Nitrogen is unlikely to consistently limit primary productivity in most tropical lakes

Despite mounting evidence that tropical lakes may experience an array of phytoplankton nutrient limitation regimes, references to low-latitude lakes being predominantly nitrogen limited remain common in the literature. To assess the current understanding of nutrient limitation regimes in tropical lakes, we performed a literature review with the following objectives: First, quantify and summarize observations of nitrogen (N), phosphorus (P), and colimitation in the collected studies. Second, identify common drivers of tropical nutrient limitation regimes. Third, provide literature-informed recommendations for future research efforts into nutrient limitation of tropical lakes. We report that not only is N not the dominant limiting nutrient in the reviewed lakes, but tropical lakes exhibit a wide range of nutrient limitation regimes, and there is often considerable heterogeneity of the dominant limiting nutrient within an individual lake. This heterogeneity is driven largely by seasonal patterns of water column stratification and precipitation, land use and land cover (LULC), and the interaction of these system characteristics with lake morphology. To accurately characterize nutrient limitation in tropical aquatic ecosystems, assessments need to include sampling across space and time in order to capture within-lake spatial heterogeneity and both inter- and intra-annual temporal variation. Whenever possible, both inferential and experimental approaches should be used in concert to determine nutrient limitation due to methodological limitations.

Automated summary

Despite common beliefs that low-latitude lakes are predominantly nitrogen limited, a literature review reveals that tropical lakes exhibit a wide range of nutrient limitation regimes, with considerable heterogeneity within individual lakes. The dominant limiting nutrient in these lakes is influenced by factors such as seasonal stratification, precipitation, land use, land cover, and lake morphology. To accurately characterize nutrient limitation, future research efforts should include spatial and temporal sampling to capture within-lake heterogeneity and both inter- and intra-annual variation. Both inferential and experimental approaches should be used to overcome methodological limitations in determining nutrient limitation.