Acute Effects Of Single And Mixed Polycyclic Aromatic Hydrocarbons Associated To Oil Spills On The Copepod Oithona Davisae . Carlos Barata1, Albert Calbet 2, Enric Sainz 2, Laura Ortíz 3, Josep Maria Bayona 3. 1 Laboratory of Environmental Chemistry, UPC, Terrassa 2 Dept. Biologia Marina i Oceanografia, CMIMA, CSIC, Barcelona 3 Dept of Environmental Chemistry, IIQAB-CSIC, Barcelona

Acknowledgements Financial Support: MEC Spanish project PETROZOO (VEM2003-20037). MEC R y C contract to Carlos Barata and Albert Calbet

Objectives Develop a modelling framework to predict the toxicity of mixture combinations of petrogenic PAHs in copepod species

Overview – in brief Effects of crude oil spills in marine planktonic food webs??? zooplankton species constitute the major food source for larval fish

Overview – in brief Polycyclic aromatic hydrocarbons (PAHs) 1. Most toxic and persistent components of class 2 fuel oils (Prestige) 2. Occur in complex mixtures Environmental fate Log Kow Toxicity – EC50 Toxicity by non-polar narcosis 1.Toxicity = F (1/log Kow) 2.Toxicity complex mixtures is additive Effect PAHs

Methods Test Species: Oithona davisae Chemicals: Analysis: SP -HPLC-UV Naphthalene, 1-methylnaphthalene, 1,2-Dimethylnaphthalene Phenanthrene,1-methylphenanthrene,3,6-dimethylphenanthrene Fluorene, Dibenzothiophene, Pyrene Analysis: SP -HPLC-UV Measured variables: Lethal , Narcosis– after 48 h (%)

Experimental design Exposure scenarios Individual exposures 10 PAHs Mixture combination of only 9 PAHs using an equitox ratio Ci = EC50j / n ; n= 9; Cj = 1/9 TUj Experimental conditions: No food supply, filtered sea water (38 0/00) 20 oC

Data analysis [ ] EC % Mobile = mobile control ´ + EC PAH Modeling % responses: Allosteric decay function EC i % Mobile = mobile control ´ 50 [ ] i + i EC PAH 50 50 100 Survival PAHs (mmol/L)

Data analysis å b log a 50 1 + ´ = K EC Log c Modelling single and mixture toxicities (EC50) of PAHj: b log a 50 1 + ´ = owj j K EC Log Kow EC50 Single - Quantitative Structure Activity Relationship (QSAR) å = n j ECx c 1 1, For cj = EC 50j /n; 1 = 50% Mixture - Concentration Addition model

Results- Single solutions Naphthalenes (% mobile vs Control) Narcosis, survival N N1 100 50 10 20 30 40 20 40 60 80 N2 100 50 5 10 15 PAHs (mmol/L)

Results- Single solutions Phenanthrenes (% mobile vs control) Narcosis, survival P 100 50 3 6 9 P1 100 50 1 2 3 PAHs (mmol/L)

Results- Single solutions Rest of PAHs (% mobile vs control) Narcosis, survival F DBT 100 50 2 4 6 8 10 2 4 Ft Py 100 50 0.0 0.3 0.6 0.9 0.0 0.2 0.4 0.6 PAHs (mmol/L)

Results- QSAR Survival Narcotization R2 =0.9 EC 50( mmol/L) 1 Log = 1 Ft 0.5 1 Log = 1 ´ log K - 5 Py EC 50 owj 1.0 j DBT 2.0 N2 EC 50( mmol/L) P1 P 5.0 F N1 20.0 N R2 =0.9 60.0 3.0 3.5 4.0 4.5 5.0 5.5 Log K ow

Mixture of 9 PAHs at their EC50/9 Results- Mixtures Mixture of 9 PAHs at their EC50/9 Survival Narcotization 125 EC 50 = 1.1 (0.9-1.3) 100 (% mobile vs control 75 50 25 1 2 3 9 å EC50 j Toxic Units = 1 = 9 j = 1

Conclusions 1. Allosteric decay function predicted accurately acute responses 2. Acute responses were inversely related to log Kow QSAR 9 PAH = Daphnia magna QSAR >100 non polar narcotics 3. Mixture toxicity of PAHs was additive following the CA model.

Risk Assessment Implications Naphthalene Alkylated Naphthalenes 1000 Highest 100 Prestige EC 50 (m g/L) 10 1 Background 0.1 1 10 100 1000 Number Mixture components

Future Work Derive QSAR models for sublethal responses 2.9 log 0.9 50 1 - ´ = owj j K EC Log Clearance rates (feeding) 3 4 5 6 182 14 N N2 mg/L Kow Prestige 2 . How toxicity of real samples (elutriates or water –accommodated fractions of fuel Oil) can be predicted from Chemical analysis using QSAR models

Thanks END Environmental Toxicology and Chemistry. Volume 24, No. 11, November 2005.