Worldwide, there have been few comparative studies on rotifer communities in subtropical lakes. We studied changes in rotifer community structure over 1 year and its relationship to several physicochemical variables in five subtropical shallow lakes in East China, covering a nutrient gradient from mesotrophy to moderate eutrophy. In these lakes, the genera Brachionus, Lecane, and Trichocerca dominated the rotifer species composition, and Polyarthra dolichoptera, Keratella cochlearis, Filinia longiseta, T. pusilla, and Anuraeopsis fissa were the dominant species. With increased nutrient loading, total rotifer abundance and species dominance increased, indicating that rotifer abundance might be a more sensitive indicator of trophic state than species composition. Comparative analyses of the six rotifer community indices calculated in this study and redundancy analysis (RDA) revealed that the two slightly eutrophic lakes and the other two moderately eutrophic lakes exhibited a high degree similarity in community structure. This suggests that the trophic state of a lake determines the rotifer community structure. In contrast, in the two moderately eutrophic lakes, the mass ratios of TN:TP and the contents of TP suggested N-limitation and cyanobacteria dominance in phytoplankton communities might be possible. In these lakes TN played a more important role in shaping the rotifer community according to stepwise multiple regression and RDA. RDA analysis also suggested that rotifer species distribution was strongly associated with trophic state and water temperature, with water temperature being the most important factor in determining seasonality.

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In this study, the annual changes of rotifer communities were observed in six lakes belonging to tropical, subtropical, and warm temperate zones. Rotifers were classified into different functional groups based on the morphology of the corona and trophi. The abundance and biomass of each functional group were compared between climatic zones, and the driving environmental factors were analyzed. Analysis of similarities (ANOSIM), and similarity percentage analysis (SIMPER) indicated distinct separation in rotifer community structure between the three climatic zones. The subtropical zone showed more functional groups, higher abundance and biomass of dominant functional groups than tropical and warm temperate zones. Asplanchna abundance and water transparency were considered as the major factors affecting rotifer functional groups in all the three climatic zones. Chlorophyll a content (Chl-a) was more important in subtropical and warm temperate zones than in tropical zone. Water temperature mainly affected rotifer functional groups in warm temperate and tropical zones, but showed less effects in subtropical zone. In addition, NO 2 − -N content was an important factor in warm temperate zone, but not in subtropical and tropical zones. Overall, classification of functional groups could be a useful method to investigate the changes of rotifer community structure in different climatic zones.

Comparative analyses of rotifer community structure in freshwater lakes among different climatic zones are limited. In this study, six freshwater lakes located in warm temperate, subtropical and tropical zones were selected to investigate the annual dynamics of rotifer communities and their major driving factors. The results indicated that rotifer community structure did not exhibit significant seasonal variations. However, significant differences were observed among climatic zones. The species number and total density of rotifers were significantly higher in subtropical lakes than in lakes from other zones (p < .05). Both multidimensional scaling and detrended correspondence analysis revealed significant separation of tropical samplings from warm temperate and subtropical samplings, which was mainly caused by the higher temperature and lower chlorophyll a content in the tropical lakes. Further analyses indicated that rotifer community structure was mainly affected by water temperature, trophic indices and pH in the warm temperate zone but by chlorophyll a content and Secchi depth in subtropical lakes. In addition, only the Simpson index was significantly associated with Secchi depth and pH in tropical lakes. Overall, these results indicated great differences in annual dynamics of rotifer communities and their driving factors among warm temperate, subtropical and tropical zones.