Species-specific phytotoxicity and greenhouse growth responses to dewatered fish-processing wastewater sludge

Dewatered sludge from fish-processing wastewater treatment contains recoverable nutrients, but evidence for direct agricultural reuse remains limited and is often weakened by pseudoreplication or unpaired chemical and biological measurements. We reanalyzed raw seed-bioassay and greenhouse data to evaluate species-specific phytotoxicity and growth responses. A 1:10 sludge-water extract was tested with lettuce (Lactuca sativa), cucumber (Cucumis sativus) and arugula (Eruca sativa) across four sampling blocks, with three control and three extract plates per block. Greenhouse responses of lettuce and arugula were evaluated under four soil treatments: lime-amended control (T1), lime plus sludge (T2), lime plus mineral NPK (T3), and sludge without lime (T4). Block-normalized germination indices averaged 344.7 ± 267.7% for lettuce, 184.3 ± 16.2% for cucumber and 164.1 ± 13.4% for arugula. The exact four-block sign-flip test was inconclusive (minimum attainable two-sided p = 0.125), highlighting limited inferential resolution despite mean indices above 100%. In the greenhouse, lettuce shoot traits did not differ among treatments; root length was lower in T4 than T1 at the nominal endpoint level, but not after across-endpoint false-discovery-rate adjustment. Arugula showed strong treatment responses: T2 produced the largest leaf number, root length, and shoot fresh and dry masses, while T4 was generally intermediate. These findings support crop-specific agronomic potential rather than a general safety claim. Field validation, matched soil/sludge chemistry, pathogen assessment and contaminant bioavailability are required before recommending agricultural application.脱水污泥（dewatered sludge）来自水产加工废水处理过程，含有可回收的营养物质，但直接农业回用的相关证据仍较为有限，且常因伪重复（pseudoreplication）或化学与生物测量不匹配而削弱可信度。本研究重新分析了原始种子生物测定（seed-bioassay）与温室试验数据，以评估物种特异性的植物毒性（phytotoxicity）与生长响应。我们以1:10的污泥水浸提液（sludge-water extract）对生菜（Lactuca sativa）、黄瓜（Cucumis sativus）和芝麻菜（Eruca sativa）开展试验，共设置4个采样区组，每个区组包含3个对照组平板与3个浸提液组平板。针对生菜与芝麻菜的温室生长响应，我们设置了4种土壤处理组：石灰改良对照组（T1）、石灰+污泥组（T2）、石灰+矿质NPK肥组（T3）以及无石灰污泥组（T4）。经区组标准化后的发芽指数（germination indices）平均值为：生菜344.7±267.7%，黄瓜184.3±16.2%，芝麻菜164.1±13.4%。精确的四区组符号翻转检验（sign-flip test）结果无定论（可获得的最小双侧p值为0.125），这表明尽管平均发芽指数高于100%，但推论分辨率有限。温室试验中，生菜的地上部性状在各处理组间无显著差异；在名义终点水平下，T4组的根长低于T1组，但经跨终点错误发现率（false-discovery rate, FDR）校正后，该差异不再显著。芝麻菜则表现出显著的处理响应：T2组的叶片数、根长以及地上部鲜重与干重均为最高，而T4组的各项指标通常处于中间水平。本研究结果支持不同作物具有差异化的农艺应用潜力，而非笼统的安全断言。在推荐其农业应用前，仍需开展田间验证、匹配的土壤/污泥化学分析、病原体评估以及污染物生物有效性（bioavailability）研究。