Iron-Limited Phytoplankton?
No comments ICEBERG A43K, SOUTHERN OCEAN– The waters of the Southern Ocean are considered High Nutrient Low Chlorophyll (HNLC) waters. In spite of abundant dissolved nitrogen, phosphorus and silica, plant biomass is not very abundant and the nutrients are un-utilized.
One explanation for this is that the lack of micronutrients limits nutrient utilization, mostly iron (Fe). In this cruise Ben Twining and Hai Lin are testing the role of icebergs on phytoplankton growth through the release of iron from melting ice.
To conduct these tests, phytoplankton from around the icebergs are enriched with iron and compared with those grown in natural waters. Four- and two-liter transparent bottles are kept at zero degrees centigrade in blue light, imitating the light field in subsurface waters. The experiment is kept for 2 or 3 weeks, with sampling at fixed time intervals.
The experiment in the ‘light van.’
After the first week the growth rate is at a maximum for this temperature, about 1 cell division every 2 to 3 days. A suite of measurements are being taken to describe phytoplankton nutrient and iron uptake, growth, biomass accumulation, cell physiology and bacteria abundance and growth.
