Iron Distribution in the Subtropical North Atlantic: The Pivotal Role of Colloidal Iron

Abstract

Key Points Size‐fractionation reveals that colloidal iron is more important than soluble iron for distribution of dissolved iron in North Atlantic Colloidal iron is the predominantly active species at key supply and removal processes of the dissolved iron cycle Global comparison suggests that the colloidal iron fraction in mesopelagic zone is determined by the local lithogenic contribution

The Importance of Water Mass Transport and Dissolved‐Particle Interactions on the Aluminum Cycle in the Subtropical North Atlantic

“…First, dAl in the upper 100 m displays a strong concentration gradient with values increasing westward from 13 to 49 nmol/kg between 31° and 58°W. This concentration gradient correlates well with that of the dissolved iron from the same study (Kunde et al., 2019). Second, a marked dAl minimum (<15 nmol/kg) was observed across the entire GApr08 zonal section between 700 and 1,500 m depth.…”

“…This would suggest that up to 50% of the measured dAl concentration at Snakepit can be attributed to the hydrothermal vent. Note that a dissolved iron concentration maximum at 3,300 m at station 4 has also been attributed to hydrothermal venting (Kunde et al., 2019). Hydrothermally derived dAl has been previously reported for the MAR (up to 53 nmol/kg at the TAG vent site, Lunel et al., 1990; Measures et al., 2015).…”

“…Dust transport and deposition is also seasonally dependent (Prospero et al., 2014). In summer, dust transport occurs at higher altitudes leading to relatively low dust deposition in the eastern tropical Atlantic, but maximum dust deposition in the western tropical Atlantic (Jickells et al., 2016; Kunde et al., 2019; Powell et al., 2015; Prospero et al., 2014). The MERRA‐2 model also showed a higher dust deposition flux to surface waters of the western Atlantic compared with the east for July 2017 (Figure S2), while over 3 years, the trend is reversed (Figure 6).…”

Enhanced trace element mobilization by Earth’s ice sheets

“…3). Colloidal species of trace metals appear more important than soluble species in supply and removal processes in oceanic and coastal systems (97), and this will almost certainly depend on the mineralogy of the colloid/nanoparticles usually included in the filterable fraction (41).…”

Co-occurrence of Fe and P stress in natural populations of the marine diazotroph &lt;i&gt;Trichodesmium&lt;/i&gt;

“…Nitrogen fixation is not the only way that Trichodesmium can acquire fixed N (Dyhrman et al, 2006;Küpper et al, 2008;Mills et al, 2004;Sañudo-Wilhelmy et al, 2001). In culture, Trichodesmium can be grown on multiple nitrogen sources including urea; in fact, it has been reported that nitrogen fixation provides less than 20 % of the fixed N demand of cells, and a revised nitrogen fixation model suggests that Trichodesmium takes up fixed N in the field (McGillicuddy, 2014;Mulholland and Capone, 1999).…”