Developing and applying a macroinvertebrate‐based multimetric index for urban rivers in the Niger Delta, Nigeria

Urban pollution of riverine ecosystem is a serious concern in the Niger Delta region of Nigeria. No biomonitoring tool exists for the routine monitoring of effects of urban pollution on riverine systems within the region. Therefore, the aim of this study was to develop and apply a macroinvertebrate-based multimetric index for assessing water quality condition of impacted urban river systems in the Niger Delta area of Nigeria. Macroinvertebrate and physico-chemical samples were collected from 11 stations in eight river systems. Based on the physico-chemical variables, the stations were categorised into three impact categories namely; least impacted stations (LIS), moderately impacted stations (MIS) and heavily impacted stations (HIS). Seventy seven (77) candidate metrics were tested and only five: Hemiptera abundance, %Coleoptera+Hemiptera, %Chironomidae+Oligochaeta, Evenness index and Logarithm of relative abundance of very large body size (>40-80 mm) were retained and integrated into the final Niger Delta urban multimetric index (MINDU). The validation data set showed a correspondence of 83.3% between the index result and the physico-chemically-based classification for the LIS and a 75% correspondence for the MIS. A performance of 22.2% was recorded for the HIS. The newly developed MINDU proved useful as a biomonitoring tool in the Niger Delta region of Nigeria, and can thus be used by environmental managers and government officials for routine monitoring of rivers and streams subjected to urban pollution.

Methods
Seasonal datasets of macroinvertebrates collected between 2008 and 2012 in selected urban rivers in the Niger Delta ecoregion of Nigeria. 

The data has been processed and used in the development of macroinvertebrate-based multimetric index for urban rivers in the Niger Delta area of Nigeria.

尼日利亚尼日尔三角洲地区的河流生态系统城市污染问题，已成为该区域备受关注的严峻环境议题。目前，该区域尚无用于常规监测城市污染对河流系统影响的生物监测工具（biomonitoring tool）。为此，本研究旨在开发并应用一套基于大型底栖无脊椎动物（macroinvertebrate）的多指标指数（multimetric index），以评估尼日利亚尼日尔三角洲地区受城市污染影响的河流系统水质状况。

研究人员从8个河流系统的11个监测点位采集了大型底栖无脊椎动物样本与理化指标样本。基于理化指标，监测点位被划分为三类污染梯度：轻度污染点位（least impacted stations, LIS）、中度污染点位（moderately impacted stations, MIS）与重度污染点位（heavily impacted stations, HIS）。

本研究共测试了77项候选指标，最终保留5项并整合为尼日尔三角洲城市多指标指数（MINDU）：半翅目（Hemiptera）丰度、鞘翅目（Coleoptera）与半翅目占比之和、摇蚊科（Chironomidae）与寡毛纲（Oligochaeta）占比之和、均匀度指数（Evenness index），以及体型>40-80mm的大型个体相对丰度的对数。

验证数据集显示，该指数结果与基于理化分类的匹配度在轻度污染点位组为83.3%，中度污染点位组为75%，而重度污染点位组的匹配度仅为22.2%。

本研究开发的MINDU可作为尼日利亚尼日尔三角洲地区有效的生物监测工具，可供环境管理者与政府官员开展受城市污染影响的河流与溪流常规监测工作。

方法
2008年至2012年间，研究人员在尼日利亚尼日尔三角洲生态区选定的城市河流中采集了大型底栖无脊椎动物的季节性数据集。
本数据集已完成处理，并用于开发针对尼日利亚尼日尔三角洲地区城市河流的大型底栖无脊椎动物多指标指数。