Records of zooplankton from 101 alpine lakes in the Western Alps

Repeated samples of zooplankton were collected from 101 lakes over a period of 19 years (2006-2024; 1-52 samples per lake; 17-47 samples per year). The sampling frequency and duration varied among lakes; some lakes were sampled throughout the entire 19-year period, while others were sampled for shorter periods (ranging from 2 to 18 years), or in some cases, just for one year. Sampling was primarily conducted in late summer (August-October), to capture the late stage of seasonal succession when most zooplankton species reach their biomass peak. Many lakes were sampled multiple times during the ice-free season (2-8 times per year), including early summer, to account for the strong seasonal dynamics of zooplankton communities.
Samples were collected using vertical net hauls (from the bottom to the surface) at the deepest point of each lake, with a conical plankton net (30 or 40 cm diameter, 50 μm mesh). After collection, samples were promptly fixed in the field using either 70% ethanol or Lugol’s iodine solution. Zooplankton samples were then concentrated to a known volume, and 3-5 subsamples of volumes ranging from 0.05 to 1 mL were extracted after homogenization using a wide-bore pipette for counting.
Abundance estimates were back-transformed to represent the number of individuals per cubic meter of water. At the conclusion of these operations, the entire sample was examined to identify taxa present at very low-density levels, which may have passed unnoticed due to subsampling. If any were found, their density was fixed to a default value of 0.1 individuals per cubic meter of water.

All 101 lakes included in the dataset are located in the Western Alps.

All data, taxonomic identifications, and nomenclature were kept at the highest possible standards for this type of ecological research.