We investigated phytoplankton Fe limitation using shipboard incubation experiments in the highߚnutrient South American eastern boundary current regime. Low ambient Fe concentrations (~0.1 nM) in water collected from the Humboldt and Peru Currents were supplemented with a range of added Fe levels up to 2.5 nM. Phytoplankton chlorophyll a, photosystem II photosynthetic efficiency, and nitrate and phosphate drawdown increased in...

In many temperate and annual grasslands, above‐ground net primary productivity (NPP) can be estimated by measuring peak above‐ground biomass. Estimates of below‐ground net primary productivity and, consequently, total net primary productivity, are more difficult. We addressed one of the three main objectives of the Global Primary Productivity Data Initiative for grassland systems to develop simple models or algorithms to estim...