Nutrient stoichiometry of linked catchment-lake systems along a gradient of land use

摘要: Summary 1. Catchments export nutrients to aquatic ecosystems at rates and ratios that are strongly influenced by land use practices, within can be processed, retained, lost the atmosphere, or exported downstream. The stoichiometry of carbon influence ecosystem services such as water quality, nutrient limitation, biodiversity, eutrophication sequestration in sediments. However, we know little about how varies along pathway from terrestrial landscapes through systems. 2. We studied nitrogen phosphorus three catchments contrasting (forest versus agriculture) column sediments downstream reservoirs. also related phytoplankton limitation abundance heterocystous cyanobacteria. 3. total N : P stream exports varied greatly among was 18, 54 140 (molar) forested, mixed-use agricultural catchment, respectively. Total mixed layers lakes less variable but ordered similarly: 35, 52 132 lake, In contrast, there variation systems C : N C : P catchment reservoir seston. 4. Phytoplankton forested lake were consistently N limited, those P shifted seasonally P- reflecting supply ratios. cyanobacteria biomass highest (potentially fixing) most abundant corresponding low ratios. 5. Despite large differences ratios, sediment burial (integrated over several decades) very remarkably similar (4.3–7.3) across budgets constructed for suggested denitrification could a major loss N, may help explain relatively buried sediment. 6. Our results show congruence between N : P, dominance cyanobacteria. retained insensitive stoichiometry, suggesting common set biogeochemical processes constrains use.