Abstract
Periphytic diatoms play important functional roles in aquatic ecosystems. Their community compositions are widely used in water quality monitoring due to their wide distribution, short reproductive cycles, and sensitivity to environmental changes. In this study, 116 samples of periphytic diatom samples were collected from lakes in the lower reaches of the Yangtze River. The weighted average without tolerance down-weighting regression method was used to develop total phosphorus (r2 = 0.661), total nitrogen (r2 = 0.699), and chemical oxygen demand (r2 = 0.423) models, and the optimal and tolerance values of 78 periphytic species were calculated. Then, a new index, the comprehensive diatom index (CDI), was established on the basis of the optima and tolerances of these 78 species concerning the three environmental variables (TP, TN, and COD) to assess the water trophic status of the lakes in this region. According to the CDI, the trophic statuses of 8, 17, 23, 30, 22, and 14 sample sites were oligotrophic, mesotrophic, light eutrophication, moderate eutrophication, heavy eutrophication, and ultra-eutrophication, respectively. The CDI was more strongly correlated with the conductivity, pH, TP, TN, COD, and TDS than other diatom indices. These results demonstrate that the CDI is a useful metric for assessing the water trophic status of the lakes in the lower reaches of the Yangtze River.
Highlights
Diatoms have been studied as environmental indicators since the 19th century [1].In particular, periphytic diatoms are widely distributed worldwide and are very sensitive to changes in limnological variables, including temperature, pH, dissolved oxygen levels, salinity, conductivity, nutrient concentrations, and turbidity [2,3,4,5,6,7]
A total of 354 diatom species were identified in the samples from 116 sampling sites within 34 lakes, but only 78 species had relative abundances of greater than 1% and a frequency among sites of greater than four, which led to their inclusion in the subsequent analysis (Table S2)
A total of 83 samples were randomly selected as the experimental group, while 33 diatom samples were used as the control group
Summary
Periphytic diatoms are widely distributed worldwide and are very sensitive to changes in limnological variables, including temperature, pH, dissolved oxygen levels, salinity, conductivity, nutrient concentrations, and turbidity [2,3,4,5,6,7]. They occur on various substrates (e.g., stones, plants, and sediments) in most water bodies. They are key components of aquatic ecosystems and play fundamental roles in food webs [8,9,10]. It has been argued that diatoms are the best biological assessment index targets for assessing water quality [12,13,14,15,16,17]
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