Lázaro Marín-Guirao

Carbon and nitrogen stable isotopes and metal concentration in food webs from a mining-impacted coastal lagoon.

Two food webs from the Mar Menor coastal lagoon, differing in the distance from the desert-stream through which mining wastes were discharged, were examined by reference to essential (Zn and Cu) and non-essential (Pb and Cd) metal concentrations and stable isotopes content (C and N). The partial extraction technique applied, which reflects the availability of metals to organisms after sediment ingestion, showed higher bioavailable metal concentrations in sediments from the station influenced by the mining discharges, in agreement with the higher metal concentrations observed in organisms, which in many cases exceeded the regulatory limits established in Spanish legislation concerning seafood. Spatial differences in essential metal concentrations in the fauna suggest that several organisms are exposed to metal levels above their regulation capacity. Differences in isotopic composition were found between both food webs, the wadi-influenced station showing higher delta(15)N values and lower delta(13)C levels, due to the discharge of urban waste waters and by the entrance of freshwater and allochthonous marsh plants. The linear-regressions between trophic levels (as indicated by delta(15)N) and the metal content indicated that biomagnification does not occur. In the case of invertebrates, since the handle strategy of the species and the physiological requirements of the organisms, among other factors, determine the final concentration of a specific element, no clear relationships between trophic level and the metal content are to be expected. For their part, fish communities did not show clear patterns in the case of any of the analyzed metals, probably because most fish species have similar metal requirements, and because biological factors also intervened. Finally, since the study deals with metals, assumptions concerning trophic transfer factors calculation may not be suitable since the metal burden originates not only from the prey but also from adsorption over the body surfaces and seawater ingestion.

Integrative ecotoxicological assessment of sediment in Portmán Bay (southeast Spain).

Portmán Bay, southeast Spain, contains the most seriously metal-contaminated sediments of the Mediterranean Sea. From 1958 to 1991, approximately 50 million tons of mine tailings were dumped into the bay, completely filling up the bay and dispersing over an extensive area of the continental platform and continental slope. The objective of our study was to characterize the nature and extent of metal contamination and the responses of natural communities to it and to assess the toxicity of the sediment deposits 10 years after mining had ceased. We studied the physical and chemical characteristics of the sediments and toxicity (of the porewater and sediment-water interface) using two sea urchin species (Arbacia lixula and Paracentrotus lividus). Metal bioavailability and patterns of macroinvertebrate community composition along the contamination gradient were also studied. Univariate and multivariate analyses showed positive correlation between the sediment metal concentrations associated to the all biological effects (sea urchins toxicity tests and benthic indices). The effects of sediment contamination on the benthic community structure are visible among sampling stations.

Pulse-discharges of mining wastes into a coastal lagoon: Water chemistry and toxicity

Historical mining activities have led to the presence of enormous quantities of mining wastes, which cover large extensions of the Cartagena-La Unión mining district (SE, Spain). In the present work, we study the pulse entrance of mining wastes through two temporary streams (wadis) into the Mar Menor coastal lagoon in two torrential rain events and during a dry period. The characteristics of the runoff pointed to the generation of acid mine drainages in wastes, the acidified stormwater runoff loaded with particulate and dissolved heavy metals causing toxicity in the lagoon waters. The dissolved metals, which mainly affected the sampling stations located close to the wadi discharges, were rapidly eliminated from the water column, whereas the particulate metals were transported further and affected a wider area. Finally, both particulate and dissolved metals are eliminated from the water column and are accumulated in the sediments of the lagoon. The results of the water toxicity tests using sea-urchin embryos indicated that water toxicity disappeared within a few days in the most distant stations, but lasted longer and depended on the climatic conditions of the subsequent days in stations closer to the wadi outlets.