Natural dynamics: understanding natural dynamics of seagrasses of the north west of Western Australia. Report of Theme 5 - Project 5.3 prepared for the Dredging Science Node

Relatively little is known of the spatial and temporal dynamics of seagrass meadows in the north west of Western Australia, but such knowledge is needed when designing and evaluating studies that aim to detect potential dredging-related impacts on seagrass, and when making predictions about the likelihood of, and speed of recovery from, such impacts. This study was undertaken to improve our understanding of the spatial and temporal patterns in seagrass composition, abundance and reproductive phenology in the Pilbara. We also characterised key environmental parameters, especially light, that influence seagrass survival and can be altered by dredging..

A modified fluorescent sensor for reporting glucose concentration in the airway lumen.

We have modified the periplasmic Escherichia coli glucose/galactose binding protein (GBP) and labelled with environmentally sensitive fluorophores to further explore its potential as a sensor for the evaluation of glucose concentration in airway surface liquid (ASL). We identified E149C/A213R GBP labelled with N,N'-Dimethyl-N-(iodoacetyl)-N'-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)ethylenediamine (IANBD, emission wavelength maximum 536nm) with a Kd for D-glucose of 1.02mM and a fluorescence dynamic range of 5.8. This sensor was specific for D-glucose and exhibited fluorescence stability in experiments for several hours. The use of E149C/A213R GBP-IANBD in the ASL of airway cells grown at air-liquid-interface (ALI) detected an increase in glucose concentration 10 minutes after raising basolateral glucose from 5 to 15mM. This sensor also reported a greater change in ASL glucose concentration in response to increased basolateral glucose in H441 airway cells compared to human bronchial epithelial cells (HBEC) and there was less variability with HBEC data than that of H441 indicating that HBEC more effectively regulate glucose movement into the ASL. The sensor detected glucose in bronchoalveolar lavage fluid (BALf) from diabetic db/db mice but not normoglycaemic wildtype mice, indicating limited sensitivity of the sensor at glucose concentrations <50μM. Using nasal inhalation of the sensor and spectral unmixing to generate images, E149C/A213R GBP-IANBD fluorescence was detected in luminal regions of cryosections of the murine distal lung that was greater in db/db than wildtype mice. In conclusion, this sensor provides a useful tool for further development to measure luminal glucose concentration in models of lung/airway to explore how this may change in disease

The effects of warming on the ecophysiology of two co-existing kelp species with contrasting distributions

The northeast Atlantic has warmed significantly since the early 1980s, leading to shifts in species distributions and changes in the structure and functioning of communities and ecosystems. This study investigated the effects of increased temperature on two co-existing habitat-forming kelps: Laminaria digitata, a northern boreal species, and Laminaria ochroleuca, a southern Lusitanian species, to shed light on mechanisms underpinning responses of trailing and leading edge populations to warming. Kelp sporophytes collected from southwest United Kingdom were maintained under 3 treatments: ambient temperature (12 °C), +3 °C (15 °C) and +6 °C (18 °C) for 16 days. At higher temperatures, L. digitata showed a decline in growth rates and Fv/Fm, an increase in chemical defence production and a decrease in palatability. In contrast, L. ochroleuca demonstrated superior growth and photosynthesis at temperatures higher than current ambient levels, and was more heavily grazed. Whilst the observed decreased palatability of L. digitata held at higher temperatures could reduce top-down pressure on marginal populations, field observations of grazer densities suggest that this may be unimportant within the study system. Overall, our study suggests that shifts in trailing edge populations will be primarily driven by ecophysiological responses to high temperatures experienced during current and predicted thermal maxima, and although compensatory mechanisms may reduce top-down pressure on marginal populations, this is unlikely to be important within the current biogeographical context. Better understanding of the mechanisms underpinning climate-driven range shifts is important for habitat-forming species like kelps, which provide organic matter, create biogenic structure and alter environmental conditions for associated communities

Threats and knowledge gaps for ecosystem services provided by kelp forests: a northeast Atlantic perspective

Kelp forests along temperate and polar coastlines represent some of most diverse and productive habitats on the Earth. Here, we synthesize information from >60 years of research on the structure and functioning of kelp forest habitats in European waters, with particular emphasis on the coasts of UK and Ireland, which represents an important biogeographic transition zone that is subjected to multiple threats and stressors. We collated existing data on kelp distribution and abundance and reanalyzed these data to describe the structure of kelp forests along a spatial gradient spanning more than 10° of latitude. We then examined ecological goods and services provided by kelp forests, including elevated secondary production, nutrient cycling, energy capture and flow, coastal defense, direct applications, and biodiversity repositories, before discussing current and future threats posed to kelp forests and identifying key knowledge gaps. Recent evidence unequivocally demonstrates that the structure of kelp forests in the NE Atlantic is changing in response to climate- and non-climate-related stressors, which will have major implications for the structure and functioning of coastal ecosystems. However, kelp-dominated habitats along much of the NE Atlantic coastline have been chronically understudied over recent decades in comparison with other regions such as Australasia and North America. The paucity of field-based research currently impedes our ability to conserve and manage these important ecosystems. Targeted observational and experimental research conducted over large spatial and temporal scales is urgently needed to address these knowledge gaps

Identification and characterisation of two haplosporidian parasites of oysters in north Western Australia

A cryptic haplosporidian parasite was detected infecting rock oysters from the Montebello Islands in north-western Australia using a PCR targeting the parasite's small ribosomal subunit gene. The PCR products were cloned and sequenced along with the remaining sections of the parasite's SSU rRNA gene. Phylogenetic analysis of the sequence generated indicated a Minchinia species (Haplosporidia). The SSU sequence generated was used to develop two in situ hybridisation assays to visualise the parasite in H/E sections as well as a PCR assay to detect the parasite. The molecular assays were assessed for specificity and sensitivity and were then used to compare the parasite to previous haplosporidian parasite infections of pearl oysters. Both assays produced positive results from the infected pearl oysters but not from other closely related haplosporidian species. An SEM and TEM electron microscopy analysis was performed on spores from both parasite species. The spores of the pearl oyster parasite had two spore wall filaments wound around the spore originating for a posterior thickening while the spores of the rock oyster parasite were covered in microtubule-like structures. These data suggests pearl oysters where co-infected with both the Haplosporidium sp. and the Minchinia sp. detected in rock oysters. No evidence of a posterior thickening could be found on the spores of the rock oyster parasite. Attempts to detect the parasite at the previous geographic sites of its detection in pearl oysters resulted in detection of the Minchinia species in tropical oysters in the Kimberley region of Western Australia by in-situ hybridisation

Detection of Minchinia occulta in samples of pearl oysters Pinctada maxima infected by Haplosporidium hinei

Objective To determine if juvenile pearl oysters (Pinctada maxima) infected with Haplosporidium hinei are also infected with another haplosporidian parasite, Minchinia occulta. Design Archived samples of pearl oysters infected with H. hinei were examined using polymerase chain reaction (PCR) assays and in situ hybridisation (ISH) to analyse and identify haplosporidians. A 144-bp and 220-bp region of Minchinia DNA were targeted by PCR and amplified DNA from formalin-fixed H. hinei-infected pearl oyster samples was sequenced. A 25-bp oligonucleotide probe targeting a variable section of the parasite's small subunit rRNA gene was used in ISH. Results The results of DNA-based diagnostic assays supported each other. The sequences obtained by PCR were found to be almost identical to M. occulta from rock oysters and the ISH assay demonstrated infection with M. occulta in affected pearl oysters. ISH indicated a prevalence of infection of 26.7% in one of the previous outbreaks. Conclusion Pearl oyster spat are susceptible to infection by a Minchinia parasite, most likely M. occulta, which was recently identified in rock oysters within the pearl-producing zones of Western Australia and is associated with mortalities of up to 80% in this species. The occurrence of haplosporidian co-infections in pearl oysters suggests the immunocompetence of juvenile oysters may be an important factor in preventing infection and therefore preventing mortalities such as those occurring in the recent outbreaks of pearl oyster oedema disease

Spore ornamentation of Haplosporidium hinei n. sp. (Haplosporidia) in pearl oysters Pinctada maxima (Jameson, 1901)

An infection of pearl oysters, Pinctada maxima, attributed to a Haplosporidium sp. by Hine and Thorne (1998) has been detected on 3 occasions and is considered to represent a serious concern to the pearling industry in Australia. The spore ornamentation of the parasite was determined by scanning electron microscopy and transmission electron microscopy. Spores of the parasite were pleomorphic, or elongated 3.5-4 mcm x 2.5-3.0 mcm in size. Two filaments were wound around the spore and originated from 2 'knob-like' posterior thickenings. Both filaments passed up one side of the spore together until just below the operculum whereupon each split and passed obliquely under the lip of the opercula lid. Each filament wrapped around the spore 4 times. The posterior thickenings seem to appear late in the development of the spore and were composed of spore wall material. A second set of branching tubular filaments composed of a different material was observed on the spore body although not on mature spores possessing a 'knob-like' posterior thickening. The ornamentation on the spores of the pearl oyster parasite was unique amongst described haplosporidian species where spore ornamentation is known. The parasite is named in this manuscript as Haplosporidium hinei n. sp

Spore ornamentation of Minchinia occulta n. sp. (Haplosporidia) in rock oysters Saccostrea cuccullata (Born, 1778)

A Minchinia sp. (Haplosporidia: Haplosporidiidae) parasite was identified infecting rock oysters and morphologically described by Hine and Thorne (2002) using light microscopy and transmission electron microscopy (TEM). The parasite was associated with up to 80% mortality in the host species and it is suspected that the parasite would be a major impediment to the development of a tropical rock oyster aquaculture industry in northern Western Australia. However, attempts to identify the parasite following the development of a specific probe for Haplosporidium nelsoni were unsuccessful. The SSU region of the parasite's rRNA gene was later characterized in our laboratory and an in situ hybridization assay for the parasite was developed. This study names the parasite as Minchinia occulta n sp. and morphologically describes the parasite using histology, scanning electron microscopy and transmission electron microscopy. The non-spore stages were unusual in that they consisted primarily of uninucleate stages reminiscent of Bonamia spp. The parasite's spores were ovoid to circular shaped and measured 4.5 mcm-5.0 mcm x 3.5-4.1 mcm in size. The nucleus of the sporoplasm measured 1.5-2.3 mcm and was centrally located. The spores were covered in a branching network of microtubule-like structures that may degrade as the spore matures

The Cardiovascular consequences of burn injury

This thesis is concerned with the cardiovascular changes which occur in the first 90 minutes after burn injury. In these studies, a full thickness burn injury of the skin was induced in anaesthetised rats using a method based on those of Arturson (1960) and Philpot (1981). Burn injury leads to many physiological changes, including falls in the cardiac output, the stroke volume of the heart and the peripheral vascular conductance, but only small changes in blood pressure and heart rate. It has been suggested that the loss of plasma volume due to leakage from damaged or dilated capillaries, leads to a decrease in venous return (i.e. preload on the heart) and therefore to a decrease in stroke volume. This thesis, however, presents evidence that the initial event leading to these cardiovascular responses is a decrease in myocardial contractility. The role of angiotensin II during the early post-burn period was investigated using captopril to block the renin-angiotensin system. Captopril protected against the falls in stroke volume and peripheral conductance. This dependence of stroke volume on peripheral conductance is most easily explained if myocardial function is impaired at the time. To obtain evidence for this hypothesis I measured cardiac function in the rat directly. I developed a measuring system which uses a fluid-filled blood pressure transducer and a BBC microcomputer to obtain measurements directly from the heart of the rat. Also, I used signal processing techniques to correct for resonance and damping artifacts inherent in such measurements. A new technique called the `drop test' was devised for measuring the resonance and damping properties of the system. Several pressure-based indices of heart muscle performance were computed from blood pressure measurements recorded from inside the left ventricle of the rat. The physiological relevance of these indices was then verified by measuring the reproducibility, sensitivity and preload/afterload dependence of the indices. In these studies, the indices derived from the second differential of left ventricular pressure were found to give the most specific indication of changes in contractility. These indices of myocardial contractility, heart rate, stroke volume and arterial blood pressure were monitored before and after burn injury. The majority of the indices of contractility were depressed by 30-40% at 20 minutes post-burn. This depression was greatest at 30 minutes post burn, but disappeared oby 60 minutes post-burn. A possible cause of the myocardial depression was investigated in two further studies. Plasma taken from a rat 5 minutes after a burn injury caused a fall in cardiac output when transfused into a recipient rat. This plasma also caused a significant deterioration in the contractile function of an isolated heart muscle preparation. (D72313/87)</p