Comparative population dynamics of six brachionid rotifers (Rotifera) fed seston from a hypertrophic, high altitude shallow waterbody from Mexico

Abstract

In hypertrophic waterbodies, seston may be an important food for planktonic rotifers. Therefore, we hypothesized that seston in the hypertrophic waterbody (Lake Xochimilco, State of Mexico) supports high diversity and density of rotifers. To test this, we conducted growth experiments using six rotifer species (Brachionus bidentatus, Brachionus budapestinensis, Brachionus calyciflorus, Brachionus caudatus, Brachionus havanaensis and Plationus patulus) cultured on three seston size fractions (< 3, 3–15 and < 15 µm) for 15 days. The three fractions of seston contained 3.15, 6.30, and 9.45 μg C ml⁻¹, respectively. The physical and chemical variables of the waterbody were fairly stable during the study period. Brachionus budapestinensis, B. calyciflorus and B. caudatus showed negative growth rates when cultured on seston size of 3–15 or < 15 µm, while B. bidentatus had negative r on < 3 µm particle size. Brachionus havanaensis and P. patulus were well adapted to feed on different sizes of seston, while B. budapestinensis and B. caudatus had higher growth on < 3 µm particle size. These results explain the high diversity and density of brachionid rotifers in this waterbody where they coexist by partitioning the available seston.