A synthesis of dominant ecological processes in intensive shrimp ponds and adjacent coastal environments in NE Australia

One of the key environmental concerns about shrimp farming is the discharge of waters with high levels of nutrients and suspended solids into adjacent waterways. In this paper we synthesize the results of our multidisciplinary research linking ecological processes in intensive shrimp ponds with their downstream impacts in tidal, mangrove-lined creeks. The incorporation of process measurements and bioindicators, in addition to water quality measurements, improved our understanding of the effect of shrimp farm discharges on the ecological health of the receiving water bodies. Changes in water quality parameters were an oversimplification of the ecological effects of water discharges, and use of key measures including primary production rates, phytoplankton responses to nutrients, community shifts in zooplankton and delta(15)N ratios in marine plants have the potential to provide more integrated and robust measures. Ultimately, reduction in nutrient discharges is most likely to ensure the future sustainability of the industry. (C) 2003 Elsevier Ltd. All rights reserved.

Plasma osmolyte concentrations and rectal gland mass of bull sharks Carcharhinus leucas, captured along a salinity gradient

Bull sharks (Carcharhinus leucas) were captured across a salinity gradient from freshwater (FW) to seawater (SW). Across all salinities, C leucas were hyperosmotic to the environment. Plasma osmolarity in FW-captured animals (642 +/- 7 mosM) was significantly reduced compared to SW-captured animals (1067 +/- 21 mosM). In FW animals, sodium, chloride and urea were 208 +/- 3, 203 +/- 3 and 192 +/- 2 mmol l(-1), respectively. Plasma sodium, chloride and urea in SW-captured C leucas were 289 +/- 3, 296 +/- 6 and 370 +/- 10 mmol l(-1), respectively. The increase in plasma osmolarity between FW and SW was not linear. Between FW (3 mosM) and 24%o SW (676 mosM), plasma osmolarity increased by 22% or 0.92% per 1parts per thousand rise in salinity. Between 24%o and 33parts per thousand, plasma osmolarity increased by 33% or 4.7% per 1 parts per thousand rise in salinity, largely due to a sharp increase in plasma urea between 28parts per thousand and 33parts per thousand. C. leucas moving between FW and SW appear to be faced with three major osmoregulatory challenges, these occur between 0-10parts per thousand, 11-20parts per thousand and 21-33parts per thousand. A comparison between C leucas captured in FW and estuarine environments (20-28%o) in the Brisbane River revealed no difference in the mass of rectal glands between these animals. However, a comparison of rectal gland mass between FW animals captured in the Brisbane River and Rio San Juan/Lake Nicaragua showed that animals in the latter system had a significantly smaller rectal gland mass at a given length than animals in the Brisbane River. The physiological challenges and mechanisms required for C leucas moving between FW and SW, as well as the ecological implications of these data are discussed. (C) 2004 Elsevier Inc. All rights reserved.

Cholinergic and adrenergic innervation of lingual salt glands of the estuarine crocodile, Crocodylus porosus

Many marine reptiles and birds possess extrarenal salt glands that facilitate the excretion of excess sodium and chloride ions accumulated as a consequence of living in saline environments. Control of the secretory activity of avian salt glands is under neural control, but little information is available on the control of reptilian salt glands. Innervation of the lingual salt glands of the salt water crocodile, Crocodylus porosus, was examined in salt water-acclimated animals using histological methods. Extensive networks of both cholinergic and adrenergic nerve fibres were identified close to salt-secreting lobules and vasculature. The identification of both catecholamine-containing and cholinergic neurons in the salt gland epithelium and close to major blood vessels in the tissue suggests the action of the neurotransmitters on the salt-secreting epithelium itself and the rich vascular network of the lingual salt glands.

Lack of an osmotic constraint on intake rate of the eastern curlew Numenius madagascariensis

Rates of food intake in animals consuming abundant prey can be constrained by the rates of digestion or excretion of ingested substances, such as salt, particularly so in the animals that regularly migrate between freshwater and saltwater environments. We tested this hypothesis in a long-distance migrant shorebird, the eastern curlew Numenius madagascariensis (suborder Charadrii), foraging on intertidal decapods in eastern Australia. We predicted that if food intake rates are constrained osmotically, individuals with access to freshwater and less saline prey (FW group) would have higher rates of food and water intake than individuals with seawater-only access (SW group). Food intake rates did not differ between the FW and SW groups (0.14 g ash-free dry mass min(-1)), nor did the water influx rates (0.75 g min(-1)). Salt intake rates were lower at FW sites (19.3 versus 23.3 mg NaCl min(-1)) and overall they were similar to those of marine birds. Food intake rate in the eastern curlew appeared limited by digestive rather than by osmoregulatory capacity.

Preliminary investigations into oxidation of paralytic shellfish poisons (saxitoxins and derivatives) in drinking water by chlorine

The fresh water cyanobacterium Anabaena circinalis produces saxitoxin (STX) and several other toxins with similar basic structural skeleton. Collectively, these toxins are known as Paralytic Shellfish Poisons or PSPs. These toxins are water soluble and can escape into the water body after cell lysis. The presence of these toxins in drinking water is a serious threat to human health. The present work has shown that Paralytic Shellfish Poisons (PSPs) in drinking water can be removed by chlorination at high pH (>9.0), provided a residual of 0.5 mg/L of free chlorine is present after 30 minutes of contact time.

Seasonal changes in the diel surfacing behaviour of the bimodally respiring turtle Rheodytes leukops

The purpose of this study was to determine whether a relationship existed between the diel surfacing trends of the bimodally respiring freshwater turtle Rheodytes leukops and daily fluctuations in specific biotic and abiotic factors: The, diel surfacing behaviour of adult R. leukops was recorded over four consecutive seasons (Austral autumn 2000 - summer 2001) within Marlborough Creek, central Queensland, Australia, using pressure-sensitive time-depth recorders. Additionally, diurnal variations in water temperature and aquatic Po-2 level, as well as the turtle's behavioural state (i.e., active versus resting), were monitored. In autumn and summer, surfacing frequency increased significantly during the daylight hours, with peak levels normally occurring around dawn (0500-0700) and. dusk (1700-1900). However, no consistent diel surfacing trend was recorded, for the turtles in winter or spring, owing to considerable variation among individual R. leukops. Diurnal surfacing trends recorded for R. leukops in, autumn and summer are attributed to periods of increased activity (possibly associated with foraging) during the daylight hours and not to daily variations in water temperature or aquatic Po-2 level. Turtles generally remained at a depth greater than 1 m throughout the day, where the effect of diel fluctuations in water temperature, (

Modern environmental improvement pathways for the coal power generation industry in Australia

In this work we assess the pathways for environmental improvement by the coal utilization industry for power generation in Australia. In terms of resources, our findings show that coal is a long term resource of concern as coal reserves are likely to last for the next 500 years or more. However, our analysis indicates that evaporation losses of water in power generation will approach 1000 Gl (gigalitres) per year, equivalent to a consumption of half of the Australian residential population. As Australia is the second driest continent on earth, water consumption by power generators is a resource of immediate concern with regards to sustainability. We also show that coal will continue to play a major role in energy generation in Australia and, hence, there is a need to employ new technologies that can minimize environmental impacts. The major technologies to reduce impacts to air, water and soils are addressed. Of major interest, there is a major potential for developing sequestration processes in Australia, in particular by enhanced coal bed methane (ECBM) recovery at the Bowen Basin, South Sydney Basin and Gunnedah Basin. Having said that, CO2 capture technologies require further development to support any sequestration processes in order to comply with the Kyoto Protocol. Current power generation cycles are thermodynamic limited, with 35-40% efficiencies. To move to a high efficiency cycle, it is required to change technologies of which integrated gasification combined cycle plus fuel cell is the most promising, with efficiencies expected to reach 60-65%. However, risks of moving towards an unproven technology means that power generators are likely to continue to use pulverized fuel technologies, aiming at incremental efficiency improvements (business as usual). As a big picture pathway, power generators are likely to play an increasing role in regional development; in particular EcoParks and reclaiming saline water for treatment as pressures to access fresh water supplies will significantly increase.

Effects of phosphorus on the growth and nitrogen fixation rates of Lyngbya majuscula: implications for management in Moreton Bay, Queensland

Significant acetylene reduction and therefore N-2 fixation was observed for Lyngbya majuscula only during dark periods, which suggests that oxygenic photosynthesis and N-2 fixation are incompatible processes for this species. Results from a series of batch and continuous-flow-culture reactor studies showed that the specific growth rate and N-2 fixation rate of L, majuscula increased with phosphate (P-PO4) concentration up to a maximum value and thereafter remained constant. The P-PO4 concentrations corresponding to the maximum N-2 fixation and maximum growth rates were -0.27 and -0.18 muM respectively and these values are denoted as the saturation values for N-2 fixation and growth respectively. Regular monitoring studies in Moreton Bay, Queensland, show that concentrations Of P-PO4 generally exceed these saturation values over a large portion of the Bay and therefore, the growth of the bloom-forming L, majuscula is potentially maximised throughout much of the Bay by the elevated P-PO4 concentrations. Results from other studies suggest that the elevated P-PO4 concentrations in the Bay can be largely attributed to discharges from waste-water treatment plants (WWTPs), and thus it is proposed that the control of the growth of L. majuscula in Moreton Bay will require a significant reduction in the P load from the WWTP discharges. If the current strategy of N load reduction for these discharges is maintained in the absence of substantial P load reduction, it is hypothesised that the growth of L, majuscula and other diazotrophs in Moreton Bay will increase in the future.

Diving behaviour of a reptile (Crocodylus johnstoni) in the wild: Interactions with heart rate and body temperature

The differences in physical properties of air and water pose unique behavioural and physiological demands on semiaquatic animals. The aim of this study was to describe the diving behaviour of the freshwater crocodile Crocodylus johnstoni in the wild and to assess the relationships between diving, body temperature, and heart rate. Time-depth recorders, temperature-sensitive radio transmitters, and heart rate transmitters were deployed on each of six C. johnstoni (4.0-26.5 kg), and data were obtained from five animals. Crocodiles showed the greatest diving activity in the morning (0600-1200 hours) and were least active at night, remaining at the water surface. Surprisingly, activity pattern was asynchronous with thermoregulation, and activity was correlated to light rather than to body temperature. Nonetheless, crocodiles thermoregulated and showed a typical heart rate hysteresis pattern (heart rate during heating greater than heart rate during cooling) in response to heating and cooling. Additionally, dive length decreased with increasing body temperature. Maximum diving length was 119.6 min, but the greatest proportion of diving time was spent on relatively short (

Sequence, circulating levels, and expression of C-type natriuretic peptide in a euryhaline elasmobranch, Carcharhinus leucas

The present study has examined expression and circulating levels of C-type natriuretic peptide (CNP) in the euryhaline bull shark, Carcharhinus leucas. Complementary DNA and deduced amino acid sequence for CNP in C leucas were determined by RACE methods. Homology of CNP amino acid sequence in C. leucas was high both for proCNP and for mature CNP when compared with previously identified elasmobranch CNPs. Mature CNP sequence in C. leucas was identical to that in Triakis seyllia and Seyliorhinus canicula. Levels of expression of CNP mRNA were significantly decreased in the atrium but did not change in either the brain or ventricle following acclimation to a SW environment. However, circulating levels of CNP significantly increased from 86.0 +/- 7.9 fmol ml(-1) in FW to 144.9 +/- 19.5 fmol ml(-1) in SW. The results presented demonstrate that changes in environmental salinity influences both synthesis of CNP from the heart and also circulating levels in C. leucas. Potential stimulus for release and modes of action are discussed. (c) 2005 Elsevier Inc. All rights reserved.

Intracellular compartmentation in planctomycetes

The phylum Planctomycetes of the domain Bacteria consists of budding, peptidoglycan-less organisms important for understanding the origins of complex cell organization. Their significance for cell biology lies in their possession of intracellular membrane compartmentation. All planctomycetes share a unique cell plan, in which the cell cytoplasm is divided into compartments by one or more membranes, including a major cell compartment containing the nucleoid. Of special significance is Gemmata obscuriglobus, in which the nucleoid is enveloped in two membranes to form a nuclear body that is analogous to the structure of a eukaryotic nucleus. Planctomycete compartmentation may have functional physiological roles, as in the case of anaerobic ammonium-oxidizing anammox planctomycetes, in which the anammoxosome harbors specialized enzymes and is wrapped in an envelope possessing unique ladderane lipids. Organisms in phyla other than the phylum Planctomycetes may possess compartmentation similar to that of some planctomycetes, as in the case of members of the phylum Poribacteria from marine sponges.

First report of intramolluscan stages of a gorgoderid digenean from a marine bivalve

A survey of bivalves from Heron Island on the Great Barrier Reef, Australia, revealed a novel digenean infection in Lioconcha castrensis (Bivalvia: Veneridae). The cercaria has oral and ventral suckers, a dorsoventrally orientated stylet embedded in the oral sucker, penetration glands, and a large tail that is inflated at its base. This morphology is broadly consistent with that of previously described gorgoderid cercariae. Partial large subunit ribosomal RNA gene (D1-D3 domains) was sequenced and aligned with sequences from other gorgoderids and related families. Phylogenetic analysis also suggests that the species belongs to the Gorgoderinae. To our knowledge, this is the first report of a gorgoderid from a marine bivalve.

Ecosystem response to antibiotics entering the aquatic environment

Awareness of antibiotics in wastewaters and aquatic ecosystems is growing as investigations into alternate pollutants increase and analytical techniques for detecting these chemicals improve. The presence of three antibiotics (ciproffoxacin, norfloxacin and cephalexin) was evaluated in both sewage effluent and environmental waters downstream from a sewage discharge. Bacteria cultured from the sewage bioreactor and receiving waters were tested for resistance against six antibiotics (ciprofloxacin, tetracycline, ampicillin, trimethoprim, erythromycin and trimethoprim/sulphamethoxazole) and effects of short term exposure (24h) to antibiotics on bacterial denitrification rates were examined. Antibiotics were detected entering the sewage treatment plant with varying levels of removal during the treatment process. Antibiotics were also detected in effluent entering receiving waters and detectable 500m from the source. Among the bacteria cultured from the sewage bioreactor, resistance was displayed against all six antibiotics tested and bacteria cultured from receiving waters were resistant against two of the antibiotics tested. Rates of denitrification were observed to decrease in response to some antibiotics and not to others, though this was only observed at concentrations exceeding those likely to be found in the environment. Findings from this preliminary research have indicated that antibiotics are entering our aquatic systems and pose a potential threat to ecosystem function and potentially human health. (c) 2004 Elsevier Ltd. All rights reserved.

Effect of rainfall as a component of climate change on estuarine fish production in Queensland, Australia

The speculation that climate change may impact on sustainable fish production suggests a need to understand how these effects influence fish catch on a broad scale. With a gross annual value of A$ 2.2 billion, the fishing industry is a significant primary industry in Australia. Many commercially important fish species use estuarine habitats such as mangroves, tidal flats and seagrass beds as nurseries or breeding grounds and have lifecycles correlated to rainfall and temperature patterns. Correlation of catches of mullet (e.g. Mugil cephalus) and barramundi (Lates calcarifer) with rainfall suggests that fisheries may be sensitive to effects of climate change. This work reviews key commercial fish and crustacean species and their link to estuaries and climate parameters. A conceptual model demonstrates ecological and biophysical links of estuarine habitats that influences capture fisheries production. The difficulty involved in explaining the effect of climate change on fisheries arising from the lack of ecological knowledge may be overcome by relating climate parameters with long-term fish catch data. Catch per unit effort (CPUE), rainfall, the Southern Oscillation Index (SOI) and catch time series for specific combinations of climate seasons and regions have been explored and surplus production models applied to Queensland's commercial fish catch data with the program CLIMPROD. Results indicate that up to 30% of Queensland's total fish catch and up to 80% of the barramundi catch variation for specific regions can be explained by rainfall often with a lagged response to rainfall events. Our approach allows an evaluation of the economic consequences of climate parameters on estuarine fisheries. thus highlighting the need to develop forecast models and manage estuaries for future climate chan e impact by adjusting the quota for climate change sensitive species. Different modelling approaches are discussed with respect to their forecast ability. (c) 2006 Elsevier Ltd. All rights reserved.