Comparing growth of the freshwater rotifer Brachionus calyciflorus in four differently modified versions of Guillard's WC medium

Abstract Rotifers and phytoplankton have been vastly used by scientists as model organisms in toxicological, eco-toxicological, ecological and other studies. In order to conduct experiments on interactions between animals and food organisms, it is necessary to develop a medium that adequately supports the growth of both algae and zooplankton without the need to alter the medium to accommodate either the algae or the animals. Several types of culture media have been developed to grow different types of organisms in particular phytoplankton and zooplankton. Little research has been carried out to compare the capacities and potentials of different types of media to rear these model organisms. Brachionus calyciflorus and Chlamydomonas reinhardtii were chosen as a model system to compare the carrying capacity of four types of media for algae and rotifers. Both of these are widely used as test organisms or together as a model system in various studies. All four types of media were modified versions of Guillard’s WC medium with #1 & #2 being based on tap-water and #3 & #4 based on Distilled water. Phytoplankton biomass was assessed by using different techniques including in-vivo fluorescence and absorbance, in-vitro chlorophyll fluorescence, pigments concentration estimates using absorbance spectra data and algae cell count. Rotifers’ growth was measured by counting and calculating the individuals per milliliter. In general, the algae grew reasonably well in all four media while rotifers only grew in the tap-water based media. Apart from some speculations, the definite reason for this significant difference in rotifer growth between tap-water based and distilled water based media is unknown and further research is needed to better explore and understand the features and capacities of different types of culture media.