Cascading effects of algal warming in a freshwater community

However, this hypothesis: a) potentially oversimplifies the relationship between algal PUFAs and temperature, and b) assumes that the nutritional requirements of consumers are not affected by temperature warming. Here we test these assumptions using a freshwater community (Scenedesmus algae, Daphnia zooplankton, Chaoborus insects). 4. We found that total algal PUFAs per unit cell size increased, but cell size decreased with warming, resulting no net effect of warming on PUFA per algal cell.

We also found a negative relationship between algal neutral lipids and temperature. Daphnia fed 12˚C-reared algae maintained higher population sizes than those fed 20˚C or 28˚C-reared algae, but the effect of algal food type diminished with increasing Daphnia rearing temperature. The indirect effects of cold-reared algae on the growth rate of Chaoborus predators were minor. 5.

These data highlight the importance of investigating the effects of temperature on both resource quality and on the nutritional needs of consumers. Our results suggest that at warmer temperatures, consumer nutritional requirements may be reduced. We caution against broad claims that the negative relationship between some algal PUFAs and temperature should result in overall declines in aquatic productivity with ongoing climate warming.

Methods

This was a laboratory experiment. Please see the manuscript for details.

Usage notes

All raw data used to create the results in the manuscript are included here.