Seagrass Herbivory Levels Sustain Site-Fidelity in a Remnant Dugong Population

Herds of dugong, a largely tropical marine megaherbivore, are known to undertake long-distance movements, sequentially overgrazing seagrass meadows in their path. Given their drastic declines in many regions, it is unclear whether at lower densities, their grazing is less intense, reducing their need to travel between meadows. We studied the effect of the feeding behaviour of a small dugong population in the Andaman and Nicobar archipelago, India to understand how small isolated populations graze seagrasses. In the seven years of our observation, all recorded dugongs travelled either solitarily or in pairs, and their use of seagrasses was limited to 8 meadows, some of which were persistently grazed. These meadows were relatively large, contiguous and dominated by short-lived seagrasses species. Dugongs consumed approximately 15% of meadow primary production, but there was a large variation (3–40% of total meadow production) in consumption patterns between meadows. The impact of herbivory was relatively high, with shoot densities c. 50% higher inside herbivore exclosures than in areas exposed to repeated grazing. Our results indicate that dugongs in the study area repeatedly graze the same meadows probably because the proportion of primary production consumed reduces shoot density to levels that are still above values that can trigger meadow abandonment. This ability of seagrasses to cope perhaps explains the long-term site fidelity shown by individual dugongs in these meadows. The fact that seagrass meadows in the archipelago are able to support dugong foraging requirements allows us to clearly identify locations where this remnant population persists, and where urgent management efforts can be directed.     

A review of research on the interactions between dugongs (<Emphasis Type="Italic">Dugong dugon</Emphasis> Müller 1776) and intertidal seagrass beds in Indonesia

Research on dugong–seagrass interactions in Indonesia was done during the period 1990 until 2005 in respectively East Aru, Maluku Province and East Kalimantan, Indonesia. This research investigated intensive rotational grazing by dugongs in intertidal inshore Halodule univervis seagrass meadows, dugong movements in relation to these grazing swards, and analyses of parameters explaining the temporal and spatial patterns of grazing in these meadows. In this paper, we report the findings of this long-term study. The patterns of movement and the results of snorkelling surveys confirmed a practice of regular recropping of restricted grazing swards by small feeding assemblages of dugongs. Dugong grazing showed a significant correlation with carbohydrate content of the below-ground biomass and no significant relation with total N. The timing of dugong grazing in these intertidal meadows coincides with high below-ground biomass and high carbohydrate content in the rhizomes of H. uninervis in the upper 0–4 cm sediment layer. Our findings support the hypothesis that temporal dugong grazing is ruled by carbohydrate content in below-ground biomass. The mechanisms of rotational grazing in restricted grazing swards are not yet well understood, and the maximisation of carbohydrates does not fully explain this phenomenon. Our research confirms that intertidal H. univervis seagrass meadows form a crucial resource for dugong survival. These relatively unknown biotopes need therefore more attention in research and conservation programmes.     

Dugong habitat use in relation to seagrass nutrients,tides, and diel cycles

The dugong is the only herbivorous mammal that is strictly marine and a seagrass community specialist. The pasture available to the dugong varies with the tides because seagrass occurs in both intertidal and subtidal areas. We GPS-tracked seven dugongs within a 24 km², intensively used seagrass habitat in subtropical Australia in winter. We modeled resource selection within the habitat by comparing the dugongs’ use of space with the distribution of seagrass in an area defined using the combined space-use of the tracked animals. Selection by dugongs for seagrass quantity (biomass) and quality (nutrients) was analyzed within six time/tide combinations to examine the influences of tidal periodicity and the diel cycle on resource selection. Dugong habitat use was consistently centered over seagrass patches with high nitrogen concentrations, except during the day at low tides when the animals had fewer habitat choices and their space use was centered over high seagrass biomass. The association of dugongs with seagrass high in starch was positive during both day and night high tides when the animals could access the intertidal areas where seagrass biomass was generally low. Associations between dugongs and seagrass species were less definite, reflecting the potential for dugongs to exploit several species. Our model of dugong resource selection suggests that nitrogen is the primary limiting nutrient for dugong populations and also confirms the preference of dugongs for high-energy foods.     

Impacts of dugong foraging on benthic animal communities in a Thailand seagrass bed

We studied the community structure and abundance of benthic animals in intertidal seagrass beds in Thailand, where dugongs (Dugong dugon) feed on the seagrass Halophila ovalis. Our objective was to examine whether the benthic community was affected by the foraging activity of the dugongs, which can cause disturbance to the sediment. We collected a total of 4156 benthic animals from three study sites and classified them into 77 different taxa. A lucinid bivalve, Pillucina sp., was the most abundant taxa (approximately 80% of individuals). Taxa richness of the benthic animals was higher in intact H.ovalis vegetation compared to dugong trails at all sites. In general, the densities of five functional groups (classified by position on/in the sediment and motility) and five dominant taxa were higher in intact seagrass vegetation compared to dugong trails, although the magnitude of this difference varied among functional groups and taxa. Densities were at least threefold higher in the seagrass vegetation than in the dugong trails for epifauna and shallow infauna, but were at most twofold higher for deep infauna. Taxa richness and abundance of the benthic animals in the dugong trails were similar between the day following, and 7–9days after, the creation of the trails. Thus, delayed and/or indirect effects of dugong herbivory on benthic communities were not detected in this study. These findings demonstrate that the foraging activity of dugongs in seagrass can have considerable impacts on the abundance and diversity of benthic organisms, although this effect varies among benthic animals with different lifestyles.     

Fine scale population structure of dugongs (Dugong dugon) implies low gene flow along the southern Queensland coastline

Populations of marine mammals can show the signature of phylogeographical breaks and restricted connectivity despite the apparent lack of physical boundaries in the marine environment and their high dispersal abilities. Dugongs (Dugong dugon) do not appear to undertake regular migrations but may show localised movement related to water temperature or seagrass availability. Previous mitochondrial DNA studies suggested that despite a strong phylogeographic break in the Torres Strait, there is local panmixia in Australian waters. In this study, we conducted a comprehensive study of the four major dugong populations in southern Queensland. We analysed genotypes of 1,293 dugongs based on 24 microsatellite loci from the four major dugong locations in the region (from south to north): Moreton Bay, Great Sandy Straits, Hervey Bay and Shoalwater Bay. Diversity levels were similar across locations (observed heterozygosity 0.48–0.52, allelic richness 4.3–4.5). There was low but significant population differentiation in southern Queensland (F_ST ranged from 0.005 to 0.040 and Jost’s D_EST ranged from 0.001 to 0.031 for microsatellite data). Bayesian clustering analysis implemented in STRUCTURE largely distinguished the southern Moreton Bay population from the three more northern populations. Twelve mitochondrial control region haplotypes identified from a subset of 182 samples confirmed significant population structuring (F_ST ranged from 0.16 to 0.28). These data suggested that the frequency and extent of dugong movements are insufficient to disrupt the long-term existence of at least two breeding populations in southern Queensland.     

Unmanned Aerial Vehicles (UAVs) for Surveying Marine Fauna: A Dugong Case Study

Aerial surveys of marine mammals are routinely conducted to assess and monitor species’ habitat use and population status. In Australia, dugongs (Dugong dugon) are regularly surveyed and long-term datasets have formed the basis for defining habitat of high conservation value and risk assessments of human impacts. Unmanned aerial vehicles (UAVs) may facilitate more accurate, human-risk free, and cheaper aerial surveys. We undertook the first Australian UAV survey trial in Shark Bay, western Australia. We conducted seven flights of the ScanEagle UAV, mounted with a digital SLR camera payload. During each flight, ten transects covering a 1.3 km² area frequently used by dugongs, were flown at 500, 750 and 1000 ft. Image (photograph) capture was controlled via the Ground Control Station and the capture rate was scheduled to achieve a prescribed 10% overlap between images along transect lines. Images were manually reviewed post hoc for animals and scored according to sun glitter, Beaufort Sea state and turbidity. We captured 6243 images, 627 containing dugongs. We also identified whales, dolphins, turtles and a range of other fauna. Of all possible dugong sightings, 95% (CI = 90%, 98%) were subjectively classed as ‘certain’ (unmistakably dugongs). Neither our dugong sighting rate, nor our ability to identify dugongs with certainty, were affected by UAV altitude. Turbidity was the only environmental variable significantly affecting the dugong sighting rate. Our results suggest that UAV systems may not be limited by sea state conditions in the same manner as sightings from manned surveys. The overlap between images proved valuable for detecting animals that were masked by sun glitter in the corners of images, and identifying animals initially captured at awkward body angles. This initial trial of a basic camera system has successfully demonstrated that the ScanEagle UAV has great potential as a tool for marine mammal aerial surveys.     

Pleistocene sea level fluctuations and the phylogeography of the dugong in Australian waters

We investigated phylogeography, demography, and population connectivity of the dugong (Dugong dugon) in Australian waters using mitochondrial control region DNA sequences from 177 Australian dugongs and 11 from elsewhere. The dugong is widespread in shallow Indo‐West Pacific waters suitable for growth of its main food, seagrass. We hypothesized that the loss of habitat and creation of a land barrier (the Torres Strait landbridge) during low sea level stands associated with Pleistocene glacial cycles have left a persisting genetic signature in the dugong. The landbridge was most recently flooded about 7,000 yr ago. Individual dugongs are capable of traveling long distances, suggesting an alternative hypothesis that there might now be little genetic differentiation across the dugong's Australian range. We demonstrated that Australian dugongs fall into two distinct maternal lineages and exhibit a phylogeographic pattern reflecting Pleistocene sea‐level fluctuations. Within each lineage, genetic structure exists, albeit at large spatial scales. We suggest that these lineages diverged following the last emergence of the Torres Strait landbridge (ca. 115 kya) and remained geographically separated until after 7 kya when passage through Torres Strait again became possible for marine animals. Evidence for population growth in the widespread lineage, especially after the last glacial maximum, was detected.     

海南省儒艮资源现状调查

为拟在海南省建立儒艮自然保护区提供科学依据,于2001 年11 月至2002 年10 月在海南省西部沿岸海域进行了为期一年的海洋环境综合调查和儒艮海上目视调查。此外还在海南省及广西壮族自治区、广东省进行了有关访问调查。调查结果表明,在广西沿岸合浦海域仍有儒艮存在。但在海南省西海域近岸未发现儒艮,且原有儒艮栖息地的海草均被破坏消失,认为目前建立海南儒艮自然保护区的条件尚不成熟。儒艮资源减少的主要原因是受人类活动加剧的影响,以及生态环境不断恶化,威胁着本种的生存。为此,亟待采取有效的管理措施和健全管理机制,加强对儒艮资源及其栖息地的保护。     

Effects of Tidal and Diel Cycles on Dugong Habitat Use

ABSTRACT Quantifying the factors influencing behaviors of aquatic mammalian grazers may enhance the generic understanding of grazer ecology. We investigated diel and tidal patterns in movements of the dugong (Dugong dugon) by Global Positioning System—tracking 12 animals in 5 inshore—intertidal and 3 offshore—subtidal habitats along the coast of Queensland, Australia. We examined effects of tide height and time of day on the dugong's distance from 1) the nearest coast, 2) water >3 m deep, 3) actual water depth (bathymetry + tide ht) experienced, and 4) distribution of the directions of movements. Both tidal and diel cycles influenced dugong movement. Tracked dugongs tended to be closer to shore at high tide than at low tide and closer to shore at night than during the day. Onshore movement was more prevalent on incoming tides and in the afternoon and evening. Offshore movement was more prevalent on outgoing tides and from midnight through the morning until midday. Tidal and diel variation in water depths used by the inshore—intertidal dugongs was small, but probably underestimated, hidden by a sampling bias in the telemetry equipment. Onshore movement at high tide allowed dugongs to exploit intertidal seagrass beds. Dugongs are closer to shore in afternoons and evenings than in mornings. This behavior may be related to the avoidance of predators or watercraft. Our findings can be used to predict spatial patterns of dugongs within areas of conservation management significance and to assess, avoid, and mitigate adverse effects of anthropogenic disturbance.     

CURRENT STATUS AND CONSERVATION NEEDS OF DUGONGS IN SOUTHERN JAPAN

We conducted aerial surveys of dugongs ( Dugong dugon ) using the line-transect method and snorkeling surveys of dugong feeding trails in 1998 and 1999 around Okinawa Island (26°30'N, 128°00'E) and the Sakishima Islands, southern Japan. A total of ten dugongs were sighted and feeding trails were confirmed in the sea grass beds off the east coast of Okinawa Island. In the Sakishima Islands, however, no dugongs were observed, and there was no evidence of feeding trails despite the existence of apparently suitable sea grass beds for feeding. The results of these surveys and other available information suggest that Okinawan dugongs represent a small, geographically isolated population. Our sightings of dugongs during the daytime, offshore of sea grass beds where feeding trails were recorded, suggest that Okinawan dugongs principally feed at night when human activities are limited. Survival of this remnant dugong population is threatened by habitat degradation and occasional entanglement mortality in fishing nets.     

Population Differentiation and Hybridisation of Australian Snubfin (Orcaella heinsohni) and Indo-Pacific Humpback (Sousa chinensis) Dolphins in North-Western Australia

Little is known about the Australian snubfin (Orcaella heinsohni) and Indo-Pacific humpback (Sousa chinensis) dolphins (‘snubfin’ and ‘humpback dolphins’, hereafter) of north-western Australia. While both species are listed as ‘near threatened’ by the IUCN, data deficiencies are impeding rigorous assessment of their conservation status across Australia. Understanding the genetic structure of populations, including levels of gene flow among populations, is important for the assessment of conservation status and the effective management of a species. Using nuclear and mitochondrial DNA markers, we assessed population genetic diversity and differentiation between snubfin dolphins from Cygnet (n = 32) and Roebuck Bays (n = 25), and humpback dolphins from the Dampier Archipelago (n = 19) and the North West Cape (n = 18). All sampling locations were separated by geographic distances >200 km. For each species, we found significant genetic differentiation between sampling locations based on 12 (for snubfin dolphins) and 13 (for humpback dolphins) microsatellite loci (F _ST = 0.05–0.09; P<0.001) and a 422 bp sequence of the mitochondrial control region (F _ST = 0.50–0.70; P<0.001). The estimated proportion of migrants in a population ranged from 0.01 (95% CI 0.00–0.06) to 0.13 (0.03–0.24). These are the first estimates of genetic diversity and differentiation for snubfin and humpback dolphins in Western Australia, providing valuable information towards the assessment of their conservation status in this rapidly developing region. Our results suggest that north-western Australian snubfin and humpback dolphins may exist as metapopulations of small, largely isolated population fragments, and should be managed accordingly. Management plans should seek to maintain effective population size and gene flow. Additionally, while interactions of a socio-sexual nature between these two species have been observed previously, here we provide strong evidence for the first documented case of hybridisation between a female snubfin dolphin and a male humpback dolphin.     

Mechanical disruption of seagrass in the digestive tract of the dugong

The cheek teeth in dugongs are considered to be largely non-functional whereas the oral horny pads are important both in mechanical disruption of the diet and in conveying seagrass through the mouth. Particle size distributions of digesta from 41 dead stranded dugongs were examined to investigate the relationship between degree of food breakdown, gut region and functional surface area of the mouthparts. The in vitro ease of fracture of major dietary seagrass species were compared. The rate of food breakdown through the gut appears to be more closely linked to fibre level of the diet than to size or age of the dugong and its mouthparts. Low fibre seagrass, for example Halophila ovalis , breaks down at a faster rate than high fibre seagrass, for example Zostera capricorni both in dugong guts and in vitro . Several structural characteristics of seagrass, including level and arrangement of fibre, and water content, make it particularly amenable to mechanical breakdown. The soft mouthparts of the dugong are highly modified so that the entire oral cavity functions to crush low fibre seagrasses. Thus, the dugong has developed an efficient method of food ingestion and mastication that is suited to processing large quantities of soft seagrass during short dive times. The potential cost to the dugong in having lost its hard dental surfaces is that it has become restricted to a low fibre diet.     

Fluctuation of Serum Sodium and Its Impact on Short and Long-Term Mortality following Acute Pulmonary Embolism

Background

Baseline hyponatremia predicts acute mortality following pulmonary embolism (PE). The natural history of serum sodium levels after PE and the relevance to acute and long-term mortality after the PE is unknown.

Methods

Clinical details of all patients (n = 1023) admitted to a tertiary institution from 2000–2007 with acute PE were retrieved retrospectively. Serum sodium results from days 1, 3–4, 5–6, and 7 of admission were pre-specified and recorded. We excluded 250 patients without day-1 sodium or had <1 subsequent sodium assessment, leaving 773 patients as the studied cohort. There were 605 patients with normonatremia (sodium≥135 mmol/L throughout admission), 57 with corrected hyponatremia (day-1 sodium<135 mmol/L, then normalized), 54 with acquired hyponatremia and 57 with persistent hyponatremia. Patients’ outcomes were tracked from a state-wide death registry and analyses performed using multivariate-regression modelling.

Results

Mean (±standard deviation) day-1 sodium was 138.2±4.3 mmol/L. Total mortality (mean follow-up 3.6±2.5 years) was 38.8% (in-hospital mortality 3.2%). There was no survival difference between studied (n = 773) and excluded (n = 250) patients. Day-1 sodium (adjusted hazard ratio [aHR] 0.89, 95% confidence interval [CI] 0.83–0.95, p = 0.001) predicted in-hospital death. Relative to normonatremia, corrected hyponatremia increased the risk of in-hospital death 3.6-fold (95% CI 1.20–10.9, p = 0.02) and persistent hyponatremia increased the risk 5.6-fold (95% CI 2.08–15.0, p = 0.001). Patients with either persisting or acquired hyponatremia had worse long-term survival than those who had corrected hyponatremia or had been normonatremic throughout (aHR 1.47, 95% CI 1.06–2.03, p = 0.02).

Conclusion

Sodium fluctuations after acute PE predict acute and long-term outcome. Factors mediating the correction of hyponatremia following acute PE warrant further investigation.     

Age-Related Decrements in Heat Dissipation during Physical Activity Occur as Early as the Age of 40

Older adults typically experience greater levels of thermal strain during physical efforts in the heat compared to young individuals. While this may be related to an age-dependent reduction in whole-body sweating, no study has clearly delineated at what age this occurs. In the present study, we report direct measurements of human heat dissipation during physical activity in the heat in males ranging in age from 20–70 years. Eighty-five males performed four 15-min bouts of cycling separated by 15-min rest periods, in a calorimeter regulated to 35°C and 20% relative humidity. Direct calorimetry was used to measure total heat loss (whole-body evaporative heat loss and dry heat exchange). We also used indirect calorimetry as a continuous measure of metabolic heat production. Body heat storage was calculated as the temporal summation of heat production and total heat loss over the experimental session. Whole-body sweat rate (WBSR) was calculated from measurements of evaporative heat loss. Males were divided into five age categories for the analysis of WBSR and body heat storage: 20–31 years (n = 18), 40–44 years (n = 15), 45–49 years (n = 15), 50–55 years (n = 21) and 56–70 years (n = 16). Relative to young males, WBSR was reduced in males aged 56–70 during each exercise (all P<0.05), in males aged 50–55 during the second (P = 0.031) and third exercises (P = 0.028) and in males aged 45–49 during the final exercise bout (P = 0.046). Although not significantly different, 40–44 years old males also had a lower rate of heat loss compared to younger males. Over the sum of two hours, the change in body heat content was greater in males 40–70 years compared to young males (all P<0.05). Our findings suggest that middle-aged and older adults have impairments in heat dissipation when doing physical activity in the heat, thus possibly increasing their risk of heat-related illness under such conditions.     

Phylogeographic Analyses of Submesophotic Snappers Etelis coruscans and Etelis “marshi” (Family Lutjanidae) Reveal Concordant Genetic Structure across the Hawaiian Archipelago

The Hawaiian Archipelago has become a natural laboratory for understanding genetic connectivity in marine organisms as a result of the large number of population genetics studies that have been conducted across this island chain for a wide taxonomic range of organisms. However, population genetic studies have been conducted for only two species occurring in the mesophotic or submesophotic zones (30+m) in this archipelago. To gain a greater understanding of genetic connectivity in these deepwater habitats, we investigated the genetic structure of two submesophotic fish species (occurring ∼200–360 m) in this archipelago. We surveyed 16 locations across the archipelago for submesophotic snappers Etelis coruscans (N = 787) and E. “marshi” (formerly E. carbunculus; N = 770) with 436–490 bp of mtDNA cytochrome b and 10–11 microsatellite loci. Phylogeographic analyses reveal no geographic structuring of mtDNA lineages and recent coalescence times that are typical of shallow reef fauna. Population genetic analyses reveal no overall structure across most of the archipelago, a pattern also typical of dispersive shallow fishes. However some sites in the mid-archipelago (Raita Bank to French Frigate Shoals) had significant population differentiation. This pattern of no structure between ends of the Hawaiian range, and significant structure in the middle, was previously observed in a submesophotic snapper (Pristipomoides filamentosus) and a submesophotic grouper (Hyporthodus quernus). Three of these four species also have elevated genetic diversity in the mid-archipelago. Biophysical larval dispersal models from previous studies indicate that this elevated diversity may result from larval supplement from Johnston Atoll, ∼800 km southwest of Hawaii. In this case the boundaries of stocks for fishery management cannot be defined simply in terms of geography, and fishery management in Hawaii may need to incorporate external larval supply into management plans.     

A Method for Investigating Population Declines of Migratory Birds Using Stable Isotopes: Origins of Harvested Lesser Scaup in North America

Background

Elucidating geographic locations from where migratory birds are recruited into adult breeding populations is a fundamental but largely elusive goal in conservation biology. This is especially true for species that breed in remote northern areas where field-based demographic assessments are logistically challenging.

Methodology/Findings

Here we used hydrogen isotopes (δD) to determine natal origins of migrating hatch-year lesser scaup (Aythya affinis) harvested by hunters in the United States from all North American flyways during the hunting seasons of 1999–2000 (n = 412) and 2000–2001 (n = 455). We combined geospatial, observational, and analytical data sources, including known scaup breeding range, δD values of feathers from juveniles at natal sites, models of δD for growing-season precipitation, and scaup band-recovery data to generate probabilistic natal origin landscapes for individual scaup. We then used Monte Carlo integration to model assignment uncertainty from among individual δD variance estimates from birds of known molt origin and also from band-return data summarized at the flyway level. We compared the distribution of scaup natal origin with the distribution of breeding population counts obtained from systematic long-term surveys.

Conclusions/Significance

Our analysis revealed that the proportion of young scaup produced in the northern (above 60°N) versus the southern boreal and Prairie-Parkland region was inversely related to the proportions of breeding adults using these regions, suggesting that despite having a higher relative abundance of breeding adults, the northern boreal region was less productive for scaup recruitment into the harvest than more southern biomes. Our approach for evaluating population declines of migratory birds (particularly game birds) synthesizes all available distributional data and exploits the advantages of intrinsic isotopic markers that link individuals to geography.     

Altered Transfer of Momentary Mental States (ATOMS) as the Basic Unit of Psychosis Liability in Interaction with Environment and Emotions

Psychotic disorders are thought to represent altered neural function. However, research has failed to map diagnostic categories to alterations in neural networks. It is proposed that the basic unit of psychotic psychopathology is the moment-to-moment expression of subtle anomalous experiences of subclinical psychosis, and particularly its tendency to persist from moment-to-moment in daily life, under the influence of familial, environmental, emotional and cognitive factors.In a general population twin sample (n = 579) and in a study of patients with psychotic disorder (n = 57), their non-psychotic siblings (n = 59) and unrelated controls (n = 75), the experience sampling paradigm (ESM; repetitive, random sampling of momentary mental states and context) was applied. We analysed, in a within-person prospective design, (i) transfer of momentary anomalous experience at time point (t–1) to time point (t) in daily life, and (ii) moderating effects of negative affect, positive affect, daily stressors, IQ and childhood trauma. Additionally, (iii) familial associations between persistence of momentary anomalous experience and psychotic symptomatology were investigated. Higher level of schizotypy in the twins (but not higher level of psychotic symptoms in patients) predicted more persistence of momentary anomalous experience in daily life, both within subjects and across relatives. Persistence of momentary anomalous experience was highest in patients, intermediate in their siblings and lowest in controls. In both studies, persistence of momentary anomalous experience was moderated by higher levels of negative affect, daily stressors and childhood trauma (only in twins), and by lower levels of positive affect. The study of alterations in the moment-to-moment transfer of subtle anomalous experience of psychosis, resulting in their persistence, helps to explain why psychotic and emotional dysregulation tend to cluster in a single phenotype such as schizophrenia, and how familial and environmental risks increase the risk of expression of psychosis from, first, subtle momentary anomalous experience to, second, observable clinical symptoms.     

Betaine and Trimethylamine-N-Oxide as Predictors of Cardiovascular Outcomes Show Different Patterns in Diabetes Mellitus: An Observational Study

Background

Betaine is a major osmolyte, also important in methyl group metabolism. Concentrations of betaine, its metabolite dimethylglycine and analog trimethylamine-N-oxide (TMAO) in blood are cardiovascular risk markers. Diabetes disturbs betaine: does diabetes alter associations between betaine-related measures and cardiovascular risk?

Methods

Plasma samples were collected from 475 subjects four months after discharge following an acute coronary admission. Death (n = 81), secondary acute MI (n = 87), admission for heart failure (n = 85), unstable angina (n = 72) and all cardiovascular events (n = 283) were recorded (median follow-up: 1804 days).

Results

High and low metabolite concentrations were defined as top or bottom quintile of the total cohort. In subjects with diabetes (n = 79), high plasma betaine was associated with increased frequencies of events; significantly for heart failure, hazard ratio 3.1 (1.2–8.2) and all cardiovascular events, HR 2.8 (1.4–5.5). In subjects without diabetes (n = 396), low plasma betaine was associated with events; significantly for secondary myocardial infarction, HR 2.1 (1.2–3.6), unstable angina, HR 2.3 (1.3–4.0), and all cardiovascular events, HR 1.4 (1.0–1.9). In diabetes, high TMAO was a marker of all outcomes, HR 2.7 (1.1–7.1) for death, 4.0 (1.6–9.8) for myocardial infarction, 4.6 (2.0–10.7) for heart failure, 9.1 (2.8–29.7) for unstable angina and 2.0 (1.1–3.6) for all cardiovascular events. In subjects without diabetes TMAO was only significant for death, HR 2.7 (1.6–4.8) and heart failure, HR 1.9 (1.1–3.4). Adding the estimated glomerular filtration rate to Cox regression models tended to increase the apparent risks associated with low betaine.

Conclusions

Elevated plasma betaine concentration is a marker of cardiovascular risk in diabetes; conversely low plasma betaine concentrations indicate increased risk in the absence of diabetes. We speculate that the difference reflects control of osmolyte retention in tissues. Elevated plasma TMAO is a strong risk marker in diabetes.     

Economic and Health Impacts Associated with a Salmonella Typhimurium Drinking Water Outbreak?Alamosa,CO, 2008

In 2008, a large Salmonella outbreak caused by contamination of the municipal drinking water supply occurred in Alamosa, Colorado. The objectives of this assessment were to determine the full economic costs associated with the outbreak and the long-term health impacts on the community of Alamosa. We conducted a postal survey of City of Alamosa (2008 population: 8,746) households and businesses, and conducted in-depth interviews with local, state, and nongovernmental agencies, and City of Alamosa healthcare facilities and schools to assess the economic and long-term health impacts of the outbreak. Twenty-one percent of household survey respondents (n = 369/1,732) reported diarrheal illness during the outbreak. Of those, 29% (n = 108) reported experiencing potential long-term health consequences. Most households (n = 699/771, 91%) reported municipal water as their main drinking water source at home before the outbreak; afterwards, only 30% (n = 233) drank unfiltered municipal tap water. The outbreak’s estimated total cost to residents and businesses of Alamosa using a Monte Carlo simulation model (10,000 iterations) was approximately $1.5 million dollars (range: $196,677–$6,002,879), and rose to $2.6 million dollars (range: $1,123,471–$7,792,973) with the inclusion of outbreak response costs to local, state and nongovernmental agencies and City of Alamosa healthcare facilities and schools. This investigation documents the significant economic and health impacts associated with waterborne disease outbreaks and highlights the potential for loss of trust in public water systems following such outbreaks.     

Improving population estimates by quantifying diving and surfacing patterns: A dugong example

Diving animals are available for detection from above the water when environmental conditions are favorable and the animals are near the surface. The number of animals that are unavailable for detection needs to be estimated to obtain unbiased population estimates. The current availability correction factors used in aerial surveys for the dugong (Dugong dugon) allow for variation in environmental conditions but use the average time dugongs spend near the surface (i.e., constant availability corrections). To improve availability estimates, we examined location and dive data from nine dugongs fitted with satellite telemetry units and time‐depth recorders (TDRs) in eastern Australia. The effects of water depth, tidal conditions, and habitat types on dugong surfacing time were examined using generalized linear mixed models (GLMMs). We found that availability for detection differed with water depth, and depth‐specific availability estimates were often lower than the constant estimates. The habitat effect was less influential, and there was no tidal effect. The number of dugongs estimated using depth‐specific availabilities were higher than those obtained using constant availabilities across water depth. Hence, information on water depth can refine availability estimates and subsequent abundance estimates from dugong aerial surveys. The methodology may be applicable to other aquatic wildlife.