Relationships between ecological risk indices for metals and benthic communities metrics in a macrophyte-dominated lake

With the aim of evaluating and comparing the correlation relationship between metal pollution and benthic structural and functional metrics, we carried out samplings of three anthropogenic disturbance levels at eight sites located in the Lake Baiyangdian that are strongly influenced by wastewater discharge (Sites 1 and 2), aquaculture and densely populated villages (Sites 3, 6, and 8), and the least human disturbances (Sites 4, 5, and 7). Benthic communities were studied in eight sample sites, and Cu, Ni, Pb, Zn, Hg, Cd, and Cr were simultaneously determined. The potential ecological risk index (RI) was calculated by Hakansonʹs methodology. The results showed that the RI for all three habitats was lower than 94, and they are in decreasing order: Habitat 1, Habitat 2, and Habitat 3. When the three sampling seasons were compared, August appeared to show the highest risk, followed by April and November. For the periphyton metrics, the best correlation was detected between chlorophyll c/chlorophyll a (Chl c/a) ratio and Eri Hg (r = −0.851, p < 0.01); for the benthic macroinvertebrate metrics, the best correlation was established between Eri Hg and community similarity index (CSI) (r = −0.983, p < 0.01). When periphyton and benthic macroinvertebrate metrics were compared, benthic macroinvertebrate metrics appeared to be more sensitive, especially the metrics of number of diptera taxa (NDT), community loss index (CLI), and CSI. Our results suggest that the benthic community would be used in biomonitoring for heavy metal pollution in the Lake Baiyangdian, China.