Opportunistic macroalgae metrics for transitional waters. Testing tools to assess ecological quality status in Portugal J. Patrı ´cio * , J.M. Neto, H. Teixeira, J.C. Marques IMAR – Institute of Marine Research, c/o Department of Zoology, Faculty of Sciences and Technology, University of Coimbra, 3004-517 Coimbra, Portugal Abstract Macroalgae communities constitute one of the ecological quality elements for the evaluation of the ecological quality status (EQS) of coastal and transitional waters, required to implement the WFD. While these algae are natural components of estuarine systems and play important roles in several estuarine processes, macroalgal blooms are of ecological concern because they can reduce the habitat quality. Several works are being carried out to set standard methods for monitoring macroalgae blooms, in order to develop tools to derive EQS based upon this biological quality element. The aim of this paper is to apply the methodology described by Scanlan et al. [Scanlan, C.M., Foden, J., Wells, E., Best, M.A., 2007. The monitoring of opportunistic macroalgal blooms for the water framework directive. Marine Pollution Bulletin 55, 162–171] to a series of data assembled in the south arm of the Mondego estuary (Atlantic coast of Portugal) con- sidering two different ecological situations. Additionally, an alternative assessment method intended to be used when no biomass data are available was also tested. In general, both options captured the inter-annual variations in accordance with the system evolution. Option 2, less expensive and time-consuming, allowed an EQS evaluation with accurate results when biomass data were not available. The results suggest that sampling should be carried out from April to June. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: WFD; Transitional waters; Opportunistic macroalgal blooms; Metrics; Eutrophication; Portugal 1. Introduction The water framework directive (WFD) aims at achieving ‘‘good water status’’ for all European waters by 2015. The WFD requires member states to assess the ecological qual- ity status (EQS) of water bodies. The EQS will be based upon the status of the biological, hydromorphological and physicochemical quality elements, with the biological elements being particularly important. In coastal and tran- sitional waters, the biological elements to be considered are phytoplankton, macroalgae and angiosperms, benthos and fishes (the latter only in transitional waters) (EEC, 2000). Plant and animal communities are often used in ecolog- ical assessment as bioindicators of ecological status (Dauer, 1993; Bricker et al., 1999; Gibson et al., 2000; EEC, 2000), because long-term anthropogenic stress is often reflected at community level (Odum, 1985; Crowe et al., 2000). How- ever, the evaluation of the ecological status is often a diffi- cult task because of spatial and temporal community variability. Consequently, the central issue in the manage- ment of ‘‘high’’ valued transitional and coastal ecosystems (Constanza et al., 1997) is the identification of key signals that indicate the degree of human impact or ecological sta- tus (Crooks and Turner, 1999). Macroalgae communities constitute one of the ecologi- cal quality elements for the evaluation of the EQS of coastal and transitional waters, required to implement the WFD, the legislation targeted at sustainable management of the European aquatic environment (Panayotidis et al., 2004). Unfortunately, large blooms of opportunistic green macroalgae occur in estuaries throughout the world (e.g. Sfriso et al., 1992; Schramm and Nienhuis, 1996; Raffaelli 0025-326X/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2007.08.003 * Corresponding author. Tel.: +351 239 836386; fax: +351 239 823603. E-mail address: jpatricio@ci.uc.pt (J. Patrı ´cio). www.elsevier.com/locate/marpolbul Available online at www.sciencedirect.com Marine Pollution Bulletin 54 (2007) 1887–1896