No abstract

Coastal lagoons are ecosystems that are relatively enclosed water bodies under the influence of both the terrestrial and the marine environment, being vulnerable to human impacts. Human activities, such as mining extraction, are significant anthropogenic coastal stressors that can negatively affect ecosystems and communities. In light of the above, the objective of this research is to examine the influence of metal mining activities on the composition of sediments of a Mediterranean coastal lagoon, named Mar Menor. This paper presents a comprehensive characterization for grain size, mineralogy, geochemistry and organic matter of sediments of this coastal lagoon, investigating their variation along space and time. Sedimentation dynamics are ruling clearly the grain size predominant in each area of the Mar Menor coastal lagoon, determining the existence of entrainment, transport and sedimentation areas. For minerals, elements and organic matter, sedimentation dynamics are also determining their distribution.

Coastal lagoons are ecosystems highly vulnerable to human impacts because of their situation between terrestrial and marine environment. Mar Menor coastal lagoon is one of the largest lagoons of the Mediterranean Sea, placed in SE Spain and subjected to major human impacts, in particular the mining of metal sulphides. As a consequence, metal concentration in water column and sediments of this ecosystem is usually higher than in other areas. For monitoring ecosystem health, the present study has assessed the ability of Cotylorhiza tuberculata for bioaccumulating metals from sea water. Up to 65 individuals were sampled at 8 different sampling stations during the summer of 2012. Although the concentration values for different elements considered were moderate (Pb: 0.04-29.50 ppm, Zn: 2.27-93.44 ppm, Cd: 0-0.67 ppm, As: 0.56-130.31 ppm) by dry weight of the jellyfish tissues (bell and oral arms combined), bioconcentration levels in relation to seawater metal concentration were extremely high. In any case, the use or disposal of these organisms should consider their metal content because of their potential environmental and health implications.

Marine aquaculture is an activity that has induced severe local losses of seagrass meadows along the coastal areas. The purpose of this study was to evaluate the capacity of an area degraded by fish-farm activities to support Posidonia oceanica seedlings. In the study site, a bay in the southeast coast of Spain where part of a meadow disappeared by fishfarm activities, seedlings inside mesh-pots were planted in three areas. Two plots were established in each area, one in P. oceanica dead matte and another inside a P. oceanica meadow. To evaluate if sediment conditions were adequate for the life of the seedlings, half of them were planted in direct contact with the sediment and the other half were planted above the surface of the sediment in each plot. Monitoring during 1 year showed that there were large differences in seedling survival between the dead matte and the P. oceanica meadow. While seedlings planted in dead matte had a high survivorship after 1 year (75%), seedlings planted in P. oceanica progressively died (survivorship of 20% after 1 year). The average leaf length of the seedlings surviving in the two substrata was not different, but the leaf area per seedling was lower in the seedlings growing inside the P. oceanica meadow during most part of the year. Seedling survivorship and vegetative development were not affected by the level of planting and suggest that the sediment conditions are adequate for the life of P. oceanica seedlings.