Input of organic matter enhances degradation of weathered diesel fuel in sub-tropical sediments Agota Horel a,b,c, ⁎, Behzad Mortazavi a,b , Patricia A. Sobecky a a University of Alabama, Department of Biological Sciences, Tuscaloosa, AL 35487, USA b Dauphin Island Sea Lab, 101 Bienville Blvd, Dauphin Island, AL 36528, USA c Institute of Soil Sciences and Agricultural Chemistry, Center for Agricultural Research, Hungarian Academy of Sciences, Herman O. St. 15, Budapest 1022, Hungary HIGHLIGHTS • Marine derived organic matter addition substantially increased diesel minerali- zation. • The type of organic matter addition im- pacts mineralization of diesel. • The fastest diesel degradation rates were observed during the first week. • Plant derived organic matter addition increased the degradation rates margin- ally. • Hydrocarbonoclastic microorganisms were present in the sediment. GRAPHICAL ABSTRACT abstract article info Article history: Received 27 March 2015 Received in revised form 22 June 2015 Accepted 24 June 2015 Available online xxxx Editor. F.M. Tack Keywords: Diesel Biodegradation Biostimulation Proteobacteria Hydrocarbon We investigated different types of biostimulation practices to enhance degradation of weathered conventional diesel fuel in sandy beach sediments from coastal Alabama. Biodegradation rates were measured following the addition of either inorganic nutrients, or organic matter derived from either plant material (Spartina alterniflora) or fish tissue (Chloroscombrus chrysurus) both common to the region. The greatest hydrocarbon degradation rates were observed in the C. chrysurus amended treatments (k = 0.0119 d -1 ). Treatment with fish-derived organic matter increased the degradation rates by 104% as compared to control treatments, while inorganic nutrient ad- dition increased the degradation rates by 57%. The addition of plant derived organic matter, however, only mar- ginally enhanced the degradation rates (~7%) during the course of the study. Bacterial 16S rRNA analyses revealed that most sediment microorganisms belonged to the classes; Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Bacteroidetes. The most frequently abundant hydrocarbon degraders were mostly similar to Achromobater sp., Microbulbifer sp., Ruegeria sp., and Pseudomonas sp. © 2015 Elsevier B.V. All rights reserved. Science of the Total Environment 533 (2015) 82–90 ⁎ Corresponding author at: University of Alabama, Department of Biological Sciences, Tuscaloosa, AL 35487, USA. E-mail address: horel.agota@agrar.mta.hu (A. Horel). http://dx.doi.org/10.1016/j.scitotenv.2015.06.102 0048-9697/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv