Bioindicators as metrics for environmental monitoring of desalination plant discharges.

Development of desalination projects requires simple methodologies and tools for cost-effective and environmentally-sensitive management. Sentinel taxa and biotic indices are easily interpreted in the perspective of environment management. Echinoderms are potential sentinel taxon to gauge the impact produced by brine discharge and the BOPA index is considered an effective tool for monitoring different types of impact. Salinity increase due to desalination brine discharge was evaluated in terms of these two indicators. They reflected the environmental impact and recovery after implementation of a mitigation measure. Echinoderms disappeared at the station closest to the discharge during the years with highest salinity and then recovered their abundance after installation of a diffuser reduced the salinity increase. In the same period, BOPA responded due to the decrease in sensitive amphipods and the increase in tolerant polychaete families when salinities rose. Although salinity changes explained most of the observed variability in both indicators, other abiotic parameters were also significant in explaining this variability.

Monitoring the effects of wastewater treatment strategies.

Wastewater disposal in coastal waters causes widespread environmental problems. Secondary treatment is expected to reduce the adverse effects of insufficiently treated wastewater. The environmental impact of sewage disposal via 18 wastewater treatment plants was analysed using the benthic opportunistic polychaetes and amphipods (BOPA) index. In previous studies this index proved to be an effective tool for monitoring sewage pollution. The impact of these discharges was highly related to treatment level, which ranged from pre-treatment to biological, as well as to flow rates and outfall position. Locations affected by pre-treated wastewater showed environmental degradation, especially marked near outfalls with higher flow rates. At most locations, biologically treated wastewater did not cause a significant impact and an improvement in ecological integrity was detected after this secondary treatment had been implemented. The impact of discharge was highly related to chemical oxygen demand (COD), suspended solids and nutrient concentrations, which are all lower in biologically treated wastewater. A 'moderate' ecological status was observed not only near sewage outfalls with high wastewater flow rates (>1,500,000 m(3)/month) with a COD over 200 mg/l but also near those with lower flow rates but with a COD over 400 mg/l. To reduce the impact of sewage disposal, it is necessary to carry out adequate treatment, have site outfalls deep enough, and implement water recycling.

Sensitivity of tanaid Apseudes latreillei (Milne-Edwards) populations to sewage pollution.

Apseudes latreillei (Milne-Edwards) is a common and abundant tanaid in soft-bottom communities from waters off East Atlantic and Mediterranean coasts. Its sensitivity to pollution is not clear despite being an abundant and widely distributed crustacean, since it has been reported as both a tolerant and sensitive species. This paper tests the sensitivity of A. latreillei to sewage discharges in fine-sand communities along the Castellon coast (W. Mediterranean). We analysed variation in tanaid populations between sites at varying distances from sewage outfalls with respect to population density, size distribution, sex ratio and their correlation with different abiotic factors of waste water and sediment. Results showed clearly that A. latreillei populations were affected by the presence of sewage outfalls, to such an extent that sewage disposal outlets produced a decrease in population density and changes in size spectra.

Testing BOPA index in sewage affected soft-bottom communities in the north-western Mediterranean.

The implementation of the European directive (ELD) 2000/60/EC has produced the development of several biotic indices based in benthic communities. These indices try to summarise ecological quality status of different communities. However, a universal index that works in all situations is difficult to establish, because there are several sources of variation. Therefore, there is the need for testing and validation of these indices which is required for making management decisions on different scales, and in different regions and communities. In this study we test one of these indices, BOPA index, developed by Dauvin and Ruellet [Dauvin, J.C., Ruellet, T., 2007. Polychaete/amphipod ratio revisited. Marine Pollution Bulletin 55, 215-224] in five locations affected by sewage disposal. These disposals are often released via outfall into shallow subtidal habitats, leading to a common source of pollution in coastal marine environments. BOPA index provides a valuable overview of the gradient status of a benthic environment, discriminating between stations more affected by discharge. Nevertheless, BOPA index, used to establish the ecological quality status, seemed to overestimate the status and hence there is the need to calibrate the thresholds between EcoQs classes as defined for these medium-to-fine sand communities, which are characteristics of shallow sublittoral soft-bottoms of the north-western Mediterranean Sea.

Effect of sewage discharge in Spisula subtruncata (da Costa 1778) populations.

Sewage discharge is a common source of pollution in coastal marine waters. Several municipal treatment plants dump treated water in medium to fine sand Spisula subtruncata communities. This bivalve is generally considered a major food source for demersal fishes, and it is important as a dominant species in structuring the macrobenthic community during the spring and summer months. We sampled within five locations affected by sewage discharge along the Castellon coast (northwest Mediterranean Sea) where S. subtruncata (da Costa 1778) is a common bivalve. Van Veen grab samples were obtained for the study of the bivalve population and to characterize the sediment. The sewage discharges studied affect Spisula populations. In the stations near the outfalls, the abundance and the average size of S. subtruncata decreased. However, this effect did not correlate with sediment characteristics, such as granulometry or pH.