Pergamon PII: S0025-326X(98) 00074-5 Marine Pollution Bulletin. Vol. 36, No. 10. pp. 833-839, 1998 © 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain 01125-326X/98/$19.110+0.1~1 Inhibition of Barnacle Settlement by the Environmental Oestrogen 4-nonylphenol and the Natural Oestrogen 17# Oestradiol Z. BILLINGHURST*t¶, A. S. CLAREt, T. FILEMANt:, J. MCEVOY§, J. READMAN~ and M. H. DEPLEDGE* *Plymouth Environmental Research Centre, University of Plymouth, Drake Circus, Plymouth, Devon PL 4 8AA, UK tMarine Biological Association of the UK, Citadel Hill, Plymouth, Devon PL1 2PB, UK ~Centre for Coastal Marine Sciences, Plymouth Marine Laboratory, Prospect Place, West Hoe, Plymouth, Devon PL1 3DH, UK §Environment Agency, Kings Meadow House, Kings Meadow Road, Reading, Berkshire RG 1 8DQ, UK The present study examines the effect of a known environmental oestrogen, 4-nonylphenol, on the settle- ment of the cypris larva of the barnacle, Balanus amphitrite. Cypris larvae were exposed to 4-nonyl- phenol in a nominal concentration range of 0.01-10.0 pg I-~. Definitive concentrations of 4-nonylphenol in the test solutions were determined by GC/MS. Cyprid settlement was reduced significantly within this concentration range, following incubation at both 25°C and 28°C for 24-48 h. A naturally occurring oestrogen, 1711 oestradioi, was used as a positive control, in the concentration range 0.01-10.0 lag i-L Larval settle- ment was inhibited by 1711 oestradiol, but the trend was the opposite to that seen with 4-nonylphenol. No evidence of endocrine disruption was demonstrated, but significant inhibition of larval settlement by both 4-nonylphenol and 1711 oestradiol indicated that the compounds may have toxic effects at environmentally realistic and naturally occurring concentrations. The potential for endocrine disruption being more signifi- cant at different developmental stages in barnacles is discussed. © 1998 Elsevier Science Ltd. All rights reserved Keywords: Barnacle settlement; Endocrine disrupter; 4-nonylphenol; Xeno-oestrogen; Vitellin Introduction Xeno-oestrogens (e.g. 4-nonylphenol, 4-NP) have been identified in, for example, sewage effluent, at levels that present a potential threat to local aquatic fauna (Abel et al., 1994a,b; Ahel and Giger, 1985; Jobling et ¶Author to whom all correspondence should be addressed. al., 1995; Palmer et al., 1998). Reproductive abnormali- ties in wildlife populations are some of the most obvious results of xeno-oestrogens (Colborn and Clement, 1992; Colborn et al., 1993). For example, links between environmental pollution and endocrine disruption have been suggested in relation to abnormal reproductive function in the Florida panther (Facemire et al;, 1995). Reproductive failure, female pairing and population decline in fish-eating birds may also be a result of endocrine disruption (Fry, 1995). In aquatic systems, examples include the dramatic effect that TBT has had on the development of the reproductive organs of neogastropods (Bettin et al., 1996; Oehlmann et al., 1996) resulting in a condition termed imposex. Imposex involves the imposition of male reproductive organs on female sex organs, potentially via the inhibition of cytochrome P450 dependent aromatase activity following endocrine disruption. A number of field and laboratory-based trials on fish species and other lower vertebrates (Purdon et al., 1994; Harries et al., 1994; Palmer et al., 1998; Sumpter and Jobling, 1995) have related a significant increase in the production of female egg-yolk protein, vitellogenin, to increased levels of xeno-oestrogens. The production of vitellogenin can be stimulated both by exposure to oestrogens and xeno-oestrogens in fish and other egg producing vertebrates (Sumpter, 1995; Palmer et al., 1998). A significant elevation of vitellogenin levels in fish is now recognised as a valuable biomarker of oestrogen exposure. To date, however, most of the available data for the impacts of xeno-oestrogens on aquatic fauna relates to fresh-water and estuarine fish (Sumpter et al., 1996; Harries et al., 1994; Heppell et al., 1995; Purdon et al., 1994). Nevertheless, there are preliminary indications that invertebrates may also be vulnerable to oestrogenic chemicals (Lee and Noone, 833