Comparative analysis of ex situ zooplankton hatching methods

Abstract

Aims This study aims to analyze the efficiency of two novel methods for ex situ zooplankton hatching experiments, compared with a traditional one. Both proposed methods were specifically designed to minimize sediment resuspension during the sampling of hatched individuals when no previous egg isolation is performed. Methods Sediment samples were collected from shallow lakes, homogenized, and incubated for 18 days under stable laboratory conditions. The traditional method (1M) involved simple water filtration from incubated sediments. The so called “inverted funnel filtering” method (2M) includes an inverted funnel located above the sediment to trap zooplankton that passes through the funnel aperture, and the “levels filtering” method (3M) involves perforated plates above the sediment. The efficiency of each method was evaluated by analyzing the cumulative abundance and number of taxa in hatched total zooplankton, rotifers, and microcrustaceans, as well as the overall composition. Results The new proposed methods significantly favored higher abundances than 1M for total zooplankton and rotifers. Even more, 3M outperformed 2M in the case of microcrustacean hatching abundances. Conclusions Our findings suggest that despite all analyzed methods being suitable for studying zooplankton hatchings, the newly proposed methods incorporating internal structures to minimize sediment resuspension displayed increased capture efficiency.