A comparison of results from two test methods for assessing the toxicity of aminotriazole to Selenastrum capricornutum

Two different test methods for assessing the toxicity of aminotriazole to Selenastrum capricornutum are compared. Growth medium composition is demonstrated to have a significant effect on the toxicity of aminotriazole.     

Protracted estuarine phase in the life cycle of the marine pufferfish Torquigener pleurogramma

The present study was undertaken to elucidate the way in which the Swan Estuary in south-western Australia is used by the common blowfish Torquigener pleurogramma, a representative of the abundant and widely distributed family Tetraodontidae. T. pleurogramm were collected by beach seine and otter trawl from the Swan Estuary between February 1977 and December 1980 and between May 1984 and February 1986. While T. pleurogramma feeds on a wide variety of organisms in the estuary, the main components of its diet are polychaetes and amphipods for fish <130 mm and bivalve molluscs for larger fish. Numbers of blowfish were inversely correlated with water depth, with densities on the banks (water depth <1.5 m) sometimes reaching 5 fish m^-2, and tended to be greater at night than during the day. The density of T. pleurogramma in the shallows was positively correlated with salinity and inversely correlated with distance from the estuary mouth. Numbers increased greatly in the latter half of 1980 and 1985 as a result of the recruitment of large numbers of the 0+ age class (i.e., fish in their first year of life). Blowfish were represented by seven age classes in the estuary and attained a maximum size of 230 mm (220 g). By the end of their first and second years of life, fish had reached approximately 90 mm (14 g) and 125 mm (39 g), respectively. Sexual maturity was generally not reached until the end of the second year of life. The presence of higher gonadosomatic indices and more mature gonads in fish collected just outside than within the estuary indicate that T. pleurogramma leaves the estuary before spawning. Comparisons between lengthfrequency data, allied with information on the prevalence and intensity of gill parasites, indicate that assemblages in estuarine and neighbouring inshore waters remain distinct for many months and that growth within the estuary is faster than in inshore marine environments.     

Spatial synchrony in coral reef fish populations and the influence of climate

We investigated spatial patterns of synchrony among coral reef fish populations and environmental variables over an eight-year period on the Great Barrier Reef, Australia. Our aims were to determine the spatial scale of intra- and interspecific synchrony of fluctuations in abundance of nine damselfish species (genus Pomacentrus) and assess whether environmental factors could have influenced population synchrony. All species showed intraspecific synchrony among populations on reefs separated by < or =100 km, and interspecific synchrony was also common at this scale. At greater spatial scales, only four species showed intraspecific synchrony, over distances ranging from 100-300 km to 500-800 km, and no cases of interspecific synchrony were recorded. The two mechanisms most likely to cause population synchrony are dispersal and environmental forcing through regionally correlated climate (the Moran effect). Dispersal may have influenced population synchrony over distances up to 100 km as this is the expected spatial range for ecologically significant reef fish dispersal. Environmental factors are also likely to have synchronized population fluctuations via the Moran effect for three reasons: (1) dispersal could not have caused interspecific synchrony that was common over distances < or =100 km because dispersal cannot link populations of different species, (2) variations in both sea surface temperature and wind speed were synchronized over greater spatial scales (>800 km) than fluctuations in damselfish abundance (< or =800 km) and were correlated with an index of global climate variability, the El Ni?o-Southern Oscillation (ENSO), and (3) synchronous population fluctuations of most damselfish species were correlated with ENSO; large population increases often followed ENSO events. We recorded regional variations in the strength of population synchrony that we suspect are due to spatial differences in geophysical, oceanographic, and population characteristics, which act to dilute or enhance the effects of synchronizing mechanisms. We conclude that synchrony is common among Pomacentrus populations separated by tens of kilometers but less prevalent at greater spatial scales, and that environmental variation linked to global climate is likely to be a driving force behind damselfish population synchrony at all spatial scales on the Great Barrier Reef.     

Octachlorodibenzo-p-dioxin in wood treatment materials and treated wood

The octachlorodibenzo-p-dioxin (OCDD) concentrations have been determined in aged samples of commercial pentachlorophenol (PCP), in wood protection formulations containing PCP and in wood treated with PCP as a preservative or as an anti-sapstain treatment. The concentrations of OCDD found in the various samples are within the range expected from the amount of commercial PCP initially present in the samples. In view of the known stability of OCDD the results are interpreted as indicating that the formulation, treatment and ageing processes have not led to any substantial conversion of PCP to OCDD; although one result indicates that outdoor exposure of treated samples increased the OCDD concentration by a factor of approximately 2 after $\text{3}\text{1}\text{2}$ years. Analysis of aged samples of treated wood indicate that OCDD is lost much less rapidly from the wood than PCP.     

Analysis of polychlorobiphenyls from used transformers for polychlorodibenzofurans

The results of analyses for polychlorodibenzofuran (PCDF) content in two samples of polychlorobiphenyl (PCB) from used electrical transformers are presented and discussed. In neither sample was there evidence for enhanced PCDF concentrations even though one of them had been subjected to overheating while in service.     

Polychlorodibenzo-p-dioxins and dibenzofurans in technical pentachlorophenol - results of a collaborative analytical exercise

Results of analyses of eight samples of technical pentachlorophenol conducted by three different analytical methods are presented and discussed.     

Regional-scale variation in the distribution and abundance of farming damselfishes on Australia’s Great Barrier Reef

Territorial damselfishes that manipulate (“farm”) the algae in their territories can have a marked effect on benthic community structure and may influence coral recovery following disturbances. Despite the numerical dominance of farming species on many reefs, the importance of their grazing activities is often overlooked, with most studies only examining their roles over restricted spatial and temporal scales. We used the results of field surveys covering 9.5° of latitude of the Great Barrier Reef to describe the distribution, abundance and temporal dynamics of farmer communities. Redundancy analysis revealed unique subregional assemblages of farming species that were shaped by the combined effects of shelf position and, to a lesser extent, by latitude. These spatial patterns were largely stable through time, except when major disturbances altered the benthic community. Such disturbances affected the functional guilds of farmers in different ways. Since different guilds of farmers modify benthic community structure and affect survival of juvenile corals in different ways, these results have important implications for coral recovery following disturbances.     

An investigation of aqueous activity coefficients at low concentrations

The activity of a chemical in solution determines its tendency to move into other media. At low concentrations (<0.01M) it is generally considered to be linearly related to concentration. A hypothetical model based on the structure of liquid water is discussed which could cause deviations from this linearity in the ppb region, a concentration much lower than that normally investigated thermodynamically, but one of great importance environmentally. Headspace experiments are reported with carbon tetrachloride and chloroform in water at concentrations down to ～10^?3 ppb but no such deviations were discerned.     

Long term changes in polychlorodibenzo-p-dioxin concentrations in wood treated with technical pentachlorophenol

Wood samples treated with technical pentachlorophenol (PCP), technical sodium pentachlorophenoxide (NaPCP) and octachlorodibenzo-p-dioxin have been exposed outdoors for periods up to $\text{2}\text{1}\text{2}$ years. Analysis of extracts from the samples show that photolytic reductive dechlorination of highly chlorinated dibenzo-p-dioxins to less chlorinated isomers occurs. However there is no discernible increase in polychlorodibenzo-p-dioxin concentrations in the technical PCP treated wood presumably because further photolytic reactions and volatilisation compete effectively with the photolytic formation. There is no evidence for formation of octachlorodibenzo-p-dioxin (OCDD) in technical PCP treated wood in this study, probably because photolytic destruction and volatilisation compete effectively with formation reactions when the initial OCDD concentration is relatively high.