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1.
Cory J. D. Matthews Sebasti��n P. Luque Stephen D. Petersen Russel D. Andrews Steven H. Ferguson 《Polar Biology》2011,34(7):1091-1096
Killer whales (Orcinus orca) occur in the eastern Canadian Arctic during the open-water season, but their seasonal movements in Arctic waters and overall
distribution are poorly understood. During August 2009, satellite transmitters were deployed onto two killer whales in Admiralty
Inlet, Baffin Island, Canada. A whale tracked for 90 days remained in Admiralty and Prince Regent Inlets from mid-August until
early October, when locations overlapped aggregations of marine mammal prey species. While in Admiralty and Prince Regent
Inlets, the whale traveled 96.1 ± 45.3 km day−1 (max 162.6 km day−1) and 120.1 ± 44.5 km day−1 (max 192.7 km day−1), respectively. Increasing ice cover in Prince Regent Inlet in late September and early October was avoided, and the whale
left the region prior to heavy ice formation. The whale traveled an average of 159.4 ± 44.8 km day−1 (max 252.0 km day−1) along the east coast of Baffin Island and into the open North Atlantic by mid-November, covering over 5,400 km in approximately
one month. This research marks the first time satellite telemetry has been used to study killer whale movements in the eastern
Canadian Arctic and documents long-distance movement rarely observed in this species. 相似文献
2.
Robert L. Pitman John W. Durban Michael Greenfelder Christophe Guinet Morton Jorgensen Paula A. Olson Jordi Plana Paul Tixier Jared R. Towers 《Polar Biology》2011,34(2):303-306
Studies have shown that killer whale (Orcinus orca) communities in high latitudes regularly comprise assemblages of sympatric ‘ecotypes’—forms that differ in morphology, behavior,
and prey preferences. Although they can appear superficially similar, recent genetic evidence suggests that breeding is assortative
among ecotypes within individual communities, and species-level divergences are inferred in some cases. Here, we provide information
on a recently recognized ‘type D’ killer whale based on photographs of a 1955 mass stranding in New Zealand and our own six
at-sea sightings since 2004. It is the most distinctive-looking form of killer whale that we know of, immediately recognizable
by its extremely small white eye patch. Its geographic range appears to be circumglobal in subantarctic waters between latitudes
40°S and 60°S. School sizes are relatively large (mean 17.6; range 9–35; n = 7), and although nothing is known about the type D diet, it is suspected to include fish because groups have been photographed
around longline vessels where they reportedly depredate Patagonian toothfish (Dissostichus eleginoides). 相似文献
3.
Ekaterina A. Borisova Olga A. Filatova Ivan D. Fedutin Alexei V. Tiunov Olga V. Shpak Erich Hoyt 《Marine Mammal Science》2020,36(3):925-938
Killer whales are top predators in marine trophic chains, and therefore their feeding preferences can substantially affect the abundance of species on the lower trophic levels. Killer whales are known to feed on many different types of prey from small fish to large whales, but a given killer whale population usually focuses on a specific type of prey. Stable isotope analysis is widely used to study whale diets, because direct observations are often impossible. Killer whale feeding habits in the western North Pacific are poorly studied, and the large-scale stable isotope analysis provides a unique opportunity to gain insights into the trophic links of this top predator. In this study, we compare the δ13C and δ15N stable isotope values from killer whale skin samples obtained in different areas of the western North Pacific from fish-eating (R-type) and mammal-eating (T-type) killer whale ecotypes. The effect of ecotype was highly significant: both carbon and nitrogen stable isotope values were lower in R-type whales than in T-type whales. The geographical variation also affected killer whale stable isotope values due to both the differences in killer whale diet and the variation in baseline stable isotope values across the study areas. 相似文献
4.
M. P. Heide-J?rgensen K. L. Laidre D. Litovka M. Villum Jensen J. M. Grebmeier B. I. Sirenko 《Polar Biology》2012,35(7):1035-1045
The purpose of this study was to evaluate summer and fall residency and habitat selection by gray whales, Eschrichtius robustus, together with the biomass of benthic amphipod prey on the coastal feeding grounds along the Chukotka Peninsula. Thirteen gray whales were instrumented with satellite transmitters in September 2006 near the Chukotka Peninsula, Russia. Nine transmitters provided positions from whales for up to 81?days. The whales travelled within 5?km of the Chukotka coast for most of the period they were tracked with only occasional movements offshore. The average daily travel speeds were 23?km?day?1 (range 9–53?km?day?1). Four of the whales had daily average travel speeds <1?km?day?1 suggesting strong fidelity to the study area. The area containing 95% of the locations for individual whales during biweekly periods was on average 13,027?km2 (range 7,097–15,896?km2). More than 65% of all locations were in water <30?m, and between 45 and 70% of biweekly kernel home ranges were located in depths between 31 and 50?m. Benthic density of amphipods within the Bering Strait at depths <50?m was on average ~54?g wet wt m?2 in 2006. It is likely that the abundant benthic biomass is more than sufficient forage to support the current gray whale population. The use of satellite telemetry in this study quantifies space use and movement patterns of gray whales along the Chukotka coast and identifies key feeding areas. 相似文献
5.
Currently, there are three recognized ecotypes (or species) of killer whales (Orcinus orca) in Antarctic waters, including type B, a putative prey specialist on seals, which we refer to as “pack ice killer whale” (PI killer whale). During January 2009, we spent a total of 75.4 h observing three different groups of PI killer whales hunting off the western Antarctic Peninsula. Observed prey taken included 16 seals and 1 Antarctic minke whale (Balaenoptera bonaerensis). Weddell seals (Leptonychotes weddellii) were taken almost exclusively (14/15 identified seal kills), despite the fact that they represented only 15% of 365 seals identified on ice floes; the whales entirely avoided taking crabeater seals (Lobodon carcinophaga; 82% relative abundance) and leopard seals (Hydrurga leptonyx; 3%). Of the seals killed, the whales took 12/14 (86%) off ice floes using a cooperative wave‐washing behavior; they produced 120 waves during 22 separate attacks and successfully took 12/16 (75%) of the Weddell seals attacked. The mean number of waves produced per successful attack was 4.1 (range 1–10) and the mean attack duration was 30.4 min (range 15–62). Seal remains that we examined from one of the kills provided evidence of meticulous postmortem prey processing perhaps best termed “butchering.” 相似文献
6.
Ingestion rates and selectivity of the Arctic pelagic amphipod Themisto libellula were studied experimentally in Kongsfjorden (Svalbard, 78°N) during the summer period. Feeding incubations were conducted
on naturally occurring copepod communities at different concentrations ranging from 25 to 250 preys L−1. The ingestion rates increased with food availability from 1.3 to 17.7 preys ind−1 day−1, which corresponded to 0.3–11% of body carbon day−1. Despite the high prey concentration used in the experiments the satiation level was not reached. We suggested that T. libellula is able to take the maximum benefit from dense patches of preys, which represent a good adaptation to the high variability
in food supply characteristic of polar environment. Copepodids stage III of Calanus spp. appeared to be the preferred preys of T. libellula. Smaller copepods such as Oithona similis and Pseudocalanus spp., were also selected but only when their relative abundance exceeded 25% of the total prey available. The potential predation
impact of T. libellula is discussed in relation to the mesozooplankton small-scale patchiness and predator abundance. 相似文献
7.
Eve Jourdain Clare Andvik Richard Karoliussen Anders Ruus Dag Vongraven Katrine Borg 《Ecology and evolution》2020,10(9):4115-4127
Ecological diversity has been reported for killer whales (Orcinus orca) throughout the North Atlantic but patterns of prey specialization have remained poorly understood. We quantify interindividual dietary variations in killer whales (n = 38) sampled throughout the year in 2017–2018 in northern Norway using stable isotopic nitrogen (δ15N: 15N/14N) and carbon (δ13C: 13C/12C) ratios. A Gaussian mixture model assigned sampled individuals to three differentiated clusters, characterized by disparate nonoverlapping isotopic niches, that were consistent with predatory field observations: seal‐eaters, herring‐eaters, and lumpfish‐eaters. Seal‐eaters showed higher δ15N values (mean ± SD: 12.6 ± 0.3‰, range = 12.3–13.2‰, n = 10) compared to herring‐eaters (mean ± SD: 11.7 ± 0.2‰, range = 11.4–11.9‰, n = 19) and lumpfish‐eaters (mean ± SD: 11.6 ± 0.2‰, range = 11.3–11.9, n = 9). Elevated δ15N values for seal‐eaters, regardless of sampling season, confirmed feeding at high trophic levels throughout the year. However, a wide isotopic niche and low measured δ15N values in the seal‐eaters, compared to that of whales that would eat solely seals (δN‐measured = 12.6 vs. δN‐expected = 15.5), indicated a diverse diet that includes both fish and mammal prey. A narrow niche for killer whales sampled at herring and lumpfish seasonal grounds supported seasonal prey specialization reflective of local peaks in prey abundance for the two fish‐eating groups. Our results, thus, show differences in prey specialization within this killer whale population in Norway and that the episodic observations of killer whales feeding on prey other than fish are a consistent behavior, as reflected in different isotopic niches between seal and fish‐eating individuals. 相似文献
8.
Knowledge of how energetic parameters relate to fluctuating factors in the natural habitat is necessary when evaluating the
role of gelatinous zooplankton in the carbon flow of coastal waters. In laboratory experiments, we assessed feeding, respiration
and growth of the ctenophore, Pleurobrachia pileus, and constructed carbon budgets. Clearance rates (F, l d−1) of laboratory-reared Acartia tonsa as prey increased as a function of ctenophore polar length (L, mm) as F = 0.17L
1.9. For ctenophores larger than about 11 mm, clearance rate was depressed in containers of 30–50 l volume. Clearance rates on
field-collected prey were highest on the copepod, Centropages typicus, intermediate on the cladoceran, Evadne
nordmanni and low on the copepods, Acartia clausi and Temora longicornis. Specific growth rates of 8–10 mm P. pileus increased with increasing prey concentrations to a maximum of 0.09 d−1 attained at prey carbon densities of 40 and 100 μg C l−1 of Artemia salina and A. tonsa, respectively. Weight-specific respiration rates increased hyperbolically with prey concentration. From experiments in which
growth, ingestion and respiration were measured simultaneously, a carbon budget was constructed for individuals growing at
maximum rates; from the measured parameters, the assimilation efficiency and net growth efficiency were estimated to be 22
and 37%, respectively. We conclude that the predation rates of P. pileus depend on ctenophore size, prey species, prey density and experimental container volume. Because the specific growth rates,
respiration, assimilation and net growth efficiencies all were affected by food availability, knowledge of the ambient prey
field is critical when evaluating the role of P.
pileus in the carbon flow in coastal waters. 相似文献
9.
Caroline R. Weir Maria Taylor Pamela A. Q. Jelbes Andrew Stanworth Philip S. Hammond 《Marine Mammal Science》2021,37(3):919-933
Little information exists on the current status of Southern Hemisphere sei whales (Balaenoptera borealis). We assessed their distribution and abundance along the west coast of the Falkland Islands (southwest Atlantic) during February and March 2018, using line transect and nonsystematic surveys. Abundance estimates were generated for a single survey stratum using design- and model-based approaches. Sightings of sei whales and unidentified baleen whales (most, if not all, likely to be sei whales) occurred from the coast to the 100 m depth isobath that marked the offshore boundary of the stratum. The modeled distribution predicted highest whale densities in King George Bay and in the waters between Weddell Island and the Passage Islands. Sei whale abundance was estimated as 716 animals (CV = 0.22; 95% CI [448, 1,144]; density = 0.20 whales/km2) using the design-based approach, and 707 animals (CV = 0.11; 95% CI [566, 877]; density = 0.20 whales/km2) using the model-based approach. For sei whales and unidentified baleen whales combined, the equivalent estimates were 916 animals (CV = 0.19; 95% CI [606, 1,384]; density = 0.26 whales/km2) and 895 animals (CV = 0.074; 95% CI [777, 1,032]; density = 0.25 whales/km2). The data indicate that the Falkland Islands inner shelf region may support globally important seasonal feeding aggregations of sei whales, and potentially qualify as a Key Biodiversity Area. 相似文献
10.
Predation can regulate prey numbers but predator behaviour in multiple-prey systems can complicate understanding of control
mechanisms. We investigate killer whale (Orcinus orca) predation in an ocean system where multiple marine mammal prey coexist. Using stochastic models with Monte-Carlo simulations,
we test the most likely outcome of predator selection and compare scenarios where killer whales: (1) focus predation on larger
prey which presumably offer more energy per effort, (2) generalize by feeding on prey as encountered during searches, or (3)
follow a mixed foraging strategy based on a combination of encounter rate and prey size selection. We test alternative relationships
within the Hudson Bay geographic region, where evidence suggests killer whales seasonally concentrate feeding activities on
the large-bodied bowhead whale (Balaena mysticetus). However, model results indicate that killer whales do not show strong prey specialization and instead alternatively feed
on narwhal (Monodon monoceros) and beluga (Delphinapterus leucas) whales early and late in the ice-free season. Evidence does support the conjecture that during the peak of the open water
season, killer whale predation can differ regionally and feeding techniques can focus on bowhead whale prey. The mixed foraging
strategy used by killer whales includes seasonal predator specialization and has management and conservation significance
since killer whale predation may not be constrained by a regulatory functional response. 相似文献
11.
Nico Varo Andy J. Green Marta I. Sánchez Cristina Ramo Jesús Gómez Juan A. Amat 《Hydrobiologia》2011,664(1):163-171
Chemical communication may inform about the location of prey, predators, co-specifics, and mate partners in zooplankton. In
this study, we evaluated several life-history traits of the rotifer, Brachionus calyciflorus, exposed to conditioned media by a rotifer predator (Asplanchna brightwelli) and a cladocera competitor (Daphnia similis), quantifying population growth and life-table demography at two algal food levels (2.0 and 0.5 × 106 cells ml−1 of Chlorella pyrenoidosa). At both food levels, B. calyciflorus grown in predator-conditioned media had lower population abundance and slower population growth rate than controls. Conversely,
the competitor-conditioned media treatments produced both higher rotifer population abundance and faster population growth
rate than controls. Life-history parameters varied significantly depending on the presence of predator and competitor-conditioned
media. The Asplanchna-conditioned media significantly decreased gross reproductive rate (GRR): 8–9 offsprings per female; net reproductive rate
(R
0): 6–7 offsprings per female; population growth rate (r): 0.34–0.37 day−1; and increased generation time (T): 5.5–5.6 days. On the other hand, The Daphnia-conditioned media significantly increased the GRR (13–14 offsprings per female); net reproductive rate (8–9 offsprings per
female); population growth rate (0.42–0.43 day−1); and decreased generation time (4.9–5.0 days). However, the effects of food level on the life-history characteristic were
not significant in both treatments. Maximum values of the population abundance and the population growth rate are significantly
influenced by the predator densities and pre-culture time. This study suggests that rotifers use variable life-history strategies
(low reproduction and high survivorship versus high reproduction and low survivorship) based on the presence of predators
and competitors. 相似文献
12.
- 1 The significance of killer whale Orcinus orca predation on baleen whales (Mysticeti) has been a topic of considerable discussion and debate in recent years. Discourse has been constrained by poor understanding of predator‐prey dynamics, including the relative vulnerability of different mysticete species and age classes to killer whales and how these prey animals avoid predation. Here we provide an overview and analysis of predatory interactions between killer whales and mysticetes, with an emphasis on patterns of antipredator responses.
- 2 Responses of baleen whales to predatory advances and attacks by killer whales appear to fall into two distinct categories, which we term the fight and flight strategies. The fight strategy consists of active physical defence, including self‐defence by single individuals, defence of calves by their mothers and coordinated defence by groups of whales. It is documented for five mysticetes: southern right whale Eubalaena australis, North Atlantic right whale Eubalaena glacialis, bowhead whale Balaena mysticetus, humpback whale Megaptera novaeangliae and grey whale Eschrichtius robustus. The flight strategy consists of rapid (20–40 km/h) directional swimming away from killer whales and, if overtaken and attacked, individuals do little to defend themselves. This strategy is documented for six species in the genus Balaenoptera.
- 3 Many aspects of the life history, behaviour and morphology of mysticetes are consistent with their antipredator strategy, and we propose that evolution of these traits has been shaped by selection for reduced predation. Fight species tend to have robust body shapes and are slow but relatively manoeuvrable swimmers. They often calve or migrate in coastal areas where proximity to shallow water provides refuge and an advantage in defence. Most fight species have either callosities (rough and hardened patches of skin) or encrustations of barnacles on their bodies, which may serve (either primarily or secondarily) as weapons or armour for defence. Flight species have streamlined body shapes for high‐speed swimming and they can sustain speeds necessary to outrun pursuing killer whales (>15–20 km/h). These species tend to favour pelagic habitats and calving grounds where prolonged escape sprints from killer whales are possible.
- 4 The rarity of observed successful attacks by killer whales on baleen whales, especially adults, may be an indication of the effectiveness of these antipredator strategies. Baleen whales likely offer low profitability to killer whales, relative to some other marine mammal prey. High‐speed pursuit of flight species has a high energetic cost and a low probability of success while attacks on fight species can involve prolonged handling times and a risk of serious injury.
13.
Chris J. Hulatt Aino-Maija Lakaniemi Jaakko A. Puhakka David N. Thomas 《Bioenergy Research》2012,5(3):669-684
Mass culture of microalgae is a potential alternative to cultivation of terrestrial crops for bioenergy production. However, microalgae require nitrogen fertiliser in quantities much higher than plants, and this has important consequences for the energy balance of these systems. The effect of nitrogen fertiliser supplied to microalgal bubble-column photobioreactor cultures was investigated using different nitrogen sources (nitrate, urea, ammonium) and culture conditions (air, 12% CO2). In 20 L cultivations, maximum biomass productivity for Chlorella vulgaris cultivated using nitrate and urea was 0.046 and 0.053 g L−1 day−1, respectively. Maximum biomass productivity for Dunaliella tertiolecta cultivated using nitrate, urea and ammonium was 0.033, 0.038 and 0.038 g L−1 day−1, respectively. In intensive bubble-column photobioreactors using 12% CO2, maximum productivity reached 0.60 and 0.83 g L−1 day−1 for C. vulgaris and D. tertiolecta, respectively. Recycling of nitrogen within the photobioreactor system via algal exudation of nitrogenous compounds and bacterial activity was identified as a potentially important process. The energetic penalty incurred by supply of artificial nitrogen fertilisers, phosphorus, power and CO2 to microalgal photobioreactors was investigated, although analysis of all energy burdens from biomass production to usable energy carriers was not conducted. After subtraction of the power, nitrogen and phosphorus energy burdens, maximum net energy ratios for C. vulgaris and D. tertiolecta cultivated in bubble columns were 1.82 and 2.10. Assuming CO2 was also required from a manufactured source, the net energy ratio decreased to 0.09 and 0.11 for C. vulgaris and D. tertiolecta, so that biomass production in this scenario was unsustainable. Although supply of nitrogen is unlikely to be the most energetically costly factor in sparged photobioreactor designs, it is still a very significant penalty. There is a need to optimise both cultivation strategies and recycling of nitrogen in order to improve performance. Data are supported by measurements including biochemical properties (lipid, protein, heating value) and bacterial number by epifluorescence microscopy. 相似文献
14.
Background
Killer whales (Orcinus orca) are the most widely distributed cetacean, occurring in all oceans worldwide, and within ocean regions different ecotypes are defined based on prey preferences. Prey items are largely unknown in the eastern Canadian Arctic and therefore we conducted a survey of Inuit Traditional Ecological Knowledge (TEK) to provide information on the feeding ecology of killer whales. We compiled Inuit observations on killer whales and their prey items via 105 semi-directed interviews conducted in 11 eastern Nunavut communities (Kivalliq and Qikiqtaaluk regions) from 2007-2010.Results
Results detail local knowledge of killer whale prey items, hunting behaviour, prey responses, distribution of predation events, and prey capture techniques. Inuit TEK and published literature agree that killer whales at times eat only certain parts of prey, particularly of large whales, that attacks on large whales entail relatively small groups of killer whales, and that they hunt cooperatively. Inuit observations suggest that there is little prey specialization beyond marine mammals and there are no definitive observations of fish in the diet. Inuit hunters and elders also documented the use of sea ice and shallow water as prey refugia.Conclusions
By combining TEK and scientific approaches we provide a more holistic view of killer whale predation in the eastern Canadian Arctic relevant to management and policy. Continuing the long-term relationship between scientists and hunters will provide for successful knowledge integration and has resulted in considerable improvement in understanding of killer whale ecology relevant to management of prey species. Combining scientists and Inuit knowledge will assist in northerners adapting to the restructuring of the Arctic marine ecosystem associated with warming and loss of sea ice. 相似文献15.
Abies faxoniana is a key species in reforestation processes in the southeast of the Qinghai-Tibetan Plateau of China. The changes in growth,
photosynthesis and nutrient status of A. faxoniana seedlings exposed to enhanced ultraviolet-B (UV-B), nitrogen supply and their combination were investigated. The experimental
design included two levels of UV-B treatments (ambient UV-B, 11.02 KJ m−2 day−1; enhanced UV-B, 14.33 KJ m−2 day−1) and two nitrogen levels (0; 20 g N m−2). The results indicated that: (1) enhanced UV-B significantly caused a marked decline in growth parameters, net photosynthetic
rate (Pn), photosynthetic pigments and F
v/F
m, (2) supplemental nitrogen supply increased the accumulation of total biomass, Pn, photosynthetic pigments and F
v/F
m under ambient UV-B, whereas supplemental nitrogen supply reduced Pn, and not affect biomass under enhanced UV-B, (3) enhanced
UV-B or nitrogen supply changed the concentration of nutrient elements of various organs. 相似文献
16.
Kanesa May Duncan 《Environmental Biology of Fishes》2006,76(2-4):139-149
Juvenile scalloped hammerhead sharks, Sphyrna lewini, are apex predators within their nursery ground in Kāne‘ohe Bay, Ō‘ahu, Hawai‘i. Understanding daily maintenance requirements of a top-level predator is an important step toward understanding its ecological impact within a nursery ecosystem. Juvenile S. lewini were fed a range of daily ration levels to examine the effect of feeding rate on growth and gross conversion efficiency. The von Bertalanffy growth model yielded the best fit to the data, predicting a maintenance ration of 115 kJ kg−1 day−1 (3.4% body weight (BW) day−1) and a maximum growth rate of 38 kJ kg−1 day−1. This finding is in agreement with the previous prediction of high energetic requirements for S. lewini. In combination with the hypothesized food limitation within Kāne‘ohe Bay, this result may explain the observed high mortality rates of S. lewini. Gross conversion efficiency, K
1, ranged from −36% to 34%, with maximum efficiency at feeding levels of 5.1% BW day−1. The growth conversion efficiency of S.␣lewini is similar to that of lemon sharks and teleost fishes. Growth rates of juvenile S. lewini are possibly restricted by their high metabolic rate, limited food availability and foraging inexperience. By directly examining the effect of ration size on growth and food conversion, it was possible to resolve discrepancies between earlier studies, which used respiratory metabolism and gut content analyses. 相似文献
17.
Whale killers: Prevalence and ecological implications of killer whale predation on humpback whale calves off Western Australia
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Robert L. Pitman John A. Totterdell Holly Fearnbach Lisa T. Ballance John W. Durban Hans Kemps 《Marine Mammal Science》2015,31(2):629-657
Reports of killer whales (Orcinus orca) preying on large whales have been relatively rare, and the ecological significance of these attacks is controversial. Here we report on numerous observations of killer whales preying on neonate humpback whales (Megaptera novaeangliae) off Western Australia (WA) based on reports we compiled and our own observations. Attacking killer whales included at least 19 individuals from three stable social groupings in a highly connected local population; 22 separate attacks with known outcomes resulted in at least 14 (64%) kills of humpback calves. We satellite‐tagged an adult female killer whale and followed her group on the water for 20.3 h over six separate days. During that time, they attacked eight humpback calves, and from the seven known outcomes, at least three calves (43%) were killed. Overall, our observations suggest that humpback calves are a predictable, plentiful, and readily taken prey source for killer whales and scavenging sharks off WA for at least 5 mo/yr. Humpback “escorts” vigorously assisted mothers in protecting their calves from attacking killer whales (and a white shark, Carcharodon carcharias). This expands the purported role of escorts in humpback whale social interactions, although it is not clear how this behavior is adaptive for the escorts. 相似文献
18.
Control of livestock diseases can become complicated when wild animals are involved. The Eurasian badger (Meles meles) is considered the principle wildlife host of Mycobacterium bovis (which causes bovine tuberculosis, bTB) in Great Britain and Ireland, but wild deer have also been implicated. Whether wild
deer are likely to perpetuate bTB in cattle depends on the exposure risks they pose, the mode of pathogen transmission, the
distances over which the disease can be transported and whether they can maintain infection within their own populations independently
of other sources. We evaluated the likely host status of each of four species of wild British deer (red, roe, fallow and Reeves'
muntjac) and the badger across a range of densities typically observed in Britain by manipulating the reproductive number
equation proposed by Anderson and May (1991). We estimate that roe deer almost certainly act as spillover hosts at densities lower than 30 km−2, red deer below 16 km−2, muntjac below 6 km−2, fallow below 4 km−2 and the badger below 2 km−2. We also estimate that muntjac will almost certainly act as maintenance hosts at densities above 56 km−2, fallow above 47 km−2 and badgers above 24 km−2. For densities between these values, we cannot be certain of the host status of these species, and for red and roe deer we
cannot be certain of host status under most natural conditions typically experienced in parts of Britain experiencing high
incidence of bTB in cattle. However, enhanced transmission rates resulting from artificially high densities such as might
be experienced at supplementary feeding sites may be sufficient to promote independent maintenance of infection. We were not
able to confidently assign host status to any species over a wide range of densities, but conclude that this is likely to
reflect reality, where host status may be affected as much by, for example, demographic fluctuations as it is by population
density. Our results imply densities below which populations of wild deer inhabiting cattle bTB hotspots ought to be maintained
in order to control the possibility of them perpetuating the cycle of intra- and interspecific M. bovis transmission. 相似文献
19.
Nitrifying granules cultivation in a sequencing batch reactor at a low organics-to-total nitrogen ratio in wastewater 总被引:4,自引:0,他引:4
It is possible to cultivate aerobic granular sludge at a low organic loading rate and organics-to-total nitrogen (COD/N) ratio
in wastewater in the reactor with typical geometry (height/diameter = 2.1, superficial air velocity = 6 mm/s). The noted nitrification
efficiency was very high (99%). At the highest applied ammonia load (0.3 ± 0.002 mg NH4+–N g total suspended solids (TSS)−1 day−1, COD/N = 1), the dominating oxidized form of nitrogen was nitrite. Despite a constant aeration in the reactor, denitrification
occurred in the structure of granules. Applied molecular techniques allowed the changes in the ammonia-oxidizing bacteria
(AOB) community in granular sludge to be tracked. The major factor influencing AOB number and species composition was ammonia
load. At the ammonia load of 0.3 ± 0.002 mg NH4+–N g TSS−1 day−1, a highly diverse AOB community covering bacteria belonging to both the Nitrosospira and Nitrosomonas genera accounted for ca. 40% of the total bacteria in the biomass. 相似文献
20.
Sánchez Fernández JF González-López CV Acién Fernández FG Fernández Sevilla JM Molina Grima E 《Applied microbiology and biotechnology》2012,94(3):613-624
This paper focuses on modelling the growth rate and exopolysaccharides production of Anabaena sp. ATCC 33047, to be used in carbon dioxide removal and biofuels production. For this, the influence of dilution rate, irradiance
and aeration rate on the biomass and exopolysaccharides productivity, as well as on the CO2 fixation rate, have been studied. The productivity of the cultures was maximum at the highest irradiance and dilution rate
assayed, resulting to 0.5 gbio l−1 day−1 and 0.2 geps l−1 day−1, and the CO2 fixation rate measured was 1.0 gCO2 l−1 day−1. The results showed that although Anabaena sp. was partially photo-inhibited at irradiances higher than 1,300 μE m−2 s−1, its growth rate increases hyperbolically with the average irradiance inside the culture, and so does the specific exopolysaccharides
production rate. The latter, on the other hand, decreases under high external irradiances, indicating that the exopolysaccharides
metabolism hindered by photo-damage. Mathematical models that consider these phenomena have been proposed. Regarding aeration,
the yield of the cultures decreased at rates over 0.5 v/v/min or when shear rates were higher than 60 s−1, demonstrating the existence of thus existence of stress damage by aeration. The behaviour of the cultures has been verified
outdoors in a pilot-scale airlift tubular photobioreactor. From this study it is concluded that Anabaena sp. is highly recommended to transform CO2 into valuable products as has been proved capable of metabolizing carbon dioxide at rates of 1.2 gCO2 l−1 day−1 outdoors. The adequacy of the proposed equations is demonstrated, resulting to a useful tool in the design and operation
of photobioreactors using this strain. 相似文献