Nitrite production by ammonia-oxidizing bacteria mediates chloramine decay and resistance in a mixed-species community.

As water distribution centres increasingly switch to using chloramine to disinfect drinking water, it is of paramount importance to determine the interactions of chloramine with potential biological contaminants, such as bacterial biofilms, that are found in these systems. For example, ammonia-oxidizing bacteria (AOB) are known to accelerate the decay of chloramine in drinking water systems, but it is also known that organic compounds can increase the chloramine demand. This study expanded upon our previously published model to compare the decay of chloramine in response to alginate, Pseudomonas aeruginosa, Nitrosomonas europaea and a mixed-species nitrifying culture, exploring the contributions of microbial by-products, heterotrophic bacteria and AOBs to chloramine decay. Furthermore, the contribution of AOBs to biofilm stability during chloramination was investigated. The results demonstrate that the biofilm matrix or extracellular polymeric substances (EPS), represented by alginate in these experiments, as well as high concentrations of dead or inactive cells, can drive chloramine decay rather than any specific biochemical activity of P. aeruginosa cells. Alginate was shown to reduce chloramine concentrations in a dose-dependent manner at an average rate of 0.003 mg l-1  h-1 per mg l-1 of alginate. Additionally, metabolically active AOBs mediated the decay of chloramine, which protected members of mixed-species biofilms from chloramine-mediated disinfection. Under these conditions, nitrite produced by AOBs directly reacted with chloramine to drive its decay. In contrast, biofilms of mixed-species communities that were dominated by heterotrophic bacteria due to either the absence of ammonia, or the addition of nitrification inhibitors and glucose, were highly sensitive to chloramine. These results suggest that mixed-species biofilms are protected by a combination of biofilm matrix-mediated inactivation of chloramine as well as the conversion of ammonia to nitrite through the activity of AOBs present in the community

Biofilm formation inhibition and dispersal of multi-species communities containing ammonia-oxidising bacteria.

Despite considerable research, the biofilm-forming capabilities of Nitrosomonas europaea are poorly understood for both mono and mixed-species communities. This study combined biofilm assays and molecular techniques to demonstrate that N. europaea makes very little biofilm on its own, and relies on the activity of associated heterotrophic bacteria to establish a biofilm. However, N. europaea has a vital role in the proliferation of mixed-species communities under carbon-limited conditions, such as in drinking water distribution systems, through the provision of organic carbon via ammonia oxidation. Results show that the addition of nitrification inhibitors to mixed-species nitrifying cultures under carbon-limited conditions disrupted biofilm formation and caused the dispersal of pre-formed biofilms. This dispersal effect was not observed when an organic carbon source, glucose, was included in the medium. Interestingly, inhibition of nitrification activity of these mixed-species biofilms in the presence of added glucose resulted in increased total biofilm formation compared to controls without the addition of nitrification inhibitors, or with only glucose added. This suggests that active AOB partially suppress or limit the overall growth of the heterotrophic bacteria. The experimental model developed here provides evidence that ammonia-oxidising bacteria (AOB) are involved in both the formation and maintenance of multi-species biofilm communities. The results demonstrate that the activity of the AOB not only support the growth and biofilm formation of heterotrophic bacteria by providing organic carbon, but also restrict and limit total biomass in mixed community systems

Mallard Use of Elevated Nesting Structures: Fifteen Years of Management in Eastern South Dakota

Studies of mallard use and nesting success on elevated structures have generally been of a short-term nature. In this report we evaluated 15 consecutive years of mallard nesting on elevated structures (baskets, cylinders, and culverts) located over standing water in wetland basins in eastern South Dakota. Our objectives were to: 1) determine long-term trends in mallard occupancy and nest success in nesting baskets, cylinders, and culverts, 2) evaluate the effects of various nest structure adaptations for enhancing mallard use and maintaining high nest success rates, and 3) provide managers with various enhancement techniques for mallard nesting structures that have proven productive in this long-term management effort

Biofilm formation inhibition and dispersal of multi-species communities containing ammonia-oxidising bacteria

© 2019, The Author(s). Despite considerable research, the biofilm-forming capabilities of Nitrosomonas europaea are poorly understood for both mono and mixed-species communities. This study combined biofilm assays and molecular techniques to demonstrate that N. europaea makes very little biofilm on its own, and relies on the activity of associated heterotrophic bacteria to establish a biofilm. However, N. europaea has a vital role in the proliferation of mixed-species communities under carbon-limited conditions, such as in drinking water distribution systems, through the provision of organic carbon via ammonia oxidation. Results show that the addition of nitrification inhibitors to mixed-species nitrifying cultures under carbon-limited conditions disrupted biofilm formation and caused the dispersal of pre-formed biofilms. This dispersal effect was not observed when an organic carbon source, glucose, was included in the medium. Interestingly, inhibition of nitrification activity of these mixed-species biofilms in the presence of added glucose resulted in increased total biofilm formation compared to controls without the addition of nitrification inhibitors, or with only glucose added. This suggests that active AOB partially suppress or limit the overall growth of the heterotrophic bacteria. The experimental model developed here provides evidence that ammonia-oxidising bacteria (AOB) are involved in both the formation and maintenance of multi-species biofilm communities. The results demonstrate that the activity of the AOB not only support the growth and biofilm formation of heterotrophic bacteria by providing organic carbon, but also restrict and limit total biomass in mixed community systems

The magnetic part of the Weyl tensor, and the expansion of discrete universes

42 pages, 27 figures42 pages, 27 figures42 pages, 27 figures42 pages, 27 figures42 pages, 27 figures42 pages, 27 figuresTC is supported by the STFC and DG by an AARMS postdoctoral fellowship

Harvest Demographics of Temperate-breeding Canada Geese in South Dakota, 1967–1995

In South Dakota, breeding giant Canada geese (Branta canadensis maxima) have increased substantially, and harvest management strategies have been implemented to maximize hunting opportunity (e.g., special early-September seasons) on local, as well as molt-migrant giant Canada geese (B. c. interior) while still protecting lesser abundant Arcticbreeding Canada geese and cackling geese (e.g., B. hutchinsii, B. minima). Information on important parameters, such as survival and recovery rates, are generally lacking for giant Canada geese in the northern Great Plains. Patterns in Canada goose band recoveries can provide insight into the distribution, chronology, and harvest pressures to which a given goose population segment is exposed. We studied spatial and temporal recovery patterns of molting Canada geese during annual banding efforts in South Dakota between 1967 and 1995. Recovery rates (% ± SE) for Canada geese increased over time in both western South Dakota (0.034 ± 0.005 [1967 to 1976], 0.056 ± 0.009 [1977 to 1986]) and eastern (0.026 ± 0.002 [1967 to 1978], 0.058 ± 0.003 [1987 to 1995]) South Dakota. Although recovery rates for Canada geese west of the Missouri River (WR) and east of the Missouri River (ER) were relatively similar, recovery distribution and harvest chronology indicate spatial and temporal differences for geese banded in these 2 geographic regions. Overall, Canada geese banded in South Dakota were recovered in 23 states and 5 Canadian provinces, and recovery distribution varied relative to banding region. Distribution of recoveries suggests a south-southwesterly movement for WR-banded geese compared to a south-southeasterly movement for ERbanded geese. For WR-banded geese, 40 to 52% and 30 to 34% of direct and indirect recoveries, respectively, occurred in December. In contrast, for ER-banded geese, 19 to 38% and 15 to 19% of direct and indirect recoveries, respectively, occurred in December. Waterfowl managers need to consider that recovery rates and harvest chronology of banded giant Canada geese may vary geographically within a state or province. Refinement of harvest management strategies at multiple spatial scales may be required