THE RELATIVE IMPACTS OF TOP-DOWN AND BOTTOM-UP PROCESSES ON ZOOPLANKTON BIOMASS AND COMMUNITY BODY SIZE IN URBAN PONDS IN ANKARA

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2023-1-25

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Kıran, Hilal

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Ponds are small and shallow water bodies that are rich in biodiversity as they provide different habitats, food, and water to aquatic and many terrestrial species. One of the biggest threats to biodiversity is urbanization because it causes increased land use, habitat fragmentation, and removal of riparian vegetation. Increased land use affects dramatically the urban pond ecosystem, i.e, changing the food web structure that is critical for the energy transfer between different trophic levels. Since zooplankton connect phytoplankton producers to higher trophic levels such as fish, changes in resource availability and predation pressure as a result of urbanization can have a significant effect on their biomass and size structure. This study aimed to assess the relative impacts of top-down and bottom-up processes on zooplankton biomass and abundance-weighted mean community body size in urban ponds in Ankara. The first hypothesis was that if bottom-up processes are dominant, zooplankton biomass and size will be associated with the phytoplankton abundance, as well as abiotic variables that influence phytoplankton density such as water clarity and nutrient concentrations. The second hypothesis was that if top-down processes are dominant, zooplankton biomass and size will be associated with predator presence and abundance. There was a positive relationship between total nitrogen (TN) concentrations with biomass and the size of total zooplankton and copepods, indicating the nitrogen limitation of the ponds, and the possible importance of the benthic zone in the trophic structure. Additionally, macroinvertebrates showed a positive relationship with total zooplankton size, and copepods’ biomass and size, indicating possible mouth-gape-limited predation on smaller zooplankton. To sum up, these findings suggest that zooplankton biomass and size in urban ponds in Ankara are influenced by both top-down (macroinvertebrate predation) and bottom-up (nutrient availability) forces.

Subject Keywords

Urbanization, Trophic Cascade, Pond, Zooplankton

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https://hdl.handle.net/11511/102117

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

H. Kıran, “THE RELATIVE IMPACTS OF TOP-DOWN AND BOTTOM-UP PROCESSES ON ZOOPLANKTON BIOMASS AND COMMUNITY BODY SIZE IN URBAN PONDS IN ANKARA,” M.S. - Master of Science, Middle East Technical University, 2023.