Regulation of phosphorus bioavailability by iron nanoparticles in a monomictic lake

Abstract

Dissolved reactive phosphorous (DRP) in lake systems is conventionally considered to predominate over other dissolved P species, however, this view neglects an important set of interactions that occurs between P and reactive iron hydroxide surfaces. This study addresses the coupling of P with dispersed iron nanoparticles in lakes, an interaction that may fundamentally alter the bioavailability of P to phytoplankton. We used diffusive gradients in thin films (DGT) and ultrafiltration to study Fe-P coupling in the water column of a monomictic lake over a hydrological year. Fe and P were predominantly colloidal (particle diameters > ~5 nm < ~20 nm) in both oxic epilimnetic and anaerobic hypolimnetic waters, but they were both DGT-labile under sub-oxic conditions, consistent with diffusion and dissolution of Fe-and-P-bearing colloids within the DGT diffusive gel. During peak stratification, increases in Fe and P bioavailability were spatially and temporally coincident with Fe nanoparticle dissolution and the formation of a deep chlorophyll maximum at 5–8 m depth. These results provide a window into the coupling and decoupling of P with mobile iron colloids, with implications for our understanding of the behaviour of nutrients and their influence on phytoplankton community dynamics.

Growth at the limits: comparing trace metal limitation of a freshwater cyanobacterium (Dolichospermum lemmermannii) and a freshwater diatom (Fragilaria crotonensis)

“…Bioavailable trace metal concentrations in the culture media are estimated to be similar to levels reported in natural systems 37 , 57 . However, the results of culture experiments must be interpreted with care as growth media, in contrast to natural waters, do not contain multiple ligands, such as humic substances and low-molecular-weight (LMW) ligands, which are active in natural systems.…”

Potential use of engineered nanoparticles in ocean fertilization for large-scale atmospheric carbon dioxide removal

“…Due to their relatively high number density, and very high specific surface area and diffusivity, nanoparticles (1-100 nm) are probably bioavailable to phytoplankton in the ocean [12][13][14][15] . The important role of naturally occurring nanoparticles is already established in natural ocean fertilization [12][13][14][16][17][18][19] . For instance, natural iron (oxyhydr)oxide nanoparticles have been proposed as a source of bioavailable iron in fluxes from glaciers 14,15 , continental sediments 13 , volcanic ashes 12 and hydrothermal vent emissions 19 .…”

“…For instance, natural iron (oxyhydr)oxide nanoparticles have been proposed as a source of bioavailable iron in fluxes from glaciers 14 , 15 , continental sediments 13 , volcanic ashes 12 and hydrothermal vent emissions 19 . Natural nanoparticles may also supply other nutrients such as phosphorus 16 . These findings suggest that the use of engineered nanoparticles (ENPs) in AOF may lead to desirable efficiencies because of their nanocharacteristics, which resemble those of their natural counterparts.…”

Bioavailability of Colloidal Iron to Heterotrophic Bacteria in Sediments, and Effects on the Mobility of Colloid-Associated Metal(loid)s

“…Sedimentary colloids, as highly reactive and potentially mobile fractions of sediments, may play an important role in maintaining the balance of nutrients and contaminants in both sediment and water, and thus affect the quality of the overlying water and downstream rivers [9]. Additionally, the co-occurrence of colloids and microorganisms in the sediment or the water column makes the colloid-associated nutrients potentially bioavailable [12] and colloid-associated contaminants potentially soluble. Therefore, the bio-sequestration of nutrients from the colloids can lead to their solubilization and the solubilization of related elements (including contaminants, if any).…”