bluuebunny/crossref_metadata_2025 huggingface dataset:
Using fractal geometry to make rapid field measurements of riverbed topography at ecologically useful spatial scales
Authors: Robson B. J. , Chester E. T. , Barmuta L. A.
Published: March 2003

A method is described for making rapid in situ field measurements of riverbed topography over spatial scales of ≅1–10 m. This method uses rolling balls to make quick, accurate measurements of river-bed roughness at several spatial scales. Random sampling and replication generate multiple estimates of the fractal dimension (d) that can be used to test for significant differences in the complexity of riverbed architecture between habitat types and spatial scales.
Regional patterns of genetic structure among Australian populations of the mud crab, Scylla serrata (Crustacea : Decapoda): evidence from mitochondrial DNA
Authors: Gopurenko David , Hughes Jane M.
Published: March 2003

The population genetic structure of the estuarine crab, Scylla serrata (Forskål, 1775), was examined among shelf-connected locations and across a historical bio-geographic barrier. Over 300 individuals were sampled from multiple locations within coastal regions (western, northern and eastern) of Australia and analysed for mutational differences at a mitochondrial coding gene (COI). Analysis of molecular variance indicated mitochondrial haplotypes to be structured regionally (P < 0.001), which contrasted with evidence of genetic panmixia within regions. Regional genetic structure broadly correlated with hydrological circulation, supporting the contention that release of propagules away from the estuary may allow genetic connectivity among widespread shelf-connected S. serrata populations. That similar patterns of maternal gene flow are absent among trans-oceanic populations may indicate that the spatial scale of effective dispersal for this species is generally limited to areas of coastal shelf. Two distinct clades of haplotypes were geographically separated either side of the Torres Strait, a narrow sea channel connecting the northern and eastern regions of coastal Australia. This pattern of historical genetic separation is concordant with a number of other marine species across northern Australia and may indicate a shared history of vicariance induced by eustasy. Alternatively, we suggest that sundering of S. serrata populations resulting in cladogenesis may have its origins outside of the northern Australian region.
Magnesium, calcium and strontium in waters of the southern Tasman Sea at the confluence of the Indian, Pacific and Southern Oceans
Authors: Müller Anja , Deckker Patrick De
Published: March 2003

Data are presented for magnesium (Mg), calcium (Ca) and strontium (Sr) analyses for surface samples and conductivity–temperature–depth profiles of waters along three main transects across the Subtropical Front (STF) and the Subantarctic Front (SAF) in a region between Tasmania and New Zealand down to 57�S. This area is at the confluence of the Indian, Pacific and Southern Oceans where the Subantarctic Mode Water (SAMW) is formed and which is characterized by well-mixed and thick (down to 1000 m) thermostads with uniform salinity and temperature. Such thermostads form at the end of winter, and two of such mode water-forming areas were sampled in October–November 1998. Magnesium and Ca are proving to be quasi-conservative elements down the water column, but there is systematic depletion for Mg compared with profiles measured in the North and South Atlantic Oceans. This offset is interpreted to be the result of hydrothermal activity in the region at the south-east Indian Ridge, which scavenges some Mg. The Circumpolar Deep Water (CDW) intersects this Ridge and upwells south of the SAF and eventually is transformed in the upper 1000 m of the water column into the SAMW. This explains the uniform Mg depletion throughout the entire depth profiles. Strontium, on the other hand, displays significant shifts near the ocean surface at many locations, and this is interpreted as the result of biogenic productivity, which engenders the precipitation of celestite microcrystals.
Distribution of zooplankton inferred from hydroacoustic backscatter data in coastal waters off Ningaloo Reef, Western Australia
Authors: Wilson Steven G. , Pauly Timothy , Meekan Mark G.
Published: March 2003

Hydroacoustic surveys were used to examine zooplankton distributions in coastal waters off Ningaloo Reef, Western Australia. Surveys were timed to coincide with the seasonal aggregation of whale sharks, Rhincodon typus, and other large zooplanktivores in these waters. The surveys examined scattering features of lagoon/shelf fronts, a series of cross-shelf transects and waters surrounding whale sharks swimming at the surface. These suggested that lagoon waters flow intrusively into shelf waters at reef passages in a layered exchange. Cross-shelf transects identified three vertical scattering layers: a surface bubble layer; a near-surface minimum layer; and a bottom maximum layer. Regions of intense mixing of lagoon and shelf waters were detected seaward and to the north of reef passages. Integrated acoustic mean volume backscatter of the bottom maximum layer increased with depth and distance offshore. Large subsurface aggregations of unidentified fauna were detected beneath whale sharks in the same area that manta rays and surface schools of euphausiids were also observed.
Occurrence and chemical form of arsenic in marine macroalgae from the east coast of Australia
Authors: Tukai R. , Maher W. A. , McNaught I. J. , Ellwood M. J. , Coleman M.
Published: March 2003

Arsenic concentrations were measured in thirteen macroalgal species from Sydney, Australia. Brown macroalgae contained, on average, more arsenic (range, mean ± s.e.: 5–173 μg g–1, 39 ± 4 μg g–1) than either green (0.12–30.2 μg g–1, 10.7 ± 0.7 μg g–1) or red macroalgae (0.11–16.9 μg g–1, 4.3 ± 0.3 μg g–1). Despite the overlap in arsenic concentrations between different macroalgal species, inter-species arsenic variation was apparent with arsenic concentrations following the order brown > green > red macroalgal species. It was concluded that the main contribution to the variation in arsenic concentration was from natural variability expected to occur between individuals of any species as a result of physiological differences.Most of the arsenic compounds in macroalgae (70–108%) could be extracted using methanol/water mixtures, with 38–95% of the arsenic compounds present in characterizable forms. All macroalgal species contained arsenoribosides (9–99%). The distribution of arsenoribosides followed a general pattern; glycerol-arsenoriboside and phosphate-arsenoriboside were common to all macroalgal species. Sulfonate-arsenoriboside and sulfate-arsenoriboside were found in brown macroalgal species and one red macroalgal species. Six macroalgal species contained high concentrations of inorganic arsenic (14.2–62.9%) and four species contained high concentrations of dimethylarsinic acid (13.3–41.1%). The variation in the distribution of arsenic compounds in marine macroalgal species appears to be related to taxonomic differences in storage and structural polysaccharides.
Chemical diversity in south-eastern Australian saline lakes. I: geochemical causes
Authors: Radke L. C. , Howard K. W. F. , Gell Peter A.
Published: March 2003

This study re-examined hydrochemical data for south-eastern Australian saline lakes using graphical techniques and reaction path models generated by PHRQPITZ. Results showed that the lakes are more diverse than previous studies have implied. Cyclic solute matrices are modified in catchments by rock–water interactions, mineral dissolution, seawater intrusion and cation-exchange reactions, and within the lakes by sulfate reduction, mixing, brine reflux, mineral precipitation and the recycling of the most soluble salts. Three different pathways of the Eugster–Jones–Hardie models are identified. The study is important because the described variations of water chemistry influence the composition of lake biota.
Groundwater delivery rate of nitrate and predicted change in nitrate concentration in Blue Lake, South Australia
Authors: Lamontagne Sébastien
Published: March 2003

Blue Lake, the principal water supply for the City of Mount Gambier (South Australia), is contaminated with nitrate (NO3–) from polluted groundwater. Using existing data, a study was undertaken to determine the past load of NO3– from groundwater entering the lake and to forecast future trends in lake NO3– concentration. Groundwater NO3– loads for the 1971–1997 period were estimated with an inverse model, which combined the long-term record for NO3– concentration in the lake with a simple NO3– mass-balance. Model results show that the load of NO3– from groundwater (18–24 metric tons (t) year–1 as N) was by far the largest source to Blue Lake between 1971 and 1997. Sinks for NO3– included pumping withdrawal (10–14 t year–1), in-lake consumption (7–10 t year–1), and groundwater outflow (0–1.8 t year–1). The NO3– concentration in incoming groundwater (4–7 mg N L–1) appears to have increased slowly but steadily during the 1971–1997 period (at a rate varying between 0.037 and 0.070 mg N L–1 year–1). By assuming that the rate of increase in groundwater NO3– concentration will remain constant, a forecast for lakewater NO3– concentration was made for the 1998–2028 period. Lakewater NO3– concentration should increase from the contemporary ~3.5 mg N L–1 to 4 or 5 mg N L–1 by 2028. In the short term (decades), the rate of pumping withdrawal will be the main determinant of NO3– concentration in the lake through its impact on the rate of groundwater inflow and the lake water residence time. Although the drinking water guideline for NO3– (11. 3 mg N L–1) may not be exceeded in the short term (decades), it may be exceeded in the longer term (centuries) as NO3– concentration in the neighbouring aquifer adjusts to the contemporary land use.
Land-use effects on water quality in an intensively managed catchment in the Australian humid tropics
Authors: Bramley R. G. V. , Roth C. H.
Published: March 2003

The minimization of environmental degradation that might arise as a result of agricultural production requires a detailed knowledge of the off-site effects of rural land use. This paper reports the results of an assessment of the effect of land use on water quality in the lower part of the catchment of the Herbert River, an intensively managed part of the humid tropics in north Queensland, where the major land uses are sugarcane production, cattle grazing and forestry. Compared with grazing and forestry, sugarcane production was found to have a significant impact on riverine water quality as evidenced by higher concentrations of nitrogen (N), phosphorus (P) and total suspended solids (TSS) in stream-waters draining land under sugarcane, a finding that was unaffected by the inclusion of sampling sites dominated by upper-catchment grazing. However, land use had no significant effect on the partitioning of N and P between mineral, organic and particulate phases in stream-waters, although the proportion in particulate form tended to be least for sugarcane-dominated sites. Irrespective of land use, the concentrations of both total N and P were dominated by soluble fractions, particularly in organic combination. These results suggest that, irrespective of the ecological impact of these nutrient and sediment loadings on freshwaters and the near-shore zone, there is considerable room for improvement in land management in the Australian humid tropics in terms of minimizing off-site export of both nutrients and sediment.
Catchability of the southern rock lobster Jasus edwardsii. I. Effects of sex, season and catch history
Authors: Ziegler P. E. , Frusher S. D. , Johnson C. R. , Gardner C.
Published: March 2003

Seasonal variation in catchability of the southern rock lobster Jasus edwardsii, was estimated in a scientific reserve in south-east Tasmania by comparing estimates of lobster density based on direct visual observations underwater with concomitant estimates from trapping surveys. Underwater density estimates of undersized and legal-sized male and female lobsters >80 mm carapace length, did not change significantly over the 14-month study period, with the exception of undersized males (≤110 mm carapace length). Sex ratios remained constant at approximately 1 : 1. In marked contrast, catch rates of males and females and the sex ratio of trapped lobsters varied strongly with season, implying that catchability varies seasonally and with sex. Catchability of males and females was highest in early summer and lowest in winter. Impact of capture on subsequent catchability appeared to be weak, since the ratios of tagged animals in the population observed underwater generally reflected recapture rates of tagged animals in trap catches. Recapture rates increased with size and were higher for medium-sized and large males than for similar-sized females. However, for each particular sex-size group, recapture rates remained relatively constant throughout the study period.
Catchability of the southern rock lobster Jasus edwardsii. II. Effects of size
Authors: Ziegler P. E. , Johnson C. R. , Frusher S. D. , Gardner C.
Published: March 2003

For most of the year, the size-frequency distribution of trap-caught southern rock lobster, Jasus edwardsii, reflected size-specific catchability rather than the size-frequency distribution of the population in a scientific reserve in Tasmania, Australia. The size-frequency distributions of the population on the ground and of lobsters captured in traps were similar only during a few months, typically during moulting and mating. Small males and females were usually under-represented in traps. Catchability generally increased with size, but varied with sex and season. During moulting and mating, size-specific catchability and relative selectivity of larger animals were similar to or lower than for smaller animals. The relative pattern of catchability throughout the year was similar for most size classes within each sex. Negative associations between small and large lobsters in traps were stronger in winter than in summer, indicating strong behavioural interactions. These interactions could explain the lower catchability of smaller lobsters. Relative selectivity estimates using tag–recapture and size-specific catchability data provided generally similar results.
Desorption of phosphate from sugarcane soils into simulated natural waters
Authors: Edis Robert B. , Bramley Robert G. V. , White Robert E. , Wood Andrew W.
Published: March 2003

A laboratory-based study of the behaviour of phosphorus (P) was carried out on the soils of the lower Herbert River catchment, Queensland, Australia. The aim was to explore the potential for P sorption or desorption by Herbert soils in associated river and estuary waters, so that the extent of problems associated with sugarcane production and soil-derived inputs to streamwater could be defined. Anion exchange resin was used as a sink for P. The equilibrium phosphate concentration (EPC) measured in simulated soil pore water (0.01M CaCl2), and the EPC in the simulated river and estuary waters were strongly correlated. Based on this, and the close relationship between P sorption and selected soil properties, it was possible to estimate P desorption using commonly measured properties. Much less desorption of P took place in simulated estuary waters than in simulated river water of much lower ionic strength. This suggests that environmental degradation arising from the downstream export of soil-borne P from Herbert cane lands is likely to be concentrated in freshwater areas. Sorption properties of P in soils of the lower Herbert appear to be closely associated with aluminium-rich minerals, rather than with iron (hydr)oxides.
Hydrodynamic and sand-transport controls on en echelon sandbank formation: an example from Moreton Bay, eastern Australia
Authors: Pattiaratchi Charitha B. , Harris Peter T.
Published: March 2003

Current meter observations from a field of en echelon sandbanks in Moreton Bay, Australia, provide insights into sandbank hydrodynamics and development. Re-circulation of sand is occurring around straight-crested, near-shore banks, but not around offshore, 'S'-shaped banks. Rather, net transport over this latter area is unidirectional (flood dominated). This is explained in the context of the evolution of the banks, in which the mature, near-shore banks have grown vertically upwards to the sea surface and thus contribute to the local generation of higher tidal harmonics and a residual current circulation pattern, whereas the crestlines of younger, 'S'-shaped banks are still mostly >5 m below the surface and do not affect the flow field significantly. For the mature, inshore banks, reversal of net sand-transport vectors over a distance of less than 1 km (from one side of an interbank channel to the other) is related to the amplification and phase modulation of the M4 tidal constituent. These observations are of relevance to dredging operations since, in order to minimize the impact on the sand-transport system, removal of sand should be from the end of the transport path. Transport paths, in turn, are identified based on directions of net sand-transport and grain size data. Observations from Moreton Bay and other locations around the world suggest that it is possible to dredge offshore sandbanks without affecting beach erosion, provided that there are no direct linkages between the offshore sandbank system and coastal deposits.
Short-term recolonization of stones in a tropical island stream
Authors: Boyero Luz , DeLope Jose Luis
Published: March 2003

The recolonization of stones by macroinvertebrates in streams can occur at very small temporal scales, an often-neglected factor in recolonization studies. In a tropical stream in Coiba National Park, Panama, 36 stones were washed and brushed and each one was subjected to four different periods of exposure in a riffle (1, 3, 9, 27 h). Ephemeroptera, together with Diptera, Trichoptera, Coleoptera, Lepidoptera and Hydracarina, were the main recolonizers. Total density of individuals, and density and relative abundance of the most common taxon (Baetidae : Ephemeroptera), showed significant variation over the four recolonization periods, partially explained by some abiotic variables (water depth, current velocity and stone shape). Taxa richness, community evenness and taxonomic composition did not vary significantly over the four periods. The recolonization of stones in the tropical stream began immediately after the disturbance, although only some community characteristics varied significantly over the first hours.
Predation by southern sea lions (Otaria flavescens) on artisanal fishing catches in Uruguay
Authors: Szteren Diana , Páez Enrique
Published: March 2003

Southern sea lions (Otaria flavescens) forage in coastal fishery grounds in shallow waters, where they interact with coastal fishing activities. The main objective of this research was to evaluate the predation of southern sea lions on artisanal fishery catches and thus determine whether interactions with sea lions affected catches. Between July 1997 and March 1998, we observed 53 fishing events onboard artisanal fishing boats in four localities. The presence and number of sea lions around the boat and the numbers of each fish species consumed by sea lions were recorded by an onboard observer. To estimate the damage caused by sea lions to fishery catches, we considered two scenarios, a conservative scenario and a maximized scenario. Predation on catches was observed in 50.9% of all the fishing events and up to four sea lions were sighted in 67.9% of fishing events. Considering a conservative scenario, predation varied from 0.8 to 9.1% of the catch per unit effort (CPUE) depending on the location. Considering the maximized scenario, predation varied from 3.4 to 46.2%. However, no significant relationship was found between CPUE and the number of sea lions in any locality or with either type of fishing gear. Furthermore, CPUE did not differ in the presence or absence of sea lion interactions and predation per unit effort did not vary between localities or seasons. It was concluded that neither the presence of sea lions nor the damage they cause were responsible for variations in CPUE.
Characteristics and consequences of movement patterns of King George whiting (Perciformes : Sillaginodes punctata) in South Australia
Authors: Fowler A. J. , Jones G. K. , McGarvey R.
Published: March 2003

The characteristics of movement of the South Australian population of King George whiting (Sillaginodes punctata) were determined through analysis of tag and recapture records collected from three tagging periods: (i) 1968–1969; (ii) 1978–1985; and (iii) 1986–1987. The characteristics were compared between the northern and southern parts of two large fishery regions, and determined for fish tagged at different sizes and ages. Fish tagged in the northern Gulf St Vincent and Spencer Gulf moved southwards up to several hundred kilometres, but those tagged in the southern areas showed no systematic directional displacement. Most fish tagged were subadults or young, immature adults at 2–4 years of age. Small, young fish did not move far until a considerable period after tagging, whereas some fish >300 mm total length (TL) at tagging moved substantial distances within only a few weeks. Fish movement resulted in a significant ontogenetic habitat shift, from relatively protected shallow waters that support extensive meadows of seagrass, to southern, exposed, deeper waters and rocky reef. As a result of this systematic, directional displacement the age structures of the fishery catches also varied systematically throughout the two regions. In the northern areas these were simple and dominated by the 3+ age class, whereas in the south they were complex and consisted of the 2+ to 17+ age classes. Because the latter were the spawning populations, fish movement is an obligate step in the life history that ultimately results in supplementation of numbers on the spawning grounds. The consequences for fishery management are discussed.
Variations in sex, length and age compositions of commercial catches of Platycephalus fuscus (Pisces : Platycephalidae) in New South Wales, Australia
Authors: Gray C. A. , Gale V. J. , Stringfellow S. L. , Raines L. P.
Published: March 2003

Commercial landings of dusky flathead (Platycephalus fuscus) from four estuaries in New South Wales (NSW), Australia, were sampled for data on sex, length and age composition between February and July each year for 2–3 years between 1995 and 1997. Landings primarily contained female fish, ranging from 55% to 93% by number for different estuaries. Flathead sampled in commercial catches ranged from 30 cm to 96 cm total length (TL), but the majority were 33–50 cm TL. Fish >40 cm TL were primarily female and male fish >45 cm TL were uncommon. The length composition of catches differed between gillnets of different mesh sizes, with the average length of fish being least in the smallest allowed mesh size of 70 mm. Fish were aged by otolith interpretation and the analysis of marginal increments indicated that one opaque and one translucent growth zone was formed each year; the opaque zone being deposited in June–August (winter) and first observed in September–October (spring). Commercial landings included fish aged 2–11+ years, but fish aged 2–4+ years dominated landings in all estuaries. The total mortality of dusky flathead in each estuary was estimated by catch curve analysis and was relatively high, ranging from 0.45 to 1.64. The data indicate that dusky flathead may be heavily exploited in NSW.
Age estimation of barracouta (Thyrsites atun) off southern New Zealand
Authors: Horn P. L.
Published: March 2003

Age determination of barracouta (Thyrsites atun) by counting translucent zones in whole otoliths was validated by examining the number of zones in otoliths from consecutive juvenile modes and following the progression of a strong year class in age-frequency distributions. Readings from whole otoliths, rather than otolith sections, do not result in under-ageing of this species. The ageing interpretation was supported by the progression of a length mode in commercial catch samples over 5 years. The available data indicated a wide variation in year class strengths between years, a characteristic that was very useful in the validation study. Von Bertalanffy growth parameters were calculated, separately by sex, for barracouta from the Southland shelf, New Zealand. Female barracouta reach a significantly larger size than males.
Folic acid in coastal waters of the Adriatic Sea
Authors: Plavšić Marta , Terzic Senka , Ahel Marijan , Berg C. M. G. van den
Published: March 2003

The concentration of folic acid (FA), an important constituent of the vitamin B group, was determined over a period of 2 years in the water column of a small meromictic saline lake on the eastern Adriatic coast (Rogoznica Lake), as well as in the western part of the northern Adriatic Sea. The FA concentration was over the range of 0.1–13.5 nM in the oxic part of Rogoznica Lake, and 0.1–22 nM in the northern Adriatic, with a maximum of 22 nM in the upper layer of the water column, possibly caused by the impact of Po River freshets on the FA concentrations. A weak but statistically significant correlation was established between photosynthetic pigment zeaxanthin, a characteristic biomarker of cyanobacteria, and FA in the oxic layer of the Rogoznica Lake (r2 = 0.3967; n = 29; P < 0.01), indicating cyanobacteria as a possible source of FA in this ecosystem. A statistically significant correlation (r2 = 0.36; n = 18; P < 0.01) between the two parameters was also found for the surface layer of the northern Adriatic (0 m). However, a low contribution of cyanobacteria to the total photosynthetic biomass in the northern Adriatic, and a lack of correlation between FA and zeaxanthin in the deeper layers of the water column, suggested that cyanobacteria were probably not the main source of FA in these waters. A stronger relationship (r2�= 0.46; n = 16; P < 0.01) between FA and chlorophyll b was found for the top 10 m of the northern Adriatic, indicating green algae as one of the possible sources of FA.
Distribution, biology and likely impacts of the introduced redfin perch (Perca fluviatilis) (Percidae) in Western Australia
Authors: Morgan David L. , Hambleton Simon J. , Gill Howard S. , Beatty Stephen J.
Published: March 2003

Within Western Australia, Perca fluviatilis is restricted to the south-western corner and is found in the Swan, Murray, Harvey, Collie, Capel, Carbunup, Margaret, Blackwood, Donnelly and Warren river systems. Age data suggest it was released into Big Brook Dam (Warren River) in 1992 or 1993, where it has since played a role in eliminating the native teleosts. Its success here is attributed to a young age at maturity, rapid growth (compared with populations elsewhere), predatory nature, large size (compared with native fish), broad environmental and habitat tolerances, and absence of predators. Gonadal development initiates in late summer, with peak spawning between August and September. Males and females attained maturity in their first and second years, respectively, which is earlier than reported for most Northern Hemisphere populations and can be attributed to their rapid growth here because of the warmer climate. At ages 1, 2, 3, 4 and 5, males, on average, attained 102, 159, 206, 246 and 280 mm total length (TL) and females had attained 104, 166, 228, 290 and 351 mm TL at the respective ages. Diets of fish 50–200 mm TL comprised mainly small aquatic invertebrates, whereas larger fish preyed almost exclusively on decapods, mainly marron (Cherax tenuimanus), and teleosts.
Escape panels to reduce by-catch in the New South Wales demersal trap fishery
Authors: Stewart John , Ferrell Douglas J.
Published: March 2003

Various sizes of wire mesh were tested as escape panels in fish traps in the New South Wales demersal trap fishery. The mesh selectivities of these escape panels were estimated using a 'parlour' trap, which is analogous to the 'covered codend' designs used to test selectivity in trawls. The results showed that we could estimate the selection size (l50) for most species based on their maximum body height and the maximum aperture of the escape panel mesh. This enabled us to make escape panel mesh that selected the main species in the fishery, snapper (Pagrus auratus), at a predetermined size. Placing the escape panel meshes with the longest axis orientated either vertically or horizontally showed that fish behaviour is important in determining mesh size selectivity. However, the selection size of some species was unaffected by the orientation of the mesh, suggesting that they were able to turn on their sides to escape. Silver trevally (Pseudocaranx dentex) formed tight schools within traps and were selected at smaller sizes when the meshes were oriented with the longest axis horizontally, suggesting that they do not turn on their sides to escape. Selectivity ogives were used with estimates of the sizes of retained and discarded fish captured in the fishery to estimate the impacts of using the escape panels tested on current landings. The results show the difficulty in designing effective escape panels in a multispecies fishery.
Variation in structural attributes of patch-forming corals and in patterns of abundance of associated fishes
Authors: Holbrook Sally J. , Brooks Andrew J. , Schmitt Russell J.
Published: March 2003

There is increasing evidence that some of the spatial variation in characteristics of local assemblages of reef fish can be explained by variation in measurable features of the habitat. At Moorea, French Polynesia, several species of the coral genus Porites form patch reefs and provide an important source of habitat structure within the lagoons. One species, Porites rus, forms structurally complex patch reefs with surface branches and numerous holes and interior cavities. In contrast, reefs composed of colonies of Porites lobata-like species are less complex; they always lack branches and interior cavities and frequently lack holes. Surveys of these reefs revealed that, as expected, abundance and species richness of fish scaled with the size of the patch reef. However, for a given size, P. rus reefs had significantly higher species richness and overall abundance than P. lobata reefs. Further, abundances of fish, at the family level, varied among sets of reefs that had different combinations of key shelter microhabitats (i.e. holes, cavities, branches). This variation in relative abundances of fish families was predictable based on the microhabitat-use patterns of the fish; the greater the utilization of a microhabitat when available, the greater the difference in abundance between those reefs and others that lacked that microhabitat. Thus, spatial variation in the structure of the fish assemblages was strongly associated with variation among the types of patch-forming corals in the variety of microhabitat features each provided.
Temporal persistence of benthic invertebrate communities in south-eastern Australian streams: taxonomic resolution and implications for the use of predictive models
Authors: Metzeling Leon , Robinson David , Perriss Stephen , Marchant Richard
Published: March 2003

Benthic macroinvertebrates are commonly used to monitor the condition of rivers and streams. Predictive models and biological objectives used in environmental policies, two tools for assessing stream condition, rely on the assumption that the communities from which the invertebrates are derived are sufficiently stable or persistent over time for valid comparisons to be made with test sites sampled years afterwards. There has only been limited testing of this in Australia and there has been no formal programme established to assess long-term changes in aquatic ecosystems. In this paper, data sets collected from the Latrobe and Yarra river systems in south-eastern Australia, sampled over periods of up to 20 years between initial and final samplings, were examined. Using multivariate analyses, it was found that stream communities were persistent at the taxonomic level of family, but significant temporal changes were apparent using species-level data. Tests of rank abundance (Friedman's and Spearman rank correlation) gave mixed results but generally lead to the same conclusions. The implications of these results are discussed with regard to changes in faunal composition, stability of rank abundances, impacts on the use of predictive models and biological objectives, and possible links to major environmental features.
Fate of juvenile school prawns, Metapenaeus macleayi, after simulated capture and escape from trawls
Authors: Broadhurst Matt K. , Barker David T. , Paterson Brian D. , Kennelly Steven J.
Published: March 2003

Two laboratory experiments were done to assess the fate of juvenile school prawns, Metapenaeus macleayi, after simulated multiple capture and escape from trawls. In the first experiment, prawns that were trawled and escaped one, five or 10 times, sustained some physical damage (mostly limited to the loss of antennae), but this was not significantly different from that sustained by control prawns that had not been trawled. Similarly, there were no significant differences between the different treatments and control prawns in their stress levels (as measured by changes in concentrations of L-lactate). Levels of L-lactate were greatest in all prawns immediately after the experiment started and then significantly reduced after 24 and 48 h. In the second experiment, treated prawns were trawled and escaped 10 times and then monitored for mortalities over 2 weeks. Compared with control prawns (that were not trawled), significantly more treated prawns died at the end of the 2 weeks, but the overall post-trawl survival rate was >89%. It is concluded that the multiple contact and escape of juvenile school prawns from trawls had minimal effect on their overall condition.
Effects of salinity on gas exchange, water relations and growth of sunflower (Helianthus annuus)
Authors: Rivelli Anna Rita , Lovelli Stella , Perniola Michele
Published: March 2003

The aim of this study was to determine the response of sunflower (Helianthus annuus L. cv. Romsum HS90) to salinity in terms of gas exchange, ionic and water relations, and growth. Experiments were carried out in the glasshouse, where sunflower plants were exposed to increasing salinity levels using water with a wide range of electrical conductivity (0.39–20 dS m–1) to provide different degrees of salt stress. The CO2 assimilation rate (A), stomatal conductance and plant aboveground dry weight (DW) significantly decreased as electrical conductivity of the soil increased. The decline in photosynthesis measured in response to salt stress was proportionally greater than the decline in transpiration, resulting in a reduction of water use efficiency, at both the leaf and whole-plant levels. Among the factors inhibiting photosynthetic activity, those of a non-stomatal nature had a greater effect. In particular, an analysis of photosynthetic CO2 assimilation rate vs intercellular CO2 concentration (A vs Ci curves) indicated a reduction in activity of Rubisco (EC 4.1.1.39) as salinity levels increased. Under severe salt-stress conditions, chlorophyll fluorescence showed a slowing of electron transport at the PSII level. Salt accumulation in the rhizosphere caused a reduction in tissue water status that was partly associated with a decline in osmotic potential (Ψπ). Leaf ionic concentration was clearly correlated with values of leaf Ψπ. However, leaf ionic concentration showed discontinuous distribution between younger and older leaves, reflecting a strategy of plants to preserve younger and more metabolically-active leaves from accumulating salt to toxic levels.
Research note: Shoot control of hypernodulation and aberrant root formation in the har1-1 mutant of Lotus japonicus
Authors: Jiang Qunyi , Gresshoff Peter M.
Published: March 2003

The har1-1 mutant of Lotus japonicus B-129-S9 Gifu is characterized by two phenotypes: greater than normal nodulation (hypernodulation) and significantly inhibited root growth in the presence of its microsymbiont Mesorhizobium loti strain NZP2235. We demonstrate that the two traits co-segregate, suggesting a single genetic alteration involving developmental pleiotropy. A cross between the mutant and genotype Funakura (with wild-type root and nodule morphology) demonstrated Mendelian recessive segregation of both phenotypes (root and nodule) in 216 F2 individuals. Using DNA-amplification fingerprinting polymorphisms in Gifu har1-1 and Funakura, the mutant locus was positioned between two markers at about 7 and 13 cM distance. Reciprocal hypocotyl grafting of shoots and roots showed that the hypernodulation and reduced root phenotypes are both predominantly controlled by the shoot.
Regulation of directional expansion by the cortical microtubule array in roots of Lemna minor
Authors: Inada Sayaka , Sonobe Seiji , Shimmen Teruo
Published: March 2003

We reported previously that uniconazole, an inhibitor of gibberellin biosynthesis, does not induce lateral swelling of root in Lemna minor L. This is inconsistent with previous reports that gibberellin inhibitors induce significant lateral swelling of organs in other plants. The present study aims to elucidate the reason for this inconsistency. We assayed cells of the cortex, which occupy a large part of root volume. Treatment with propyzamide, a microtubule-disrupting agent, induced increases in root diameter due to increases in radial and tangential diameters of cells in all tissues, particularly the cortex. Additionally, cortical microtubules of cortical cells were almost removed, and the orientation of cellulose microfibrils became random. Thus, in the root cortex, cortical microtubules regulate orientation of cellulose microfibrils. When plants were cultured in the presence of uniconazole the diameter of roots decreased, mainly due to decreases in cell width in the middle layer of cortex. Arrangement of cellulose microfibrils of cortical cells remained transverse after uniconazole treatment. Although cortical microtubules were fragmented by uniconazole treatment, they also remained arranged in the transverse direction. It seems that fragmented but transversely arranged cortical microtubules can orient cellulose microfibrils transversely.
Differential responses of tallgrass prairie species to nitrogen loading and varying ratios of NO3 - to NH4+
Authors: Lane Diana R. , BassiriRad Hormoz
Published: March 2003

Worldwide atmospheric N deposition varies in both quantity and composition of inorganic N forms (NO3– and NH4+). Many studies designed to assess the potential consequences of N pollution, however, pay little attention to the relative abundance of N forms. We hypothesized that native species with different physiological properties will show varying responses to different forms and amounts of N deposition. Here, we assessed the responses of six herbaceous species native to tallgrass prairies in North America to increased N loading at differing ratios of NO3– : NH4+. Individual plants of each species were grown for roughly 80 d in a sand culture under field conditions, three N levels (0.1, 1, 3 mM N), and three ratios of NO3– : NH4+ (1:1, 4:1, 1:3). Analysis of total biomass and relative growth rate revealed a significant 3-way interaction between N level, NO3– : NH4+ ratio, and species. We found that the C3 grasses showed a greater relative response to increasing N addition than did C4 grasses or forbs. We also found a strong correlation between specific root uptake capacity for N and growth response to N level, for five of the six species. Specific leaf area of green leaves and % N of senesced leaves both showed a significant N-level by ratio interaction. Cautiously interpreted, these species-specific responses in growth and tissue quality could lead to changes in community-level and ecosystem dynamics as atmospheric N deposition continues to rise. We suggest that future studies addressing the potential impacts of N loading on natural communities use inorganic N compositions that are consistent with those expected from atmospheric deposition.
Expression of selected drought-related genes and physiological response of Greek cotton varieties
Authors: Voloudakis Andreas E. , Kosmas Sotirios A. , Tsakas Spyros , Eliopoulos Elias , Loukas Michael , Kosmidou Kyratso
Published: March 2003

Drought-tolerant cotton varieties are very important for Greece and throughout the world. Four Greek cotton varieties (Zeta 2, Zeta 5, Korina and Eva) and an Australian variety (Siokra L23) were subjected to three water-stress levels (0.0, –0.1 and –0.3 MPa). Morphological and physiological parameters studied were plant height, total leaf area, shoot, root and total plant fresh and dry weights, stomatal resistance (SR), water potential (Ψ w), and relative water content. Siokra L23 was confirmed to be the most drought-tolerant variety based on its high SR and Ψ w , it's having the smallest total leaf area, and expression of drought-tolerance-related genes. The Greek cotton varieties were ranked from most to least drought tolerant as follows: Eva, Korina, Zeta 2, Zeta 5.Molecular responses of the cotton varieties were studied by investigating the expression of five drought-tolerance-related genes, namely, trehalose-6-P synthase, heat-shock protein calmodulin-binding homolog, late embryogenesis abundant (Lea) proteins 14A and 5D, and NAD(P)H oxidase. Reverse transcription–polymerase chain reaction was performed utilizing total RNA samples isolated after a 4-d drought treatment (i.e. at the end of the stress period). Heat-shock protein calmodulin-binding homolog was induced by water stress in drought-tolerant varieties (Eva and Siokra L23) and Zeta 2. This correlation between physiological and molecular data for this gene allows it to be used in cotton breeding programs. Trehalose-6-P synthase and NAD(P)H oxidase genes were not expressed in almost all varieties and treatments. In contrast, the Lea genes showed, with minor exceptions, expression that was independent of variety and treatment. Eva and Korina varieties should be used under conditions of water shortage, whereas Zeta varieties provide a significant advantage to the grower when planted under conditions of high water availability.
Restriction of nyctinastic movements and application of tensile forces to leaves affects diurnal patterns of expansion growth
Authors: Walter Achim , Feil Regina , Schurr Ulrich
Published: March 2003

Leaves of Ricinus communis L. show strong nyctinastic movements as well as diurnal variations of growth activity, combined with prominent basipetal gradients of relative growth rate. A novel technique, using digital image sequence processing, is able to resolve such spatio–temporal patterns of leaf growth with high resolution. In this paper we analyse the impact of prevention of nyctinastic movements, and the potential of tensile forces to overcome the retarding effects. Tensile forces affected leaf expansion and tissue expansibility in a dose–response relation. In a comparison with freely-growing leaves, an appropriate, optimal tensile force was identified that rebuilt the natural diurnal course of leaf expansion. With this tensile force, undisturbed patterns of temporal and spatial growth distribution as well as undisturbed concentrations of major cations, amino acids or soluble sugars were observed. However, diurnal fluctuations in starch content of almost fully-grown leaves were affected by the treatment and could not be compensated by tensile forces. This effect might point to a connection between diurnal growth variations of the leaf vein, biomechanical forces that synchronize growth within the vein, and metabolism of carbohydrates as growth substrates of the vein. We therefore hypothesize that interveinal tensions, which are produced during nyctinastic leaf movements, are (i) required for undisturbed leaf growth and (ii) can be simulated by application of adequate tensile forces.
Biomass production, transpiration rate and endogenous abscisic acid levels in grafts of flacca and wild-type tomato (Lycopersicon esculentum)
Authors: Chen Guoxiong , Lips S. Herman , Sagi Moshe
Published: March 2003

ABA is a plant signalling-molecule that plays a key role in regulating stomatal response, stress-tolerance responses, and coordinated growth of roots and shoots. Knowledge of the relationship between endogenous ABA level and plant growth is essential for improving plant growth and productivity. The wild-type tomato Rheinlands Ruhm (RR) and its flacca mutant were grafted in order to determine the relationship between endogenous ABA levels and biomass production. The flacca genotype is an ABA-deficient mutant, characterized by high stomatal conductance during the day or the night, high transpiration rate, marked tendency to wilt, and smaller size. Flacca scions grafted on to wild-type rootstock (Fs/Wr) exhibited higher ABA levels, lower transpiration rate, and higher water content than those of a control graft of flacca scion on flacca rootstock (Fs/Fr). Fs/Wr exhibited a lower ABA concentration, xylem exudate rate, ABA xylem-loading rate, and dry weight biomass in wild-type rootstock than in control grafts of wild-type scion on wild-type rootstock (Ws/Wr). Flacca rootstock grafted to wild-type scion (Ws/Fr) showed a higher ABA level, xylem exudation rate, ABA xylem-loading rate, dry weight biomass and length than grafts to flacca scion (Fs/Fr). Ws/Fr did not induce significant changes in wild-type scion as compared with Ws/Wr. In double grafts, flacca shoot fresh weight was significantly increased in flacca scion and wild-type scion grafted on to flacca rootstock (Fs + Ws/Fr) or wild-type rootstock (Fs + Ws/Wr). There was a significant linear relationship between biomass and ABA in scions (r=0.997, P=0.001). These results support the notion that ABA increases growth of tomato seedlings via improved stomatal control.
Review: Mechanisms of anoxia tolerance in plants. I. Growth, survival and anaerobic catabolism
Authors: Gibbs Jane , Greenway Hank
Published: March 2003

Anoxia can be one consequence of waterlogging and submergence of plants. Anoxia in plant tissues reduces the rate of energy production by 65–97% compared with the rate in air. Thus, adaptation to anoxia always includes coping with an energy crisis. Tolerance to anoxia is relevant to wetland species, rice cultivation and transient waterlogging of other agricultural and horticultural crops. This perspective, in two parts, examines mechanisms of anoxia tolerance in plants. Part 1 covers anoxia tolerance in terms of growth and survival, the interaction of anoxia tolerance with other environmental factors, and the development of anoxic cores within plant tissues. Equally importantly, Part 1 also examines anaerobic carbohydrate catabolism (principally ethanolic fermentation in plants) and its regulation. We put forward two modes of anoxia tolerance, one based on reduced rates of anaerobic carbohydrate catabolism and the other on accelerated rates (Pasteur effect). Further, Part 1 examines mechanisms of post-anoxic injury. In Part 2 (Greenway and Gibbs, manuscript in preparation) we consider flow of the limited amount of energy produced under anoxia to processes essential for cell survival. We show that acclimation to anoxia in plants involves integration of a set of sophisticated characteristics, as a consequence of which the habitat within the anoxic cell is a very different world to that of the aerobic cell.