Organochlorine contaminants in seabird eggs from the Pacific coast of Canada, 1971–1986

Eggs were collected from seven seabird species at colonies on the British Columbia coast from 1983 to 1986 and analyzed for organochlorine contaminants. Total PCB levels (wet weight) were highest in double-crested cormorants (Phalacrocorax auritus) from the Fraser estuary (2.91 mg kg^-1) and the Strait of Georgia (3.79 mg kg^-1). Highest DDE levels were in fork-tailed storm-petrels (Oceanodroma furcata) from the Queen Charlotte Islands (1.68 mg kg^-1). Organochlorine levels were generally lower in eggs from the mid 1980s than in those collected in the early 1970s. Organochlorine levels in Pacific alcids and hydrobatids foraging in offshore locations were compared to those in the same or ecologically similar species from the Canadian Atlantic coast. DDT- and HCH-related compounds were higher in Pacific populations while levels of dieldrin, oxychlordane, and HCB were generally lower. With the exception of -HCH, levels of all measured organochlorines were lower in cormorants breeding in the Fraser River estuary than in cormorants from the St. Lawrence River estuary on the Atlantic coast.     

Biomagnification factors (fish to Osprey eggs from Willamette River,Oregon, U.S.A.) for PCDDs,PCDFs, PCBs and OC pesticides

A migratory population of 78 pairs of Osprey (Pandion haliaetus) nesting along the Willamette River in westernOregon was studied in 1993. The study was designed to determinecontaminant concentrations in eggs, contaminant concentrationsin fish species predominant in the Ospreys diet, andBiomagnification Factors (BMFs) of contaminants from fish specieseaten to Osprey eggs. Ten Osprey eggs and 25 composite samplesof fish (3 species) were used to evaluate organochlorine (OC)pesticides, polychlorinated biphenyls (PCBs), polychlorinateddibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans(PCDFs). Mercury was also analyzed in fish. Geometric meanresidues in Osprey eggs were judged low, e.g., DDE 2.3 g g^-1 wet weight (ww), PCBs 0.69 g g^-1, 2,3,7,8-TCDD 2.3 ng kg^-1, and generally well below known threshold values for adverse effects on productivity, and the population was increasing. Osprey egg residue data presentedby River Mile (RM) are discussed, e.g., higher PCDDs were generally found immediately downstream of paper mills and eggsfrom the Willamette River had significantly elevated PCBs and PCDDs compared to reference eggs collected nearby in the CascadeMountains. Prey remains at nest sites indicated that the Largescale Sucker (Catostomus macrocheilus) and NorthernPikeminnow (Ptychocheilus oregonensis) accounted for an estimated 90.1% of the biomass in the Osprey diet, and composite samples of these two species were collected from different sampling sites throughout the study area for contaminant analyses. With the large percentage of the fishbiomass in the Osprey diet sampled for contaminants (and fisheaten by Ospreys similar in size to those chemically analyzed),and fish contaminant concentrations weighted by biomass intake, a mean BMF was estimated from fish to Osprey eggs for the largeseries of contaminants. BMFs ranged from no biomagnification(0.42) for 2,3,7,8-TCDF to 174 for OCDD. Our findings for themigratory Osprey were compared to BMFs for the resident HerringGull (Larus argentatus), and differences are discussed. Webelieve a BMF approach provides some basic understanding ofrelationships between contaminant burdens in prey species offish-eating birds and contaminants incorporated into their eggs,and may prove useful in understanding sources of contaminants inmigratory species although additional studies are needed.     

A regional algorithm to model mesozooplankton biomass along the southwestern Bay of Bengal

A three-dimensional regression analysis attempted to model mesozooplankton (MSP) biomass using sea surface temperature (SST) and chlorophyll-a (Chl-a). The study was carried out from January 2014 to July 2015 in the southwestern Bay of Bengal (BoB) and sampling was carried out on board Sagar Manjusha and Sagar Purvi. SST ranged from 26.2 to 33.1 °C while Chl-a varied from 0.04 to 6.09 μg L^?1. During the course of the study period, there was a weak correlation (r?= 0.32) between SST and Chl-a statistically. MSP biomass varied from 0.42 to 9.63 mg C m^?3 and inversely related with SST. Two kinds of approaches were adopted to develop the model by grouping seasonal datasets (four seasonal algorithms) and comprising all datasets (one annual algorithm). Among the four functions used (linear, paraboloid, the Lorentzian and the Gaussian functions), paraboloid model was best suited. The best seasonal and annual algorithms were applied in the synchronous MODIS-derived SST and Chl-a data to estimate the MSP biomass in the southwestern BoB. The modelled MSP biomass was validated with field MSP biomass and the result was statistically significant, showing maximum regression coefficient for the seasonal algorithms (R²?=?0.60; p?=?0.627; α?= 0.05), than the annual algorithm (R²?=?0.52; p?=?0.015, α?=?0.05).     

Trace elements (Cu,Zn, and Hg) and δ<Superscript>13</Superscript>C/δ<Superscript>15</Superscript>N in seabird subfossils from three islands of the South China Sea and its implications

Seabird subfossils were collected on three islands of the Xisha Archipelago, South China Sea. Via elemental analysis, we identified that bird guano was a significant source for heavy metals Cu, Zn, and Hg. Cu and Zn levels in these guano samples are comparable to their levels in wildbird feces, but guano Hg was lower than previously reported. Trophic positions significantly impacted transfer efficiency of heavy metals by seabirds. Despite of a common source, trace elements, as well as stable isotopes (i.e., guano δ¹³C and collagen δ¹⁵N), showed island-specific characteristics. Bird subfossils on larger island had relatively greater metal concentrations and revealed higher trophic positions. Partition of element and isotope levels among the islands suggested that transfer efficacy of seabirds on different islands was different, and bird species were probably unevenly distributed among the islets. Island area is possibly a driving factor for distributions of seabird species.     

Metals in feathers of sooty tern, white tern, gray-backed tern, and brown noddy from islands in the North Pacific

Levels of heavy metals are usuallyhigher in adult than young birds because they eatlarger, more contaminated prey, or because they havehad longer to accumulate metals in their tissues.Further, levels of contaminants are usually less inbirds nesting on remote, offshore islands than inbirds breeding closer to mainland areas that areurbanized and industrialized. We examined the featherlevels of arsenic, cadmium, chromium, lead, manganese,mercury, and selenium in adult sooty terns (Sterna fuscata), gray-backed terns (Sterna lunata), and brown noddy (Anous stolidus, and adult and young white terns (Gygis alba, fromMidway Atoll, and in adult and young sooty terns andadult brown noddy from Manana Island, Hawaii (chicksof other terns were not available). We tested andrejected the null hypotheses that metal levels are notsignificantly different among species, ages, andlocations. Despite their small size, adult white ternshad the highest levels of lead, arsenic and tin. Brownnoddies had the highest levels of cadmium, chromium,manganese, and selenium. Sooty and white terns had thehighest levels of mercury. Sooty tern adults hadsignificantly higher levels of cadmium, mercury, andselenium than young, while young had significantlyhigher levels of arsenic and manganese. White ternadults had significantly higher levels of selenium andtin than young, while young had higher levels ofcadmium and mercury than adults. Except for mercury,there were significant inter-location differenceswithin species in all heavy metals. Contrary toexpectation, where the differences were great, metalsgenerally were higher in the feathers of terns andnoddies from Midway than from Manana.     

Environmental Assessment of the Impact of Ozone to the Neuston of the Sea-Surface Microlayer of the Gulf of Mexico

Substantial amounts of NOx (146 000 t/y) and total hydrocarbons (294 000 t/y) are released to the marine atmosphere by the large number of oil and gas operations over Federal waters of the Gulf of Mexico (GOM). Under appropriate meteorological conditions these emissions react to form ozone (0–54 g/m3 over-water) which can affect the marine environment. Using a dry deposition model, this work examines the amount of ozone derived from oil and gas offshore operations and deposited in the sea surface of the Gulf of Mexico, and assesses its impact on the neuston of the sea-surface microlayer. Surface integrated estimates of ozone deposited from oil and gas operations over the sea surface ranges from 400 kg to 1800 kg which results in sea surface concentrations of 15 g/m3. This estimate and the actual toxic ozone levels suggest no acute, toxic impacts to the neuston. However, indirect effects may occur through changes to the pelagic foodwebs and organic carbon pathways. Another potential pathway for ozone impacting the environment is through the production of bromate. Based on the concentrations and time scales (11–139 days) only sublethal effects appear to occur, but uncertainties associated with this assessment need to be further studied. From an ecological perspective, the environmental impacts and risks of NOx and VOC discharges from offshore platforms need to be assessed for neuston and other components of the marine ecosystem.     

Particle-phase Polycyclic Aromatic Hydrocarbon Emissions from Non-catalysed, In-use Four-stroke Scooters

Metals and radionuclide levels in marine birds of the Aleutians are of interest because they are part of subsistence diets of the Aleut people, and can also serve as indicators of marine pollution. We examined geographic and species-specific variations in concentrations of radionuclides in birds and their eggs from Amchitka, the site of underground nuclear tests from 1965 to 1971, and Kiska Islands (a reference site) in the Aleutians, and the levels of lead, mercury and cadmium in eggs. In 2004 we collected common eiders (Somateria mollissima), tufted puffins (Fratercula cirrhata), pigeon guillemot (Cepphus columba) and glaucous-winged gulls (Larus glaucescens) from Amchitka and Kiska, and eggs from eiders and gulls from the two island. We also collected one runt bald eagle (Haliaeetus leucocephalus) chick from both Amchitka and Kiska Islands. For most species, the levels of radionuclide isotopes were below the minimum detectable activity levels (MDA). Out of 74 cesium-137 analyses, only one composite (gulls) was above the MDA, and out of 14 composites tested for plutonium (Pu-239, 240), only one exceeded the MDA (a guillemots). Three composites out of 14 tested had detectable uranium-238. In all cases, the levels were low and close to the MDAs, and were below those reported for other seabirds. There were significant interspecific differences in metal levels in eggs: gulls had significantly higher levels of cadmium and mercury than the eiders, and eiders had higher levels of lead than gulls. There were few significant differences as a function of island, but eiders had significantly higher levels of cadmium in eggs from Kiska, and gulls had significantly higher levels of mercury on Kiska. The levels of cadmium and mercury in eggs of eiders and gulls from this study were above the median for cadmium and mercury from studies in the literature. The levels of mercury in eggs are within the range known to affect avian predators, but seabirds seem less vulnerable to mercury than other birds. However, the levels of mercury are within the action levels for humans, suggesting some cause for concern if subsistence Aleuts eat a large quantity of eggs.     

Cadmium Contamination in Wild Birds as an Indicator of Environmental Pollution

Cadmium (Cd) is an environmental pollutant that has serioustoxicity in humans and animals and causes Itai-Itai disease.However, there is little available information on itscontamination in wildlife as an indicator of environmentalpollution. The Cd contents in the kidney and liver of 85 wildbirds from 9 different prefectures in Japan were investigated.The ranges of the Cd contents in the kidney and liver in allbirds were ND-174.4 and ND-21.2 g g^-1 dry wt.,respectively. The mean Cd contents were higher in theoil-contaminated birds than those in the non-contaminated ones.Furthermore, a strong correlation was obtained only between theCd contents in the kidney and those in the liver of theoil-contaminated seabirds and not in the other non-contaminatedones. These results suggest that wild birds reflect the levelof environmental contamination which should be monitored.     

PCB and p,p′-DDE in Lake Geneva brown trout (Salmo trutta L.), and their use as bioenergetic indicators

Gross growth efficiency of Lake Geneva brown trout (Salmo trutta) was estimated by monitoring age-related PCB and p,p-DDE accumulation, food contamination and annual growth.Estimation was carried out using 3-, 4-, and 5-yr old fish. Roach (Rutilus rutilus) were determined as the main component of trout diet. Estimated growth efficiency coefficients were 0.4 (3–4 yr old fish) and 0.17 (4–5 yr old fish). Nevertheless numerous parameters can affect the result; their respective influences are discussed.Related to fish age, PCB and p,p-DDE concentrations increase if expressed on a wet weight basis, but not if expressed on a lipid weight basis.At the same age, organochlorine residue concentrations keep similar values for trout and roach in spite of different trophic levels. Growth must be considered as a more dilution factor of PCB and p,p-DDE in trout compared with roach.     

Inorganic and organic contaminants in Alaskan shorebird eggs

Many shorebird populations throughout North America are thought to be declining, with potential causes attributed to habitat loss and fragmentation, reduced prey availability, increased predation, human disturbance, and increased exposure to environmental pollutants. Shorebirds may be particularly vulnerable to contaminant exposure throughout their life cycle, as they forage primarily on invertebrates in wetlands, where many contaminants accumulate disproportionately in the sediments. Therefore, it is important to document and monitor shorebird populations thought to be at risk and assess the role that environmental contaminants may have on population declines. To investigate potential threats and provide baseline data on shorebird contaminant levels in Alaskan shorebirds, contaminant concentrations were evaluated in shorebird eggs from 16 species residing in seven geographic distinct regions of Alaska. Similar to previous studies, low levels of most inorganic and organic contaminants were found, although concentrations of several inorganic and organic contaminants were higher than those of previous studies. For example, elevated strontium levels were observed in several species, especially black oystercatcher (Haematopus bachmani) sampled in Prince William Sound, Alaska. Additionally, contaminant concentrations varied among species, with significantly higher concentrations of inorganic contaminants found in eggs of pectoral sandpiper (Calidris melanotos), semipalmated sandpiper (Calidris pusilla), black oystercatcher, and bar-tailed godwit (Limosa lapponica). Similarly, significantly higher concentrations of some organic contaminants were found in the eggs of American golden plover (Pluvialis dominica), black-bellied plover (Pluvialis squatarola), pacific golden plover (Pluvialis fulva), bar-tailed godwit, and semipalmated sandpiper. Despite these elevated levels, current concentrations of contaminants in shorebird eggs suggest that breeding environments are relatively free of most contaminants and that contaminant concentrations are below levels (except potentially strontium) that would likely affect the survival of individuals and consequently regulate the species at the population level.     

Variation of phytoplankton assemblages of Kongsfjorden in early autumn 2012: a microscopic and pigment ratio-based assessment

Phytoplankton species distribution and composition were determined by using microscopy and pigment ratios in the Kongsfjorden during early autumn 2012. Variation in sea surface temperature (SST) was minimal and matched well with satellite-derived SST. Nutrients were generally limited. Surface phytoplankton abundance ranged from 0.21?×?10³ to 10.28?×?10³ cells L^?1. Phytoplankton abundance decreased with depth and did not show any significant correlation with chlorophyll a (chl a). Column-integrated phytoplankton cell counts (PCC) ranged from 94.3?×?10⁶ cells m^?2 (Kf4) to 13.7?×?10⁶ cells m^?2 (Kf5), while chl a was lowest at inner part of the fjord (6.3 mg m^?2) and highest towards the mouth (24.83 mg m^?2). Biomass from prymnesiophytes and raphidophytes dominated at surface and 10 m, respectively. The contribution of Bacillariophyceae to biomass was low. Generally, heterotrophic dinoflagellates were great in abundance (12.82 %) and ubiquitous in nature and were major contributors to biomass. Various chl pigments (chl b, chl c, phaeopigments (phaeo)) were measured to obtain pigment/chl a ratios to ascertain phytoplankton composition. Phaeo were observed only in inner fjord. Chl b:a ratios and microscopic observations indicated dominance of Chlorophyceae at greater depths than surface. Furthermore, microscopic observations confirmed dominance of chl c containing algae throughout the fjord. The study indicates that pigment ratios can be used as a tool for preliminary identification of major phytoplankton groups. However, under the presence of a large number of heterotrophic dinoflagellates such as Gymnodinium sp. and Gyrodinium sp., pigment signatures need to be supplemented by microscopic observations.     

Monitoring bio-available marine contaminants with mussels (Mytilus edulis L) in the Netherlands

After discussing the usefulness of mussels (e.g. Mytilus edulis) for investigating contamination in the marine environment, four cases are presented:

1. A survey of Cu bioavailability in and around the Eastern Scheldt during one winter (1974–1975);
2. A surveillance with a six years interval (1974; 1980) of the bioavailability of Zn along the Dutch North Sea coast.
3. A monitoring programme over the period 1972–1980 showing the decrease in bioavailable Hg in the water column of the Ems-Dollard estuary after decreased emissions at Delfzijl.
4. Retrospective monitoring of two PCB's, as a background for the effectiveness of legal restrictions to PCB use.

These four cases are considered a first step in understanding the effects of pollutants in marine ecosystems. In depth physiological, histological and biochemical studies could lay the basis for improved routine biological effect monitoring.     

Optimization of the Microwave-Assisted Solvent Extraction of Petroleum Hydrocarbons in Marine Sediment and Soil

A microwave-assisted solvent extraction (MASE) technique was developed for the quantitative extraction of gasoline- and diesel-range petroleum hydrocarbons (PHs) from soil and marine sediment samples. The influence of different extracting solvents, extraction temperature and duration of extraction on the recoveries of PHs was evaluated using a two-level orthogonal array design (OAD) with a OA8(27) matrix. Gas chromatographic-mass spectrometry (GC-MS) in multiple selective ion monitoring (MSIM) mode was used for the analysis of the PHs in environmental samples. The spiking range of the PHs in the environmental samples was between 1 to 1000 g/g. Good recoveries (>80%) could be obtained for most of the PHs using the optimum MASE conditions. The limit of detection (LOD) achieved by the GC-MS-MSIM was 0.02 g/g. A preliminary survey for the levels of PHs in marine sediment and soil samples from different parts of Singapore was carried out using the method.     

Biomagnification of mercury in trophic relation of Great Cormorant (Phalacrocorax carbo) and fish in the Vistula Lagoon, Poland

Total mercury (Hg) concentrations were determined by CV-AAS in selected tissues (liver, kidney, and muscle) of the Great Cormorant and some fish species (herring, ruffe, European smelt, tench, roach, Crucian carp, and Prussian carp) from the Vistula Lagoon ecosystem (Poland). Significant correlations between Hg concentrations in the kidneys and muscle of cormorants (U test, p?<?0.05) were found; levels of the metal were highest in the birds?? liver and kidneys. Total Hg concentrations in the fish decreased in the following order: roach > Prussian carp > Crucian carp > tench > European smelt > ruffe > herring. The biomagnification factor of Hg for the cormorant relative to the fish decreased in the following sequence: herring > ruffe > European smelt > tench > Crucian carp > roach = Prussian carp. It was significantly greater than unity, especially for the cormorant?Cherring trophic relationship. This implies that Hg is biomagnified in the cormorant in relation to its prey.     

Lead in hawks,falcons and owls downstream from a mining site on the Coeur d'Alene River,Idaho

Mining and smelting at Kellogg-Smelterville, Idaho, resulted in high concentrations of lead in Coeur d'Alene (CDA) River sediments and the floodplain downstream, where American Kestrels (Falco sparverius), Northern Harriers (Circus cyaneus), Red-tailed Hawks (Buteo jamaicensis), Great Horned Owls (Bubo virginianus), and Western Screech-owls (Otus kennicotti) nested. Nestling American Kestrels contained significantly higher (P=0.0012) blood lead concentrations along the CDA River (0.24 µg/g, wet wt) than the nearby reference area (0.087 µg/g). A 35% inhibition of blood -aminolevulinic acid dehydratase (ALAD) in nestling Northern Harriers (P=0.0001), 55% in nestling American Kestrels (P=0.0001) and 81% in adult American Kestrels (P=0.0004) provided additional evidence of lead exposure in the CDA River population. In nestling American Kestrels and Northern Harriers, ALAD activity was negatively correlated with lead in blood. An earlier report on Ospreys (Pandion haliaetus) showed slightly less inhibition of ALAD than in American Kestrels, but no significant reduction in hemoglobin or hematocrit and no negative influence on production rates. The adult and nestling American Kestrels along the CDA River contained about twice as much blood lead as Ospreys during the same years (adult 0.46 vs. 0.20 µg/g, and nestling 0.24 vs. 0.09 µg/g), but adults showed a 7.5% reduction in hemoglobin (P=0.0356) and nestlings an 8.2% reduction in hemoglobin (P=0.0353) and a 5.8% reduction in hematocrit (P=0.0482). We did not observe raptor deaths related to lead, and although the production rate for American Kestrels was slightly lower along the CDA River, we found no significant negative relation between productivity and lead. Limited data on the other raptors provide evidence of exposure to lead along the CDA River. Several traits of raptors apparently reduce their potential for accumulating critical levels of lead which is primarily stored in bones of prey species.The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged.     

Metals in Herring and Great Black-Backed Gulls from the New York Bight: the Role of Salt Gland in Excretion

We examined the tissue distribution ofmetals in the herring (Larus argentatus) andgreat black-backed (Larus marinus) gullsobtained near the John F. Kennedy Airport, on LongIsland, New York, to determine whether there werespecies differences and whether levels in the saltgland were sufficiently high to suggest that thisorgan may be serving an excretory function. For mostorgans, herring gulls had significantly higher levelsof lead (except for liver), but significantly lowerlevels of mercury (except in the salt gland) thangreat black-backed gulls. For all metals exceptarsenic, there were significant differences inconcentrations among tissues for both species. Greatblack-backed gulls had much higher concentrations ofcadmium in kidney than in any other organ and this wasmuch higher than the level in herring gulls; herringgulls had much higher levels than black-backs of leadin salt glands. For both species, concentrations inkidney, liver and salt gland were generally higherthan in heart muscle or pectoral muscle. For herringgulls, the concentrations of all metals in the saltglands were not significantly different from the organwith the highest values (liver or kidney). For greatblack-backed gulls this was true only for lead,selenium, chromium, and mercury. We examined theratio of metals in all organs to the liverconcentration. Very low ratios (<0.25) were foundfor lead in heart and muscle of both species, andselenium in heart and muscle of herring gulls. Highratios (>2) included lead (2.75:1) and cadmium(14.3:1) in kidney of black-backs. In greatblack-backs the kidney:salt gland ratio was >1.5:1except for mercury (1.31:1) and chromium (0.83:1),while in herring gulls all ratios were between 0.7 and1.2, except for mercury (0.46:1), reflecting therelatively higher concentrations of metals in the saltgland of this species. We suggest that most heavymetals seem to be concentrating in the salt glands ofgulls, within an order of magnitude of the kidneyconcentration, and that salt glands may be serving asignificant excretory function for these cations.     

Duck Populations as Indicators of Landscape Condition in the Prairie Pothole Region

The Prairie Pothole Region of the northern GreatPlains is an important region for waterfowl production becauseof the abundance of shallow wetlands. The ecologicalsignificance of the region and impacts from intensiveagriculture prompted the U.S. Environmental Protection Agency to select it as one ofthe first areas for developing and evaluating ecologicalindicators of wetland condition. We examined hypothesizedrelations between indicators of landscape and wetlandconditions and waterfowl abundance on 45 40 km² study sites in North Dakota for1995–1996. Landscape condition was defined a priori as the ratio of cropland area to total upland area surroundingwetlands. Measures of waterfowl abundance included estimatednumbers of breeding pairs (by species and total numbers) and , a species-specific correction factor which effectively adjusts breedingpair estimates for annual or area-related differences in pondsize. Landscape indicators and waterfowl measures varied among regions. Results indicated that most areas in the Coteau region are ofmuch higher quality for ducks than those in the Drift Plain,and areas in the Red River Valley are of the poorest qualityfor ducks. Regression models demonstrated the impact ofagricultural development on breeding duck populations in the PrairiePothole Region. The most consistent landscape indicators ofwaterfowl abundance were percent of cropland and grassland. Models were inconsistent among years and species. Thepotential biotic indicators of landscape and wetland condition examined here wouldbe appropriate for temporal trend analyses, but because ofinherent geographic variability would not be appropriate forsingle-year geographic trend analyses without more extensiveevaluations to improve explanatory models.     

Assessing spatio-temporal trend of vector breeding and dengue fever incidence in association with meteorological conditions

Th aim of this study is to investigate spatio-temporal trends of dengue vector breeding and epidemic (disease incidence) influenced by climatic factors. The spatio-temporal (low-, medium-, and high-intensity periods) evaluation of entomological and epidemiological investigations along with climatic factors like rainfall (RF), temperature (T_max), relative humidity (RH), and larval indexing was conducted to develop correlations in the area of Lahore, Pakistan. The vector abundance and disease transmission trend was geo-tagged for spatial insight. The sufficient rainfall events and optimum temperature and relative humidity supported dengue vector breeding with high larval indices for water-related containers (27–37%). Among temporal analysis, the high-intensity period exponentially projected disease incidence followed by post-rainfall impacts. The high larval incidence that was observed in early high-intensity periods effected the dengue incidence. The disease incidence had a strong association with RF (r = 0.940, α = 0.01). The vector larva occurrence (r = 0.017, α = 0.05) influenced the disease incidence. Similarly, RH (r = 0.674, α = 0.05) and average T_max (r = 0.307, α = 0.05) also induced impact on the disease incidence. In this study, the vulnerability to dengue fever highly correlates with meteorological factors during high-intensity period. It provides area-specific understanding of vector behavior, key containers, and seasonal patterns of dengue vector breeding and disease transmission which is essential for preparing an effective prevention plan against the vector.     

Probabilistic Modelling of Cattle Farm Distribution in Australia

A probabilistic Bayesian method called weights of evidence (WofE) was used to develop a synthetic dataset of cattle farm locations at a national scale across Australia. The synthetic dataset was required for the modelling of livestock movements with a view to assessing biosecurity implications. The WofE method is based on the analysis of spatial relationships between evidential patterns with respect to an event, such as the actual location of a farm. The evidential patterns of cattle farms were derived from maps of land use, land tenure, drainage systems, roads, settlements and long-term averaged rainfall. These evidential patterns were used for delineating and ranking land areas suitable for cattle farming. For each evidential pattern statistics such as a positive weight, a negative weight and a contrast were calculated for estimating the degree of correlation between the evidential patterns and known farm locations. The integrated evidential patterns of known farms were then used for estimating posterior probabilities and splitting land into five different classes according to its suitability for farming.

Mercury, Methylmercury, and Selenium Concentrations in Eggs of Common Loons (Gavia immer) from Canada

Concentrations of Hg and Se were determined for a total of 125Common Loon (Gavia immer) eggs collected from lakes in Alberta, Saskatchewan, Ontario, Quebec, New Brunswick and NovaScotia, Canada between 1972 and 1997. Resulting data were compared to Hg and/or Se concentrations known or suspected tocause reproductive impairment in birds. Organic (methyl) Hg analyses were also performed on a subset of 24 loon eggs. Thirty-nine of 125 eggs had total Hg levels exceeding those (0.6 g g^-1 ww, or 2.5 g g^-1 dw)previously reported to be associated with reproductive impairment in common loons (Barr, 1986), and 9 of 125 eggshad Hg concentrations higher than the level associated withreproductive impairment in birds generally 1 g g^-1 ww; (Thompson, 1996). Selenium concentrations in loon egg samples were less than levels known to cause reproductiveimpairment in birds. A weak but significant positive correlation was observed between egg-Hg and -Se concentrations(r = 0.511, p < 0.05). On average, methylmercury accounted for about 87% of total Hg in 24 eggs analysed for both total and organic Hg. In this subset of eggs, the relationship between organic (methyl) Hg and Se was significant (r = 0.538, p = 0.007) while that found between inorganic Hg and Se in the same eggs was not significant (r = 0.353, p = 0.091). This relationship was unexpected and was contrary to relationships established for organic and inorganic Hg vs. Se in adult loon liver and kidney tissue (Scheuhammer et al., 1998b).