Feeding preference and deterrence in rabbitfish Siganus fuscescens for the cyanobacterium Lyngbya majuscula in Moreton Bay, south‐east Queensland, Australia

Rabbitfish Siganus fuscescens preferences for Lyngbya majuscula collected from three bloom locations in Moreton Bay, Queensland, Australia, were tested along with a range of local plant species in the laboratory. Consumption of L. majuscula by fish did not differ between wild and captive‐bred fish ( P  = 0·152) but did differ between bloom location ( P  = 0·039). No relationship was found between consumption rates and lyngbyatoxin‐a concentration ( r ² = 0·035, P  = 0·814). No correlation existed between C : N and proportion of food consumed when all food types were analysed statistically, whereas a clear correlation was observed when L. majuscula was removed from the calculations. In simulated bloom conditions, fish avoided ingestion of L. majuscula by feeding through gaps in the L. majuscula coverage. Both wild and captive‐bred S. fuscescens showed a distinct feeding pattern in 10 day no‐choice feeding assays, with less L. majuscula being consumed than the preferred red alga Acanthophora spicifera . Lyngbya majuscula however, was consumed in equal quantities to A. spicifera by wild S. fuscescens when lyngbyatoxin‐a was not detectable. Wild fish probably do not preferentially feed on L. majuscula when secondary metabolites are present and are not severely impacted by large L. majuscula blooms in Moreton Bay. Furthermore, poor feeding performance in both captive‐bred and wild S. fuscescens suggests that they would exert little pressure as a top‐down control agent of toxic L. majuscula blooms within Moreton Bay.     

Distribution and toxicity of a new colonial Microcystis aeruginosa bloom in the San Francisco Bay Estuary,California

The first distribution, biomass and toxicity study of a newly established bloom of the colonial cyanobacteria Microcystis aeruginosa was conducted on October 15, 2003 in the upper San Francisco Bay Estuary. Microcystis aeruginosa was widely distributed throughout 180 km of waterways in the upper San Francisco Bay Estuary from freshwater to brackish water environments and contained hepatotoxic microcystins at all stations. Other cyanobacteria toxins were absent or only present in trace amounts. The composition of the microcystins among stations was similar and dominated by demethyl microcystin-LR followed by microcystin-LR. In situ toxicity computed for the >75 m cell diameter size fraction was well below the 1 g l^–1 advisory level set by the World Health Organization for water quality, but the toxicity of the full population is unknown. The toxicity may have been greater earlier in the year when biomass was visibly higher. Toxicity was highest at low water temperature, water transparency and salinity. Microcystins from the bloom entered the food web and were present in both total zooplankton and clam tissue. Initial laboratory feeding tests suggested the cyanobacteria was not consumed by the adult copepod Eurytemora affinis, an important fishery food source in the estuary.     

Use of guilds for modelling avian responses to vegetation in the Intermountain West (USA)

Aim Individually focused conservation management of many species is expensive and logistically impractical. Mesofilter conservation methods may facilitate the simultaneous management of multiple species. We used data on distributions of two sets of avian guilds, based on dependence on riparian vegetation and on nest location, to relate occurrence rates to environmental variables. Variables were selected by expert opinion and are likely to be affected by changes in climate and land use. Location Data were collected from 2001–06 in four adjacent mountain ranges in the central Great Basin (Lander, Nye and Eureka counties, Nevada, USA): the Shoshone Mountains and the Toiyabe, Toquima and Monitor ranges. Methods Data on occurrence of birds, vegetation composition and vegetation structure were obtained in the field. Geographical coordinates and the normalized difference vegetation index were derived from a digital elevation model and a satellite image. To construct a general model for guilds as a whole, while allowing flexibility for variation in the functional responses of individual species, we applied multivariate adaptive regression splines. Results The predictive capacity of expert knowledge of relationships between birds and vegetation was inconsistent. Latitude, longitude and elevation may constrain the response of some guilds to changes in vegetation structure and composition. Guild‐based models were useful for modelling species with sparse distributions, which are difficult to model individually. In essence, this method supplements models for the individual species with patterns for the guild to which they belong. Main conclusions Guilds of birds appeared to have predictable associations with selected attributes of vegetation structure and composition. The criteria by which species are grouped into guilds may affect the success of predictions and management interventions. Our derived models offer the potential to predict effects on the avifauna of management or climate‐driven change in vegetation.     

Detection of persistent microcystin toxins at the land–sea interface in Monterey Bay,California

Blooms of toxin-producing Microcystis aeruginosa occur regularly in freshwater systems throughout California, but until recently potential impacts in the coastal ocean have been largely ignored. Twenty-one sites in and around Monterey Bay were surveyed for evidence of microcystin toxin (2010–2011) at the land–sea interface. Following this initial survey four major watersheds in the Monterey Bay area were surveyed (2011–2013) for microcystin concentration, nutrients, alkalinity and water temperature to identify potential environmental factors correlated with the abundance of microcystin at the land–sea interface. During the first year microcystin was detected in 15 of 21 sites. Data from years two and three were analyzed by principal components analysis and mixed effects model. Results indicated that coastal nutrient loading (nitrate, phosphate silicate, ammonium, urea), were statistically significant predictors of the microcystin concentrations in the watersheds with clear evidence for seasonality at some sites. Microcystin was frequently at highest concentration in the autumn; however, at some locations high levels of toxin were measured during spring. Because this toxin has the ability to biomagnify and persist within food webs, elevated levels within the watershed may decrease potential for health and survival of wildlife and humans exposed to freshwater and marine waters. The widespread occurrence of microcystin at low to moderate levels throughout the year and throughout the sampled watersheds demonstrates the potential difficulty for management.     

Attempts to model the bloom dynamics of Pyrodinium, a tropical toxic dinoflagellate

For the first time, several models have been used to aid in the understanding of the bloom dynamics of Pyrodinium bahamense var. compressum, the major causal organism of toxic algal blooms in Manila Bay and several areas in the tropical world. The complex life cycle of Pyrodinium includes the formation of cysts that settle at the sediments, which can serve as the inoculum for the next bloom.The seasonal variation of temperature and salinity reflects the combined effects of convection and water column stability, which can control vertical movement of plankton and other parameters essential to its growth. The significance of wind forcing appears to be related to the potential to resuspend cysts. In the absence of wind, tidal currents in the inner part of the bay may be too weak to induce resuspension. The addition of wind results in a significant increase in bottom current velocity. Off Cavite at the southeast, bottom velocity is enhanced by orbital motion due to waves, one of the reasons why sediments off this area are dominated by sandy material. The strong vertical mixing of the water column at depths of less than 10 m may influence nutrient and consequently, plankton populations.The wave field during the southwest monsoon indicates that its contribution to the bottom velocity dominates in this area of the bay.Bloom simulations using combined bio-physical parameters show that direction of advection is almost always along wind direction. The dispersal distances increases if the Pyrodinium cells are found higher in the water column. For cells originating from southeastern (Cavite) sources, the direction of transport is slightly towards the north. In either case, the formation of cysts after a bloom is adjacent to the northern area (Pampanga) for blooms originating from the western side (Bataan) and along the eastern side (Parañaque–Manila) for blooms originating from the southeastern side (Cavite). Comparison with a few records of bloom occurrences in Manila Bay shows some consistent features. Reports of these blooms also showed that they occurred almost always during spring tides. There appears to be two main systems for bloom formation: one fed by cyst beds in the west (Bataan) which is advected along the west–northwest coast (Bataan–Bulacan) while the other one is fed by the southeast (Cavite) cyst beds that dominates in the east-southeast (Parañaque–Cavite) area.     

Health Risk from the Use of Roof-Harvested Rainwater in Southeast Queensland,Australia, as Potable or Nonpotable Water,Determined Using Quantitative Microbial Risk Assessment

A total of 214 rainwater samples from 82 tanks were collected in urban Southeast Queensland (SEQ) in Australia and analyzed for the presence and numbers of zoonotic bacterial and protozoal pathogens using binary PCR and quantitative PCR (qPCR). Quantitative microbial risk assessment (QMRA) analysis was used to quantify the risk of infection associated with the exposure to potential pathogens from roof-harvested rainwater used as potable or nonpotable water. Of the 214 samples tested, 10.7%, 9.8%, 5.6%, and 0.4% were positive for the Salmonella invA, Giardia lamblia β-giardin, Legionella pneumophila mip, and Campylobacter jejuni mapA genes, respectively. Cryptosporidium parvum oocyst wall protein (COWP) could not be detected. The estimated numbers of Salmonella, G. lamblia, and L. pneumophila organisms ranged from 6.5 × 10¹ to 3.8 × 10² cells, 0.6 × 10° to 3.6 × 10° cysts, and 6.0 × 10¹ to 1.7 × 10² cells per 1,000 ml of water, respectively. Six risk scenarios were considered for exposure to Salmonella spp., G. lamblia, and L. pneumophila. For Salmonella spp. and G. lamblia, these scenarios were (i) liquid ingestion due to drinking of rainwater on a daily basis, (ii) accidental liquid ingestion due to hosing twice a week, (iii) aerosol ingestion due to showering on a daily basis, and (iv) aerosol ingestion due to hosing twice a week. For L. pneumophila, these scenarios were (i) aerosol inhalation due to showering on a daily basis and (ii) aerosol inhalation due to hosing twice a week. The risk of infection from Salmonella spp., G. lamblia, and L. pneumophila associated with the use of rainwater for showering and garden hosing was calculated to be well below the threshold value of one extra infection per 10,000 persons per year in urban SEQ. However, the risk of infection from ingesting Salmonella spp. and G. lamblia via drinking exceeded this threshold value and indicated that if undisinfected rainwater is ingested by drinking, then the incidences of the gastrointestinal diseases salmonellosis and giardiasis are expected to range from 9.8 × 10° to 5.4 × 10¹ (with a mean of 1.2 × 10¹ from Monte Carlo analysis) and from 1.0 × 10¹ to 6.5 × 10¹ cases (with a mean of 1.6 × 10¹ from Monte Carlo analysis) per 10,000 persons per year, respectively, in urban SEQ. Since this health risk seems higher than that expected from the reported incidences of gastroenteritis, the assumptions used to estimate these infection risks are critically examined. Nonetheless, it would seem prudent to disinfect rainwater for use as potable water.Roof-harvested rainwater has received significant attention as a potential alternative source of potable and nonpotable water in regions where water is scarce (37). To encourage the use of roof-harvested rainwater, governmental bodies of many countries, such as Australia, Denmark, Germany, India, and New Zealand, are providing subsidies to residents to encourage the use of rainwater for domestic purposes. The use of rainwater is quite common in Australia, particularly in rural and remote areas, where reticulated mains or town water is not available. Recent water scarcity in several capital cities prompted the use of rainwater as an alternative source. For instance, the Queensland State Government initiated the “Home Water Wise Rebate Scheme,” which provides subsidies to Southeast Queensland (SEQ) residents who use rainwater as nonpotable water for domestic purposes (49). Over 260,000 householders were granted subsidies up to December 2008, when the scheme was concluded.There is a general community feeling that roof-harvested rainwater is safe to drink, and this is partially supported by limited epidemiological evidence (26). Some studies have reported that roof-harvested rainwater quality is generally acceptable for use as potable water (13, 29). In contrast, the presence of potential pathogens, such as Aeromonas spp. Campylobacter spp., Campylobacter jejuni, Salmonella spp., Legionella pneumophila, Giardia spp., Giardia lamblia, and Cryptosporidium spp., in roof-harvested rainwater samples has been reported (2, 9, 34, 45, 47, 48). Such pathogens can cause gastrointestinal illness in humans, with nausea, vomiting, and/or diarrhea occurring within 12 to 72 h (Salmonella enterica serovar Typhimurium) to 9 to 15 days (Giardia lamblia) after ingestion of contaminated water. L. pneumophila can cause the respiratory infection pneumonia, and the fatality rate can be 50% in immunocompromised patients (57).Direct routine monitoring of the microbiological quality of source water for all possible pathogens is not economically, technologically, or practically feasible. Consequently, traditional fecal indicators, such as fecal coliforms, Escherichia coli, and enterococci, have long been used to determine the presence of pathogens. Most studies assess the quality of roof-harvested rainwater based on the numbers of these fecal indicators (13, 30). However, the major limitation in using fecal bacteria as indicators is their poor correlation with the presence of pathogenic microorganisms in water (2, 30). An alternative is the measurement of pathogens using traditional culture-based methods. However, there are several limitations of such methods, including the underestimation of the bacterial number due to the presence of injured or stressed cells (10) and the fact that certain microorganisms in environmental waters can be viable but not culturable (39). Culture-based methods are also generally laborious and costly. Recent advances in molecular techniques such as PCR technology enable rapid, specific, and sensitive detection of many pathogens. Advances in PCR methodology also enable the quantification of potential pathogens in source water that are otherwise difficult and/or laborious to culture using traditional microbiological methods. In view of this, we used binary PCR (presence/absence)- and quantitative PCR (qPCR)-based assays to first detect and then quantify zoonotic pathogens in samples from roof-harvested rainwater in SEQ residential houses.The aims of the research study were 2-fold: (i) to quantify the number and frequency of occurrence of Salmonella, G. lamblia, and L. pneumophila organisms in a range of domestic water tanks in SEQ by using qPCR-based methods and (ii) to apply quantitative microbial risk assessment (QMRA) analysis in order to estimate the risk of infection from exposure to these pathogens found in roof-harvested rainwater. The uniqueness of this study stems from the fact that instead of measuring fecal indicators, the pathogens that are capable of causing illness were quantified and this information was combined with QMRA to assess the human health risk of using roof-harvested rainwater as potable or nonpotable water.     

Use of a multiple addition bioassay to determine limiting nutrients in eagle lake,California

This investigation uses anin vitro enrichment bioassay (in which all essential nutrients except one are added to each culture) to determine which nutrients are important to algal growth in Eagle Lake. The technique was developed when it was discovered that addition of individual nutrients produced little if any growth response. Laboratory bioassays correlated well with comparative studies in the lake. A great deal of variation was found throughout the year but P, N, Fe, and S were found to be limiting at one time or another. The north and south basins of the lake, which differ in morphometry, were also found to differ in the intensity spectrum of limitation. While P was the most important nutrient in both basins, the other nutrients were more limiting in the north basin than the south, and Fe, which was least limiting in the south, was very important in the north. The multiple enrichment bioassay has several advantages over other bioassays. Supported in part by Research Corporation     

Use of sandbanks by terns in Queensland,Australia: a priority for conservation in a popular recreational waterway

Many terns (Laridae) from the northern hemisphere overwinter in Australia, but they are rarely covered comprehensively in bird counts in Australian coastal waterways. We conducted censuses over 3 years on terns in an increasingly popular recreational waterway at the northern end of Moreton Bay, known as Caloundra sandbanks, to provide the first overview of the relative abundance of non-breeding tern species on estuary-type sandbanks in Australia. The maximum number of birds counted was > 43,000, of which over 90% belonged to six species of terns. The most abundant tern species was the common tern Sterna hirundo longipennis which reached > 38,000 in one Austral summer. Other northern-breeding migrant terns were the white-winged black tern Chlidonias leucopterus ( > 17,000) and the little tern S. albifrons sinensis ( >11,000), which also breeds in Australia. These migrant terns arrived at Caloundra sandbanks at around late-October and a vast majority had departed by mid-April. Numbers were generally highest from late-December through to early-April. An additional three Australian-breeding terns of smaller population sizes frequented the sandbanks. Density of terns using the habitats could reach a peak of 600 ha⁻¹ during the warmer months of the year, coinciding with peak human recreational activities. In light of the results, Caloundra sandbanks should be regarded as an Area of International Importance based on criteria contained in the Ramsar Convention. The situation at Caloundra sandbanks presents challenges to recreational and tourism issues, requiring review of traditional government priorities in the conservation of wetlands based primarily on waders.     

Use of two-dimensional gel electrophoresis to differentiate morphospecies of Alexandrium minutum, a paralytic shellfish poisoning toxin-producing dinoflagellate of harmful algal blooms

Contamination of shellfish with paralytic shellfish poisoning toxins (PST) produced by toxic harmful algal blooms (HABs) have been negatively affecting the shellfish and aquaculture industries worldwide. Therefore, accurate and early identification of toxic phytoplankton species is crucial in HABs surveillance programs that allow fish-farmers to take appropriate preventive measures in shellfish harvesting and other aquaculture activities to overcome the negative impacts of HABs on human health. The identification of toxic dinoflagellates present in the water is currently a time-consuming operation since it requires skillful taxonomists and toxicologists equipped with optical and scanning electron microscopes as well as sophisticated equipment, for example, high-performance liquid chromotography-fluorescence detection. In this paper, a two-dimensional gel electrophoresis (2-DE)-based proteomic approach was applied to discriminate between toxic and nontoxic strains of Alexandrium minutum. Variation in morphological features between toxic and nontoxic strains was minimal and not significant. Also, variation in 2-DE protein patterns within either toxic or nontoxic strains was low, but pronounced differences were detected between toxic and nontoxic strains. The most notable differences between these strains were several abundant proteins with pIs ranging from 4.8 to 5.3 and apparent molecular masses between 17.5 and 21.5 kDa. Groups of proteins, namely NT1, NT2, NT3, and NT4, were consistently found in all nontoxic strains, while T1 and T2 were prominent in the toxic strains. These specific protein spots characteristic for toxic and nontoxic strains remained clearly distinguishable irrespective of the various growth conditions tested. Therefore, they have the potential to serve as "taxonomic markers" to distinguish toxic and nontoxic strains within A. minutum. Initial studies revealed that the expression pattern of T1 was tightly correlated to toxin biosynthesis in the examined alga and may be used to serve as a potential toxin indicator.     

Risk of symptomatic dengue for foreign visitors to the 2014 FIFA World Cup in Brazil

Brazil will host the FIFA World Cup™, the biggest single-event competition in the world, from June 12-July 13 2014 in 12 cities. This event will draw an estimated 600,000 international visitors. Brazil is endemic for dengue. Hence, attendees of the 2014 event are theoretically at risk for dengue. We calculated the risk of dengue acquisition to non-immune international travellers to Brazil, depending on the football match schedules, considering locations and dates of such matches for June and July 2014. We estimated the average per-capita risk and expected number of dengue cases for each host-city and each game schedule chosen based on reported dengue cases to the Brazilian Ministry of Health for the period between 2010-2013. On the average, the expected number of cases among the 600,000 foreigner tourists during the World Cup is 33, varying from 3-59. Such risk estimates will not only benefit individual travellers for adequate pre-travel preparations, but also provide valuable information for public health professionals and policy makers worldwide. Furthermore, estimates of dengue cases in international travellers during the World Cup can help to anticipate the theoretical risk for exportation of dengue into currently non-infected areas.     

Mark-release-recapture study to measure dispersal of the mosquito Aedes aegypti in Cairns, Queensland, Australia

In Queensland, Australia, in response to isolated cases of dengue infection, larval control of the vector Aedes aegypti (L.) (Diptera: Culicidae) is targeted at breeding sites within 200 m of a case and interior spraying with a pyrethroid adulticide is targeted at premises within 100 m. To ascertain whether these limits are appropriate, we conducted a mark-release-recapture study to measure the dispersal of female Ae. aegypti in the city of Cairns where transmission occurs. Female mosquitoes reared from wild collected eggs were differentially marked with fluorescent dust depending on whether they were to be released blood-fed or non-blood-fed, and a total of 1,948 females was released. A total of 132 sticky ovitraps was set at 64 premises within a 200 m radius and collections of trapped adults were made at 5-15 days post-release. Sixty-seven females (3.4%) were recaptured, with the furthest being caught 200 m from the release point, and the mean distance travelled was 78 m. Overall, 23.1% of the recaptures outside the release site were taken beyond 100 m by day 15. Dispersal was comparable for both blood-fed and non-blood-fed releases. There was a significant tendency for dispersal to be in a north-westerly direction, probably because of the presence of numerous containers and heavy shading by trees in this direction and a busy road to the south of the release point that appeared to inhibit dispersal. The results suggest that adulticiding may have to be extended beyond 100 m if more than 8 days have elapsed since female Ae. aegypti could have fed upon a viraemic dengue case. The study also shows that dispersal is not random, and that it may be possible to maximize vector control by taking into account environmental factors that affect the direction of female mosquito flight.     

A Regional Ecological Risk Assessment of the Kaipara Harbour,New Zealand,Using a Relative Risk Model

A regional ecological risk assessment was conducted for the Kaipara Harbour catchment in New Zealand. The Relative Risk Model was used to prioritize management of the sources of stress and habitats of concern in the basin. Semi-structured interviews with 25 representative stakeholders were conducted to obtain the resource-users’ perspectives and to identify the regional stressor sources and receptor habitat data for the model. For this risk analysis we divided the catchment into nine ecological districts. Mixed-methodological approaches including content analysis, geospatial analysis, and source documentation were used to categorize source and habitat rankings, based on the relative abundance of each in the nine ecological districts. Risk characterization revealed that fishing pressure and tidal energy pose the largest sources of perceived risk to the catchment; shellfish and Maui dolphin habitats are the receptors estimated to be at greatest risk; and the Kaipara and Rodney ecological districts are the sub-regions estimated with the greatest combined risk. A Monte Carlo analysis confirmed the source inputs and revealed greater uncertainty than the estimated habitat input results. The results of this assessment can be used by policy-makers, conservation groups, and municipalities to inform the future management efforts in the harbor and catchment.     

Impacts of a Toxic <Emphasis Type="Italic">Microcystis</Emphasis> Bloom on the Macroinvertebrate Fauna of Lake Elphinstone,Central Queensland,Australia

The biological, physical and chemical properties of Lake Elphinstone were studied during a dense, toxic cyanoprokaryote bloom dominated by Microcystis. Decreases in total abundance and richness in macroinvertebrate communities coincided with increases in Microcystis toxicity. Water quality was characterized by high light attenuation values caused by abiogenic turbidity and shading and absorbance from thick algal scums. The study highlights the potential for multidimensional environmental impacts associated with toxic cyanoprokaryote blooms, and the consequent implications for the management of shallow, inland and tropical lakes that are susceptible to toxic blooms.     

Phylogeography of the scarab beetle Antitrogus parvulus Britton (Coleoptera: Scarabaeidae) in south-eastern Queensland, Australia

Abstract  This study surveys the population genetic structure of Childers canegrub, Antitrogus parvulus , to elucidate its population dynamics and gene flow. Antitrogus parvulus is a pest of sugarcane in the Bundaberg region and this knowledge can be used to optimise integrated pest management practices. Here, base-pair differences in the cytochrome oxidase II gene ( COII ) were used to characterise haplotypic diversity, infer levels of gene flow, and phylogenetic relationships of alleles and their phylogeographical structure. There were 28 unique haplotypes among the 70 sequenced individuals from the seven locations. All three variance components (among regions, among populations, within populations) are highly significant, with highest genetic diversity among regions and lowest among populations within regions. A positive correlation between migration rates and geographical distance and significant phylogeographical structure between four main geographical regions. The main implication of these findings for pest management is that if a grower can eliminate an existing infestation within a field, then reinvasion will be slow and further outbreaks within that field are unlikely to occur. The low dispersal ability of females also means that any resistance to insecticides that develops is likely to remain localised, but will rapidly become dominant within the affected population.     

Phylogeographic characteristics of hypervariable regions in the mitochondrial genome of a cosmopolitan,bloom‐forming raphidophyte,Heterosigma akashiwo

The global distribution of phytoplankton is defined by many events, including long‐term evolutionary processes and shorter time span processes (e.g., global climate change). Furthermore, human‐assisted, unintentional dispersion, including the transport of live fish and spat for aquaculture, and transfer of aquatic microorganisms contained in ship ballast water, may aid the spread of phytoplankton. To understand the phylogeographic history of a species, the development of useful molecular markers is crucial. We previously reported a hypervariable mitochondrial gene in the cosmopolitan bloom‐forming alga, Heterosigma akashiwo. In this study, we identified two additional hypervariable segments in the H. akashiwo mitochondrial genome, one a protein coding sequence, and the other an intergenic region, by comparing the whole mitogenomes of strains obtained from various geographic origins. Interestingly, the newly identified hypervariable protein coding sequence was a paralogue of the previously identified gene, and both sequences showed tendencies to correlate with latitude of geographic origin. However, the hypervariable intergenic sequence did not show a clear correlation with origin. Our results demonstrated that the protein coding sequences may serve as useful tools for understanding the phylogeographic history of H. akashiwo, and they may crucially function in adaptation of the species to the environment.     

Adaptation of the Forecasting Model DOWNCAST for Determination of Downy Mildew Epidemics of Oilseed Poppy in Tasmania, Australia

Peronospora cristata, causing downy mildew, has become an economically important pathogen of oilseed poppy (Papaver somniferum) since its first record in Tasmania in 1996. DOWNCAST, originally developed for downy mildew of onion, was evaluated for its ability to predict sporulation and infection of poppy by P. cristata. To assess the influence of the parameters within DOWNCAST, two modifications (POPCAST1 and POPCAST2) of the standard DOWNCAST model were also developed and tested. Initial accuracy of determination of sporulation events by DOWNCAST was 75%, while POPCAST1 (but not POPCAST2) was a significantly more accurate predictor of sporulation events (86%) than DOWNCAST (χ² = 5.74, P = 0.025). This increase in accuracy was attributed to increasing both the rainfall threshold inhibitory to sporulation from 0.2 to 3.0 mm, and the relative humidity threshold for induction and development of sporulation from 95% to 96%. While DOWNCAST, POPCAST1 and POPCAST2 had accuracies of infection determination of 65%, 80% and 75%, respectively, chi‐squared analysis indicated no significant difference between models. Preliminary field evaluation indicated that POPCAST1 and POPCAST2 were more sensitive in detecting early infection events than DOWNCAST. Field observations indicated that conditions are frequently conducive for downy mildew spread, therefore the ability to predict early season infection events would allow growers to reduce initial infection rates, and thus inoculum loads later in the season. POPCAST1 and POPCAST2 represent a significant step towards the development of a predictive model for downy mildew in poppy crops.     

The use of the land survey record to reconstruct pre-European vegetation patterns in the Darling Downs, Queensland, Australia

The Darling Downs is an extremely arable district in south eastern Queensland that has lost the majority of its native vegetation cover to agriculture. Vegetation references from land survey charts produced during the late 19th and early 20th century aided the reconstruction of the original vegetation patterns in the Darling Downs. Nearly 5000 references to vegetation were located for the study area and formed the basis of a vegetation map. The survey plans contain reference to seventy-three plant names which could generally be aligned to existing species, the majority of which are trees. The surveyors also referred to vegetation structure with terms such as 'open', 'shrubby' and 'dense'. The ambiguous use of some references and the lack of adequate coverage of surveyor's charts for some sections of the study area did not allow for the production of an accurate and comprehensive map using the survey record in isolation. An iterative process evolved where (i) a working map of the vegetation was produced from the survey record; (ii) the map was ground-truthed with existing remnants and ambiguities in surveyors' terminology clarified; (iii) for gaps in the record, hypotheses concerning eradicated vegetation were erected from knowledge of the environmental correlates of existing remnants; and (iv) these hypotheses were tested from areas where the survey record is comprehensive. Some vegetation types cannot be distinguished reliably on the basis of their physical environment and the distinction between these types for mapping was reliant on either the evidence from the survey record or remaining paddock trees. These processes enabled relatively accurate mapping of the pre-European vegetation of the study area at 1:100,000 scale. Comparison of the survey record and the vegetation of existing remnants suggests that overstorey composition and understorey density have changed little during European management within remnants.     

Some chemical factors regulating the growth of <Emphasis Type="Italic">Lyngbya majuscula</Emphasis> in Moreton Bay,Australia: importance of sewage discharges

The relative importance of the additions of iron (Fe), phosphorus (P) and the chelating agent EDTA in promoting the growth of Lyngbya majuscula in waters collected from the NW region of Moreton Bay was investigated using a series of continuous-flow growth studies. In addition, the possible impact of sewage/waste-water treatment plant (WWTP) discharges on the growth of L. majuscula was investigated in a series of batch and semi-continuous-flow growth studies. A preliminary study on the potential of phytoplankton growth in the receiving waters to affect the productivity of L. majuscula was also conducted. The results from the continuous-flow growth studies show that the growth rates of L. majuscula in the NW Moreton Bay waters were stimulated by the addition of EDTA alone but were not stimulated by the addition of P. The additions of P + EDTA, FeEDTA and P + FeEDTA did not result in higher growth rates than those obtained by the addition of EDTA alone. These results demonstrate that the productivity of L. majuscula in the NW Moreton Bay waters was not limited by P and that the addition of Fe did not affect the productivity. The stimulation effect of EDTA could be due to various reasons but we hypothesise that the principal reason for the stimulation is that EDTA increases the bioavailability of non-labile Fe species already present in the water. The results of the batch and semi-continuous-flow growth studies show that diluted (100:1) WWTP discharge water and the receiving waters impacted by WWTP discharges supported significant growth of L. majuscula and that the addition of EDTA to those waters increased the growth potential of L. majuscula. Also the growth of phytoplankton in a sample of the receiving waters impacted by WWTP discharges significantly reduced the growth rate of L. majuscula but the addition of EDTA restored the growth rate to near its maximum value. These results suggest that phytoplankton growth (and probably that of the associated bacterioplankton) could reduce the bioavailability of trace chemical factors needed for the growth of L. majuscula in Moreton Bay and in particular, could reduce the bioavailability of Fe. Overall the results support the hypothesis that growth of L. majuscula in Moreton Bay is often limited by the bioavailability of Fe and the principal reason for this is the lack of supply of suitable organic ligands/chelators, not the lack of Fe per se. Handling editor: D. Hamilton     

A bloom of Lyngbya majuscula in Shoalwater Bay, Queensland, Australia: An important feeding ground for the green turtle (Chelonia mydas)

Lyngbya majuscula, a toxic cyanobacterium, was observed blooming during June–July (winter) 2002 in Shoalwater Bay, Queensland, Australia, an important feeding area for a large population of green turtles (Chelonia mydas). The bloom was mapped and extensive mats of L. majuscula were observed overgrowing seagrass beds along at least 18 km of coast, and covering a surface area of more than 11 km². Higher than average rainfall preceded the bloom and high water temperatures in the preceding summer may have contributed to the bloom. In bloom samples, lyngbyatoxin A (LA) was found to be present in low concentration (26 μg kg⁻¹_{(dry weight)}), but debromoaplysiatoxin (DAT) was not detected. The diet of 46 green turtles was assessed during the bloom and L. majuscula was found in 51% of the samples, however, overall it contributed only 2% of the animals’ diets. L. majuscula contribution to turtle diet was found to increase as the availability of the cyanobacterium increased. The bloom appeared to have no immediate impact on turtle body condition, however, the presence of a greater proportion of damaged seagrass leaves in diet in conjunction with decreases in plasma concentrations of sodium and glucose could suggest that the turtles may have been exposed to a substandard diet as a result of the bloom. This is the first confirmed report of L. majuscula blooming in winter in Shoalwater Bay, Queensland, Australia and demonstrates that turtles consume the toxic cyanobacterium in the wild, and that they are potentially exposed to tumour promoting compounds produced by this organism.