Sessile rotifers (Rotifera) exhibit strong seasonality in a shallow,eutrophic Ramsar site in Mexico

To better understand the sessile rotifer community of a shallow, eutrophic lake, we monitored over a 1‐year period the monthly changes in the density and diversity of rotifers on the roots of the common water hyacinth, Eichhornia crassipes, which served as a representative hydrophyte. Selected physical and chemical parameters of the water were also determined. Mean annual density of all sessile species was 630 individuals per ml. Species of Collothecacea (n = 7) were most abundant. Of the 12 species of Flosculariaceae (Flosculariidae), Sinantherina socialis occurred seasonally, while Ptygura beauchampi was most common across all seasons. The Shannon–Wiener diversity index was highest (H′ = 2.8) in April, but decreased in January (H′ = 1.3). Applying the concept of the guild ratio (functional‐based analysis) we found that raptorial species (Collothecacea) were dominant over most of the year (June–February), while microphagous Flosculariidae were dominant during the warm, drier season (March–May). BEST (optimal matching of biota to environment, including stepwise search) analysis and canonical correspondence revealed that temperature, dissolved oxygen, pH, turbidity, and transparency strongly influenced sessile rotifer dynamics. We also found significant correlations between the density of some species and physicochemical variables. These species included Collotheca ambigua, C. coronetta, C. ornata, C. campanulata, C. tenuilobata, and Stephanoceros millsii in the Collothecacea; and Beauchampia crucigere, Limnias melicerta, L. ceratophylli, Ptygura crystallina, P. melicerta, and Sinantherina ariprepes in the Flosculariidae. Our study shows that the communities of sessile rotifers were structured by abiotic factors and that the guild ratio is useful for understanding the relationship between sessile rotifers and their substrata.