This is one of few studies to comprehensively examine seasonality and phytoplankton nutrient deficiency in sub-tropical lakes over multiple years, to our knowledge. We tested whether phytoplankton communities in two sub-tropical impoundments in the mid-hills of Nepal were nitrogen (N)-, phosphorus (P)-, or co-deficient in N and P across pre-monsoon, monsoon, and post-monsoon seasons spanning a decade. Nutrient limitation to phytoplankton growth was assessed via in situ stoichiometry of N and P (N:P ratios) and nutrient stimulation experiments (NSEs). The experiments indicated co-deficiency of N and P in 97-100% of NSEs in all seasons. N-deficiency was common (>60% of N:P ratios and similar to 90% of NSEs) during the rainy monsoon, but P-deficiency occurred twice as often as N-deficiency during drier seasons (pre- and post-monsoon). These findings provide perspective for the ongoing debate over N and P as limiting nutrients in freshwater ecosystems by incorporating seasonality and corresponding hydrology. We also re-visit long-standing assumptions regarding the nutrient status of sub-tropical lakes. The warm, stratified season does not fully illustrate lake processes, and more research during dry periods will inform how seasonality affects phytoplankton nutrient deficiencies across aquatic systems.
1.Univ Missouri, Div Biol Sci, Columbia, MO 65211 USA 2.Univ Missouri, Sch Nat Resources, Columbia, MO 65211 USA 3.Univ Alberta, Civil & Environm Engn, Edmonton, AB T6G 1H9, Canada 4.Nepal Agr Res Council, Kathmandu, Nepal 5.Univ Michigan, CIGLR, Ann Arbor, MI 48108 USA
Recommended Citation:
Rowland, Freya E.,North, Rebecca L.,McEachern, Preston,et al. Phytoplankton nutrient deficiencies vary with season in sub-tropical lakes of Nepal[J]. HYDROBIOLOGIA,2019-01-01,833(1):157-172