Contrasting impacts of warming and browning on periphyton

Abstract

Northern lakes are becoming warmer and browner due to increasing colored dissolved organic matter (cDOM) concentrations that affect algal growth through light inhibition and nutrient supplementation. Still, attached algae (periphyton) are often neglected in field and mesocosm studies despite their tendency to outgrow algae in the water column (phytoplankton). Consequently, impacts of browning and warming on periphyton are understudied, and it is unclear to what extent periphyton utilizes pelagic nutrients. This study shows that periphyton growing on nutrient-poor substrates efficiently utilizes pelagic nutrients associated with browning. However, while periphyton accrual increased with increasing cDOM and associated nutrients, the accrual decreased with warming, likely due to thermal compensation mechanisms and/or community shifts. Browning and warming thus strongly affect periphyton accrual, but in contrasting ways.

Experimental warming and browning influence autumnal pelagic and benthic invertebrate biomass and community structure

“…Another potential mechanism may be increased periphyton acting as an alternate food source. A study conducted within the same experimental system in 2018 found that enclosures with greater DOC and nutrients had increased periphyton production (Puts et al, 2023). Daphnia sp.…”