Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul Diagnostic tool to ascertain marine phytoplankton exposure to chemically enhanced water accommodated fraction of oil using Fourier Transform Infrared spectroscopy Manoj Kamalanathan a, ⁎ , Kathleen A. Schwehr b , Laura Bretherton d , Jennifer Genzer a , Jessica Hillhouse a , Chen Xu b , Alicia Williams e , Peter Santschi b,c , Antonietta Quigg a,c a Department of Marine Biology, Texas A&M University at Galveston, Galveston, TX 77553, United States b Department of Marine Science, Texas A&M University at Galveston, Galveston, TX 77553, United States c Department of Oceanography, Texas A&M University, College Station, TX 77845, United States d Environmental Science, Mount Allison University, New Brunswick, E4L 1E4, Canada e Department of Marine Sciences, University of New England Biddeford, 04005, Maine, USA ARTICLE INFO Keywords: Macromolecules FTIR Phytoplankton Oil Dispersant ABSTRACT Phytoplankton alter their macromolecule composition in response to changing environmental conditions. Often these changes are consistent and can be used as indicators to predict their exposure to a given condition. FTIR- spectroscopy is a powerful tool that provides rapid snapshot of microbial samples. We used FTIR to develop signature macromolecular composition profiles of three cultures: Skeletonema costatum, Emiliania huxleyi, and Navicula sp., exposed to chemically enhanced water accommodated oil fraction (CEWAF) in artificial seawater and control. Using a multivariate model created with a Partial Least Square Discriminant Analysis of the FTIR- spectra, classification of CEWAF exposed versus control samples was possible. This model was validated using aggregate samples from a mesocosm study. Analysis of spectra and PCA-loadings plot showed changes to car- bohydrates and proteins in response to CEWAF. Overall we developed a robust multivariate model that can be used to identify if a phytoplankton sample has been exposed to oil with dispersant. 1. Introduction The 2010 Deepwater Horizon Oil Spill in the Gulf of Mexico was addressed by aerial and underwater application of the EPA-approved chemical dispersant Corexit (Kujawinski et al., 2011). After the spill, immense amounts of marine snow were visible both in surface waters and in sediment traps (Passow et al., 2012). Marine snow is char- acterized as visible aggregates formed as a result of the inter-cross- linking of exopolymeric substances (EPS) secreted by microbes, both phytoplankton and bacteria (Passow et al., 2012; Quigg et al., 2016). These microbes play an important role in dispersion and degradation of oil during a spill. As they constitute the bottom of the food chain, their association with oil and dispersant could lead to biomagnification and/ or bioaccumulation of toxic components transferred to the food web (Torres et al., 2008; Quigg, 2008). The exact mechanism of how a dispersant affects growth and development across trophic levels still remains to be established (Lönning and Hagström, 1976; Hagström and Lönning, 1977; Lewis and Pryor, 2013; Almeda et al., 2014a, b; Lively and McKenzie, 2014). These effects can nonetheless be observed far from the site of an oil spill and dispersant (i.e., Corexit) application such that it is likely to obfuscate the source. Therefore, an easy mode of detection to predict the exposure of phytoplankton and bacteria to chemically enhanced (Corexit) water accommodated oil fraction (CEWAF) would be very beneficial. Both phytoplankton and bacteria change their cellular macro- molecular composition depending on their growth environment. For example, several reports have suggested an increase in lipid and a de- crease in protein and chlorophyll concentrations in phytoplankton growing in nitrogen-limited conditions (Kamalanathan et al., 2016; Rodolfi et al., 2009; Griffiths and Harrison, 2009). Similarly, phosphate limitation has also been known to increase the lipid content in phyto- plankton (Kamalanathan et al., 2015; Sharma et al., 2012; Liang et al., 2013). In diatoms, silicate limitation has been found to induce lipid production (Jiang et al., 2012). This sort of consistency allows for prediction of the consequences of environmental growth conditions on phytoplankton, as recently reviewed by Finkel et al. (2016). Such characteristic changes in response to oil and/or dispersant is as yet not available. Fourier Transform Infrared (FTIR) spectroscopy is a method https://doi.org/10.1016/j.marpolbul.2018.03.027 Received 7 November 2017; Received in revised form 15 March 2018; Accepted 16 March 2018 ⁎ Corresponding author. E-mail address: manojka@tamug.edu (M. Kamalanathan). Marine Pollution Bulletin 130 (2018) 170–178 0025-326X/ © 2018 Published by Elsevier Ltd. T