Effects of green algal concentrations on the life history characteristics of Daphnia magna
Abstract
As eutrophication levels continue to rise, it is important to understand how increases in algal biomass will affect other food web components. In this study, we used Scenedesmus acutus, a species of green algae, to determine potential implications on the reproductive patterns of Daphnia magna. We tested six concentrations of S. acutus: 0.1 mg C/L, 0.25 mg C/L, 0.5 mg C/L, 0.75 mg C/L, 1.0 mg C/L, and 2.0 mg C/L. These specific quantities were chosen to represent a gradient of good quality for carbon that is consistent with different levels of eutrophication. Utilizing life-table experiments, we recorded life history characteristics over the course of two weeks. We tested for total reproduction, age at first reproduction, clutch size, and number of clutches. We discovered that higher levels of green algae resulted in greater reproductive characteristics as compared to lower levels. We concluded that D. magna grown in the 1.0 mL treatment produced the greatest reproductive output. Additionally, our data showed reproductive patterns were disrupted with more extreme concentrations of green algae, which was exhibited through a decrease in D. magna reproduction in the 0.1 mL treatment sample. We did not test for growth characteristics in this study, so future research could account for these characteristics. However, our data clearly shows a relationship between green algal concentrations and the reproductive patterns of D. magna, which can be used to better understand the impacts of eutrophication in freshwater ecosystems.