Daphnia galeata performance along food quantity gradients of mixed Rhodomonas, Pseudomonas and terrestrial particulate organic material
(English)Manuscript (preprint) (Other academic)
Unproductive lakes are often characterized by high inputs of allochthonous dissolved and particulate organic carbon compared to autochthonous carbon, resulting in low phytoplankton abundances and high heterotrophic bacterial biomass. Thus, metazooplankton in these lakes feed on a mixture of phytoplankton, bacteria and terrestrial particulate organic material (t-POM) where the proportions of these components can be highly variable. As the nutritional value of the different food components varies, the dilution of phytoplankton (high-quality food) with high proportions of bacteria and/or t-POM (low-quality food) is expected to affect the performance of unselective filter feeders such as Daphnia. We tested how different combinations of constant concentrations of phytoplankton and increasing additions of bacterioplankton or t-POM affect zooplankton performance. We found that increasing the concentrations of both the bacterium Pseudomonas and t-POM relative to phytoplankton (Rhodomonas) negatively affected Daphnia survival, growth and reproduction when Rhodomonas was available at non-limiting concentrations (0.37 and 0.55 mgC L-1). When Rhodomonas quantity was low (0.22 mgC L-1), the addition of Pseudomonas led to better Daphnia performance except at very high concentrations of the bacterium relative to Rhodomonas. In contrast, the addition of t-POM was detrimental for overall Daphnia performance at low Rhodomonas quantity. These results imply that the ability of zooplankton to use low-quality food is affected by the availability of high-quality food. Further, food sources that do not fulfil dietary requirements of grazers may still provide nutritional benefits as long as other complimentary food components are available in sufficient quantities to compensate for mineral and/or biochemical deficiencies.
heterotrophic bacteria, phytoplankton, food quality, allochthonous, autochthonous, zooplankton
Research subject Limnology
IdentifiersURN: urn:nbn:se:umu:diva-62277OAI: oai:DiVA.org:umu-62277DiVA: diva2:576951
FunderFormasSwedish Research Council, 2007-5523