Warming, Not Light and nutrients, Could Drive Dissolved Oxygen Availability in Shallow Lake Ecosystems

Due to ongoing climate change, northern lakes have become warmer. Warming is predicted to influence dissolved oxygen (DO) availability, indirectly. However, few studies have investigated this indirect role of warming as a controlling factor of DO. Here, we experimentally tested impacts of warming (+ 3 C) on DO availability of four enclosures compared to four ambient-condition enclosures. The results showed that DO is significantly lower in the heated enclosures compared to the ambient, rather than light availability (PAR) was higher in the heated enclosures during the experiment. DO in both groups of enclosures was significantly correlated to water temperature (WT) and phytoplankton chlorophyll-a (Chl-a) concentration, not to PAR and nutrients. While phytoplankton Chl-a was not correlated to nutrient concentrations, it was negatively impacted by warming treatment compared to ambient enclosures. We can conclude that warming, rather than nutrient availability and increased PAR, could indirectly reduce DO for the whole-ecosystem in shallow lakes. Our results confirm the idea of including primary trophic levels in the studies that trying to understand drivers of DO availability with ongoing climate warming, especially, in shallow lake ecosystems.