, Daphnia fatty acid composition matched that of their diet much more closely than it did the fatty(More)
We examined the relative nutritional values of natural phytoplankton and particulate detritus for zooplankton growth in a detritus-rich environment. Seston was collected seasonally from four different habitat types in a tidal freshwater system and fed to juvenile Daphnia magna under controlled culture conditions by use of a flow-through design. Seston(More)
1. A series of experiments examined growth of Daphnia magna on three algal diets (Rhodomonas minuta, Scenedesmus acutus and Synechococcus sp.) at varying physiological states [nitrogen and phosphorus (P) limitations] to test whether variation in algal fatty acid and/or elemental composition can predict Daphnia growth. 2. These algae differed widely in their(More)
We conducted a series of experiments using the herbivorous zooplankter Daphnia pulex to investigate the nutritional importance of dietary polyunsaturated fatty acids (PUFAs). Daphnia were fed three different diets: (1) a PUFA-deficient cyanophyte mixture, (2) a cyanophyte mixture with fatty acid (FA) amendments, or (3) a PUFArich cryptophyte mixture. We(More)
To investigate the potential for heterotrophic organisms to upgrade the food quality of seston, we performed decay experiments using a non-toxic Microcystis aeruginosa (cyanobacteria) monoculture. The experiment was performed in darkness with aeration using a microbial inoculum collected from a hypereutrophic pond. Chlorophyll a concentrations decreased(More)
We modified the stable isotope mixing model MixSIR to infer primary producer contributions to consumer diets based on their fatty acid composition. To parameterize the algorithm, we generated a 'consumer-resource library' of FA signatures of Daphnia fed different algal diets, using 34 feeding trials representing diverse phytoplankton lineages. This library(More)
We examined whether seston food quality was a significant factor to predict zooplankton, specifically Daphnia pulex, biomass dynamics in Lake Berryessa, California, U.S.A. The seston composition changed dramatically during the study period. Total macrozooplankton to seston biomass ratios were high during the springtime, as was D. pulex biomass. In monthly(More)