Bleaching response of corals and their <Emphasis Type="Italic">Symbiodinium</Emphasis> communities in southern Africa

The high-latitude coral communities of southern Africa suffered minimal impacts during past mass bleaching events. Recent reports indicate an increase in bleaching frequency during the last decade, yet the actual levels of thermal stress and contributing factors in these bleaching events, and the degree of acclimatisation or adaptation on these reefs are poorly understood. During the 2005 warm-water anomaly in the southern Indian Ocean we conducted bleaching surveys and collected samples for genotyping of the algal symbiont communities at 21 sites in southern Mozambique and South Africa. Coral bleaching reached unprecedented levels and was negatively correlated with both latitude and water depths. Stylophora pistillata and Montipora were the most susceptible taxa, whereas three common branching corals had significantly different bleaching responses (Stylophora > Acropora > Pocillopora). Temperature records indicated that localised strong upwelling events coupled with persistent above-average seawater temperatures may result in accumulated thermal stress leading to bleaching. Symbiodinium in 139 scleractinian corals belonged almost exclusively to clade C, with clade D symbionts present in only 3% of the colonies. Two atypical C subclades were present in Stylophora and Pocillopora colonies and these were more abundant in shallow than deeper sites. Taxon-specific differences in bleaching responses were unrelated to different clades of algal symbionts and suggest that Symbiodinium C subtypes with diverse thermal tolerance, coupled with acclimatisation and morphology of the host colony influence the bleaching response. Additionally, the predominance of putatively thermal-sensitive Symbiodinium in southern African corals may reflect a limited experience of bleaching and emphasises the vulnerability of these reefs to moderate levels of thermal stress.     

Assessment of Jatropha curcas L. biodiesel seed cake toxicity using the zebrafish (Danio rerio) embryo toxicity (ZFET) test

Consequent to the growing demand for alternative sources of energy, the seeds from Jatropha curcas remain to be the favorite for biodiesel production. However, a significant volume of the residual organic mass (seed cake) is produced during the extraction process, which raises concerns on safe waste disposal. In the present study, we assessed the toxicity of J. curcas seed cake using the zebrafish (Danio rerio) embryotoxicity test. Within 1-h post-fertilization (hpf), the fertilized eggs were exposed to five mass concentrations of J. curcas seed cake and were followed through 24, 48, and 72 hpf. Toxicity was evaluated based on lethal endpoints induced on zebrafish embryos namely egg coagulation, non-formation of somites, and non-detachment of tail. The lowest concentration tested, 1 g/L, was not able to elicit toxicity on embryos whereas 100 % mortality (based also on lethal endpoints) was recorded at the highest concentration at 2.15 g/L. The computed LC50 for the J. curcas seed cake was 1.61 g/L. No further increase in mortality was observed in the succeeding time points (48 and 72 hpf) indicating that J. curcas seed cake exerted acute toxicity on zebrafish embryos. Sublethal endpoints (yolk sac and pericardial edema) were noted at 72 hpf in zebrafish embryos exposed to higher concentrations. The observed lethal endpoints induced on zebrafish embryos were discussed in relation to the active principles, notably, phorbol esters that have remained in the seed cake even after extraction.     

Analysis of PM2.5and PM10 in the Atmosphere of Mexico City during 2000-2002

Abstract

During the last 10 years, high atmospheric concentrations of airborne particles recorded in the Mexico City metropolitan area have caused concern because of their potential harmful effects on human health. Four monitoring campaigns have been carried out in the Mexico City metropolitan area during 2000-2002 at three sites: (1) Xalos-toc, located in an industrial region; (2) La Merced, located in a commercial area; and (3) Pedregal, located in a residential area. Results of gravimetric and chemical analyses of 330 samples of particulate matter (PM) with an aerodynamic diameter less than 2.5 μm (PM_2.5) and PM with an aerodynamic diameter less than 10 μm (PM₁₀) indicate that (1) PM_2.5/PM₁₀ average ratios were 0.42, 0.46, and 0.52 for Xalostoc, La Merced, and Pedregal, respectively; (2) the highest PM_2.5 and PM₁₀ concentrations were found at the industrial site; (3) PM_2.5 and PM₁₀ concentrations were lower at nighttime; (4) PM_2.5 and PM₁₀ spatial averages concentrations were 35 and 76 μg/m³, respectively; and (5) when the PM_2.5 standard was exceeded, nitrate, sulfate, ammonium, organic carbon, and elemental carbon concentrations were high. Twenty-four hour averaged PM_2.5 concentrations in Mexico City and Sao Paulo were similar to those recorded in the 1980s in Los Angeles. PM₁₀ concentrations were comparable in Sao Paulo and Mexico City but 3-fold lower than those found in Santiago.     

Spread and potential impact of the recently introduced European green crab,Carcinus maenas,in central California

Our study examines the potential impact of the European green crab Carcinus maenas on communities of coastal embayments of western North America. We document the current distribution and range expansion of this species beyond San Francisco Bay, where C. maenas first became established along this coast in 1989–1990, and we test the effect of C. maenas predation on different species and sizes of infaunal invertebrates in field and laboratory experiments. In our samples from eight coastal locations in central California collected between June 1993 and May 1994, we found no green crabs at the two closest embayments south of San Francisco Bay and found the crabs in all four embayments sampled within 120 km north of San Francisco Bay, up to and including Bodega Harbor. C. maenas was not present in samples from sites farther north. This northward range expansion is apparently the result of larval recruitment by a single cohort, corresponding to the predominant northern transport of surface waters and the approximate distance water moves during larval green crab development. At Bodega Harbor, the current northern range limit, the C. maenas population is now well established and reproducing. Females and males became sexually mature within their first year at 40 mm carapace width, molting approximately monthly from summer through fall, and females were ovigerous in late fall of their first year at 50 mm. We expect larvae from this population to recruit locally and to the north, promoting episodic range extensions as new populations are established and reproduce. Enclosure experiments conducted during the summer of 1993 at the intertidal sandflats of Bodega Harbor showed that C. maenas significantly reduced densities of the most abundant taxa, including the bivalves Transennella confusa and T. tantilla, the cumacean Cumella vulgaris, and the amphipod Corophium sp. Furthermore, Carcinus maenas selectively removed larger (>3 mm) rather than smaller (<1 mm) Transennella spp. in both field and laboratory experiments. Based on the available data from this and other studies of green crabs, and our 10 yr study of community dynamics at Bodega Harbor, we predict C. maenas will significantly alter community structure, ecological interactions, and evolutionary processes in embayments of western North America.     

Citrus essential oils and their influence on the anaerobic digestion process: An overview

Citrus waste accounts for more than half of the whole fruit when processed for juice extraction. Among valorisation possibilities, anaerobic digestion for methane generation appears to be the most technically feasible and environmentally friendly alternative. However, citrus essential oils can inhibit this biological process. In this paper, the characteristics of citrus essential oils, as well as the mechanisms of their antimicrobial effects and potential adaptation mechanisms are reviewed. Previous studies of anaerobic digestion of citrus waste under different conditions are presented; however, some controversy exists regarding the limiting dosage of limonene for a stable process (24–192 mg of citrus essential oil per liter of digester and day). Successful strategies to avoid process inhibition by citrus essential oils are based either on recovery or removal of the limonene, by extraction or fungal pre-treatment respectively.     

The Chemical Composition and Flow of the River Lea, Spain

Weekly measurements of chemical composition were made at four sampling sites on the Lea River (Spain) between July 1985 and August 1986. at two stations there were gauging-weirs for stream discharge monitoring. Conductivity, pH, alkalinity, silicon, calcium, magnesium, sodium, potassium, ammonia, nitrate, sulphate, chloride, reactive phosphate, and total phosphate, were recorded in each site.

Results were analysed using multiple regression techniques to study the relationship between flow and chemical components.

Conductivity, alkalinity, calcium, magnesium and sulphate were strongly related to flow, decreasing in concentration with increased flow. Ammonia, potassium, reactive phosphate and total phosphate varied most widely, with peaks at times of heavy rainfall. Nitrate increased at times of high discharge, with little variation between sampling points. Silicon decreased in summer and autumn in the lower catchment area whilst chloride and sodium were higher in the lower catchment of the River Lea.     

Exposure estimates to Fusarium mycotoxins through cereals intake

Mycotoxins are harmful substances produced by fungi in several commodities with a widespread presence in foodstuffs. Human exposure to mycotoxins occurs mainly by contaminated food. The quantitation of mycotoxins in cereal-based food, highly consumed by different age population, is of concern. In this survey, 159 cereal-based samples classified as wheat, maize and rice-based, have been evaluated for the occurrence of patulin, deoxynivalenol, 3-acetyl-deoxynivalenol, fusarenon-X, diacetoxyscirpenol, nivalenol, neosolaniol, HT-2, T-2 and zearalenone by gas chromatography–tandem mass spectrometry. Intakes were calculated for average consumers among adults, children and infants and compared with the tolerable daily intakes (TDI). Data obtained were used to estimate the potential exposure levels. 65.4% of the samples were contaminated with at least one mycotoxin and 15.7% of the analyzed samples showed co-occurrence of mycotoxin. The dietary exposure to HT-2 and T-2 toxins was estimated as 0.010 and 0.086 μg kg⁻¹ bw d⁻¹, amounting to 10% and 86% of the TDI, for adults and infants respectively. These results back up the necessity to take a vigilant attitude in order to minimize human intake of mycotoxins.