Exploring the distribution patterns of macroinvertebrate signature traits and ecological preferences and their responses to urban and agricultural pollution in selected rivers in the Niger Delta ecoregion, Nigeria

Macroinvertebrate signature traits' and ecological preferences' distribution patterns and their responses to urban and agricultural pollution were explored in rivers-draining urban-agricultural catchments within the Niger Delta ecoregion of Nigeria. Physico-chemical variables (water temperature, electrical conductivity, depth, flow velocity, dissolved oxygen, biochemical oxygen demand, nitrates and phosphates) were sampled alongside macroinvertebrates in 17 sites of 11 rivers for a period of five years (2008-2012). Physico-chemically based classification using principal component analysis classify selected sites into least impacted sites (LIS), moderately impacted sites (MIS) and heavily impacted sites (HIS). The results based on RLQ [physico-chemical variables (R), macroinvertebrate taxa (L) and traits and ecological preferences (Q)] and fourth-corner analyses showed that preference for permanent attachment, high sensitivity to oxygen depletion, moderate sensitivity to oxygen depletion and large body size (> 20-40 mm) which were associated with LIS were also positively correlated with DO; thus, they were deemed sensitive to urban-agricultural pollution. Detritus (CPOM) and very small body size (< 5 mm) that were associated with HIS were deemed tolerant to urban-agricultural pollution. Box plots and Kruskal-Wallis test revealed that all sensitive traits and ecological preferences were not significantly different between LIS, MIS and HIS (p > 0.05) except for large body size, while tolerant traits CPOM and very small body size were significantly highest at HIS (p < 0.05). Generally, the study observed differential patterns in the distribution of traits and ecological preferences to urban-agricultural pollution.