Natalia Venturini

Polycyclic aromatic hydrocarbons and changes in the trophic structure of polychaete assemblages in sediments of Todos os Santos Bay, Northeastern, Brazil

Polycyclic aromatic hydrocarbons (PAHs) and the trophic structure of polychaete assemblages were studied in sediments at 28 stations in Todos os Santos Bay. Total PAH concentrations varied from 8 to 4163 ng g(-1) dry weight. The indexes used for the determination of PAH origin suggested both pyrolytic and petrogenic sources. A total of 397 individuals of polychaetes was recorded which were classified in three trophic groups. The PCA ordination resulted in the formation of three groups of stations, Group I characterised by sandy sediments, low organic content, low total PAH concentration and percentage of potentially harmful PAH was dominated by subsurface deposit-feeders. The other two groups (IIa and IIb), showed similar percentages of silt and clay, however, Group IIb formed by those stations with high total organic carbon, total nitrogen, sulphur contents, high total PAH concentration and percentage of potentially harmful PAH was dominated by carnivores. Trophic changes could be explained by the level of exposure to PAH effects relative to differences in the life style and feeding strategies between deposit-feeders and carnivores.

Characterization of the benthic environment of a coastal area adjacent to an oil refinery, Todos os Santos Bay (NE-Brazil)

In order to determine the sedimentological and physico-chemical characteristics of the benthic environment and also the level, distribution and probable sources of aliphatic and polycyclic aromatic hydrocarbons, sediment samples were collected at 28 stations in the northeast portion of Todos os Santos Bay. The centre and the east region of the study area showed characteristics of depositional environments with the predominance of silt and clay and high percentages of TOC, nitrogen and sulphur. The molar C/N ratios varied between 8.8 and 27.6 indicating a mixed origin of organic matter with variable marine and continental contributions. Total aliphatic hydrocarbon concentrations ranged between 1.56 and 246.91 µg.g-1 dry weight, corresponding the high concentrations to the stations situated in the centre and in the east region of the study area. The UCM represented between 60 and 96% of the total aliphatic hydrocarbons, indicating a high degree of anthropogenic contribution and the presence of petroleum degraded residues. Total PAH concentrations varied from 8 to 4163 ng.g-1 dry weight. The highest total PAH concentration was recorded at station 5 situated adjacent to the oil refinery.

Macrobenthos and multi-molecular markers as indicators of environmental contamination in a South American port (Mar del Plata, Southwest Atlantic).

We evaluated benthic habitat quality along a presumed contamination gradient in the Mar del Plata port (Southwestern Atlantic) by coupling biological and chemical proxies in a multidisciplinary approach. Organic matter and photosynthetic pigment contents were higher in silty-clay bottoms of the inner port sites. Levels of all fecal steroids decreased from the inner sites to the port inlet. High concentrations of coprostanol in the inner sites seemed to derive from a permanent population of sea lions rather than from sewage outfalls due to coprostanol/epicoprostanol ratio (IV) values <2.5. PAHs levels were also higher in the inner sector, related to both biomass combustion and petroleum combustion associated to local marine traffic. High disturbance and low ecological status were reflected in low benthic diversity and high AMBI values in the inner sites.

A multi-molecular marker assessment of organic pollution in shore sediments from the Río de la Plata Estuary, SW Atlantic

Organic pollution was evaluated in surface sediments along the middle portion of the Río de la Plata Estuary, SW Atlantic. A multi-molecular marker approach was performed to identify major sources of organic compounds using diagnostic indices. The relative contribution of different sources of hydrocarbons was quantified by source apportionment employing Principal Component Analysis/Multiple Linear Regression (PCA/MLR) as chemometric technique. All molecular markers indicated high chronic organic pollution in the stations of Montevideo Bay. Main sources of aliphatic and polycyclic aromatic hydrocarbons were petroleum inputs and combustion, due to oil transport and refinement, harbour activities and vehicular emissions. Major sources of linear alkylbenzenes and steroids were industrial and domestic sewage. Although, significant anthropogenic inputs, a natural footprint of terrestrial higher plants contribution was recognized. Multi-molecular marker and comprehensive assessments can improve the establishment of more precise regulation actions to reduce pollution levels.

Warm-phase ENSO events modulate the continental freshwater input and the trophic state of sediments in a large South American estuary

We studied the changes in geochemical variables in the middle section of Rio de la Plata estuary during the 2009–2010 El Nino–Southern Oscillation (ENSO) event. Protein, organic matter, chlorophyll-a and phaeopigment content of surface sediments were significantly correlated with the increased continental freshwater input associated with high total monthly rainfall. During the warm-phase ENSO event, river flow was 5-fold larger than average historical levels, which led to a steady decrease in salinity values and the highest levels of geochemical variables. The evidence presented herein suggests that warm-phase ENSO events increase the trophic state of the sediments because of the increased freshwater input. Thus, our findings may be useful to anticipate potential eutrophication episodes in the study area.

Assessing the ecological quality status of a temperate urban estuary by means of benthic biotic indices.

Benthic indices are commonly used tools for assessing the environmental quality, because they represent a simple source of scientific information. However, their performance could vary depending on the application area and perturbation types, thus they should be tested before used in other remote geographic regions. This study aims to test the use of some of the most widely common benthic biotic indices for assessing the environmental quality of Montevideos coastal zone at a seasonal scale against many physicochemical variables. From all the evaluated indices, AMBI appears to be the most suitable one to assess the environmental quality. The study also allowed us to infer the most relevant physicochemical variables: protein, lipid and heavy metal sediment concentration. Additionally, site-specific threshold effect levels for heavy metals and biopolymers were established, which appear to be useful to determine tolerable levels of such stressors in future assessments or monitoring programs for the study area.

Fatty acid biomarkers of organic matter sources and early diagenetic signatures in sediments from a coastal upwelling area (south-eastern Brazil)

Sediment bulk parameters and fatty acid biomarkers were used to investigate the relative contribution of major sources of particulate organic matter during upwelling and non-upwelling conditions, at organic enriched sites on the south-eastern Brazilian coast. The degradation state of the organic material and its implications for benthic food webs were also evaluated. Temperature and salinity values indicate the intrusion of the South Atlantic Central Water in spring with a strong influence at station 4S. C:N ratios and fatty acid biomarkers suggest that sedimentary particulate organic matter is mainly autochthonous and originated from phytoplankton, zooplankton and bacteria, with a minor terrestrial contribution. Short-chain saturated fatty acids predominated, indicating the prevalence of partially degraded detritus. An exception was station 4S, where polyunsaturated fatty acids dominated, indicating the input of labile organic matter linked to upwelling of the South Atlantic Central Water. Fatty acid concentrations and the organic carbon content of the sediments suggest that food quantity is not a limiting factor for benthic fauna. Despite the high organic background of the sediments, the sporadic inputs of labile organic matter associated with South Atlantic Central Water intrusions may produce an important impact on benthic fauna and on the biogeochemistry of the sediments.

Integrated assessment of contaminants and monitoring of an urbanized temperate harbor (Montevideo, Uruguay): a 12-year comparison

A cidade de Montevideu, com mais de 1,5 milhoes de habitantes, circunda a Baia de Montevideu, onde um dos portos mais ativos e poluidos da America do Sul esta localizado. No presente trabalho, foram avaliados esterois fecais, metais traco, compostos organoclorados e derivados de petroleo nos sedimentos superficiais do Porto de Montevideu, analisando sua distribuicao espacial no interior do porto, bem como em dois dos principais tributarios que chegam ao interior da baia. Especificamente para os sitios do porto, foi realizada uma comparacao temporal dos metais pesados e hidrocarbonetos, considerando dados preteritos de 12 anos. Foram observadas alteracoes significativas nos sitios estudados. Metais, tais como o Pb, Cr e Zn, apresentaram reducao nas suas concentracoes, enquanto os hidrocarbonetos alifaticos aumentaram seus valores em quase todas as estacoes. Foram observadas tambem diferencas entre o verao e o inverno, sugerindo mudancas no padrao de sedimentacao, nos ingressos de substâncias e/ou mudancas hidrodinâmicas na area. Os resultados podem vir auxiliar na compreensao do estado atual e para o desenvolvimento de medidas de gestao necessarias para melhorar a qualidade ambiental do porto e da baia.

Diatoms, protein and carbohydrate sediment content as proxies for coastal eutrophication in Montevideo, Rio de la Plata Estuary, Uruguay

A study on sediment surface diatom composition in relation to both protein/carbohydrate content and salinity was carried out in Montevideo Bay and the adjacent coastal zone. Samples were seasonally taken during one year along a human impact gradient, and the trophic conditions were assessed from the biochemical composition of the surface sediment organic matter. The co-occurrence of the marine-brackish (Actinocyclus curvatulus, Actinocyclus gallicus, Coscinodiscus excentricus, Coscinodiscus radiatus, Hyalodiscus subtilis, Paralia sulcata) and freshwater diatom flora (Aulacoseira granulata, Aulacoseira italica, Aulacoseira muzzanensis, Actinocyclus normanii, Amphora copulata, Cyclotella meneghiniana, Nitzschia linearis), suggests myxohaline estuarine conditions in the study area. The sampling stations located within the bay, close to several contamination sources, exhibited hypertrophic conditions as indicated by the highest levels of protein content, but also by the high relative abundances of Actinocyclus normanii and Cyclotella meneghiniana, as both diatom species are very well established cosmopolitan proxies of aquatic degradation. The levels of both protein and carbohydrate content, but also photosynthetic pigments, recorded in the adjacent coastal zone suggest meso-eutrophic conditions as contamination levels from the inner bay might become diluted off shore. Multivariate diatom species-environmental data relationships, indicate that the trophic gradient is hierarchically more important than salinity in explaining the diatom distribution. The present data imply an improvement in our ability of assessing organic contamination in the study area, since both biological and biopolymer variables were introduced for the first time as a tool for assessing the benthic health/degradation in one of the most populated regions of the Rio de la Plata.

Benthic trophic status of aquatic transitional environments with distinct morphological and dynamic characteristics on the south-western Atlantic coast

The benthic trophic status of Uruguayan coastal estuarine habitats (permanently open estuaries and open or closed coastal lagoons) was evaluated, twice in 1 year and at different spatial scales, using the amount and biochemical composition of the sedimentary organic matter. Nested hierarchical ANOVAs were applied to evaluate differences at the habitat level, among sites for each type of estuarine habitat (three estuaries and three lagoons) and between sectors located at different distances from the sea (inner v. outer sectors). Morphological and hydrodynamic differences between the two types of habitats explained site-to-site variations in eutrophic conditions in the open or closed coastal lagoons and meso-oligotrophic conditions in permanently open estuaries. These differences followed the patterns found for sediment grain size, with inner sectors (lower-energy areas) favouring the accumulation of finer sediments and higher amounts of degraded–detrital organic matter. In autumn, biochemical parameters indicated the dominance of aged and more degraded organic matter, with both types of habitats having a low nutritional value no matter which sector was considered. By contrast, in spring, biochemical composition showed the prevalence of fresh and more labile sedimentary organic matter with a high food value, especially in the outer sectors.