scholarly journals Variations of nitrogen and phosphorus limitation along the environmental gradient in alpine grasslands on the Northern Xizang Plateau

2021 ◽  
Vol 45 (5) ◽  
pp. 444-455
Author(s):  
Ning ZONG ◽  
Pei-Li SHI ◽  
Guang-Shuai ZHAO ◽  
Li-Li ZHENG ◽  
Ben NIU ◽  
...  
Keyword(s):  
Environmental Gradient ◽  
Phosphorus Limitation ◽  
Alpine Grasslands ◽  
Nitrogen And Phosphorus ◽  
Xizang Plateau

Soil C mineralization and temperature sensitivity in alpine grasslands of the Qinghai-Xizang Plateau

2014 ◽  
Vol 37 (11) ◽  
pp. 988-997 ◽  
Author(s):  
Li XU ◽  
Shu-Xia YU ◽  
Nian-Peng HE ◽  
Xue-Fa WEN ◽  
Pei-Li SHI ◽  
...  
Keyword(s):  
Temperature Sensitivity ◽  
C Mineralization ◽  
Alpine Grasslands ◽  
Soil C ◽  
Xizang Plateau

scholarly journals Active reconfiguration of cytoplasmic lipid droplets governs migration of nutrient-limited phytoplankton

2021 ◽  
Author(s):  
Anupam Sengupta ◽  
Jayabrata Dhar ◽  
Francesco Danza ◽  
Arkajyoti Ghoshal ◽  
Sarah Elisabeth Mueller ◽  
...  
Keyword(s):  
Lipid Droplets ◽  
Red Tide ◽  
Mechanical Energy ◽  
Optimal Growth ◽  
Active Role ◽  
Phosphorus Limitation ◽  
Vertical Movement ◽  
Nitrogen And Phosphorus ◽  
And Migration ◽  
Motile Species

As open oceans continue to warm, modified currents and enhanced stratification exacerbate nitrogen and phosphorus limitation, constraining primary production. The ability to migrate vertically bestows motile phytoplankton a crucial – albeit energetically expensive – advantage toward vertically redistributing for optimal growth, uptake and resource storage in nutrient-limited water columns. However, this traditional view discounts the possibility that phytoplankton migration may be actively selected by the storage dynamics when nutrients turn limiting. Here we report that storage and migration in phytoplankton are coupled traits, whereby motile species harness energy storing lipid droplets (LDs) to biomechanically regulate migration in nutrient limited settings. LDs grow and translocate directionally within the cytoplasm to accumulate below the cell nucleus, tuning the speed, trajectory and stability of swimming cells. Nutrient reincorporation reverses the LD translocation, restoring the homeostatic migratory traits measured in population-scale millifluidic experiments. Combining intracellular LD tracking and quantitative morphological analysis of red-tide forming alga, Heterosigma akashiwo , along with a model of cell mechanics, we discover that the size and spatial localization of growing LDs govern the ballisticity and orientational stability of migration. The strain-specific shifts in migration which we identify here are amenable to a selective emergence of mixotrophy in nutrient-limited phytoplankton. We rationalize these distinct behavioral acclimatization in an ecological context, relying on concomitant tracking of the photophysiology and reactive oxygen species (ROS) levels, and propose a dissipative mechanical energy budget for motile phytoplankton for alleviating nutrient limitation. The emergent resource acquisition strategies, enabled by distinct strain-specific migratory acclimatizing mechanisms, highlight the active role of the reconfigurable cytoplasmic LDs in vertical movement. By uncovering a mechanistic coupling between dynamics of intracellular changes to physiologically governed migration strategies, this work offers a tractable framework to delineate diverse strategies which phytoplankton may harness to maximize fitness and resource pool in nutrient-limited open oceans of the future.

scholarly journals Simulating the effects of phosphorus limitation in the Mississippi and Atchafalaya River plumes

2012 ◽  
Vol 9 (11) ◽  
pp. 4707-4723 ◽  
Author(s):  
A. Laurent ◽  
K. Fennel ◽  
J. Hu ◽  
R. Hetland
Keyword(s):  
Gulf Of Mexico ◽  
Primary Production ◽  
Inorganic Nitrogen ◽  
Circulation Model ◽  
Phosphorus Limitation ◽  
Early Summer ◽  
Nitrogen And Phosphorus ◽  
River Plumes ◽  
Northern Gulf Of Mexico ◽  
Plume Region

Abstract. The continental shelf of the northern Gulf of Mexico receives high dissolved inorganic nitrogen and phosphorus loads from the Mississippi and Atchafalaya rivers. The nutrient load results in high primary production in the river plumes and contributes to the development of hypoxia on the Louisiana shelf in summer. While phytoplankton growth is considered to be typically nitrogen-limited in marine waters, phosphorus limitation has been observed in this region during periods of peak river discharge in spring and early summer. Here we investigate the presence, spatio-temporal distribution and implications of phosphorus limitation in the plume region using a circulation model of the northern Gulf of Mexico coupled to a multi-nutrient ecosystem model. Results from a 7-yr simulation (2001–2007) compare well with several sources of observations and suggest that phosphorus limitation develops every year between the Mississippi and Atchafalaya deltas. Model simulations show that phosphorus limitation results in a delay and westward shift of a fraction of river-stimulated primary production. The consequence is a reduced flux of particulate organic matter to the sediment near the Mississippi delta, but slightly enhanced fluxes west of Atchafalaya Bay. Simulations with altered river phosphate concentrations (±50%) show that significant variation in the spatial extent of phosphorus limitation (±40% in July) results from changes in phosphate load.

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