Effect of dung deposition on small-scale patch structure and seasonal vegetation dynamics in mountain pastures

Cattle activity greatly influences plant species composition and biomass production of grassland ecosystems. Dung deposition by cattle together with grazing and trampling can be considered as one of the important factors driving vegetation dynamics in pastures. The objective of this study was to investigate at 10-cm and 1-month resolution the plant community dynamics induced by dung deposition in two plant communities (a mesotrophic and an oligotrophic grassland) in a pasture of the Swiss Jura Mountains. Vegetation was sampled four or three times during the vegetation period in contiguous 10 cm × 10 cm quadrats from the centre of the dung pat to a distance of 60 cm. A lower grazing intensity near the dung pat was recorded for all observation periods. In the mesotrophic grassland the canopy was higher near the dung pat already one week after dung deposition. Vegetation around dung pats was submitted to two opposite fertilizing and grazing gradients, which induced changes in vegetation texture and structure at fine scale and short term. We observed a positive rank correlation between species turnover and distance to the dung for both communities, suggesting a seasonal stabilizing effect of dung on the plant composition of their direct surroundings (0–10 cm) likely due to cattle avoidance. Since dung pats are dropped every year in different locations, they create in the pasture a shifting mosaic of nutrient availability and grazing intensity inducing at seasonal scale micro-successions in plant communities.     

Contrasting temporal trends and relationships of total organic carbon, black carbon, and polycyclic aromatic hydrocarbons in rural low-altitude and remote high-altitude lakes

Historical records of total organic carbon (TOC), black carbon (BC), and polycyclic aromatic hydrocarbons (PAHs) were reconstructed in dated sediment cores from four nearby lakes in central Switzerland. In the sub-Alpine Lake Thun, located at 558 m a.s.l., the proximity to anthropogenic emission sources is reflected in higher input of BC and PAHs into sediments with fluxes only slightly decreasing during the last decades. PAH/BC ratios are relatively high and correlation between levels of total PAHs and BC is almost inexistent in Lake Thun, probably due to the presence of less condensed forms of the BC spectrum (char BC) that is underestimated with the chemothermal oxidation method applied in this study. The sediment profiles of TOC, BC, and PAHs are noticeably different in the mountain lakes located around 2000 m a.s.l. In Lake Engstlen, the PAH/BC ratios, as well as the correlation between PAHs and BC, point towards appreciable amounts of predominantly light soot particles. Light soot particles have higher mobility and can, therefore, be efficiently transported to this remote site. The proglacial Lake Oberaar is shown to be a receptor of BC and PAHs released by the fast melting adjacent glacier acting as a secondary source for these conservative species temporarily stored in the glacier ice. Finally, Lake Stein is in strong contrast to all other lakes. High flux of BC into Lake Stein, combined with constant temporal evolutions of BC and PAHs, and in particular BC/TOC ratios approaching 100% are all strong indications for a geogenic presence of graphite in its catchment area.     

Unexplained gonad alterations in whitefish (Coregonus spp.) from Lake Thun, Switzerland: levels of persistent organic pollutants in different morphs

Since 2000, a surprisingly high number of macroscopical gonad alterations has been reported in whitefish (Coregonus spp.) from Lake Thun, Switzerland. This unique phenomenon is still unexplained and has received much public attention. As one possible trigger for these effects, the presence of persistent, bioaccumulative and toxic compounds acting as endocrine disruptors in the lake has been discussed. In this study, concentrations of selected persistent organic pollutants were examined in two morphs of whitefish from Lake Thun and their link to the observed abnormalities was investigated. Analyzed compound classes included polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and dibenzofurans, polychlorinated naphthalenes, polybrominated diphenyl ethers and hexabromocyclododecanes. The target substances were identified in all samples and concentrations of the analyzed compounds were highly correlated among each other. These correlations show that the analyzed substances have the same distribution pattern throughout the lake and that uptake, accumulation and elimination processes are similar. Significant differences in contaminant levels within the samples existed between the two analyzed morphs of whitefish, most likely due to different age, food patterns and growth rate. No difference in contaminant levels was observed between fish with abnormal gonads and fish with normal gonads, suggesting no causal link between the investigated lipophilic organohalogen compounds present in fish and the observed gonad abnormalities in whitefish from Lake Thun. A comparison to existing data shows that concentrations in Lake Thun whitefish are at the lower bound of contaminant levels in whitefish from Swiss lakes or from European waters.     

Occurrence and sources of selected phenolic endocrine disruptors in Ria de Aveiro,Portugal

Background, aim and scope  

Ria de Aveiro (Portugal) is a shallow coastal lagoon of high economic and ecological importance. Hardly any data on its chemical pollution by polar organic pollutants are available in literature. This study focused on the presence and sources of a series of phenolic endocrine-disrupting compounds (EDCs) in this area, including parabens, alkylphenolic compounds and bisphenol-A (BPA). A number of possible sources of pollution are present in the area, including the large harbours present in the lagoon, the city of Aveiro and the rivers discharging into the area. A recently constructed submarine wastewater outfall, located a few kilometres from the lagoon inlet has also been suggested as a possible source of pollution to Ria de Aveiro in several publications. The aim of the current field study was to investigate the occurrence and main sources of phenolic endocrine disruptors in Ria de Aveiro.     

Impact of DOM from composted "alperujo" on soil structure, AM fungi, microbial activity and growth of Medicago sativa

Water-soluble extracts from compost may represent an alternative nutrient and organic matter source for crop production under drip irrigation. Dissolved organic matter (DOM), extracted from composted "alperujo", the main by-product from the Spanish olive oil industry, was applied to soil alone or in combination with either Glomus intraradices Schenck and Smith or a mixture of G. intraradices, Glomus deserticola (Trappe, Bloss. and Menge) and Glomus mosseae (Nicol and Gerd.) Gerd. and Trappe. Response measurements included mycorrhizal colonisation, nutrient uptake and growth of Medicago sativa and microbiological and physical properties in the rhizosphere. Dissolved organic matter was added to soil at concentrations of 0, 50, 100 or 300mgCkg(-1) substrate. During the four months of the experiment, the plants were harvested three times. Both mycorrhizal inoculation treatments significantly increased soil aggregate stability. Only the mycorrhizal inoculations increased microbial biomass C and protease and phosphatase activities and decreased water-soluble C, particularly the mixture of arbuscular mycorrhizal fungi. At the third harvest, the greatest increase in growth of M. sativa was observed in the inoculated plants with shoot biomass being 38% greater than for plants grown in the soil amended with the highest dose of DOM and 57% greater than for control plants. The addition of DOM was not sufficient to restore soil structure and microbial activity and did not affect the mycorrhizal development of introduced populations of arbuscular mycorrhizal fungi, but, depending on the dose, its fertiliser efficiency for improving plant growth was apparent.     

A simplified headspace biochemical oxygen demand test protocol based on oxygen measurements using a fiber optic probe.

Batch respirometric tests have many advantages over the conventional biochemical oxygen demand (BOD) method for analysis of wastewaters, including the use of nondiluted samples, a more rapid exertion of oxygen demand, and reduced sample preparation time. The headspace biochemical oxygen demand (HBOD) test can be used to obtain oxygen demands in 2 or 3 days that can predict 5-day biochemical oxygen demand (BOD5) results. The main disadvantage of the HBOD and other respirometric tests has been the lack of a simple and direct method to measure oxygen concentrations in the gas phase. The recent commercial production of a new type of fiber optic oxygen probe, however, provides a method to eliminate this disadvantage. This fiber optic probe, referred to here as the HBOD probe, was tested to see if it could be used in HBOD tests. Gas-phase oxygen measurements made with the HBOD probe took only a few seconds and were not significantly different from those made using a gas chromatograph (t test: n = 15, R2 = 0.9995, p < 0.001). In field tests using the HBOD probe procedure, the probe greatly reduced sample analysis time compared with previous HBOD and BOD protocols and produced more precise results than the BOD test for wastewater samples from two treatment plants (University Area Joint Authority [UAJA] Wastewater Treatment Plant in University Park, Pennsylvania, and The Pennsylvania State University [PSU] Wastewater Treatment Plant in University Park). Headspace biochemical oxygen demand measurements on UAJA primary clarifier effluent were 59.9 +/- 2.4% after 2 days (HBOD2) and 73.0 +/- 3.1% after 3 days (HBOD) of BOD, values, indicating that BOD5 values could be predicted by multiplying HBOD2 values by 1.67 +/- 0.07 or HBOD3 by 1.37 +/- 0.06. Similarly, tests using PSU wastewater samples could be used to provide BOD5 estimates by multiplying the HBOD2 by 1.24 +/- 0.04 or by multiplying the HBOD3 by 0.97 +/- 0.03. These results indicate that the HBOD fiber optic probe can be used to obtain reliable oxygen demands in batch respirometric tests such as the HBOD test.