A number of factors will influence the Fe:Al ratio of suspended and sinking particles, including the differential scavenging of iron and aluminium from the dissolved phase (Moore and Braucher, 200
cool , the photo-reduction and release of iron from particulates into the dissolved phase (Zhu et al., 1993), the biological enhancement of iron dissolution through biological processing (Hutchins et al., 1993) and the chemical enhancement of iron dissolution through complexation to natural organic ligands (Kraemer et al., 2005). All of the processes can and will alter the Fe:Al ratio of particulates, and timescales for these
gamma-Secretase inhibitor IX processes to occur are also likely to vary. For example, depending on physio-chemical conditions, processes affecting the Fe:Al ratio might vary from minutes to days for particulate organic
matter whereas it is likely to be hours to months for lithogenic material (Wuttig et al., 2013). As mentioned, we used a constant Fe:Al ratio of 0.18 to ascribe the lithogenic and biogenic iron pools, this value is close to the value of 0.21 ± 0.03 (n = 23, one outlier, 0.89, removed) obtained for Harbour sediments from the North Island, New Zealand (Stoffers et al., 1983). However, we acknowledge that a variable Fe:Al may be more appropriate for such non steady-state conditions, such as those that can occur during a phytoplankton bloom, but we lack the knowledge to fully define how such ratios vary temporally and spatially at the FeCycle II study site.
