Threshold Responses of Zooplankton Community to Freshwater Salinization in a Gradient Mesocosm Experiment

Date

2026-1-22

Author

ARIK, İrem Gamze

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

62
views

0
downloads

Cite This

Freshwater salinization is accelerating globally and poses major risks to lake ecosystems by altering zooplankton community structure and in turn their functions in the ecosystem, including regulation of nutrient cycling, water clarity. Yet the mechanisms through which increasing salinity reshapes zooplankton biomass, diversity, and ecosystem functioning remain poorly resolved. A 5-month salinity gradient mesocosm experiment was carried out to quantify how gradient of salinity affects zooplankton biomass, taxonomic richness, community composition, and resource use efficiency (RUE). Salinity was manipulated from 0.5 to 50 g/L in total 16 different salt concentrations, and zooplankton responses were analyzed using generalized linear mixed models (GLMMs) with spline terms and Threshold Indicator Taxa Analysis (TITAN). Zooplankton biomass declined steeply at relatively low salinities (7 g/L), continued to decline towards 30 g/L salinity, and remained near zero at higher salinities (30-50 g/L salinity). Species richness and community composition shifted substantially along the gradient, with sensitive cladocerans and copepods disappearing and rotifers dominating at elevated salinities. RUE showed a significant nonlinear response, decreasing rapidly up to 10 g/L salt concentration, stabilizing at intermediate salinities (10-30 g/L), and declining again above 30 g/L salt concentration. TITAN identified consistent taxon-specific thresholds and a community-level threshold near 12 g/L salt concentration. Together, these results demonstrate substantial losses of zooplankton taxonomic and functional integrity under even moderate salinization, with potential consequences for trophic stability and ecosystem functioning in freshwater lakes, highlighting the importance of identifying ecological thresholds for effective management and conservation.

Subject Keywords

Freshwater salinization, Zooplankton community structure, Ecological thresholds, Resource use efficiency

URI

https://hdl.handle.net/11511/118723

Collections

Graduate School of Natural and Applied Sciences, Thesis