Evaluating environmental contamination in Ria Formosa (Portugal) using stress indexes of Spartina maritima

Species of Spartina are potentially useful for biomonitoring coastal system s because they are abundant in the intertidal and have a wide geographic di stribution in temperate zones. In this study, three indexes of physiologica l stress, thiolic protein concentration, adenylic energy charge (AEC) index [AEC = ATP + 0,5ADP/(ATP + ADP + AMP)] and photosynthetic efficiency (F-v/ F-m), are measured in Spartina maritima plants collected at four sites and compared with metal concentrations in the sediments and Spartina tissues. T wo sites were close to urban centers and two were located further away, in less contaminated areas. Concentrations of copper, cadmium, lead and zinc w ere determined by atomic absorption spectrophotometry, thiolic proteins wer e determined by polarography and adenilic nucleotides were determined by hi gh performance liquid chromatography. Photosynthetic efficiencies were meas ured with a fluorometer. The sediments of sites closer to urban centers had higher concentrations of metals than the sites located further away. Metal concentration within plants did not follow this spatial pattern, probably due to spatial differences in metal bioavailability, uptake rates, internal transport and excretion processes. Concentrations of all metals studied we re higher in underground plant structures than aerial, except cadmium whose levels were not significantly different. On the other hand, the stress ind exes followed the spatial pattern of metals in the sediment. Thiolic protei n concentrations were higher in plants from polluted sites, and were three to four times higher in aerial than in underground plant structures, Leaf A EC ratios and photosynthetic efficiencies were lower in plants from pollute d sites indicating that they were growing under stressful conditions. We co nclude that the use of these indexes in S. maritima represent a useful tool to monitor contamination in Ria Formosa lagoon as they provide an integrat ed measure of the toxicological burden of contamination. (C) 2000 Elsevier Science Ltd. All rights reserved.