An in vitro biofilm model system to facilitate study of microbial communities of the human oral cavity.

The human oral cavity is host to a diverse microbiota. Much of what is known about the behaviour of oral microbes derives from studies of individual or several cultivated species, situations which do not totally reflect the function of organisms within more complex microbiota or multispecies biofilms. The number of validated models that allow examination of the role that biofilms play during oral cavity colonization is also limited. The CDC biofilm reactor is a standard method that has been deployed to study interactions between members of human microbiotas allowing studies to be completed during an extended period under conditions where nutrient availability, and washout of waste products are controlled. The objective of this work was to develop a robust in vitro biofilm-model system from a pooled saliva inoculum to study the development, reproducibility and stability of the oral microbiota. By employing deep sequencing of the variable regions of the 16S rRNA gene, we found that the CDC biofilm reactor could be used to efficiently cultivate microbiota containing all six major phyla previously identified as the core saliva microbiota. After an acclimatisation period, communities in each reactor stabilised. Replicate reactors were predominately populated by a shared core microbiota; variation between replicate reactors was primarily driven by shifts in abundance of shared operational taxonomic units. We conclude that the CDC biofilm reactor can be used to cultivate communities that replicate key features of the human oral cavity and is a useful tool to facilitate studies of the dynamics of these communities.

A method of identifying priority spatial patterns for the management of potential ecological risks posed by heavy metals.

An approach of identifying priority spatial patterns in response to different ecological risk levels associated with heavy metals (HM) is proposed. First, ecological hotspots (EH) are delineated by integrating NDVI-based assessment with the impact assessment of anthropogenic impact sources. Second, the HM potential ecological risks index (PERI) is calculated and spatially interpolated. Finally, the EH with different PERI values are identified through logic calculation. Study results show that 45.2% of the study region has low HM risks, 53.2% with moderate HM risks, and only 1.6% with high HM risks. In addition, the percentage of EH with low HM risks is 6.5%; the percentage with moderate HM risks is 5.4%; and the percentage with high HM risks is 0.4%. The EH with low and moderate HM ecological risks are proposed to be the regions in priority for management. This approach is potentially useful to HM ecological risk assessment and HM contamination management around the world.

Using heavy metals to detect the human disturbances spatial scale on Chinese Yellow Sea coasts with an integrated analysis.

An integrated approach involving landuse patterns obtained from landuse data and heavy metal contents of the top 10 cm surface soil layer samplings was proposed to detect the characteristic spatial scale of non-point source human disturbances on the Yellow Sea coast in China. Circular plots, with radii of 200, 500, 1000, 1500, and 2000 m were set up to represent five spatial scales. We proposed a human impact index (HII) using the landuse data to model the human disturbances. Multivariate statistics of the 10 heavy metals, Cr, Co, Fe, Mn, Ni, V, Zn, Cu, Ti, and Sr, were done. Finally curve estimation between HII and heavy metals was also done. The results showed that: (1) multivariate statistics, including principal component analysis, cluster analysis and the 1-tailed Pearson correlation analysis showing that elements Cr, Cu, Fe, Mn, Ni, V, Zn, and Co could be interpreted as anthropogenic elements and (2) of all the heavy metals showing statistical significance from the curve estimation, in general, the 1000 m scale HII had the best modeling result. We concluded that the characteristic spatial scale of human disturbances on Yellow Sea coast might be 1000 m.

Evaluation of potential habitat with an integrated analysis of a spatial conservation strategy for David's deer, Elaphurus davidians.

How to assess the potential habitat integrating landscape dynamics and population research, and how to reintroduce animals to potential habitats in environments highly human disturbed are still questions to be answered in conservation biology. According to behavioral research on Elaphurus davidians, we have developed a suitability index and a risk index to evaluate the potential habitats for the deer. With these indices, we conducted two transect assessments to evaluate the gradient change of the target region. Then, taking rivers as border lines, we tabulated the forest areas, high grassland area and total area and then compared the forest and high grassland area in each subregion. Furthermore, we computed the land use transfer matrix for the whole Yancheng coast during 1987-2000. We also computed human modified index (HMI) in six subregions. Lastly with a geographical information system support we obtained the spatial distribution of the indices and evaluation of the whole potential habitats from a neighborhood analysis. The transect assessment showed that the suitability of the coastal area was higher than that of the inland area for the deer, while the southern area was higher than the northern. Landscape metrics and HMI analysis showed that different landscape patterns and different anthropogenic disturbance existed within the region, and the increasing human disturbance was the key factor causing the pattern dynamics. The evaluation of potential habitats showed that there was an estimated carrying capacity of no more than 10,000 for David's deer reintroduction into the natural area. Also the reintroduction strategy was discussed. This integrated approach linked the population research and the landscape metrics, and the dataset with different scale; thus, it is an approach likely to be useful for the protection of other large animal in a landscape highly disturbed by humans.

Effects of topography on simulated net primary productivity at landscape scale.

Local topography significantly affects spatial variations of climatic variables and soil water movement in complex terrain. Therefore, the distribution and productivity of ecosystems are closely linked to topography. Using a coupled terrestrial carbon and hydrological model (BEPS-TerrainLab model), the topographic effects on the net primary productivity (NPP) are analyzed through four modelling experiments for a 5700 km(2) area in Baohe River basin, Shaanxi Province, northwest of China. The model was able to capture 81% of the variability in NPP estimated from tree rings, with a mean relative error of 3.1%. The average NPP in 2003 for the study area was 741 gCm(-2)yr(-1) from a model run including topographic effects on the distributions of climate variables and lateral flow of ground water. Topography has considerable effect on NPP, which peaks near 1350 m above the sea level. An elevation increase of 100 m above this level reduces the average annual NPP by about 25 gCm(-2). The terrain aspect gives rise to a NPP change of 5% for forests located below 1900 m as a result of its influence on incident solar radiation. For the whole study area, a simulation totally excluding topographic effects on the distributions of climatic variables and ground water movement overestimated the average NPP by 5%.

A practical application of Driscoll's equation for predicting the acid-neutralizing capacity in acidic natural waters equilibria with the mineral phase gibbsite.

A practical application of Driscoll's equation for predicting the acid-neutralizing capacity (ANC) in acidic waters equilibria with the mineral phase gibbsite is reported in this paper. Theoretical predication values of ANC are compared with the experimental data obtained from different literatures. The effect of aluminum (Al) on the value of ANC is investigated. It indicates that Al plays an important role in regulating the buffering effects in acidic natural waters. Failure to consider Al in acidic waters may bias assessment results in certain situations so as to overestimate the ANC values in response to increase in atmospheric deposition.

Dynamics of aluminum speciation in forest-well drainage waters from the Rhode River watershed, Maryland.

This paper reports an investigation of the dynamics of aluminum (Al) speciation in the forest-well waters from study site 110 of the Rhode River watershed, a representative sub-unit of Chesapeake Bay. Seasonal changes of Al speciation are evaluated by a modified MINEQL computer model using chemical equilibrium calculation. It was found that Al-F and Al-Org complexes were the dominate forms, whereas toxic forms of Al3+ and Al-OH were not significant. This indicates that Al toxicity is not very serious in the Rhode River area due to the high concentrations of fluoride and organic materials, even though sometimes pH is very low (approximately 4). Increased H+ or some other associated factors may be responsible for the decline in fish and amphibian population on the watershed.