Transitional and freshwater bioassessments: One site, two perspectives? J.M. Neto a,⇑ , M.J. Feio a , H. Teixeira a , J. Patrício a , S.R.Q. Serra a , J.N. Franco b , A.R. Calapez a , E. Constantino a a IMAR – Institute of Marine Research, Marine and Environmental Research Centre, Faculty of Sciences and Technology, University of Coimbra, 3004-517 Coimbra, Portugal b CIIMAR, Rua dos Bragas 269, 4450-123 Porto, Portugal article info Keywords: FSTZ Oligohaline–freshwater zone Benthos WFD Pollution sensitivity Quality status abstract The freshwater–saltwater-transition-zone was analysed using two different sampling protocols and assessment methodologies, developed for freshwater and estuaries, to compare their agreement level in terms of community composition and quality assessments. The use of different protocols resulted in significant differences in macroinvertebrate communities, in index scores and initially in quality classes. After modifications in the sensitivity scores of the IBMWP and AMBI indices (average scores or the use of a score of the other index when both were present), the differences were largely reduced and quality clas- ses became coincident for the assessments provided by IPtIs and BAT tools. Such harmonisation of quality assessments for adjacent water categories (e.g., large rivers vs. transitional waters), exemplified here as an harmonisation in one of the metrics comprised in the assessment tools, is essential as it has direct implications on the expansion and accomplishment of River Basin Management Plans committed by the Water Framework Directive. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction In Europe, the assessment of the ecological integrity of aquatic systems has been extensively investigated in recent years, mainly prompted by the need to implement the Water Framework Direc- tive (WFD, 2000/60/EC). This directive established a framework for the development of integrated policies for the protection and enhancement of water quality status within all European water bodies by taking into account biological, physical–chemical and hydro-morphological quality elements. The obligation to use the WFD supports evident progress in the knowledge of biological communities from freshwater, transitional and coastal waters throughout Europe (Birk et al., 2012). However, the type of infor- mation produced within different water body categories could be quite heterogeneous. Often, different research teams, despite hav- ing similar scientific objectives, work in specific and well-defined habitats, use different sampling strategies for the same biological quality element and employ diverse classification methodologies to infer the ecological quality of each water category. This is due to what we may call the ‘‘historical context’’ of bioassessment, which has resulted in distinct expertise teams with specific sam- pling strategies adapted to habitat conditions and analytical methodologies. On the other hand, there is a growing demand to look at the aquatic environment as an integrated unit that is made up of several water bodies with clear and distinct features that have transition zones (sensu Yarrow and Marin, 2007), where attributes are shared between adjacent areas and, simultaneously, show new and unique properties. Often, due to several different constraints, these transition zones that are geographically stuck between the traditional ‘‘domains of expertise’’ have been modestly investi- gated. An increasing number of researchers (e.g., Rundle et al., 1998; Attrill and Rundle, 2002) consider the freshwater–saltwater transition zone (FSTZ) to be one of these neglected ecological boundaries that could also be one of the most biologically produc- tive sections of a river (Vincent and Dobson, 1999). These transi- tion zones could be areas where important changes occur in the community, such as the reduction in abundance of mayflies and some feeding groups (Marshall and Bailey, 2004) and the concom- itant increase in dominance of other groups in the community with the salinisation of freshwaters (Cushing et al., 1983; Brown et al., 1998). Although few studies have assessed and/or discussed the macrobenthic conditions at this interface area (e.g., Attrill and Run- dle, 2002; Cortelezzi et al., 2007; Sousa et al., 2008; Medeiros et al., 2012; Thompson et al., 2012), information regarding subtidal ben- thic communities indicates that the FSTZ is characterised by a low- er species diversity when compared to higher salinity areas (Jordan and Sutton, 1984; Teixeira et al., 2008; Medeiros et al., 2012). In the scope of the WFD, ecological quality status classifications need to be coherent and consistent between regions, biological quality elements and water categories (WFD, 2000/60/EC). How- ever, for practical reasons, the aquatic environment has been arti- ficially divided into smaller parts: ground and surface waters, 0025-326X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.marpolbul.2013.10.048 ⇑ Corresponding author. Tel.: +351 239855760; fax: +351 239823603. E-mail address: jneto@ci.uc.pt (J.M. Neto). Marine Pollution Bulletin 78 (2014) 153–164 Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul