Water quality and presence of pesticides in a tropical coastal wetland in southern Mexico

The water quality of the Pozuelos-Murillo lagoon system in southern Mexico was evaluated during three periods between March and October 2002, with particular emphasis on the detection of organochlorine and organophosphorous pesticide residues in water and sediments. Physicochemical and microbiological parameters of water were also measured and integrated in a water quality index (WQI). Multivariate analysis was used to regionalise the lagoon system as a function of the behaviour of all measured parameters. Solid phase micro-extraction followed by gas chromatography (SPME-GC) was used for pesticide analysis. The concentration of phosphorous was found to be higher than that of nitrogenous compounds. This, besides a deficiency in dissolved oxygen and a high organic matter concentration (as COD), reflects eutrophication processes in some areas of the system. Measured levels of faecal coliforms and oils and greases were above the limits established by Mexican law and comparable to the concentrations reported for other highly polluted systems in Mexico. Residues of DDD (2.0 microg L(-1)) in water and DDE (247 ng g(-1)) and endosulfan I (814 ng g(-1)) sediments were detected by SPME-GC. The spatial distribution of these contaminants implies major potential risks because the most polluted sites were found to be those with the highest fishing activity. Although in general the WQI is on acceptable levels (65-80%), some contamination problems are evident.     

Long-term abundance patterns of macroalgae in relation to environmental variables in the Tagus Estuary (Portugal)

Seasonal and inter-annual patterns of macroalgal abundance in a Tagus Estuary oyster reef are described. Macroalgal abundance was estimated as canopy percent cover by three permanent point intercept transects over a 7-year period. Four categories were defined, corresponding to bare substrate and three different macroalgal functional-form groups: (1) ULVA, foliose group, included Ulva spp.; (2) GRACIL, terete corticated macrophyte group, included only Gracilaria gracilis; and (3) FILAM, small (<10 cm) filamentous group, including eight species. A canonical correspondence analysis (CCA) showed that: (1) ULVA were associated with long and hot days, being usually dominant during spring and especially summer; (2) FILAM were associated with mild temperatures and relatively long days, abundant in spring but showed frequent peaks in summer; and (3) GRACIL were also favoured by spring season, although associated to lower temperature and less daylight hours than FILAM. GRACIL and FILAM were present throughout the year. On the contrary, ULVA were absent or with low cover during colder periods. A negative correlation between GRACIL and FILAM seems to indicate competition between the two categories. The applied models explained 23.3% of the temporal variance in category abundance. Rainfall negatively affected macroalgal cover, as indicated by the positive correlation between rainfall and bare substrate. Our conclusions are in agreement with previous studies that consider algae as excellent environmental integrators, even on a small scale, due to a strong link between the macroalgal communities and relevant environmental variables. It is also relevant that this study used open-access databases of environmental variables, which open up new possibilities for mining existing data resources in new ways. Due to large inter-annual variability, long-term studies are essential to understand population dynamics in estuarine phytobenthic communities.     

Witnessing North Atlantic westerlies variability from ships’ logbooks (1685–2008)

A monthly index based on the persistence of the westerly winds over the English Chanel is constructed for 1685–2008 using daily data from ships’ logbooks and comprehensive marine meteorological datasets. The so-called Westerly Index (WI) provides the longest instrumental record of atmospheric circulation currently available. Anomalous WI values are associated with spatially coherent climatic signals in temperature and precipitation over large areas of Europe, which are stronger for precipitation than for temperature and in winter and summer than in transitional seasons. Overall, the WI series accord with the known European climatic history, and reveal that the frequency of the westerlies in the eastern Atlantic during the twentieth century and the Late Maunder Minimum was not exceptional in the context of the last three centuries. It is shown that the WI provides additional and complementary information to the North Atlantic Oscillation (NAO) indices. The analysis of WI series during the industrial era indicates an overall good agreement with the winter and high-summer NAO, with the exception of several multidecadal periods of weakened correlation. These decoupled periods between the frequency and the intensity of the zonal flow are interpreted on the basis of several sources of non-stationarity affecting the centres of the variability of the North Atlantic and their teleconnections. Comparisons with NAO reconstructions and long instrumental indices extending back to the seventeenth century suggest that similar situations have occurred in the past, which call for caution when reconstructing the past atmospheric circulation from climatic proxies. The robustness and extension of its climatic signal, the length of the series and its instrumental nature make the WI an excellent benchmark for proxy calibration in Europe and Greenland.     

Influence of upwelling and river runoff interaction on phytoplankton assemblages in a Middle Galician Ria and Comparison with northern and southern rias (NW Iberian Peninsula)

The first oceanographic research (hydrography, nutrient salts, chlorophyll, primary production and phytoplankton assemblages) in a Middle Galician Ria was carried out in Corme-Laxe during 2001, just a year before the Prestige oil spill, being the only reference to evaluate eventual changes in the phytoplankton community. Due to the small size of this ria (6.5 km²), oceanographic processes were driven by the continental water supplied by Anllons River during the wet season (20–30 m³ s⁻¹ in winter), and the strong oceanic influence from the nearby shelf during the dry season. The annual cycle showed a spring bloom with high levels of chlorophyll (up to 14 μg Chl-a L⁻¹) and primary production (3 g C m⁻² d⁻¹) and a summer upwelling bloom (up to 8 μg Chl-a L⁻¹ and 10 g C m⁻² d⁻¹) where the proximity of the Galician upwelling core (<13.5 °C at sea surface) favors the input of upwelled seawater (up to 9 μM of nitrate and silicate) to the bottom ria layer, even during summer stratification events (primary production around 2 g C m⁻² d⁻¹). Thus, phytoplankton assemblages form a “continuum” from spring to autumn with a predominance of diatoms and overlapping species between consecutive periods; only in autumn dinoflagellates and flagellates characterized the phytoplankton community. In the Middle Rias as Corme-Laxe, the nutrient values, Chl-a, primary production and phytoplankton abundance for productive periods were higher than those reported for the Northern (Ria of A Coruña) and Southern Rias (Ria of Arousa) for year 2001; this suggests the importance of the hydrographic events occurring in the zone of maximum upwelling intensity of the Western Iberian Shelf, where a lack of annual cycles studies exists.     

Haul-out pattern of itinerant male Antarctic fur seals (Arctocephalus gazella) at Laurie Island, South Orkney Islands

The seasonal haul-out pattern of itinerant male Antarctic fur seals ( Arctocephalus gazella ) was determined by regular counts at Mossman Peninsula, Laurie Island, South Orkney Islands, from 1996 to 2005. Small numbers of animals began to arrive at the beach in late December/early January (mean date 28 December Ø 15 days, n= 10). Peak numbers of animals ashore changed considerably between seasons. In 1996, 1998 and 2001, peak numbers were registered in March (6/3, 18/3 and 6/3, respectively). Numbers peaked in 1997, 1999 and 2005 at the end of January/beginning of February (26/1,2/2 and 28/1, respectively). In 2000, 2002, 2003 and 2004 peaks were registered in the third week of February (15/2, 22/2, 14/2 and 20/2, respectively). Peaks in numbers of seals ashore also varied between years, being minimum during 2001 (2531 individuals) and maximum during 2006 (16 610 individuals). In March 1998 the coasts of Laurie Island were surveyed by navigating inflatable boats near the shoreline; 18 haul-out places were identified. The big differences in peak numbers, as well as in the dates of peak events among years, suggest that local conditions could have an effect on the numbers of animals hauled out in a given year. It may therefore be difficult to predict trends from summer censuses in non-breeding places.     

Inorganic arsenic speciation in the waters of the Penzé estuary (NW France): Seasonal variations and fluxes to the coastal area

Over this one-year study, the variations of inorganic As species were examined monthly along the salinity gradient of the Penzé estuary (NW France) in relation with different biogeochemical parameters. In most cases, dissolved As exhibited a non-conservative behaviour which resulted from the competition between two major processes. In the upstream section of the estuary, a strong input of both total inorganic As and As(III) occurred. Then, the removal of the same species, under precipitation of iron oxides/oxyhydroxides, was observed in the low-salinity range (S < 10). Using our experimental data, the fluxes of the various As species were estimated for the first time in estuarine waters. Inputs from the river were mainly constituted of particulate As (∼70%). Conversely, dissolved species were predominant in the net fluxes (∼65%) and As(III) accounted for ∼15% of the dissolved net flux.     

Biomarkers of exposure and effect in the Brazilian flounder Paralichthys orbignyanus (Teleostei: Paralichthyidae) from the Patos Lagoon estuary (Southern Brazil)

Biomarkers of exposure (liver metallothionein-like proteins content and catalase and glutathione S-transferase activities) and effect (liver lipoperoxidation and blood cell DNA damage) of contaminants were analyzed in the Brazilian flounder Paralichthys orbignyanus from the Patos Lagoon estuary (Southern Brazil). Flounders were collected for a year in two sites: "Coroa do Boi" (polluted site) and "Saco do Justino" (non-polluted site). Results indicated that micronucleated cells frequency was the best biomarker to distinguish flounders from the two sites. Taken together, data from DNA damage analyses (micronucleus test and comet assay) indicated that flounders from the non-polluted site efficiently repaired the DNA breaks, contrary to those from the polluted site, which probably had their DNA repair system inhibited or exhausted. Furthermore, data from enzyme activities (catalase and GST) and lipid peroxidation indicated that flounders from the polluted site were under oxidative stress in summer and autumn.     

U–Pb evidence for a polyorogenic evolution of the HP–HT units of the NW Iberian Massif

. A isotope dilution thermal ionisation mass spectrometry U-Pb geochronological study was carried out on the high-pressure and high-temperature units (HP-HT units) overlying the oceanic suture in the Allochthonous Complexes of the NW Iberian Variscan Belt. The rocks investigated are seven granulite- to eclogite-facies paragneisses and one leucosome within mafic high-pressure granulites in the Ordenes and Cabo Ortegal Complexes of NW Spain. U-Pb dating of zircon, monazite, titanite and rutile reveal the presence of a pervasive Early Ordovician metamorphic event at ca. 500-480 Ma and a later Early Devonian event at ca. 400-380 Ma. The U-Pb ages, in conjunction with petrological and structural data, indicate that the high-pressure event recorded by these rocks is Early Ordovician in age. Monazite ages in the paragneisses suggest that peak metamorphic conditions were reached at ca. 500-485 Ma. Subsequently, the rock ensemble underwent exhumation accompanied by partial melting and zircon growth at ca. 485-470 Ma. Melting of mafic granulites was coeval with this latter episode as indicated by zircon crystallisation age in the leucosomes dated at ca. 486 Ma. Based on these data and on the general features of magmatism and metamorphic evolution, it is proposed that this process took place at a convergent plate boundary within a peri-Gondwanan oceanic domain. Monazite, titanite and rutile data in some of the samples studied show evidence of a second metamorphic episode that took place between ca. 400 and 380 Ma (with a peak at ca. 390-385 Ma). This Early Devonian event, at variance with the previous one, was not pervasive, but, rather, was localised in areas of intense Variscan tectonothermal reworking. It is claimed that this later metamorphic event was recorded by the U-Pb system in areas where monazite and titanite growth was enhanced by fluid circulation in highly strained rocks (Variscan shear zones). According to previous structural studies and Ar-Ar dating of fabrics, this Early Devonian episode took place as the HP-HT units were deformed and thrusted upon the ophiolitic units in the early stages of the Variscan collision.