The relationships between producers (e.g., macrophytes, phytoplankton and epiphytic algae) and snails play an important role in maintaining the function and stability of shallow ecosystems. Complex relationships exist among macrophytes, epiphytic algae, phytoplankton and snails. We studied the effects of snail communities (consisting of Radix swinhoei, Hippeutis cantori, Bellamya aeruginosa and Parafossarulus striatulus) on the biomass of phytoplankton and epiphytic algae as well as on the growth of three species of submerged macrophytes (Hydrilla verticillata, Vallisneria natans and one exotic submerged plant, Elodea nuttallii) in a 90-day outdoor mesocosm experiment conducted on the shore of subtropical Lake Liangzihu, China.

This dataset including morphological data of three group organisms: freshwater snails, macrophytes and epiphytic algae. In addition, the environmental parameters were included. Morphological data of snails is including biomass (g) and number (ind.). Morphological data of macrophytes is including biomass (g). Epiphytic algae data is including abundance (N, cells). Phytoplankton data is including biomass (Chl-a, μg/L).

Snail: All snail individuals (adults and offspring) were collected from the aquariums and the quantity and fresh mass were determined. Before weighing, the snails were drained and allowed to dry on absorbent paper for 5 min (wiping the surface of snails and letting the liquid drain from their body) and then gently blotting until the surface was dry to ensure consistency among the samples

Macrophytes: The macrophyte samples were carefully washed with distilled water at least three times. Then, the number of leaves in each sample was quantified (including the selected leaf for area measurement and algae collection). All samples were then dried to a constant weight in a drying oven at 60°C. The dry weight of biomass of the submerged macrophytes was determined using an electronic scale.

Epiphytic algae: Fifty leaves of H. verticillata, 50 leaves of E. nuttallii and 5 leaves of V. natans were carefully selected to ensure uniformity in growth state and size before placing each into a wide-mouth plastic bottle with 200 ml of pure water in the respective aquarium. Periphyton were removed with a banister brush in water and preserved in a well-labelled plastic container, with 2 mL of Lugol’s solution to fix them. The area of selected leaves was measured with an area meter (LI-3100C, LI-COR, USA). The epiphytic algae sample was centrifuged at 4000 rpm for 10 min, and the supernatant was discarded. Then, the volume was adjusted to 30 mL and mixed. The number and species of epiphytic algae were counted using a counting plate at 400× under an optical microscope. For each sample, 50 microscopic fields of vision were examined and counted. Species richness (S) of each sample was quantified as the number of species in the sample, and the abundance (N, cells).

Phytoplankton biomass: chlorophyll a (Chl-a) was measured with a handheld chlorophyll fluorometer probe (HYDROLAB DS5, HACH, United States) in the field tests.

Environmental parameters: For each aquarium, the water temperature (T), dissolved oxygen (DO), conductivity (Cond) and pH of the water were measured with a portable water quality monitor (PROPLUS, YSI, United States) in the field tests. Turbidity (Turb) was measured with a chromometer (DR900, HACH, USA). We collected 1 L water samples from each aquarium with depth integration (under water 30 cm) for chemical analysis and stored them on ice. Then, TN, TP and ammonia nitrogen (NH3-N) were analysed with a flow injection analyser (QC8500, LACHAT, USA). Chemical oxygen demand (COD) was analysed with a digestion solution for each corresponding parameter and landscape photometry (DR900, HACH, USA).

This dataset including morphological data of three group organisms: freshwater snails, macrophytes and epiphytic algae. In addition, the environmental parameters were included. There are no missing values in this dataset.