The aim of this study was to establish the effect of temporal variation of the alga Caulerpa prolifera cover on the composition and stability of the associated crustacean community. Forty‐five crustacean species were found, amphipods and tanaidaceans being the most abundant groups. The stations were grouped mainly based on the gradient of algal cover, independently of location or sampling period (MDS analyses). Considering separately epifaunal and infaunal species, the epifauna occurred mainly at high cover (HC) and medium–low cover (MLC) stations, while the infauna occurred at MLC and unvegetated (UV) stations. Infaunal species were predominant in all stations and sampling periods, and the abundance and numbers of epifaunal species showed a clear dependence of algal cover. To quantify the loss of biodiversity due to the plant cover variations, we applied the average and variation in taxonomic distinctness (Δ+ and Λ+, respectively). The HC stations, especially those with fewer algal cover variations along the study period, showed few fluctuations of Δ+,and Λ+ was usually located near mean; however, UV stations tended to fall in the area where the statistical power of the test is reduced and showed more oscillations of Λ+. The ability of these indices to test the fauna composition in function of the alga presence is discussed.

The caprellids of shallow-water localities from the Mexican Central Pacific coast are investigated. The Mexican Pacific coast is poorly known, unlike more northern sites such as the California coast where c. 40 species have been reported. Hence, this is the first study dealing with the caprellidean fauna of this area. Seven species in three genera were found (four of which are new to science): Aciconula acantho-

The spatial-temporal variation of subtidal macrofauna communities of the OdielTinto estuary, one of the most polluted areas in the world, was studied along a sampling period of 4 years (and 3 sampling events). This system has shown typical water and sediment characteristics of estuarine areas although the inner stations showed high concentrations of heavy metals. The structure of the macrofauna community was associated with granulometry, the percentage of organic matter and the heavy metals.Like in other estuaries, the community was dominated by polychaetes (especially by small size opportunistic taxa), meanwhile the crustaceans were the least abundant. Some changes during the sampling period were: slight increment in richness and diversity; greater presence of molluscs and crustaceans in the inner zones; a more homogeneous spatial distribution of opportunistic taxa and a higher number of taxa involved in the differences among the estuary areas. The period of study does not allow assuring that these changes have been due to a true improvement or to natural cycles of the communities in naturally stressed systems. So that it would be necessary the establishment of a long-term monitoring programme to study the evolution of the macrofauna communities to state if the corrective measures could achieve an improvement of this environment. This programme should focus on the study of macrobenthic community's structure and on those selected parameters which have been the major structuring factors for these communities.

As a result of the increased urban and agricultural development in coastal environments, estuaries are among the most modified and threatened aquatic ecosystems. This study used stable isotopes to examine the effects of human impacts by contrasting the food web structures of two Iberian estuaries exposed to different degrees of human pressure. More complex feeding pathways were found in the more altered estuary (Guadalquivir). Greater spread among species along the carbon axis suggests that the primary consumers exploit organic matter with various origins, whereas different nitrogen signals of the secondary consumers suggest that they feed on different suites of prey. In contrast, the similar isotopic signals of secondary consumers in the relatively little influenced estuary (Guadiana) suggests similarity in diet composition and feeding on the same organic matter sources. Understanding trophic interactions in estuaries is vital for defining proper management and conservation, and the preliminary data provided here are one step in this direction.

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