Submerged plants may have substantial growth in shallow water lakes under nitrogen deposition: a theoretical investigation

Understanding shallow water lakes is important because they are not only subjected to a number of natural and anthropogenic stressors but are also able to switch from clear states with high levels of biodiversity to dominance by suspended sediments, phytoplankton, or floating plants. Such switches are often influenced by high levels of nitrogen deposition, which may reduce the diversity of submerged plant communities, suppressing benthic animal and plant life. Therefore, it is important to predict potential effects of nitrogen on such a change. I modeled competition for light and nutrients between floating and submerged plants under low and high nutrient levels. Both types of plants were randomly chosen in their trait space by varying their average trait values by +/-25%. Surprisingly, I found that submerged plants could perform better under high nitrogen by having substantial growth rates. Further, I found that responsiveness to nitrogen deposition is greater in shallow lakes with low biomass than high biomass. My results suggest that shallow lakes with low productivity may respond strongly to nitrogen deposition. Moreover, albedo may increase in the future over shallow lakes. Thus, future warming over shallow lakes may be higher than current predictions. Earth System Models should allow the trait values of submerged and floating plants to vary when making predictions about future climatic conditions.