Butyltins, polyaromatic hydrocarbons, organochlorine pesticides, and polychlorinated biphenyls in sediments and bivalve mollusks in a mid-latitude environment from the Patagonian coastal zone.

Butyltins (BTs), polyaromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), and polychlorinated biphenyls (PCBs) were assessed in a mid-latitude environment of the Patagonian coast, distant from significant pollutant sources. Bioaccumulation processes through bottom sediment resuspension were suggested by BTs level (expressed as ng of tin [Sn] g(-1) dry wt) found in surface sediment (

The bacterial community structure of hydrocarbon-polluted marine environments as the basis for the definition of an ecological index of hydrocarbon exposure.

The aim of this study was to design a molecular biological tool, using information provided by amplicon pyrosequencing of 16S rRNA genes, that could be suitable for environmental assessment and bioremediation in marine ecosystems. We selected 63 bacterial genera that were previously linked to hydrocarbon biodegradation, representing a minimum sample of the bacterial guild associated with this process. We defined an ecological indicator (ecological index of hydrocarbon exposure, EIHE) using the relative abundance values of these genera obtained by pyrotag analysis. This index reflects the proportion of the bacterial community that is potentially capable of biodegrading hydrocarbons. When the bacterial community structures of intertidal sediments from two sites with different pollution histories were analyzed, 16 of the selected genera (25%) were significantly overrepresented with respect to the pristine site, in at least one of the samples from the polluted site. Although the relative abundances of individual genera associated with hydrocarbon biodegradation were generally low in samples from the polluted site, EIHE values were 4 times higher than those in the pristine sample, with at least 5% of the bacterial community in the sediments being represented by the selected genera. EIHE values were also calculated in other oil-exposed marine sediments as well as in seawater using public datasets from experimental systems and field studies. In all cases, the EIHE was significantly higher in oiled than in unpolluted samples, suggesting that this tool could be used as an estimator of the hydrocarbon-degrading potential of microbial communities.

Alkane biodegradation genes from chronically polluted subantarctic coastal sediments and their shifts in response to oil exposure.

Although sediments are the natural hydrocarbon sink in the marine environment, the ecology of hydrocarbon-degrading bacteria in sediments is poorly understood, especially in cold regions. We studied the diversity of alkane-degrading bacterial populations and their response to oil exposure in sediments of a chronically polluted Subantarctic coastal environment, by analyzing alkane monooxygenase (alkB) gene libraries. Sequences from the sediment clone libraries were affiliated with genes described in Proteobacteria and Actinobacteria, with 67 % amino acid identity in average to sequences from isolated microorganisms. The majority of the sequences were most closely related to uncultured microorganisms from cold marine sediments or soils from high latitude regions, highlighting the role of temperature in the structuring of this bacterial guild. The distribution of alkB sequences among samples of different sites and years, and selection after experimental oil exposure allowed us to identify ecologically relevant alkB genes in Subantarctic sediments, which could be used as biomarkers for alkane biodegradation in this environment. 16 S rRNA amplicon pyrosequencing indicated the abundance of several genera for which no alkB genes have yet been described (Oleispira, Thalassospira) or that have not been previously associated with oil biodegradation (Spongiibacter-formerly Melitea-, Maribius, Robiginitomaculum, Bizionia and Gillisia). These genera constitute candidates for future work involving identification of hydrocarbon biodegradation pathway genes.

Sources and distribution of aliphatic and polyaromatic hydrocarbons in coastal sediments from the Ushuaia Bay (Tierra del Fuego, Patagonia, Argentina).

The environmental quality of Ushuaia Bay, located at the southernmost tip of South America, is affected by the anthropogenic pressure of Ushuaia city. In this study, levels and sources of hydrocarbons in coastal sediments were assessed. Aliphatic hydrocarbon fractions ranged between 5.5 and 1185.3 µg/g dry weight and PAHs from not detected to 360 ng/g. Aliphatic diagnostic indices, the nalkanes homologous series occurrence, Aliphatic Unresolved Complex Mixtures (AliUCMs), and pristane and phytane isoprenoids indicated a petrogenic input. Some sites showed biogenic features masked by the anthropogenic signature. Particularly in port areas biodegradation processes were evident. PAH ratios showed a mixture of petrogenic and pyrogenic sources. Aliphatic and aromatic UCMs were strongly correlated, reflecting chronic pollution. Three areas were distinguished inside the bay: (1) east, with low hydrocarbons impact; (2) central, where hydrocarbons accumulation was related to source proximity and sediment characteristics; (3) south-west, where sediment characteristics and current circulation favour hydrocarbons accumulation.