The effect of engineered iron nanoparticles on growth and metabolic status of marine microalgae cultures Eniko Kadar a, ⁎, Paul Rooks a , Cara Lakey a, b , Daniel A. White a a Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth PL1 3DH, UK b School of Biomedical and Biological Sciences, University of Plymouth, Drake Circus, Plymouth, UK abstract article info Article history: Received 9 August 2012 Received in revised form 7 September 2012 Accepted 7 September 2012 Available online 9 October 2012 Keywords: Zero-valent nano iron Nanoparticles Pavlova lutheri Isochrysis galbana Tetraselmis suecica Lipid profile Synthetic zero-valent nano-iron (nZVI) compounds are finding numerous applications in environmental re- mediation owing to their high chemical reactivity and versatile catalytic properties. Studies were carried out to assess the effects of three types of industrially relevant engineered nZVI on phytoplankton growth, cellular micromorphology and metabolic status. Three marine microalgae (Pavlova lutheri, Isochrysis galbana and Tetraselmis suecica) were grown on culture medium fortified with the nano-Fe compounds for 23 days and subsequent alterations in their growth rate, size distribution, lipid profiles and cellular ultrastructure were assessed. The added nano Fe concentrations were either equimolar with the EDTA-Fe conventionally added to the generic f/2 medium (i.e. 1.17 × 10 -5 M), or factor 10 lower and higher, respectively. We provide evi- dence for the: (1) broad size distribution of nZVI particles when added to the nutrient rich f/2 media with the higher relative percentage of the smallest particles with the coated forms; (2) normal algal growth in the presence of all three types of nZVIs with standard growth rates, cellular morphology and lipid content comparable or improved when compared to algae grown on f/2 with EDTA-Fe; (3) sustained algal growth and normal physiology at nZVI levels 10 fold below that in f/2, indicating preference to nanoparticles over EDTA-Fe; (4) increased total cellular lipid content in T. suecica grown on media enriched with uncoated nZVI25, and in P. lutheri with inorganically coated nZVI powder , when compared at equimolar exposures; (5) significant change in fatty acid composition complementing the nZVI powder -mediated increase in lipid content of P. lutheri; (6) a putative NP uptake mechanism is proposed for I. galbana via secretion of an extra- cellular matrix that binds nZVIs which then become bioavailable via phagocytotic membrane processes. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Engineered Fe-rich nanoparticles (NPs) are key multifunctional ma- terial applied in many different fields of modern technology including environmental remediation (reviews of Zhang, 2003; Mueller and Nowack, 2010), the food industry (Fidler et al., 2004), and medical diag- nostics (Cheng et al., 2005). Owing to their high chemical reactivity and capability to act as electron donors to catalyse a wide variety of reac- tions (Zhang, 2003) zero-valent iron nanoparticles (nZVI) in particular have been applied to decontamination of ground and surface waters, as well as industrial wastewaters polluted with a diverse group of com- pounds (Zhang, et al., 2010). In theory the use of nano-iron for in situ decontamination is more promising than in practise owing to issues re- garding oxidation and aggregation and gelation, which however are being constantly improved by stabilising agents applied on the ZVI NPs (Mueller and Nowack, 2010). With such a widespread produc- tion/usage and with improved stability engineered nZVIs inevitably reach aquatic ecosystems (Readman et al., 2011), which already are naturally enriched with colloidal iron nanoparticles (Whang and Dei, 2003). Phytoplankton is therefore naturally exposed to elevated levels of NPs, both natural (via cloud processing of mineral dusts/volcanic ash) and engineered forms (from green technologies and various ma- rine applications), but the mechanisms involved are not clear. Biological interactions especially in the case of the organic stabilising agents used to improve the mobility of nZVIs in the environment have been underestimated (Lerner et al., 2012) with potential negative impacts overlooked (Kadar et al., 2011, in press). Iron NPs can produce various reactive oxygen species (ROS) via Fenton-type reactions (LeBel et al., 1992) that cause oxidative injury to cells via lipid peroxidation and ox- idation of thiol groups on proteins and DNA (Kadar et al., 2010a, b; Kadar et al., 2011, in press; Keenan et al., 2009; Li et al., 2009; Auffan et al., 2008; Fernaeus and Land, 2005; Zhou et al., 2003). Paradoxically, Fe is also an essential micronutrient for phytoplankton as it is required in fundamental cellular functions like photosynthesis and respiration and consequently its availability controls phytoplankton productivity, community structure, and ecosystem functioning in vast regions of the global ocean (reviewed by Gledhill and Buck, 2012). The biological availability of Fe is highly dependent on its chemical speciation as Science of the Total Environment 439 (2012) 8–17 ⁎ Corresponding author. Tel.: +44 1752 633450 (direct); fax: +44 1752 633101. E-mail address: enik@pml.ac.uk (E. Kadar). URL: http://www.pml.ac.uk (E. Kadar). 0048-9697/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.scitotenv.2012.09.010 Contents lists available at SciVerse ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv