Effects of Floc & Lock technique materials on the enzymatic activity of benthic macroinvertebrates

The Floc & Lock (F&L) technique is a promising approach for mitigating eutrophication. However, gaps remain regarding its effects on benthic fauna directly exposed to the applied materials. In this study, we evaluated the effects of polyaluminium chloride (PAC) and lanthanum-modified bentonite (LMB) on the activity of the enzymes acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and trypsin in the snail Melanoides tuberculata (Müller, 1774) and larvae of the insect Chironomus sancticaroli (Strixino & Strixino, 1981). We tested the hypothesis that exposure to PAC and/or LMB alters the activity of these enzymes in benthic macroinvertebrates in a species-dependent manner. Under in vivo experimental conditions, enzymatic responses were assessed after 72 h of exposure to the following treatments: control (no materials), + PAC, + LMB, and the combined treatment + LMB and PAC. In addition, in vitro assays for enzymatic inhibition were conducted. AChE was strongly inhibited in larvae, with reductions exceeding 90% in treatments containing PAC, whereas M. tuberculata showed a mean reduction of approximately 50%. BChE exhibited contrasting responses: marked reduction in larvae under + LMB and PAC and increased activity in snails exposed to PAC, suggesting a greater capacity for metabolic compensation in M. tuberculata. Trypsin showed a dual response, with in vivo enhancement under combined treatment and direct in vitro inhibition, indicating compensatory digestive adjustments. These results demonstrate that the application of the F&L technique can induce significant species-dependent alterations in the enzymatic biomarkers of benthic macroinvertebrates, underscoring the need to incorporate these biomarkers into ecological risk assessments for F&L applications in eutrophic reservoirs.