I. García-Asencio

Crustacean assemblages in a polluted estuary from South-Western Spain

The spatial-temporal variation in crustacean assemblages of the Odiel-Tinto estuary, one of the most polluted areas in the world, was studied in 2000, 2002 and 2004. The crustacean assemblages were mainly established according to the natural gradient from estuarine to marine environment (based on water and sediment characteristics such as dissolved oxygen, salinity, granulometry or organic content). Pollutants such as copper, zinc or phosphates could also explain partially this pattern based on BIOENV and canonical correspondence analyses. However, there were clear symptoms of perturbation, mainly in the inner areas, such as a low number of species and a low abundance, especially in relation to the typical estuarine species (e.g. Cyathura carinata, Corophium spp.). This study provides baseline information which can be used as a reference point in a long-term perspective.

Distribution and trophic structure of annelid assemblages in a Caulerpa prolifera bed from southern Spain

Abstract The main subject of this study was to evaluate the effects of the temporal variation of the Caulerpa prolifera cover on the composition and trophic structure of the annelid assemblage in a meadow from Southern Spain. A total of 51 species of polychaetes and 1 oligochaete were identified, of which only 6 species represented more than 80% of the total dominance (the oligochaete Aktedrilus cf. monospermathecus, the capitellids Notomastus latericeus and Capitella capitata, the syllid Exogone verugera, the nereidid Neanthes caudata and the cirratulid Aphelochaeta filiformis). The annelid assemblage was similar to others found in seagrass systems from nearby geographic areas. As opposed to other taxonomic group such as molluscs and crustaceans, annelid distribution was more influenced throughout the meadow by the percentage of organic matter in sediment than by algal cover. With respect to trophic structure, the meadow was dominated quantitatively by surface and subsurface deposit feeders; surface deposit feeders and carnivores showed the more homogeneous distribution throughout sampling periods and stations; omnivores were abundant in high cover and high organic matter content stations, meanwhile subsurface deposit feeders were abundant in the rest of the meadow.

BENFES, a new biotic index for assessing ecological status of soft-bottom communities. Towards a lower taxonomic complexity, greater reliability and less effort

The new biotic index BENFES (Benthic Families Ecological Status Index) for assessing the ecological status of soft-bottom communities based on presence/absence at the taxonomic family level, is described. BENFES was primarily developed for the communities from the Guadalquivir estuary (South-western Spain), but the aim of the present work was to evaluate the reliability and validity of this index for its application in the Water Framework Directive (WFD), especially as a preliminary and rapid assessment method for monitoring the ecological status of transitional and coastal waters. BENFES was compared with five widely used indices (BOPA, BO2A, BENTIX; AMBI and M-AMBI) in several studies from Southwestern Spain. In addition, we have also established comparisons between these indices and the most commonly used Shannon-Wiener diversity. M-AMBI and BENFES showed the best agreement in ecological status assignation and were the most useful and discriminant between the studied areas. BENTIX was a good discriminant in coastal areas but was severe with the environmental condition from estuaries; BOPA/BO2A did not show clear trends in most of the zones; and AMBI tended to provide overestimations of the ecological status. In conclusion, BENFES shows several advantages such as lower taxonomic resolution, greater reliability and only requiring presence/absence. All this implies a huge possibility to perform a simplified monitoring routine for the control of the ecological quality of water bodies.

Crustacean assemblages along the Guadiana River estuary (south-western Iberian Peninsula)

The spatial distribution of the subtidal crustacean assemblages of the Guadiana River estuary was studied previous to the building of the Alqueva Dam (the biggest dam in Europe). The differences between an estuarine and marine environment seem to be the main reason responsible for the composition and distribution of the crustaceans along the study zone. The Guadiana estuary has shown high number of species in comparison with other nearby estuaries and this richness seems justified by the scarce influence of pollutants (most of them have shown low or moderate values) and their hydrodynamic and granulometric characteristics ( 7 6 species were found, 39 in the estuarine area). A gradient of enrichment and structuring of the assemblages was shown from the upstream to the marine zones and a spatial segregation of species was found along this estuarine environmental gradient, e.g. the amphipod Corophium multisetosum and the isopod Cyathura carinata in the upper estuary; the amphipod Bathyporeia cf. pilosa and the isopods Lekanesphera levii and Saduriella losadoi in the middle estuary; the amphipod Melita hergensis in the mouth; and a high number of species in the marine area. Since the Alqueva Dam will reduce the river discharges and may cause changes in the abiotic characteristics such as granulometry of sediments or salinity, this study establishes a baseline against which a monitoring programme or follow-up studies could measure any significant effects of the dam or related impacts.

Littoral caprellids (Crustacea: Amphipoda) from the Mexican Central Pacific coast, with the description of four new species

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 acanthosoma Chess, 1989; Caprella equilibra Say, 1818; Caprella mendax Mayer, 1903; Caprella pitu sp. nov.; Liropus isabelensis sp. nov.; Paracaprella carballoi sp. nov.; and Paracaprella isabelae sp. nov. All the species are fully illustrated. http://zoobank.org/urn:lsid:zoobank.org:pub:B04D3837-E7E1-4DA5-A8ED-28CA7BF1E1AF

Impact of dredged-material disposal on soft-bottom communities in a recurrent marine dumping area near to Guadalquivir estuary, Spain

This study assesses the effects of dredged material disposal in a recurrent marine dump near the Guadalquivir Estuary (south-western Spain). We compared the changes observed with two reference areas combining a classical ecological approach with new stable isotope techniques to analyse trophic structure. We detected permanent changes in the macrofaunal community structure as well as in the diversity and biotic indices applied, which showed higher values in the disposal area. The community in the marine dump had lost the natural temporal variations observed in the reference areas. These effects could be due to the last disposal event carried out in the summer of 2015 or to the recurrent disposals since 2010. Despite the structural changes shown by the benthic community, these impacts were not reflected in the food web structure of the marine dump. Our results confirm the high variability of disposal disturbances. Hence, we recommend performing studies in every disposal event, merging different functional and structural approaches.

Maintenance dredging impacts on a highly stressed estuary (Guadalquivir estuary): A BACI approach through oligohaline and polyhaline habitats

Understanding the effects of dredging in estuaries is a hard task due to the difficulty of implementing an adequate environmental diagnosis, as a consequence of the salinity gradient and anthropogenic disturbances. To assess the effects of maintenance dredging work on the Guadalquivir estuary (southwestern Spain), we used a Before-After-Control-Impact (BACI) approach to determine both direct and indirect effects in two salinity ranges. No effects were found on water and sediment physicochemical characteristics. The small impacts on dredged areas were followed by a rapid recovery of opportunistic species. The poor status of the benthos does not permit the detection of significant effects on macrofaunal community structure. The use of stable isotopes analysis to determine impacts on food web structure showed that changes over time seem to be explained by natural temporal variation rather than the dredging works. This paper emphasises the need to define proper management and conservation plans to improve the status of the benthic communities of the Guadalquivir estuary.