Seasonal baseline of nutrients and stable isotopes in a saline lake of Argentina: biogeochemical processes and river runoff effects

The seasonal variability of inorganic and organic nutrients and stable isotopes and their relations with plankton and environmental conditions were monitored in Lake Chasicó. Principal component analysis evidenced the strong influence of the river runoff on several biogeochemical variables. Silicate concentrations were controlled by diatom biomass and river discharge. Higher values of nitrate and soluble reactive phosphorus (SRP) indicated agricultural uses in the river basin. Elevated pH values (～9) inhibiting nitrification in the lake explained partially the dominance of ammonium: ～83 % of dissolved inorganic nitrogen (DIN). The low DIN/SRP ratio inferred nitrogen limitation, although the hypotheses of iron and CO₂ limitation are relevant in alkaline lakes. Particulate organic matter (POM) and dissolved organic matter (DOM) were mainly of autochthonous origin. The main allochthonous input was imported by the river as POM owning to the arid conditions. Dissolved organic carbon was likely top-down regulated by the bacterioplankton grazer Brachionus plicatilis. The δ¹³C signature was a good indicator of primary production and its values were influenced probably by CO₂ limitation. The δ¹⁵N did not evidence nitrogen fixation and suggested the effects of anthropogenic activities. The preservation of a good water quality in the lake is crucial for resource management.     

Assessing the ecological effects of human impacts on coral reefs in Bocas del Toro,Panama

Environmental and biological reef monitoring was conducted in Almirante Bay (Bahía Almirante) in Bocas del Toro, Panama, to assess impacts from anthropogenic developments. An integrated monitoring investigated how seasonal temperature stress, turbidity, eutrophication and physical impacts threatened reef health and biodiversity throughout the region. Environmental parameters such as total suspended solids [TSS], carbon isotopes (δ¹³C), C/N ratios, chlorophyll a, irradiance, secchi depth, size fractions of the sediments and isotope composition of dissolved inorganic carbon [DIC] of the water were measured throughout the years 2010 and 2011 and were analysed in order to identify different impact sources. Compared to data from Collin et al. (Smithsonian Contributions to the Marine Sciences 38:324–334, 2009) chlorophyll a has doubled at sites close to the city and the port Almirante (from 0.46–0.49 to 0.78–0.97 μg l^?1) and suspension load increased, visible by a decrease in secchi depth values. Visibility decreased from 9-13 m down to 4 m at the bay inlet Boca del Drago, which is strongly exposed to river run off and dredging for the shipping traffic. Eutrophication and turbidity levels seemed to be the determining factor for the loss of hard coral diversity, most significant at chlorophyll a levels higher than 0.5 μg l^?1 and TSS levels higher than 4.7 mg l^?1. Hard coral cover within the bay has also declined, at some sites down to <10 % with extremely low diversities (7 hard coral species). The hard coral species Porites furcata dominated the reefs in highly impacted areas and showed a strong recovery after bleaching and a higher tolerance to turbidity and eutrophication compared to other hard coral species in the bay. Serious overfishing was detected in the region by a lack of adult and carnivorous fish species, such as grunts, snappers and groupers. Study sites less impacted by anthropogenic activities and/or those with local protection showed a higher hard coral cover and fish abundance; however, an overall loss of hard coral diversity was observed.     

Biomonitoring of heavy metals (Cd,Hg, and Pb) and metalloid (As) with the Portuguese common buzzard (Buteo buteo)

The accumulation of heavy metals in the environment may have a wide range of health effects on animals and humans. Thus, in this study, the concentrations of arsenic (As), cadmium (Cd), lead (Pb), and mercury (Hg) in the blood and tissues (liver and kidney) of Portuguese common buzzards (Buteo buteo) were determined by inductively coupled plasma-mass spectrometer (ICP-MS) in order to monitor environmental pollution to these elements. In general, Hg and As were the elements which appeared in the highest and lowest concentrations, respectively. A highest percentage of non-detected concentration was found for blood Cd (94.6 %) but, in turn, it was the only metal that was detected in all kidney samples. The kidney was the analyzed sample which showed the highest concentrations of each element evaluated. Statistically, significant differences among blood, liver, and kidney samples were observed for As and Cd (P?相似文献   

Epiphyte toxicity bioassay for ecotoxicological and coastal monitoring

Marine epibionts are organisms that grow on submerged surfaces. Those found on seagrass leaves are especially important because of their interactions with the plants, their contribution to primary production in these ecosystems, and their role as food source for heterotrophic fauna. Given the relative lack of ecotoxicological studies on epibionts, the aim of this study is to evaluate the effect of environmental pollution on epiphytes experimentally attached to artificial devices (mimes) consisting of thermally-sealed silicone tubes supported on bamboo sticks that mimic the morphology of seagrasses and serve as an anchor surface for marine epibionts. Mimes were installed on the sea floor in subtidal waters of the Rio San Pedro (Cádiz), collected after 28 days, and incubated in the laboratory with environmental concentrations of atrazine (herbicide), Irgarol (anti-fouling substance), and copper. Tube-dwelling diatoms formed the major component of the epiphyte community. Average surface covering, chlorophyll, and biomass content did not show significant differences between controls and treatments. The glutathione peroxidase activity increased significantly with 4 μg L^?1 of atrazine and 5 μg L^?1 of copper. This enzymatic activity increase seems to be sufficient to prevent oxidative cellular damage by removing reactive oxygen substances produced by oxidative stress; in addition to this enzyme, there might be other antioxidant enzymes which have not been measured in this study, that have also protected the organism from oxidative damage. Thus, the measurement of antioxidant enzymatic activity in epiphytes may be a useful toxicity indicator for coastal biomonitoring.     

Community metabolism in a deep (stratified) tropical reservoir during a period of high water-level fluctuations

As long as lakes and reservoirs are an important component of the global carbon cycle, monitoring of their metabolism is required, especially in the tropics. In particular, the response of deep reservoirs to water-level fluctuations (WLF) is an understudied field. Here, we study community metabolism through oxygen dynamics in a deep monomictic reservoir where high WLF (~10 m) have recently occurred. Simultaneous monitoring of environmental variables and zooplankton dynamics was used to assess the effects of WLF on the metabolism of the eutrophic Valle de Bravo (VB) reservoir, where cyanobacteria blooms are frequent. Mean gross primary production (P _g) was high (2.2 g C m^?2 day^?1), but temporal variation of P _g was low except for a drastic reduction during circulation attributed to zooplankton grazing. The trophogenic layer showed net autotrophy on an annual basis, but turned to net heterotrophy during mixing, and furthermore when the whole water-column oxygen balance was calculated, considering the aphotic respiration (R _aphotic). The high total respiration resulting (3.1 g C m^?2 day^?1) is considered to be partly due to mixing enhanced by WLF. Net ecosystem production was equivalent to a net export of 3.4 mg CO₂?m^?2 day^?1 to the atmosphere. Low water levels are posed to intensify boundary-mixing events driven by the wind during the stratification in VB. Long-term monitoring showed changes in the planktonic community and a strong silicon decrease that matched with low water-level periods. The effects of low water-level on metabolism and planktonic community in VB suggest that water-level manipulation could be a useful management tool to promote phytoplankton groups other than cyanobacteria.     

Use of native mosses as biomonitors of heavy metals and nitrogen deposition in the surroundings of two steel works

A biomonitoring survey using the moss species Hypnum cupressiforme Hedw. was conducted in the surroundings of two steel plants located in the North of Spain. Levels of V, Cr, Ni, Cu, Zn, As, Cd, Hg, Pb and N were determined. Very high concentrations in the areas of study were detected when compared to nearby unaffected regions. Similar trends were observed for all the elements in the differently orientated transects, showing an appreciable influence of the NW prevailing winds of the region in the dispersion of pollutants, as well as a clear decreasing gradient in the concentrations of metals in mosses within a distance of 1500 meters from the facilities. A differentiation between the elements emitted by the chimney as result of the industrial activity (V, Cr, Ni, Cu and As) and those with a high presence in steel slag deposits (Zn, Cd, Hg and Pb) was observed. The range of contamination was also established by means of the Contamination Factor, indicating a category 4 out of 6 categories, which shows the high levels reported in the areas of study. A different dynamic was registered for nitrogen regarding the rest of the heavy metals analysed except for Hg, probably due to the elevated volatility and mobility of both elements, as well as their high persistence in the atmosphere.     

Fractions and background concentrations of potentially toxic elements in Hungarian surface soils

This work established background concentrations for the pseudo total (HNO₃ + H₂O₂-soluble), mobilisable (NH₄-acetate + EDTA-soluble) and mobile (1?M NH₄NO₃-soluble) element fractions of Hungarian surface soils that can be used as reference values for the soil quality standards. The 193 soils investigated were taken from the Hungarian Soil Information and Monitoring System. The background values for Al, As, B, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr and Zn were given as a range covering 95% of the variance of the representative samples. The differences between observed element concentrations and the calculated background values indicated anthropogenic or pedogenic impact in each fraction. The comparison of the calculated background values with the Hungarian quality standards and the contamination limit values of other countries showed that the limit values of a certain region or country are not suitable for other areas. Generally, Mn and Al had the highest, while Cd had the lowest concentration in each fraction. Cr and Al were the least and Sr was the most mobile element. The principal component analysis indicated different geochemical and physico-chemical behaviour of the elements in the fractions; the pseudo total fraction was influenced more by the geological behaviour, while mobilisable and mobile fraction explained a much higher proportion of the total variance of soil physico-chemical properties than soil geochemical properties. The Cd–Ni and Co–Mn element pairs were always in the same principal component in each fractions indicating similar geogenic origin and showing that their solubility changes are similar in function of soil properties.