Effect of norfloxacin on algae–cladoceran grazer–larval damselfly food chains: Algal morphology-mediated trophic cascades

• Published in: Chemosphere (Oxford) Vol. 256; p. 127166
• Main Authors: Wan, Lingling, Long, Yaoyue, Hui, Jin, Zhang, Hao, Hou, Zhiyong, Tan, Jiexin, Pan, Ying, Sun, Shucun
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-10-2020
• Subjects: Antibiotic; Behavior-mediated indirect interaction; Food chain; Morphology-mediated indirect interaction; Morphology-mediated indirect interaction; Antibiotic; Behavior-mediated indirect interaction; Food chain
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2020.127166

Antibiotic norfloxacin (NOR) has recently been demonstrated to affect the swimming behavior of zooplankton species and phytoplankton-zooplankton interactions, which may further affect trophic cascades. To test this hypothesis, two food chains (Scenedesmus quadricauda–Daphnia magna–larval damselfly and Chlorella vulgaris–D. magna–larval damselfly) were used to examine the effect of NOR concentrations (0, 0.5, 5, and 25 mg L−1) on trophic cascades. In the absence of NOR, larval damselflies reduced grazer density and increased algal density, regardless of algal species. In the presence of NOR, increasing NOR concentration strengthened the positive effect of larval damselflies on the growth of C. vulgaris because larval damselflies suppressed grazer density more efficiently resulting from reduced swimming ability in the grazers. Conversely, increasing NOR concentration reduced the positive effect on the growth of S. quadricauda due to inhibited grazer-induced colony formation in S. quadricauda. Therefore, exposure to NOR altered the direction and strength of trophic cascades and showed species-specific differences, depending on algal morphology-mediated indirect interactions. These findings provide novel insights into how NOR affects aquatic food chains and reveal the importance of algal traits in determining trophic cascades.
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•Without NOR, suppressed grazer density by damselflies promoted algal growth.•NOR increased the positive impacts of damselflies on C. vulgaris growth.•NOR reduced the positive impacts of damselflies on S. quadricauda growth.•NOR altered trophic cascades and showed species-specific differences.•The above differences depend on algal morphology-mediated indirect interactions.