{"id":1671,"date":"2026-04-28T15:56:58","date_gmt":"2026-04-28T15:56:58","guid":{"rendered":"https:\/\/currents.bigelow.org\/?p=1671"},"modified":"2026-04-28T15:56:58","modified_gmt":"2026-04-28T15:56:58","slug":"field-notes-bermuda","status":"publish","type":"post","link":"https:\/\/currents.bigelow.org\/?p=1671","title":{"rendered":"Field Notes: Bermuda"},"content":{"rendered":"\n
\"\"
Postdoc Susanna Michael and SRS Ben Twining pose in front of the R\/V Atlantic Explorer<\/em> before setting sail from Bermuda in November.<\/figcaption><\/figure>\n\n\n\n

By Susanna Michael<\/strong>, Postdoctoral Scientist, Bigelow Laboratory for Ocean Sciences<\/p><\/p>\n\n\n\n

This March, I swapped Maine mud season for Bermuda spring \u2014 with plenty of sun and 70-degree temps \u2014 and set sail on the R\/V Atlantic Explorer<\/em> for a week of trace metal sampling.<\/p>\n\n\n\n

\"\"\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
The researchers enjoy beautiful warm-weather sunsets each night.<\/figcaption><\/figure>\n\n\n\n

As a postdoc with Senior Research Scientist Ben Twining, I\u2019m part of a team studying the role of dissolved organic carbon in the formation of what\u2019s called authigenic iron. This work builds on previous studies<\/a> that researchers in our group participated in to determine the importance of the \u201ccolloidal shunt,\u201d a proposed mechanism for moving iron from the surface to the deep ocean.<\/p>\n\n\n\n

Iron is an essential nutrient for phytoplankton \u2014 it\u2019s critical for photosynthesis, among other things \u2014 and while it is abundant in the Earth\u2019s crust (and on a rusty ship!), it\u2019s found in very small quantities in the ocean.<\/p>\n\n\n\n

It also has a complicated chemistry.<\/p>\n\n\n\n

In order for phytoplankton to use iron from the water, it must be either truly dissolved or bound to small organic molecules called ligands. Think about making pour-over coffee: the coffee that passes through the filter is your dissolved fraction; the grounds left behind are the particles.<\/p>\n\n\n\n

Historically, we have considered particulate iron in two pools. One pool is \u201cland derived,\u201d or lithogenic, which is chemically resistant to breakdown or use by phytoplankton. The other pool is called \u201clabile,\u201d and we think of it as largely comprised of biological particles.<\/p>\n\n\n\n

Lately, though, we\u2019ve been focused on a third pool of particulate iron. Authigenic iron is also labile, but formed in the water column through chemical precipitation and the aggregation of tiny <\/em>iron particles called colloids. We think that the formation of these particles may be facilitated by dissolved organic carbon in the seawater. Because iron is so important for phytoplankton growth, understanding this different form of iron and its role in the iron cycle is essential for creating models that better predict primary production.<\/p>\n\n\n