Light color and nutrient availability alter trophic transfer from algae to zooplankton

Jake Swanson , Jeff Dudycha

Freshwater plankton communities experience both natural variation of light color and nutrient availability and shifts due to eutrophication and brownification. These changes can alter algal community structure, but whether variation of light color impacts trophic transfer from algae to zooplankton is unknown because most research ignores color and focuses on light intensity. We used microcosms inoculated with natural algal communities to test whether differences in light color and nutrients alter trophic transfer to zooplankton. We found that light color is an important driver of differences in Daphnia survival and trophic transfer, with the effects of nutrients and trophic pathways differing among light colors. As lakes experience eutrophication and brownification, understanding how shifts in light color impact food webs, and whether these effects are mediated by nutrient availability, is essential to predicting how ecosystem functioning may change in response to these two phenomena.