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The European Marine Strategy Framework Directive (MSFD) requires EU Member States (MS) to achieve Good Environmental Status (GEnS) of their seas by 2020. We address the question of what GEnS entails especially with regard to the level at which targets are set (descriptors, criteria, indicators), to scales for assessments (regional, sub-divisions, site-specific), and to difficulties in putting into practice the GEnS concept. We propose a refined and operational definition of GEnS, indicating the data and information needed to all parts of that definition. We indicate the options for determining when GEnS has been met, acknowledge the data and information needs for each option, and recommend a combination of existing quantitative targets and expert judgement. We think that the MSFD implementation needs to be less complex than shown for other similar directives, can be based largely on existing data and can be centred on the activities of the Regional Seas Conventions.

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Over the last few decades, the excessive growth of macroalgae and decline of seagrass beds, associated with increased eutrophication, has become a worldwide problem. It is known that submersed aquatic vegetation (SAV) offers stable habitats, allowing the continuous availability of food and protection against predators and contributing to biodiversity, sediment stability and water transparency when compared to areas covered by macroalgae mats. In the Mondego estuary (Portugal), several mitigation measures (nutrient-load reduction, seagrass-bed protection and freshwater-circulation enhancement) were implemented in 1998 in order to promote the recovery of the seagrass beds and the entire surrounding environment following a long period of eutrophication. Here the success of this restoration project is evaluated by comparing the water nutrient concentrations, the extent of seagrass cover and the dynamics of the bivalve Scrobicularia plana before and after the implementation of the management measures. During the period in which environmental quality declined, S. plana's adult abundance, total biomass and growth production also declined, parallel with the almost total disappearance of Zostera noltii. After the implementation of management measures, dissolved nutrients and green macroalgal blooms were much reduced, and seagrass beds started to recover. The S. plana population also responded positively, becoming more structured (including individuals of all age classes), with higher biomass and growth production.

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The feeding ecology, growth and spatialetemporal abundance and distribution of Pomatoschistus microps (Krøyer, 1838) and Pomatoschistus minutus (Pallas, 1770) were studied between June 2003 and June 2004, based on beam trawl surveys and macrobenthic samples conducted in the Mondego estuary, Portugal. Polychaetes, molluscs and amphipods were the most important items in the diet of P. microps, while for P. minutus the dominant preys were polychaetes, mysids and decapods. Pomatoschistus microps' recruitment lasted for six months and was composed of three new cohorts per year. Pomatoschistus minutus had an uncommon long reproductive season, from April to November, and population segregation was found, corresponding to the two reproductive peaks. Populations of both species were composed mainly of 0-group individuals with sand gobies presenting a more extended life span. In the Mondego estuary, inter-and intra-specific spatial segregation occurred between the two species and between the 0C and 1C age groups of P. microps. Ó 2005 Elsevier Ltd. All rights reserved.Keywords: Pomatoschistus; diet overlap; life cycle; competition; resource partitioning; Mondego estuary IntroductionHigh fish abundance concentrated in particular areas, is a common feature in estuarine fish communities (Elliott et al., 2002). Consequently, co-occurrence of several similar morphological types (e.g. species of Soleidae, Mugilidae, Gobiidae) with overlap of ecological niches within the communities is expected. Spatial and temporal distribution, abundance patterns of fish assemblages as well as resource partitioning, are therefore, important and interesting issues for understanding the structure and dynamics of these communities (Cabral, 2000). Competition exists when the requirements of two or more individuals for a particular resource exceed the supply of that resource in the environment; or, if their demands do not exceed the supply, but they compete directly to obtain this resource. The study of diet is often used to evaluate competition between fish species (Elliott et al., 2002).Trophic and habitat segregation are among the most important aspects of resource partitioning in fish communities but it has been difficult to assess and prove the main force behind this process (Ross, 1986a). Evidences of coexistent Gobiidae species exhibiting vertical spatial segregation, temporal segregation in spawning and absence of niche shifts when one species was temporarily absent have been reported by NorteCampos and Temming (1994). The Gobiidae is a particularly successful family in both tropical and temperate seas, well represented in estuarine and freshwater environments. Gobiidae present more than 2000 species (Bouchereau and Guelorget, 1998) and virtually all gobies exhibit demersal eggs, male parental care and highly variable number of spawnings per season (Miller, 1984).In the Mondego estuary, four species of Gobiidae are present: Pomatoschistus microps (Krøyer, 1838), Pomatoschistus and Miller, 1966). Although it is usually an annual spe...

The Mondego estuary, a shallow warm-temperate intertidal system located on the west coast of Portugal, has for some decades been under severe ecological stress, mainly caused by eutrophication. Water circulation in this system was, until 1998, mainly dependent on tides and on the freshwater input of a small tributary artificially controlled by a sluice. After 1998, the sluice opening was effectively minimised to reduce the nutrient loading, and the system hydrodynamics improved due to engineering work in the upstream areas. The objective of the present study was to evaluate the effect of the mitigation measures implemented in 1998. Changes to the hydrodynamics of the system were assessed using precipitation and salinity data in relation to the concentrations of dissolved inorganic nutrients, as well as the linkage between dissolved N:P ratios and the biological parameters (phytoplankton chlorophyll a concentrations, green macroalgal biomass and seagrass biomass). Two distinctive periods were compared, over a ten year period: from January 1993 to January 1997 and from January 1999 until January 2003. The effective reduction in the dissolved N:P atomic ratio from 37.7 to 13.2 after 1998 is a result of lowered ammonia, but not the oxidised forms of nitrogen (nitrate plus nitrite), or increased concentrations of dissolved inorganic phosphorus. Results suggest that the phytoplankton is not nutrient limited, yet maximum and mean biomass of green macroalgae was reduced by one order of magnitude after the mitigation measures. This suggests that besides lowering the water residence time of the system, macroalgal growth became nitrogen limited. In parallel to these changes the seagrass-covered area and biomass of Zostera noltii showed signs of recovery.

The biological features, population dynamics and secondary production of Carcinus maenas were studied between June 2003 and June 2004 in four areas within the Mondego estuary, Portugal. Benthic samples were collected monthly, during the night, at high water of spring tides using a 2-m beam trawl, and plankton samples were collected monthly, during the day, at high tide with a Bongo net. Only the first zoeae stage of C. maenas larvae was found in the plankton; it was collected at all sampling stations throughout the year. A continuous pattern of benthic recruitment was observed in the upstream areas of the estuary with the highest peaks occurring in the spring 2004. Females carrying eggs were also caught through the year, although mainly in downstream areas. Juveniles' sex-ratio was favourable to males at almost all the sites sampled. Ventral carapace colour varied between green and orange-red, with the proportion of the green morphotype increasing with the increasing distance from the mouth of the estuary. The proportion of crabs in moult also increased from downstream to upstream areas. For both sexes the crab population showed a similar size structure throughout the year. The upstream areas of the estuary were characterized by the dominance of juveniles, with adults migrating to downstream areas. The average annual production of C. maenas, P (growth production), was estimated at 0.08 g m ÿ2 y ÿ1 AFDW, and the average annual biomass (B) was estimated at 0.058 g m ÿ2 , resulting in a P=B ratio of 1.4.