A time-series of iron and other micronutrients at Station ALOHA!

Sailing on the R/V Kilo Moana

Profiling the water column

How much iron sinks below the surface?

The Hawaii Ocean Time-series program travels to Station ALOHA 10 times a year. Over the next few years we will be tagging along to measure how iron, cobalt, manganese and other metals vary over the seasonal cycle, and how quickly these micronutrients cycle through the ocean.

Recent measurements have suggested that humans contribute a large source of iron to the atmosphere, that then falls on the ocean. Our time series observations will determine how this anthropogenic source compares to the natural processes that add iron to the oceans, such as deposition of desert dust.

Exploring the ocean's cobalt cycle

Of all the elements required for life, cobalt is found at the lowest concentrations in the oceans. As a result, we're still learning about its sources and sinks, and how phytoplankton acquire cobalt from seawater.

The end result of the marine cobalt cycle is the accumulation of massive quantities of cobalt in deep sea sediments, manganese nodules and crusts.

Building of mapping efforts conducting by the GEOTRACES program, we are investigating how cobalt in the oceans can changes between seasons and over 1000s to millions of years, using time-series observations and reconstructions of the past cobalt cycle from sediment cores.

Investigating micronutrient limitation with cultures and models

There's more iron in a drop of blood than there is in a ton of seawater, but life in the oceans still requires iron, and many other scarce metals, to grow.

Phytoplankton and other microbes have evolved to minimize these requirements, but no one has figured out how to replace the crucial roles of iron in photosynthesis and respiration.

By growing key phytoplankton in the lab, we can figure out how much iron they need and assess if they can survive in harsh marine environments where iron is lowest...