title: The use of sedimentary %C, %N, delta(15)N, and Pb concentrations to assess historical changes in anthropogenic influence on Portuguese estuaries.
abstract: Vertical profiles of C, N, delta(15)N and Pb were measured in the Mondego and Mira estuaries as markers that conveyed notions as to the relative influence of anthropogenic influence over the past decades. Recent carbon changes in both estuaries may reflect changes in estuarine productivity, probably as a consequence of sediment reworking and erosion, and also of losses in salt marsh area and dwarf eelgrass beds. delta(15)N values began to diverge considerably before the %C and %N and were higher in Mondego. delta(15)N signatures detected N enrichment at relatively low rates, and indicated that Mondego received more enriched N than Mira. Lead concentrations differed between estuaries, with higher concentrations in Mondego. The secular increase in %N, Pb, and delta(15)N signatures was significantly related to human density in the watersheds of the estuaries and were sensitive indicators of anthropogenic activity.
authors.affiliation: IMAR, Institute of Marine Research, Department of Botany, University of Coimbra, Travessa Martim de Freitas, Coimbra, Portugal. pcastro@ci.uc.pt
authors.forename: Paula
authors.initials: P
authors.lastname: Castro
authors.forename: Ivan
authors.initials: I
authors.lastname: Valiela
authors.forename: Helena
authors.initials: H
authors.lastname: Freitas
mesh_terms: D002244:Carbon / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods; D019015:Geologic Sediments / Q000032:analysis*; D006801:Humans; D007220:Industrial Waste / Q000032:analysis; D007854:Lead / Q000032:analysis; D009584:Nitrogen / Q000032:analysis; D009587:Nitrogen Isotopes / Q000032:analysis; D010575:Pesticides / Q000032:analysis; D011156:Population Density; D011174:Portugal; D045483:Rivers / Q000737:chemistry*; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D007220:Industrial Waste; D009587:Nitrogen Isotopes; D010575:Pesticides; D014874:Water Pollutants, Chemical; D007854:Lead; D002244:Carbon; D009584:Nitrogen