Effects of Daphnia magna on the Concentration and Size Distribution of Suspended Particles

Suspended particles are key components of aquatic ecosystems that modulate the biogeochemical processes of natural waters. The filter feederDaphnia magnacan alter suspended particle characteristics and aquatic habitats, while habitat variations in turn affect its growth and reproduction. This study primarily investigated the impacts ofD. magnaon the concentration and size distribution of suspended particles, and explored its particle size selectivity. Three particle types, namely kaolinite (KN), montmorillonite (MN) and natural particles (NP), were adopted for experiments, and natural particles were further divided into three size fractions (<150 μm, <96 μm, <75 μm). The results demonstrated thatD. magnasignificantly reduced suspended particle concentrations via ingestion, with the most prominent effect observed within the initial three hours of experimentation, verifying its practical value for wastewater remediation. Though classified as a non-selective filter feeder,D. magnaexhibited distinct particle size selectivity for identical substances. Fine particles (<8 μm) presented higher bioavailability and were preferentially ingested byD. magna. Additionally, the regulatory effects ofD. magnaon particle size distribution were closely associated with its particle digestion process, which depended on inherent particle properties, including composition and organic matter content.