The role of algae (Isochrysis galbana) enrichment on the bioaccumulation of benzo[a]pyrene and its eects on the blue mussel Mytilus edulis O.S. Okay a , P. Donkin b, *, L.D Peters c , D.R Livingstone c a TU È BI . TAK, MRC, Energy Systems and Environmental Research Institute, PO Box 21, 41470, Gebze, Kocaeli, Turkey b CCMS, Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth PL1 3DH, UK c CCMS, Plymouth Marine Laboratory, Citadel Hill, Plymouth PL1 2PB, UK Received 17 February 1999; accepted 15 October 1999 ``Capsule'': An alga containing benzo[a]pyrene was fed to the common mussel Mytilus edulis to study transfer of organic contaminants in a simulated food chain. Abstract The role of algal concentration in the transfer of organic contaminants in a food chain has been studied using the ubiquitous model polycyclic aromatic hydrocarbon benzo[a]pyrene (BaP) as the contaminant, Isochrysis galbana as the phytoplankton food source, and the common mussel (Mytilus edulis) as the primary consumer. The eect of algal concentration on BaP uptake by M. edulis was determined by feeding M. edulis daily with I. galbana which had previously been kept in the presence of BaP for 24 h. Four combinations of concentrations of algae and BaP were used to give ®nal exposure concentrations of 30,000 or 150,000 algal cells ml 1 in combination with either 2 or 50 mg BaP l 1 . BaP concentrations were determined ¯uorometrically in rest tissues (excluding digestive glands) and digestive gland microsomal fractions of M. edulis after 1, 7 and 15 days exposure, and also in isolated algae. Potentially toxic eects of BaP on M. edulis were examined in terms of blood cell lysosomal membrane damage (neutral red dye retention assay) and induction of digestive gland microsomal mixed-function oxygenase (MFO) parameters [BaP hydroxylase (BPH) and NADPH-cytochrome c (P450) reductase activities]. BaP bioaccumulation in rest tissues (and to a lesser extent in digestive gland microsomes) of M. edulis increased with both increasing BaP and algal exposure concentrations, and over time, producing maximal bioconcentration factors in rest tissues after 15 days exposure to 150,000 algal cells ml 1 and 50 mg BaP l 1 of 250,000. The ®ve-fold higher concentration of algae increased BaP bioaccumulation by a factor of approximately 2 for 50 mg BaP l 1 at day 15. Blood cell neutral red dye retention time decreased linearly with increasing log 10 tissue BaP body burden, indi- cating an increased biological impact on M. edulis with increasing BaP exposure possibly due to a direct eect of BaP on blood cell lysosomal membrane integrity. An increase was seen in NADPH-cytochrome c reductase activity, and indicated in BPH activity, with 1 but not 7 or 15 days exposure to BaP, indicating a transient response of the digestive gland microsomal MFO system to BaP exposure. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Benzo[a]pyrene; Bioaccumulation; Blood cell; Isochrysis galbana; Lysosomal stability; Mixed-function oxygenase; Mytilus edulis 1. Introduction Polycyclic aromatic hydrocarbons (PAHs) con- taminate the aquatic environment and consequently those aquatic organisms consumed by man. Many PAHs are well-known mutagens and carcinogens. The US Environmental Protection Agency has recognised 16 PAHs as priority contaminants, and eight are included as possible carcinogens (Menzie et al., 1992). Benzo[a]- pyrene (BaP) is a potentially toxic contaminant and a powerful carcinogen. Mussels are suspension-feeders and ®lter food from the water column. All have a pumping and ®ltering mechanism capable of bioaccumulating lipophilic con- taminants including PAHs. During recent decades, much research has focused on contaminant levels in mussels. The ``Mussel Watch'' monitoring programme is one approach to assessing environmental contamination 0269-7491/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S0269-7491(99)00282-1 Environmental Pollution 110 (2000) 103±113 www.elsevier.com/locate/envpol * Corresponding author. Tel.: +44-1752-633100; fax: +44-1752- 633101. E-mail address: pd@wpo.nerc.ac.uk (P. Donkin).