Thiol pools and glutathione redox ratios as possible indicators of copper toxicity in the green macroalgae Enteromorpha spp. from the Scheldt Estuary (SW Netherlands, Belgium) and Thermaikos Gulf (Greece, N Aegean Sea)Interactions of copper with trace metals and thiols in the macro-algae Enteromorpha prolifera (O.F. Müll) J.Ag. grown in water of the Scheldt Estuary (Belgium and S.W. Netherlands)Effects of cadmium, zinc and nitrogen status on nonprotein thiols in the macroalgae Enteromorpha spp. from the Scheldt Estuary (SW Netherlands, Belgium) and Thermaikos Gulf (Greece, N Aegean Sea)Trace metal interactions in the macroalga Enteromorpha prolifera (O.F. Müller) J.Ag.,grown in water of the Scheldt estuary (Belgium and SW- Netherlands) in response to cadmium exposure