PS 50-58
The effect of anthropogenic nitrogen and sedimentation on primary producers: Do tadpoles matter?
Freshwater habitats comprise some of the most altered ecosystems on Earth, primarily due to anthropogenic changes in hydrology and nutrient cycling. Many freshwater systems in North America are limited by nitrogen and phosphorus, so the addition of these nutrients can cause harmful algal blooms. Along with nutrient addition, sediment loading due to dust storms and erosion can result in alterations to community structure, biomass, and primary productivity in freshwater systems. Several groups of animals have been shown to directly influence sediment accrual rate, including shrimp, fish, crayfish, and stoneflies. Larval amphibians (tadpoles) could also directly influence sediment accrual and nitrogen cycling. Sediment clearing and grazing by amphibians could affect growth of primary producers in three ways: 1) tadpoles could increase the amount of nitrogen suspended in the water column, increasing the growth of suspended primary producers (phytoplankton); 2) tadpoles can clear sediment from surfaces, thereby increasing light available for primary producers attached to surfaces (periphyton); 3) tadpole grazing on primary producers (phytoplankton and periphyton) could reduce biomass of these primary producers. We used a fully factorial experimental design to test the effects of tadpole grazing and sediment clearing on photosynthetic organisms.
Results/Conclusions
We observed interactions among primary producers, tadpoles, and ostracods in the presence of nitrate additions. No effect of sediment was observed on primary producers or tadpole behavior. Understanding the connections among species and how those connections influence the response of functional groups in the community (i.e. primary producers) is increasingly important in the face of local and global environmental changes.