Abstract
Indices of biotic integrity (IBIs) are widely used to assess aquatic ecosystem health. However, there are few studies on their relationships. Based on fish, macroinvertebrate and plankton survey data collected in the Ganjiang River system from 2016 to 2017, redundancy analysis (RDA) and canonical correspondence analysis (CCA) were used to analyze how the community structures of these organisms respond to environmental variables. The fish IBI (F-IBI), benthic macroinvertebrate IBI (B-IBI), and phytoplankton IBI (P-IBI) were applied to evaluate the health status of the aquatic ecosystem. A Kruskal–Wallis test (p < 0.05) and Spearman’s correlation coefficient analysis were performed to evaluate the spatiotemporal heterogeneity of the results. Our results suggested that the F-IBI-, B-IBI-, and P-IBI-based assessments indicated good, fair, and healthy Ganjiang River system ecosystem health statuses, respectively, and significant differences existed among these indices (p < 0.05). The main environmental factors affecting F-IBI, B-IBI, and P-IBI were different. At the temporal scale, the F-IBI and B-IBI were stable, while the P-IBI fluctuated obviously. The consistency between the F-IBI and B-IBI results was better than that between each of these indices and the P-IBI results, and the consistency was better on a larger scale. These research results show that comprehensive assessments based on multiple groups rather than a single group can better characterize the impacts of environmental pressures on water ecosystems.
Highlights
Freshwater, the lifeblood of human existence, has no substitute
This study demonstrates that the ecosystem health assessments performed based on different biological groups exhibited significant differences (p < 0.05)
The stepwise linear regression results showed that the main environmental factors affecting index of biotic integrity (IBI) were different, and that the factor affecting fish IBI (F-IBI) was elevation; those affecting benthic macroinvertebrate IBI (B-IBI) were the elevation, water temperature (WT), dissolved oxygen (DO), and NH3-N; and those affecting phytoplankton were the WT, NH3N, DO, CODCr, and total phosphorus (TP)
Summary
Freshwater, the lifeblood of human existence, has no substitute. in recent decades, human activities have caused rapid declines in the biodiversity of freshwater ecosystems [1] and have introduced serious environmental and social problems [2–4]. Fish-based indices include the preliminary reservoir fish assemblage index (RFAI) [11], the regional pressure index (RPI) [12], and the Ohio River Fish Index (ORFIn) [13]; macroinvertebrate-based indices include the Indice Biotique Macroinvertébrés de Guyane (IBMG) [14], the Semi-quantitative Multimetric Index (SMI) [15], the multimetric index (I2M2) [16], the phytoplankton-based indices Phytoplankton Index of Biotic Integrity (P-IBI) [17], new multimetric Index [18], and Index of Size spectra Sensitivity of Phytoplankton (ISS-Phyto) [19] Most of these indicators are targeted at specific regions and based on a single biological group, while lacking in an overall evaluation of the ecosystem, which may ignore the multiple sources of environmental pressure
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