Aquatic Toxicology 146 (2014) 230–238 Contents lists available at ScienceDirect Aquatic Toxicology jou rn al hom epage: www.elsevier.com/locate/aquatox PAH effects on meio- and microbial benthic communities strongly depend on bioavailability J. Fredrik Lindgren a,∗ , Ida-Maja Hassellöv a , Ingela Dahllöf b a Department of Shipping and Marine Technology, Chalmers University of Technology, 41296 Gothenburg, Sweden b Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, 405 30 Gothenburg, Sweden a r t i c l e i n f o Article history: Received 29 May 2013 Received in revised form 20 November 2013 Accepted 21 November 2013 Keywords: Bioavailability PAH Community composition Inorganic nutrient flux Marine sediment Nitrification Denitrification a b s t r a c t The effects of anthropogenic pollutants in dissimilar habitats can vary depending on differences in bioavailability. The factors determining bioavailability are not yet fully understood. This study was performed to evaluate whether analysis of total PAH concentrations in sediments is a satisfactory mea- surement to indicate environmental effects or if bioavailability is needed to be taken into account. We have here performed a 60-day experiment, where nominal PAH concentrations of 1300 g/kg sediment were added to three different marine sediments. Meiofaunal and microbial communities were analyzed for alterations in community response at 30 and 60 days. Results showed that bioavailability of PAHs varied between the three different sediments. Nonethe- less, the petroleum addition gave rise to significant negative effects on all three sediments at both time points. The two direct measurements of toxicity on the microbial community, potential nitrification and denitrification, displayed a lower effect of the PAH addition in the muddy sediment at both time points, compared to the other two sediment types. No effects were seen in the analysis of meiofaunal community structure. Measurements of PAH bioavailability in the three sediment types concurred with the results from the microbial community, revealing a lower bioavailability in the muddy sediment compared to the other two sediment types, 34% compared to sandy and 18% compared to organic at day 0. At day 60 it was 61% lower compared to sandy and 20% lower compared to organic. The negative effects of the PAH addition on the microbial nitrogen cycle were in six out of eight cases best correlated to the amount of alkylated bioavailable PAH in the sediments, and thus microbial nitrogen cycle is a possible good indicator for assessing PAH-induced stress. The results presented here have implications for risk analysis studies of petroleum-contaminated marine sediments; consequently, sediment characteristics and its effects on bioavailability are important to include. In addition, these results add to the understanding that bioavailability measurements of PAHs are a more correct assessment compared to measurements of total PAH concentrations, and need to be included when estimating effects of PAHs in marine benthic communities. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Petroleum and its different distillation products enter the marine environment by for example shipping activities, petroleum extraction, and natural seepage (Farrington and McDowell, 2004). The petroleum components often accumulate in marine sedi- mentary habitats through sedimentation of heavier fractions or of suspended particles that the components have adsorbed to (Kingston, 2002; Rogowska and Namiesnik, 2010). At low concen- trations sub-lethal effects can be induced in biota by the most toxic fraction of petroleum, the polycyclic aromatic hydrocarbons (PAHs) (Martinez-Gomez et al., 2010; NRC, 2003; Wells et al., ∗ Corresponding author. Tel.: +46 317722664; fax: +46 317722647. E-mail address: f.lindgren@chalmers.se (J.F. Lindgren). 1995). These effects can manifest themselves by lowered fecundity and growth, cancerogenic effects and lowered resistance to other stresses (Fleeger et al., 2003; Hack et al., 2007). Typically, measurements of total PAH content are performed when assessing habitats affected by petroleum pollution (Mehler et al., 2011). However, total concentrations may not be very indica- tive of effects, as bioavailability of the compounds has to be taken into account (Akkanen et al., 2012). Bioavailability varies depending on the physical, chemical and biological characteristics of the habi- tat and determines the extent of which compounds absorbs onto, or into and across biological membranes (available for uptake), and is often expressed as a fraction of the total amount of pol- lutant the biota is exposed to (Fairbrother et al., 2007; Heijden and Jonker, 2009). PAHs are likewise affected by bioavailability conditions. However, it is not well understood how and to what extent the bioavailability of PAHs varies between sediments with 0166-445X/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.aquatox.2013.11.013