Hydrobia ulvae imposex levels at Ria de Aveiro (NW Portugal) between 1998 and 2007: a counter-current bioindicator? Susana Galante-Oliveira, * Isabel Oliveira, M ario Pacheco and Carlos M. Barroso Received 30th April 2009, Accepted 7th September 2009 First published as an Advance Article on the web 13th October 2009 DOI: 10.1039/b908597a Imposex expression in prosobranch gastropods has been widely used as a biomarker of tributyltin (TBT) pollution. Estuaries have been described as the most affected areas by this problem since they usually enclose the main TBT sources—ports, dockyards and marinas—resulting from the compound’s application as a biocide in antifouling paints on ships. Using Hydrobia ulvae as a bioindicator, the current work addresses the most reliable methods to reduce the influence of critical variables, such as the animals’ size, on imposex levels assessment for TBT pollution monitoring and presents its temporal trends from 1998 to 2007 in Ria de Aveiro (NW Portugal) to evaluate the effectiveness of recent legislation applied to reduce TBT environmental levels. H. ulvae imposex levels did not decrease in this estuarine system during the last decade despite the implementation of the EU Regulation No. 782/2003. Instead, there was a global significant increase in the percentage of females affected by imposex and a slight increase of the vas deferens sequence index (VDSI), contrasting with what has been described for other bioindicators in the same study area. These results show that different biology/ecology traits determine distinct routes of TBT uptake and/or bioaccumulation, pointing the importance of choosing the bioindicator depending on the compartment that is being monitored (sediment vs. water). Sediment ingestion as feeding habit is discussed and pointed as a reason to choose H. ulvae as a bioindicator of TBT pollution persistence in sediment. It is therefore predicted that the response of different prosobranch species around the world may diverge according to the compartment that is being monitored and that female masculinisation may not be completely eradicated in the near future due to TBT persistence in sediments. Introduction Ria de Aveiro is a shallow estuarine system located in NW Portugal covering an area of 66 to 83 km 2 depending on the tide level. 1 This system has a high economical potential, supporting fishing and aquaculture activities and providing conditions for the established industry, shipyard, ports and marina facilities. In addition, Ria de Aveiro is classified as a special protected area by the European Union (EU) nature and biodiversity policy ‘Natura 2000 Network’. 2 Hence, this is an ecosystem of consid- erable importance, requiring active management of its environ- mental quality. Tributyltin (TBT) pollution has been monitored in Ria de Aveiro in a regular basis since 1998 in order to evaluate its ecological impact and temporal evolution in response to succes- sive legislative actions to banish the use of this organotin (OT) compound from antifouling formulations. 3–6 The first EU action was to forbid the application of organotin based antifouling paints (hereafter designated as ‘‘OT paints’’) on boats <25m in length through the Directive 89/677/EEC. 7 However, this measure was ineffective in many areas where the naval traffic included larger vessels, as it was the case of Ria de Aveiro in which TBT levels remained almost unaltered for several years after the Directive’s transposition in 1993. 3,8,9 In 2001, the International Maritime Organization (IMO) adopted the ‘International Convention on the Control of Harmful Antifouling Systems on Ships’ (AFS Convention), 10 which called for a worldwide prohi- bition on the OT paints application in all kind of vessels by the CESAM & Department of Biology, University of Aveiro, 3810-193 Aveiro, Portugal. E-mail: susana.oliveira@ua.pt; Fax: +351 234426408; Tel: +351 234370350 ext. 22752 (LEME) Environmental impact Tributyltin (TBT), a biocide largely applied in antifouling paints since the late 60s, is one of the most toxic substances ever delib- erately introduced to the marine environment by mankind. One of the best documented adverse impacts of TBT in non-target organisms is imposex—the superimposition of male sexual characters in females. Legal restrictions on the use of tributyltin have been applied over the last decades till a definitive global ban in 2008. The current work points out that while some gastropods species show a decrease of imposex following the amelioration of TBT levels in the water column as a consequence of the ban, others that live and feed on sediment (e.g. Hydrobia ulvae) may not recover for many years due to long term persistence of TBT in sediment. 500 | J. Environ. Monit., 2010, 12, 500–507 This journal is ª The Royal Society of Chemistry 2010 PAPER www.rsc.org/jem | Journal of Environmental Monitoring Downloaded by EAWAG-EMPA LIBRARY on 28 November 2012 Published on 13 October 2009 on http://pubs.rsc.org | doi:10.1039/B908597A View Article Online / Journal Homepage / Table of Contents for this issue