Long-term variability in deposited fine sediment and macroinvertebrate communities across different land-use intensities in a regional set of New Zealand rivers

Macroinvertebrate communities in running waters are commonly used as bioindicators of fine sediment pollution, but few studies evaluate impacts across multiple years. We used a 5-year dataset from 46 rivers in Southland, New Zealand to investigate the consistency of the relationship between deposited fine sediment and stream macroinvertebrates across three categories of agricultural land-use intensity (low, medium, and high). We also compared the performance of four widely used invertebrate stream health metrics and their recently developed sediment-specific counterparts. Linear and non-linear regressions were fitted and effect sizes were interpreted to identify biologically meaningful relationships (r2 ≥ 0.1). Sites within medium-intensity catchments showed the greatest number of such relationships (29 of 40 cases), compared to low- (8) or high-intensity catchments (23). Invertebrate metrics responded more frequently, and mostly negatively, to increasing sediment in medium- and high-intensity catchments. Overall, sediment-specific metrics performed better than their widely used counterparts. Our findings show that land-use intensity influences the multi-year dynamics of deposited fine sediment and the corresponding stream invertebrate responses. These temporal dynamics can be substantial and should be considered in future stream biomonitoring efforts.

流水生境中的大型无脊椎动物（macroinvertebrate）群落常被用作细泥沙污染的生物指示物，但现有研究鲜有针对其跨多年度影响的评估。本研究依托新西兰南地大区46条河流的5年监测数据集，探究了沉积细泥沙与溪流大型无脊椎动物之间的关联一致性，分析覆盖低、中、高三类农业土地利用强度梯度。此外，本研究还对比了四类广泛应用的无脊椎动物溪流健康指数，及其新近开发的泥沙专属对应指标的表现效能。研究通过拟合线性与非线性回归模型，并结合效应量解读，以识别具有生物学意义的关联（决定系数r²≥0.1）。相较于低强度集水区（8组有效关联）与高强度集水区（23组），中强度集水区内的有效关联数量最多，达40组中的29组。在中、高强度集水区中，无脊椎动物健康指数对泥沙含量升高的响应更为频繁，且整体呈负向关联。总体而言，泥沙专属指标的表现优于其通用对照指标。本研究结果表明，土地利用强度会影响沉积细泥沙的多年动态特征，以及与之对应的溪流无脊椎动物响应模式。这类时间动态特征往往较为显著，未来的溪流生物监测工作应将其纳入考量范畴。