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

Abstract

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.

Nutrient loading from a sustainably certified aquaculture operation dwarfs annual nutrient inputs from a large multi-use watershed, Lake Yojoa, Honduras

“…However, current ASC standards only require that operators maintain ≤ 65% change in diurnal dissolved oxygen, ≤ 20 μg L -1 P in and ≤ 4 μg L -1 Chlorophyll a in surface waters, and limit annual P loading to 20 kg per metric ton of Tilapia produced. An express limit on P only without consideration of N may be particularly problematic given the varied and heterogenous nutrient limitation landscape of tropical lakes (Fadum and Hall 2023).…”