Data from: The importance of phytoplankton biomolecule availability for secondary production

The growth and reproduction of animals is affected by their access to
resources. In aquatic ecosystems, the availability of essential
biomolecules for filter-feeding zooplankton depends greatly on
phytoplankton. Here, we analyzed the biochemical composition, i.e., the
fatty acid, sterol and amino acid profiles and concentrations as well as
protein, carbon, nitrogen, and phosphorus content of 17 phytoplankton
monocultures representing the seven most abundant phytoplankton classes in
boreal and sub-arctic lakes. To examine how the differences in the
biochemical composition between phytoplankton classes affect their
nutritional quality for consumers, we assessed the performance of Daphnia,
on these diets. Furthermore, we defined the most important biomolecules
regulating the somatic growth and reproduction of Daphnia, expecting that
higher concentrations of certain biomolecules are needed for reproduction
than for growth. Finally, we combined these results with phytoplankton
field data from over 900 boreal and sub-arctic lakes in order to estimate
whether the somatic growth of Daphnia is sterol-limited when the natural
phytoplankton communities are cyanobacteria-dominated. Our analysis shows
that Daphnia grows best with phytoplankton rich in sterols, ω-3 fatty
acids, protein, and amino acids. Their reproduction follows food sterol
and ω-3 concentration as well as C:P-ratio being two times higher in
Daphnia feeding on cryptophytes than any other diet. Interestingly, we
found that a high dietary ω-6 fatty acid concentration decreases both
somatic growth and reproduction of Daphnia. When combined with
phytoplankton community composition field data, our results indicate that
zooplankton is constantly limited by sterols in lakes dominated by
cyanobacteria (≥40% of total phytoplankton biomass), and that the absence
of cryptophytes can severely hinder zooplankton production in nature.