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We undertook a qualitative study that explored exercise participation and exercise promotion in the multiple sclerosis (MS) community who live in regional or remote areas of Australia. By simultaneously gathering views from persons with MS, carers, healthcare providers and healthcare managers we aimed to gather unique perspectives which represented views from across socio-ecological levels of MS healthcare.We used interpretive description methodology, and conducted semi-structured interviews or focus groups with people with MS (We identified three themes with 10 subthemes. The first theme was "Factors associated with exercise engagement" for the people with MS, from individual, interpersonal, organisational and community/public policy perspectives. The second theme was "Factors influencing the MS community's promotion of exercise" focusing on carers, healthcare providers and healthcare systems. The third theme was "Motivators to increase exercise promotion" which should be delivered by the MS community across varying socio-ecological levels of healthcare to encourage exercise participation.We identified new evidence on the factors which influence the MS community's promotion of exercise and we now better understand that training on exercise should be provided to the wider MS community, and exercise services should be considered locally and perhaps delivered via teleheath.IMPLICATIONS FOR REHABILITATIONCohesive healthcare campaigns, and clinical guidelines based on empirical evidence should be established for symptom management in MS with a focus on the role of exercise.Symptom management strategies should consider the whole MS community, including patients, carers, healthcare professional and healthcare co-ordinators.Internal factors (e.g., emotion and motivation) and broader factors (e.g., funding and location) must be considered when designing exercise interventions in persons with MS.

The Australian multiple sclerosis (MS) community experienced two recent major crises, widespread bushfires and the COVID 19 pandemic. We aimed to understand the needs of persons with MS during times of crisis.A consumer-directed mixed-method study. We included an online survey, semi-structured interviews, and a workshop with persons with MS, carers, healthcare professionals, and disability advocates. Data were collected via: (1) 176 people completing online surveys to identify crisis concerns and communications, (2) 29 people completing online interviews on bushfire and pandemic impact, and (3) 13 people participating in a crises-priorities workshop. Descriptive data were calculated for survey response, and a general inductive analytical approach was taken with interview and workshop responses.The most significant concerns were bushfire smoke exposure and disease-modifying-medication and susceptibility to COVID-19 (66% and 63% mean concern score, respectively). Interviews indicated crises experiences from the bushfires, and the pandemic overlapped respective of changes in mood and symptom stability. For bushfires, a need for future preparations, and for the pandemic, the benefits of social restrictions, disclosing personal health information and increased care burden were important.Multiple crises challenged the MS community but offered lessons for healthcare in future crises. Continued progress in centralised crisis information, with considered use of telehealth and rural healthcare support, is needed.Implications for rehabilitationThe MS community showed high concerns for the effect of toxic smoke from the 2019/2020 Australian bushfires and, separately, for the disease-modifying-medication and susceptibility to COVID-19.The MS community placed priority on a crisis management plan for individuals.Reduced social activity due to restrictions was beneficial for MS symptom self-awareness and may help overall fatigue management.Healthcare system preparation must prepare to alleviate increased carer workload at times of crisis.

The literature, and previously unpublished data from the authors’ laboratories, shows that the δ13C of organic matter in marine macroalgae and seagrasses collected from the natural environment ranges from –3 to –35‰. While some marine macroalgae have δ13C values ranging over more than 10‰ within the thallus of an individual (some brown macroalgae), in other cases the range within a species collected over a very wide geographical range is only 5‰ (e.g. the red alga Plocamium cartilagineum which has values between –30 and –35‰). The organisms with very negative δ13C (lower than –30‰) are mainly subtidal red algae, with some intertidal red algae and a few green algae; those with very positive δ13C values (higher than –10‰) are mainly green macroalgae and seagrasses, with some red and brown macroalgae. The δ13C value correlates primarily with taxonomy and secondarily with ecology. None of the organisms with δ13C values lower than –30‰ have pyrenoids. Previous work showed a good correlation between δ13C values lower than –30‰ and the lack of CO2 concentrating mechanisms for several species of marine red algae. The extent to which the low δ13C values are confined to organisms with diffusive CO2 entry is discussed. Diffusive CO2 entry could also occur in organisms with higher δ13C values if diffusive conductance was relatively low. The photosynthesis of organisms with δ13C values more positive than –10‰ (i.e. more positive than the δ13C of CO2 in seawater) must involve HCO3- use.

We compared the effects of the effects of self-instructions in the form of prose or song lyrics in the acquisition of gross motor tasks in 4 third-grade children. We taught participants 4 pairs of gross motor tasks, with one task in each pair taught with prose self-instructions and the other taught with song lyric self-instructions. Both self-instruction procedures were effective for teaching tasks; however, acquisition was quicker with song lyric self-instruction for 4 task pairs, acquisition was quicker with prose self-instruction for 3 task pairs; and similar for 1 task pair. Participants were then able to select their preferred method of self-instruction for a novel, applied skill. Two participants selected song-lyric self-instructions and 2 participants selected prose self-instructions.

Summary Extreme climatic events will dictate the response of ecosystems to climate change, yet are understudied in marine ecosystems. The interaction of stressors from such events has the potential to amplify negative impacts and drive ecosystems into alternate states. Here, we show a drastic response of a temperate seagrass species (Amphibolis antarctica) in Shark Bay – a World Heritage Site in Western Australia at a temperate–tropical transition zone – to two stressors driven by concurrent extreme climatic events: a marine heatwave (Ningaloo Nina) and the Gascoyne floods that impacted the west coast of Australia in the austral summer of 2010–2011. Widespread defoliation (leaf loss) of A. antarctica was observed in the months following the extreme events and was highest at sites affected by flooding (Wooramel River floods). We propose that the negative impact was magnified by the synergistic interactions both stressors had on the carbon balance of the plant. The elevated temperatures increased plant demand for carbon, which could not be met through photosynthesis due to turbid floodwaters reducing light availability, resulting in the plant having a negative carbon balance. Two years following the extreme events, recovery of leaf biomass was evident, though still 7–20% of historical averages. In contrast, below-ground biomass decreased by an order of magnitude in the two years following the events. As below-ground reserves underpin the tolerance of large seagrass species like A. antarctica to disturbances, the declining trajectory of below-ground biomass will likely manifest as a loss of resilience in A. antarctica to future disturbances. Synthesis. Given the ecological importance of Amphibolis antarctica in Shark Bay as a foundation species – accounting for 85% (˜3700 km2) of the cover of seagrasses in Shark Bay – predicted increases in the frequency and magnitude of similar climatic events could have catastrophic implications for the future of this World Heritage embayment. Where extreme climatic events overlap and cause multiple, synergistic stressors to plant communities, ecological responses are likely to be more extreme, particularly in ecosystems where foundation species exist near upper thermal tolerance limits.

Absorption of light and radiation use efficiency (RUE) were measured in a dense stand of the seagrass Amphibolis griffithii in Warnbro Sound, a temperate marine embayment in southern Western Australia. Total light intercepted by the canopy was measured and compared with dry weight leaf production, under both summer and winter conditions. RUE was found to be higher in winter (1.56 g MJ–1) than summer (1.01 g MJ–1). These values are very similar to values measured for annual crop plants and emphasise the value of applying theory developed for terrestrial crop plants to seagrasses. Canopy extinction coefficients were 0.93 m–1 in winter and 0.44 m–1 in summer. There were large differences in hours above saturating irradiance (H sat) between the top (Hsat = 5 h 14 min) and base (18 min) of the canopy in winter. Energy flows in A. griffithii suggest that this species is highly susceptible to short-term perturbations in incident irradience during the winter period as the energy stored within the rhizomes is small relative to daily respiratory demands.

The contribution of recruitment to local population dynamics of plants is limited by production of seeds or availability of suitable sites for establishment of seedlings. Viviparous seedlings of the seagrass Amphibolis antarctica have been observed in great numbers within gaps in meadows of other seagrass species. We conducted a field experiment to assess the extent to which production of viviparous seedlings or availability of suitable sites limits recruitment of A. antarctica into gaps in seagrass meadows. At each of six gaps, seedlings of A. antarctica were transplanted at two densities onto three substrata; sand, seagrass matte (exposed rhizomes and sheath material) and established seagrass meadow. Seedling survival was tracked over 2 months and seedling survival half-lives were compared among treatments. Planting density had no effect on total survivorship, suggesting that increased seedling production would not increase recruitment rates. Physical dislodgement of seedlings by wave and current forces was the primary factor impeding successful recruitment. Of the substrata tested, the best potential establishment sites were associated with the matte of dead seagrass rhizome and sheath fibre. Seedlings entangled in seagrass matte fibres required greater force to remove, and we propose that the entangling nature of matte enhances seedling survival and establishment. The force needed to dislodge seedlings from sand was constantly exceeded by the current velocities acting upon seedlings during the study, and we suggest that the 100% loss of seedlings from sand was driven by hydrodynamic forcing. Seedling loss in the seagrass meadow plots was accelerated by contact with adult seagrass, which increased the rate of seedling dislodgement through the sweeping of leaves across the substratum. Recruitment in the population of A. antarctica examined in this study was limited by the availability of suitable establishment sites, such as those provided by the seagrass matte substratum along the fringe of meadow gaps. The ability of A. antarctica seedlings to recruit to seagrass meadow gaps allows local population persistence of this species in areas dominated by other seagrass species.

In south-western Australia, the isopod Limnoria agrostisa commonly burrows into leaf clusters and immature shoots of Amphibolis griffithii. The isopod also burrows into the sheath and rhizomes of Posidonia species. In A. griffithii, the isopod consumes new tissue within the sheath, damaging or destroying the meristem. This results in malformation of new leaves or destruction of whole leaf clusters with the potential to reduce the photosynthetic area of a shoot. The isopod has been found in all but one meadow of A. griffithii examined over 1,000 km of the Western Australian coastline. It was present throughout the year and showed little variation in abundance. Young were produced year round, but were more abundant in the summer months. Females, 3.5 mm in length or larger, produced 2–5 young that were brooded within the leaf cluster or base of an immature shoot. Within a meadow, 40–70% of shoots and 10–20% of leaf clusters were damaged by isopods. Seasonal trends were not consistent, but damage appeared to be higher in summer when isopod abundance was higher. Approximately 40% of clusters were destroyed by isopod damage. Isopods attack shoots of all ages, but damage was often located on apical clusters. There was no evidence that isopod damage initiated branching or leaf cluster formation. Estimations of clusters damaged or destroyed may be conservative, as only those clusters remaining on a shoot could be counted, and cluster loss could not be quantified. Examination of defoliated stems on upright shoots and horizontal rhizomes indicated that many were destroyed by isopods. The effect of L. agrostisa although substantial appears to be a feature of healthy seagrasses throughout southern Australia.

The western rock lobster ( Panurilus cygnus George.) is a conspicuous consumer in the coastal ecosystems of temperate Western Australia. We used stable isotope analysis and gut content analysis to determine the diet and trophic position of western rock lobsters from mid-shelf coastal ecosystems (35–60 m depth) at three locations. Lobsters were primarily carnivorous, and no consistent differences in diet were detected with varying lobster size, sex or among locations. The main components of the diet were bait (from the fishery) and small crustaceans – crabs and amphipods/isopods. Foliose red algae, bivalves/gastropods and sponges were minor contributors to diet. The diet of lobsters in deep coastal ecosystems differed from the results of previous studies of diets of lobsters from shallow coastal ecosystems. In particular, coralline algae and molluscs – important prey in studies of lobsters from shallow coastal ecosystems – were minor components of the diet. These differences are likely to reflect differences in food availability between these systems and potentially, differences in choice of prey by lobsters that inhabit deeper water. Given the high contribution of bait to lobster diet, bait is likely to be subsidizing lobster production in deep coastal ecosystems during the fishing season.

Sulphide concentrations in estuarine sediments are likely to increase with increased organic matter fluxes (eutrophication) and increased temperatures (global warming). The short-term effects of sulphide on the growth, nutrition and morphology of the seagrass Halophila ovalis (R.Br.) Hook. f. were investigated in situ. Sediments within a H. ovalis meadow were enriched with Na2S equivalent to 0, 1.1 and 4.2 g m -2 . Sulphide diffusion tubes were estimated to increase sulphide con- centrations by 1 to 4 mmol l -1 , concentrations typical of elevated sulphide measured in natural sys- tems. Biomass, internode distance and growth rate (mg apex -1 day -1 ) were determined, and plant material was analysed for soluble carbohydrate, carbon, nitrogen and phosphorus. Sulphide expo- sure caused significant reduction in growth (63%), average leaf weight (30%) and internode distance (15%). Above-ground tissue phosphorus concentration and internode distance were significant pre- dictors of growth (R 2 = 0.63, p < 0.01). These results demonstrate the plasticity of H. ovalis in response to a short-term sulphide pulse, and may have implications for recovery from transient sulphide stress.

South–west Australia contains extensive seagrass meadows along 2,500 km of coastline from the shallow subtidal to 50+ m water depths, and in many of the 51 bar-built estuaries along the coast. There are geomorphological differences between the south and west coasts that result in different patterns of swell exposure influencing the processes that structure seagrass habitats. In this paper, ‘sheltered’, ‘exposed’ and ‘estuarine’ seagrass habitat types are defined for south–west Australia to synthesize processes influencing seagrass communities. Sheltered habitats in south–west Australia are characterized by high light, low to moderate water motion and sporadic disturbance from storms, making them ideal habitats for a diversity of seagrass assemblages. Exposed seagrass habitats are characterized by the presence of strong and consistent ocean swells (3–8 m), predominantly from the south or south–west and seagrasses exhibit a suite of adaptive traits to survive the effects of exposure to ocean swell and associated sand movement. These include morphological features such as heavy fiber reinforcement to strengthen the aboveground stems or leaves, deep vertical rhizomes and life history traits such as rapid growth and high seed set. Within estuarine habitats highly dynamic seagrass communities are the result of fluctuating annual cycles in temperature, light and salinity. Compared to global seagrass meadows, coastal south–west Australian seagrass habitats experience high light, low nutrients and high water movement. Despite these differences, similarities with other regions do exist and here we place the habitats of south–west Australia into a global context using comparative data. The wide array of morphology and life history traits displayed among seagrass species of south–west Australia are presented in a conceptual model including habitat type, physical stressors and seagrass responses. The combination of adaptations to the habitats and processes that define them make south–west Australia a region where there is an unusually high number of co-occurring seagrass species, the highest in the world for a temperate environment (19 species), and approaching the species diversity of many tropical environments. Linking aspects of seagrass habitat, physical aspects of the environment and seagrass life history provides a context for applying knowledge gained from seagrasses in south–west Australia to other coastal ecosystems throughout the world.

This study examines the narratives of 15 youth workers on their experiences with service provision for homeless and street-involved youth. Workers discussed a need to have a versatile approach which can be tailored to an individual youth's circumstances. Establishing a connection based upon valuing, respecting, and liking a youth allows for the development of a trusting relationship which is essential for effective interventions. Also addressed was the social context of this work including relationships among staff, agency structure, and the impact of the stigmatization of homelessness. Lastly, the process of becoming an effective worker was addressed, including the establishment of clear boundaries, recognizing the rewarding aspects of the work, and avoiding burnout.

Essential nutrients for seagrass growth may be derived from benthic decomposition of organic matter. To test this idea, cores of Halophila ovalis (seagrass-vegetated) and unvegetated sediment (control) were amended with either particulate organic matter (POM) or dissolved organic matter (DOM) to test whether a positive feed-back loop exists, where increased organic matter results in increased seagrass nutrients. POM was added in the form of seagrass wrack (0, 1, 5, 12 g core −1 ) and DOM was added with sucrose diffusion tubes at the root zone (0, 0.8, 2.4, 5.2 g core −1 ). Cores were incubated under saturating light conditions (12 h light/12 h dark) at 18 °C, for 4 weeks. Results suggest a complex balance between positive and negative effects of organic matter enrichment. Whilst leaf molar concentrations of N and P of H. ovalis increased (by 15 and 30% respectively), plant growth declined (up to 50% relative to control) for both DOM and POM enrichments. Phosphate was removed from sediment porewater following POM addition and most likely translocated to the leaves. Stressors other than nutrient limitation (e.g. biogeochemical constraints) reduce growth and affect the nutrient dynamics of the seagrass and should be the focus of future work.

Potential food sources and dominant invertebrates and fishes were collected for the examination of variability in 13 C/ 12 C and 15 N/ 14 N to determine the sources of carbon available to consumers within a Western Australian Posidonia sinuosa -dominated seagrass bed. Autotrophs showed a wide distribution of δ 13 C values, with P. sinuosa at −11.3 ± 0.8‰ and macroalgae ranging from −16.6 to −31.7‰. This variation allowed us to successfully identify macroalgae as the main contributor of carbon to the trophic structure, although no distinction could be made between epiphytic macroalgae on seagrass, or allochthonous macroalgal sources. The range in δ 15 N ratios among potential food items at the trophic base was too small to make it useful as tracer of nitrogen flow pathways, but it consistently increased from macrophytes and detritus (4.1–6.8‰), to invertebrates (5.7–7.4‰) located near the middle of the food web, to fishes (8.3–11.9‰), with piscivorous species such as Leviprora inops generally having a higher 15 N. δ 13 C of seston (−12.8‰) and sedimentary organic matter (−8.7‰) indicate that seagrass material is the main contributor to these two carbon pools, and that very little of it contributes to animal biomass.

1. Surrogates aim to predict species diversity and to minimize sampling effort. Here the value of surrogates for marine macroalgae is tested. 2. Higher taxonomic levels and dominant taxa were evaluated as surrogates for detecting patterns in macroalgal species diversity (derived from species-level biomass data) in the Recherche Archipelago, Western Australia. 3. Data were stratified by two island groups (inshore and offshore), three depth intervals ( 20 m), and two exposures to wave energy. Correlations between similarity matrices from surrogate and species diversity data matrices were analysed using a modified Spearman rank correlation (rs). The ability of surrogates to detect differences between exposures to wave energy was also investigated using analysis of similarity. Species diversity data were aggregated to higher taxonomic levels and were either fourth-root or presence/absence (richness) transformed. 4. Species richness was the most consistent surrogate (rs-values>0.69, P=0.001). Genus-level richness was also strongly correlated to species diversity in the Recherche Archipelago, except in depths 20 m, family- and order-level biomass data were suitable surrogates owing to the abundance of Alariaceae (Order Laminariales) represented by a single genus and species. Surrogates using biomass data from the orders Laminariales, Ceramiales, Dictyotales and Fucales were also successful at offshore islands in middle to deeper depths. 6. At inshore islands in depths 10–20 m and >20 m, genera from the orders Gigartinales, Fucales and Ceramiales were strongly correlated to species biomass data. 7. Surrogates, like species richness, that were strongly correlated to species biomass data were also able to distinguish between exposures to wave energy, based on analysis of similarity tests. 8. Sampling effort would be reduced if collecting richness data in species-rich macroalgal assemblages such as those found in temperate Australia. Copyright © 2006 John Wiley & Sons, Ltd.

Nutrient concentrations and seasonal differences in atomic ratios (N:P) in plant tissue of Posidonia coriacea Kuo and Cambridge and Zostera tasmanica Aschers (formerly Heterozostera tasmanica (Syst Bot 27 (2002) 468) were measured from multiple locations on Success Bank, southwestern Australia, and used to infer nutritional constraints on seagrass vegetative growth, particularly by phosphorus. Posidonia plant tissue at the west site had higher nitrogen than the east site in both summer and winter. Nitrogen concentrations increased in winter, particularly in sheath tissue, but there was little change in root nitrogen concentrations between sites or seasons. Nitrogen concentrations of leaf tissue were all less than median seagrass values reported by Duarte (Mar Ecol Prog Ser 67 (1990) 201). The seasonality in nutrient concentrations in plant tissues suggests greater nutritional constraints in summer, during periods of high growth. Vegetative growth of Posidonia coriacea was more nutrient limited than that of Zostera tasmanica . Translocation of nutrients along rhizomes to the apex may ensure that growing points are not nutrient limited and that growth can be maintained, and was more apparent in Z. tasmanica than P. coriacea . Sexual reproduction placed large demands on P. coriacea through the high investment of nutrients into fruit, resulting in reduced nutritional constraints on successful seedling recruitment by initially providing seedlings with nutrients.

The canopy structure and reproductive phenology of the seagrasses Posidonia australis Hook. f. and Posidonia sinuosa Cambridge and Kuo were studied at Warnbro Sound, near Perth, Western Australia. Canopy and inflorescence height, shoot density, leaf area, leaf biomass, inflorescence density and density of other reproductive units were obtained from six (0.04 m 2 ) cores of each of the species. Leaf area and biomass were divided into 5 cm height classes and constructed into an in situ canopy profile. Vegetative shoot density was 913±45 shoots m −2 in the P. australis canopy and 1.475±140 shoots m −2 in the P. sinuosa canopy. Total leaf area index of the P. australis canopy (4.1±0.1 m 2 m −2 ) was less than that of the P. sinuosa canopy (7.0±0.2 m 2 m −2 ). There were fewer flowers in the P. sinuosa canopy (10±2 flowers m −2 ) than in the P. australis canopy (16±2 flowers m −2 ). Mean inflorescence length was 36.5±1.2 cm in the P. australis canopy and 13.4±4.7 cm in the P. sinuosa canopy. Leaf area index at flower height was significantly higher in the P. sinuosa canopy (0.70±0.07 m 2 m −2 ) than the P. australis canopy (0.25±0.02 m 2 m −2 ). Reproductive phenology was studied from surveys of tagged inflorescence in situ. Anther dehiscence in P. australis canopy occurred from mid August to mid September and in the P. sinuosa canopy from early to late September. Pollen/ovule ratios of P. australis were similar to that of P. sinuosa . Pollen viability was longer in P. australis than in P. sinuosa . The similar pollen production but low leaf area around flowers, longer pollination period of P. australis flowers result in greater pollination success than for P. sinuosa flowers.

any sacoglossans (opisthobranch gastropods) have the potential for carbon acquisition from photosynthesis by plastids sequestered from their macroalgal food as well as by ingestion, digestion and assimilation of the organic carbon derived from the alga. A new method for obtaining a minimum estimate of the fraction of sacoglossan carbon supplied from photosynthesis by kleptoplastids is suggested, based on the mass balance of stable carbon isotopes at the natural abundance level. The method involves comparison of 13C/12C ratios in sacoglossans with those of the algae on which they are found. Differences in ratios between alga and sacoglossan are used to give a minimum estimate of carbon acquisition by kleptoplasty, granted assumptions about the range of 13C/12C fractionation values which can occur for marine photolithotrophs. The new method is applied to several green (ulvophycean) alga–sacoglossan associations from Rottnest Island, Western Australia, and the values compared with those obtained previously by other means. The method suggests values of up to 0.6 of the total carbon input to the sacoglossans from photosynthesis by their kleptoplastids. To improve the estimates of the minimum role of kleptoplastidy in the carbon nutrition of sacoglossans, further information is needed: (1) on the fidelity of a given sacoglossan to a given algal individual (or species), (2) on the 13C/12C ratio of the part of the alga ingested by the sacoglossan, and (3) on the allocation of dietary organic carbon and of kleptoplastidic photosynthate to carbon lost in respiration, mucopolysaccharide production and gametes (and hence not sampled with the animal).

Halophila ovalis occupies about 20% (461 ha) of the Swan–Canning Estuary. To assess the role of this plant in the biogeochemical cycling of the estuary, its biomass, nutrient dynamics and oxygen release from its roots to the sediment were investigated. This paper describes a conceptual model developed to extrapolate these findings to the whole estuary. The model follows changes in H. ovalis meadows in the Swan–Canning Estuary on a seasonal basis over an annual cycle. Total maximum seagrass biomass was estimated as 346 t dry weight (DW) in summer, declining in winter. In spring, although H. ovalis biomass did not increase, tissue nutrient concentrations were higher when external nutrient concentrations were high. From spring to summer, when external nutrient concentrations in the water column were severely depleted, shoot to root–rhizome biomass ratios changed from 1 : 1 in winter to 1 : 1·5 in summer. Plant tissue nutrients also decreased in root–rhizomes and increased in shoots, indicating an allocation of internal nutrient resources to the shoots for growth. Despite depletion of nitrogen in the water column, ammonium was still available in the sediment. Ammonium concentrations in the sediment porewater decreased in summer, suggesting H. ovalis meadows were a sink for ammonium. With an increase in biomass in summer, including the density of roots, oxygen release from H. ovalis roots subsequently increased. H. ovalis meadows act as a substantial sink for nutrients in the Swan–Canning Estuary in spring and summer. In winter, when there are large losses of plant biomass, H. ovalis meadows become a source of nutrients to the estuary. Copyright © 2001 John Wiley & Sons, Ltd.

Benthic vegetation plays an important role in determining the fate of nitrogen inputs to estuaries, thus influencing their degree of eutrophication. This study investigated the role of benthic vegetation as a sink for anthropogenic inputs of nitrate and ammonium into Wilson Inlet, a mesotrophic estuary in southwestern Australia. The dominant aquatic angiosperm in Wilson Inlet is Ruppia megacarpa Mason. We examined: (1) whether R. megacarpa leaves remove inorganic N (as nitrate and/or ammonium) from the water column, despite the presence of a layer of epiphytes; (2) whether the macrophyte and its epiphytes are equally important in the removal of inorganic N from the water column; and (3) whether inorganic N taken up by leaves is translocated to other plant parts. We added inorganic 15 N nitrogen, as ammonium, nitrate, or both, to aquaria containing intact cores of sediment, R. megacarpa and attached epiphytes, and unfiltered estuary water. We measured depletion of nitrogen species from the water column and incorporation of 15 N into components of the core. Epiphytes removed more nitrate and ammonium from the water column than R. megacarpa, despite having 25 % of the biomass of the macrophyte. Maximum rates of nitrate uptake were 4.6 (for epiphytes) and 2.0 μmol h -1 g -1 DW (for R. megacarpa), and maximium rates of ammonium uptake were 35 (for epiphytes) and 23 pmol h -1 g -1 DW (for R. megacarpa). The presence of ammonium reduced rates of nitrate uptake, indicating that benthic vegetation prefers ammonium as a nitrogen source. Using mass spectrometry, we recovered between 37 and 45% of the added 15 N nitrogen. The remainder was transformed to either organic nitrogen in the water column by algal epiphytes or nitrogen gas via coupled nitrification-denitrification in the sediment. This experiment indicates ecosystem-scale responses to dissolved inorganic nitrogen which would not have been observable from experiments conducted with isolated plants. Benthic vegetation in Wilson Inlet removes nitrate and ammonium quickly from the water column. Depending on water mixing, it may reduce transient increases in the concentration of these nutrients to background levels within 30 h. This process may be responsible for maintaining low water-column concentrations and reducing the likelihood of algal blooms.

Studies to determine the ecological significance of seagrasses in Owen Anchorage, Western Australia, have been undertaken to allow government to assess the effects of dredging proposals that result in the removal of seagrasses. Ecological significance was broadly defined to include physical, chemical, biological and cultural attributes. The study area (Owen Anchorage) is characterised by a mosaic of bare sand and patchy assemblages of a mixture of seagrass species. These seagrass meadows are quite unlike the more prominent monospecific meadows in more sheltered waters. Previously, seagrass research in Western Australia had focused almost exclusively on these monospecific meadows. To assess the effects of short-, medium- and long-term dredging on the ecological significance of the study area, a large study was implemented, with tasks based on the attributes used in the definition. These included detailed spatial and temporal investigations of the primary producers (seagrasses and algae), the secondary consumers (invertebrates and fish), and their interactions. Two techniques were used to assess the ecological significance of the study area. The first involved a matrix of biological characteristics that calculated proportional losses of seagrass meadows relative to the areas left after dredging. Stochastic processes were introduced using @risk software, with values based on extensive and intensive field measurements. Linkage with an interactive geographic information system database was developed to better represent seagrass dynamics. The second involved defined beneficial uses (i.e. the way society uses or values an area) of the study area. Preliminary results specific to the individual tasks and more general modelling results are presented to show the value of this multidisciplinary approach in addressing the ecological significance of seagrasses.

Effective management of estuarine systems that contain submerged aquatic macrophytes, requires knowledge of whether macrophyte populations are stable, increasing or decreasing in terms of aerial coverage and abundance. This study established three transects within Wilson Inlet and monitored them five times during 1996 for percent cover of Ruppia megacarpa and maximum depth limits of these meadows. Secchi depth data collected weekly in the Inlet for water quality monitoring were used for comparison. Percentage cover of R. megacarpa varied along the length of the transects and also between sampling times. This variation was partially explainable by variation in light availability, but was affected by other factors within the system. Overall sites and times, the maximum depth limit of R. megacarpa was at approximately 24% of incident irradience. This value is high in comparison to other submerged macrophytes and suggests that R. megacarpa is not limited by light. Its distribution may be limited by sediment type, with the seagrass being confined to coarser sediments in the Inlet. It was concluded that R. megacarpa depth distribution in Wilson Inlet is not currently limited by light, and so a minimum acceptable Secchi depth cannot be recommended. Repeated measurement of permanent transects for percent cover and canopy height, replicated within each meadow and along each transect, is recommended.

Seagrasses in temperate Australia persist on sand habitats in shallow coastal environments by recruitment from seedlings and lateral spread of rhizomes from existing meadows. These colonizing processes, combined with seagrass loss from physical disturbance, result in a mosaic of sand and seagrass habitats. Here we describe these changing seagrass landscapes on Success Bank, Western Australia over a 20-year period, using aerial photographs. The 4 ha landscape units (LUs), selected from areas of current Posidonia coriacea Cambridge and Kuo and Amphibolis griffithii (Black) Den Hartog meadows, were analyzed for seagrass cover from aerial photographs from 1972, 1982 and 1993. Two LUs for each species were chosen from three regions (west, central and east) across Success Bank. Changes in landscape features of LUs were then summarized into total area and length of edge to area ratios of seagrass patches and meadows. Seagrass cover in LUs increased by 20,000 to 30,000 m −2 between 1972 and 1993. Such a large increase in seagrasses has not been documented elsewhere in Australia for these seagrass genera. Seagrass expansion was observed as an increase in the number and size of seagrass patches ( 2 ). A simple model of seagrass colonization, based only on radial extension via rhizome growth, was constructed to test whether such large increases in seagrass cover could be accounted for solely by rhizome elongation. The model fitted observed increases in seagrass cover in some, but not all landscape units. The greatest divergence was in the western region where observed cover was higher than modeled rates. In central and eastern regions the modeled and observed increase in seagrass cover were similar. From aerial photographs, seagrasses have been actively colonizing Success Bank over the last 20 years. These observed changes can be accounted for by published rates of horizontal rhizome elongation for some, but not all, landscape units, suggesting that rhizome elongation is only part of the active seagrass colonization process observed on Success Bank. Future studies should target more accurate assessment of rhizome elongation rates, and colonization by seedlings of P. coriacea and A. griffithii , which were observed in great numbers. Whether the observed increase in seagrass cover is a phenomenon unique to Success Bank and to the seagrass species studied, or more generally applicable to other locations and seagrasses, also requires further study.

An unusual double membrane structure, or 'annulus' located within leaf blade epidermal cells of the euryhaline seagrass Halophila ovalis may be an important site for ion transport and storage during osmotic adjustment. Cuttings of marine and estuarine H. ovalis were cultured for 4 weeks in enriched seawater at 35‰ and 25‰, respectively (the salinities in which they were growing at the time of collection) and 15‰ below these habitat salinities. In a second experiment, plants growing at low salinity were returned to their habitat salinities. Paradermal sections of severed leaves revealed that the double membrane structure was in fact tonoplast encircled by protoplast and present only in the cells of marine plants. Cell responses differed between marine and estuarine plants. Marine H. ovalis plants were intolerant of prolonged exposure to low salinity (20‰). Plant mortality reached 75% within 3 weeks, and plants continued to deteriorate following their return to marine salinity (35‰). Estuarine H. ovalis were healthy at 20‰ and plants grew well at 10‰, but appeared stressed after 4 weeks. Chloroplasts were swollen and few in number, while the number of cells with visible vacuoles increased under low salinity conditions. Leaf senescence was accelerated by approximately 1 week when compared to control plants grown at habitat salinities. Cell surface area, leaf and internode length and rhizome diameter decreased with prolonged exposure to low salinity. These structural changes were reversed when estuarine plants were returned to 25‰ salinity. Differences in the salinity tolerance of marine and estuarine H. ovalis may result from acclimation or the emergence of ecotypes, as occurs in algae with wide salinity distributions.

Radial oxygen loss (ROL) was measured as a function of distance behind the tip for roots of the seagrass Halophila ovalis (R.Br.) Hook f. The effects of shoot illumination and leaf area on ROL were also examined as were the porosity and anatomy of the roots, rhizomes and petioles of H. ovalis . For plants taken from the Swan Canning Estuary, Western Australia, the porosities of roots, rhizomes and petioles were 15%, 27% and 17%, respectively. ROL from roots in an O 2 -free and saline medium was measured using root-sleeving cylindrical platinum O 2 electrodes. The shoots were submerged in aerated seawater during the measurements. ROL was substantially higher when the shoots were exposed to saturating light and it decreased markedly in the dark. These findings, and experiments in which the leaves were excised, show that O 2 lost radially from the roots was photosynthetically derived. Moreover, ROL showed a marked gradient along the root; ROL decreased from an average maximum value of 72 ng cm −2 min −1 at 0.5 cm behind the root tip to only 4 ng cm −2 min −1 at 3 cm, the most basal position tested. These data show that roots of H. ovalis contain `a barrier to ROL' in the more basal regions, an adaptation shown by other workers to enhance the growth of roots of wetland macrophytes into anaerobic sediments.

A highly seasonal input of water-borne nutrients flows into Geographe Bay from a network of agricultural drainage systems, from July to September (winter) when the drains flow. Near-shore nutrient concentrations increased from 15 to 150 μg l −1 for total phosphorus and from 200 to 2000 μg l −1 for total nitrogen. However, greater than 100 m offshore, these nutrients were no longer detectable. The yearly input from terrestrial sources (255 tonnes of nitrogen) accounts for two-thirds of the nitrogen required to produce maximum biomass of the seagrass Posidonia sinuosa . Other sources of nutrients are likely to be important in maintaining seagrass biomass and productivity. These sources include seagrass wrack decomposition, sediment nutrient release and groundwater inflow to the embayment. Nitrogen appeared to be the limiting nutrient for seagrass growth in Geographe Bay in summer when nutrients were not in excess.

Allozyme diversity was surveyed at 15 loci across 22 populations of the hydrophilous seagrass Posidonia australis (Hook. f). Substantial genetic variation was detected (HT = 0.311) with a high proportion of this variation partitioned between populations (GST = 0.623). The high value of GST is attributed to large geographical distances between many of the populations and several of the extreme north-western populations having fixed homozygous genotypes. Southwestern populations of P. australis were the most variable and these correlate with the highest species diversity in this genus. Intermediate levels of genetic diversity are observed in P. australis when compared with other hydrophilous angiosperms. Average gene diversity values for hydrophilous taxa surveyed to date indicate lower HT and higher GST values than an average reported for 468 plant taxa. Patterns of genetic variability in different regions of the distribution of P. australis may reflect past evolutionary diversification into novel environments and subsequent dispersal following the rifting of Australia from Antarctica in the early Tertiary.

Ammonium acquisition and internal allocation of nitrogen in the seagrass Amphibolis antarctica ((Labill.) Sonder ex. Aschers.) were studied on freshly collected plants in laboratory experiments. The uptake kinetics were studied from the depletion of ammonium in split chamber experiments, while N uptake by entire plants and internal allocation patterns were studied using 15 N techniques on culture plants. The uptake of ammonium was concentration dependent and followed Michaelis-Menten kinetics. Maximum uptake rates for leaves were 5–38-fold higher than for the root-rhizome complex and the ammonium uptake by leaves was transiently enhanced when plants were suddenly exposed to ammonium. Transiently elevated uptake rates were relatively short-lived and only significant at very high substrate concentrations. Amphibolis rarely, or never, experience nitrogen concentrations that high, and so, surge uptake has only little ecological relevance. The uptake of ammonium at low and ecologically relevant substrate concentrations could only supply about 70% of the nitrogen demand of rapid Amphibolis growth during summer and the remaining 30% had to be met from internal sources. The 15 N experiments showed that both young and old leaves took up nitrogen but most of the nitrogen taken up by old leaves was immediately exported to young actively growing plant parts. Also, nitrogen was re-mobilized and subsequently exported from old to young plant parts. This export of re-mobilized nitrogen could supply about 36% of the nitrogen incorporated into young actively growing tissues, thus lowering the demand for external nitrogen by an equivalent amount. Re-mobilization and subsequent allocation of nitrogen from old plant tissues seem to be an important way to reduce the demand for external nitrogen in Amphibolis and, therefore, this seagrass seems well adapted to sustain rapid growth in nutrient-poor environments.

Few detailed studies have been published on genetic variation in seagrasses except those on the monoecious Zostera marina L. or the hermaphrodite Posidonia australis Hook. f. This paper presents allozyme, RFLP and reproductive biology data on Amphibolis antarctica (Labill.) Sonder&Aschers, one of the 75 per cent of all seagrass species which are dioecious. Collections were made from approximately one-third of the species range in Western Australia. Its only congener, A. griffithii (J. M. Black) den Hartog, was collected from one site to provide a comparison. Flowering was observed in 25 per cent of the shoots surveyed and the average sex ratio was 3.8: 1 (F:M) which it has been suggested indicates sexual reproduction. No genetic variation was found within or between populations at 14 allozyme loci. 18S RFLPs and M13 DNA fingerprinting gave few satisfactory results but also did not exhibit any variability. Allozyme variation was observed between A. antarctica and A. griffithii, the only congeneric species. The lack of allozyme and DNA variation within A. antarctica indicates a potentially low level of outbreeding, a highly clonal reproductive system or a very efficient genetic system in A. antarctica. The hypothesis that the dioecious reproductive system evolved in seagrasses to maximize outbreeding and genetic variability, proposed by several authors, is questioned in light of these data.

Isopods of the genus Lynseia have been found burrowing (leaf mining) in meadow forming seagrasses (Posidonia) from Western Australia. These small (1.5–1.8 mm) isopods burrow beneath the epidermis consuming the mesophyll, forming a linear mine of similar width to the isopod along the leaf lamina. At Rottnest Island in January 1991, 75% of Posidonia australis Hook. f. and 66% of Posidonia sinuosa Cambridge and Kuo leaves were burrowed by isopods. Isopods were found in leaves of all sizes, but number of burrows, number of isopods and the length of burrows increased in older leaves. In P. australis, there were 3.15 ± 0.1 burrows and 2.6 ± 0.1 isopods per burrowed leaf, in P. sinuosa there were 2.9 ± 0.1 burrows and 2.48 ± 0.2 isopods per burrowed leaf. Isopods were mobile, vacating older burrows and forming new ones. Male and female isopods were found in pairs within burrows and young isopods were then brooded within the burrows, forming new branches from the parent burrow. Within monospecific stands of P. australis and P. sinuosa there were 2950 and 2280 isopods m−2 respectively. Mean length of individual burrows was 22 mm in P. australis and 28 mm in P. sinuosa. Total burrow length per leaf (mean ± SE) was 69.6 ± 3.6 mm in P. australis and 81.7 ± 4.7 mm in P. sinuosa. The consumption of leaf tissues and the resulting lines of weakness along burrow lines may have negative effects on the seagrass. Burrows facilitate entry of water, bacteria and fungi to the blade, leading to localised tissue death. Epiphytes may proliferate along burrow lines, owing to surface roughness or solute loss associated with the burrow. Burrows also split and increase fragmentation of leaves in storm events. Loss of photosynthetic area due to epiphytic growth and fragmentation of the leaves may reduce the growth of Posidonia. These potential effects of lynseid seagrass leaf miners may be important if the seagrass meadow was already under stress.

Propagule dispersal in Sargassum spp. was studied from reproductive adults as a single point source of reproductive adults and distributed naturally throughout a bed. Dispersal from single sources was investigated by staining 80 reproductive thalli, tying them together at one location, and sampling released propagules by suctioning the substratum with a venturi suction pump at distances up to 2 m from the stained thalli. Dispersal from many reproductive adults within the bed was determined using limestone settlement plates placed within and outside a subtidal Sargassum bed containing reproductive thalli that were releasing propagules. Numbers of settled propagules were subsequently compared with the numbers of macroscopic recruits visible 2–3 months after propagule release and then with mortality of these recruits. From a single source, dispersal of propagules was highly localized with most propagules settling within 1 m (≈98%). Densities of settled propagules declined exponentially with distance from their source. The rate of decline was variable and significantly different (at p = 0.05) between repeated experiments. Propagule settlement was greater within Sargassum beds than beyond them and the source of many of the propagules settling beyond the Sargassum bed appears to be the local bed itself. Mortality of settled propagules was very high with 0.0045% surviving to visible recruits. Further exponential losses occurred such that only 0.0001% survived for 12 months. Propagules of Sargassum disperse locally, most settling within their bed of origin. Highly localized propagule dispersal and settlement could lead to patchy distributions of recruits within and outside a Sargassum bed. The high mortality of recently settled propagules suggests that recruitment into the local adult population could at times be uncoupled from local propagule dispersal. The causes of high mortality of recently settled propagules is unknown and deserves further study.

The seagrass Halophila ovalis (R.Br.) Hook f. is the dominant benthic plant of the Swan/Canning Estuary, southwestern Australia. This paper describes the biomass, distribution and primary production of this plant in relation to environmental factors. Halophila ovalis occupied 550–600 ha in the lower reaches of the estuary, approximately 20% of the area of the main estuarine basin. Over 99% of the seagrass was in water less than 2 m deep (relative to “datum”, an extreme low water reference mark set in 1892). Distribution in the main estuarine basin differed little between 1976 and 1982, although the species was more ephemeral in the Canning Estuary. Uniform stands of Halophila ovalis reached a biomass of up to 120 g dry weight (DW) m−2 in late summer/early autumn, and maximum productivities of up to 40 g DW m−2 day−1 in summer. At peak biomass, the area of Halophila ovalis in the estuary represented approximately 350 t DW of plant material, 4200 kg of nitrogen and 630 kg of phosphorus. Average productivity was 500 g C m−2 year−1, although uniform stands in shallow waters attained up to 1200 g C m−2 year−1. The biomass, productivity and biometry of Halophila ovalis were strongly influenced by salinity, temperature and light supply. The main growing period was summer, when marine salinities prevailed, and light supply and temperature were highest. Salinity, temperature and light were lowest during winter. Field and laboratory studies indicated that during years of average river discharge (1980, 1982), Halophila ovalis was little affected by the salinity range experienced (15–35‰). However, during 1981, a year of high discharge, conditions of low salinity and poor light supply caused severe declines in biomass, particularly in the Canning Estuary. Light was considered the more important factor controlling growth, since the waters of the estuary are generally turbid, and subject to sudden increases in turbidity. The effects of salinity, temperature and light were investigated by growing sprigs in artificial seawater culture and measuring growth increments. Each factor was investigated separately; salinity values ranged from 5 to 45‰, temperature from 10 to 25°C and light from 0 to 400 μE m−2 s−1. Halophila ovalis grew actively at salinities from approximately 10 to 40‰. Saturating irradiance was approximately 200 μE m−2 s−1 (10% of surface PAR) and compensation point was approximately 40 μE m−2 s−1 (2% of full sunlight PAR). Temperatures lower than 15°C severely limited productivity, and at 10°C no growth occurred, although plants did not die. Productivity increased from 15 to 20°C by a factor of seven, and a further 30% from 20 to 25°C. The highest observed growth rate, approximately 2.1 mg DW per apex day−1, was reached at 25°C. These results were incorporated into a model to determine how much of the variance in productivity could be accounted for by these three factors, assuming independent action. The model was relatively successful at predicting seasonal growth responses, but underestimated spring productivity, probably because the unpredictable light climate in spring in the Swan River was not fully simulated.

Walker, D. I. and Cambridge, M. L. 1994. An experimental assessment of the temperature responses of two sympatric seagrasses, Amphibolis antarctica and Amphibolis griffithii, in relation to their biogeography.

The importance of annual recruitment to the structure of adult stands of Sargassum was determined for a mixed species Sargassum bed at Rottnest Island, Western Australia. The morphologically similar species Sargassum spinuligerum Sonder, S. distichum Sonder, and S. podacanthum Sonder grew together in the shallow subtidal (6 m). Positive species determinations were only possible when thalli were reproductive, so recruits, bases, and vegetative annuals for all species were grouped together. Densities of recruits, perennial bases, vegetative annuals, and reproductive annuals were determined at monthly intervals from 20 randomly placed 0.25-m−2 quadrats. Recruitment and mortality for recruits and adults were further determined at three monthly intervals from 6-×-1-m−2 permanent quadrats. The density of adults varied little with season (between 32 and 58 m−2). Growth of annuals was initiated in April, thalli became reproductive by late August–early September, and senescence occurred in December–January. Density of recruits was highly variable (1.6–210 individuals-m−2) and peaked seasonally during late summer (January–February) and then declined rapidly. Adults showed a complete turnover of thalli in the bed over 25–27 months. Adult mortality was compensated by annual recruitment from propagules (43%) and vegetative regeneration from fragments of holdfasts left on the reef (57%). A seasonal pattern in survivorship was observed for adults that grew from recruits with higher initial numbers and lower mortalities for August and November cohorts. Little seasonally was observed in survivorship of adults that grew vegetatively from remnant crusts. Although initial cohort sizes were smaller for adults grown from recruits than from remnant crusts, mortality was lower, resulting in similar contributions to adult density from both recruits and remnant crusts. Recruitment from propagules and vegetative regeneration played an important role in buffering the adult stand from high rates of mortality and reducing seasonal variation in adult density and contributed to the persistence and seasonal structure of Sargassum beds at Rottnest Island.

Seagrasses are the structural species of one of the most important coastal ecosystems worldwide and support high levels of biodiversity and biomass production. Posidonia is one of the most ancient seagrass genera and displays a contrasting disjunct biogeographic pattern. It contains one single species in the Northern Hemisphere, P. oceanica, which is endemic to the Mediterranean Sea, and has up to 8 recognized taxa in the Southern Hemisphere, which in Australia are divided into 2 complexes, P. ostenfeldii and P. australis. A phylogeny based on a nuclear marker (rRNA-ITS) revealed an ancient split between the northern (i.e. Mediterranean) and southern (i.e. Australian) taxa, followed by a separation of the 2 recognized Australian complexes. However, the species belonging to the P. ostenfeldii complex were indistinguishable, suggesting an ecotypic origin or a recent speciation. Therefore, among the 7 morphologically described Australian species only 4 species lineages can be discriminated. The organelle markers nad7 intron, trnL-F and matK/trnK intron were not informative for reconstructing the phylogeny of this genus, and the mitochondrial markers exhibited a strikingly slow evolutionary rate relative to other genome regions.

Australia has large areas of seagrass, rich in diversity, which flourish in clear, relatively low-nutrient coastal waters. Seagrass losses in recent years have been extensive with over 45 000 ha lost. The major wide-spread human-induced declines of seagrass, from 11 sets of locations around Australia, are summarized. The reasons for these losses are discussed, most being attributable to reduced light intensity, but in many cases, other factors interact to make the process of loss more complex. These declines result in loss of habitat and productivity, and increased sediment mobility. Recovery and recolonization from such losses are rare; thus, the destruction of seagrass has long-term consequences. Increasing awareness of the risks and better understanding of seagrass systems is leading to better management practices.

Dispersal of propagules from fertile thalli of Sargassum spinuligerum was measured in situ using a novel technique. Propagules were stained with Toluidine Blue while still attached to parent thalli. After 24 h, the density of settled propagules was determined at different distances from the stained thalli with a venturi suction sampler Previous measurements of propagule or spore dispersal have not differentiated sources, measured only distances of dispersal outside existing stands of marine algae, and combined propagule dispersal and settlement patterns with post-settlement survival. However, the technique described here allows direct measurement of propagule dispersal in marine algae. Dispersal of propagules was highly localized. Numbers of recovered stained propagules differed between November and December 1990 and these differences are assumed to reflect different levels of release. The December study had a greater total number of recovered propagules (approximately 100000 versus 12 000 collected in November) and a more rapid decline in settlement density with distance (96 % of stained propagules were collected within 0.25 m of parent thalli). There was an exponential decline in the densities of stained propagules (m-) with distance 98 % were collected within 1 m of parent thalli. The localized dispersal pattern observed in this study fits previous descriptions of contagious patterns of recruitment in Sargassm and observed clumping of adults of other fucalean algae.

Seedlings of the viviparous seagrass, Amphibolis antarctica (Labill.) Sonder et Aschers., were grown in artificial seawater cultures ranging in salinity from 35 to 65%. These corresponded to the range of naturally occuring salinities in Shark Bay, Western Australia, where A. antarctica is the most abundant seagrass. Seedlings showed marked senescence within five days of being placed in a salinity of 65%. Leaf production rates resembled those of adult plants in situ and, as for field measurements, maximum rates were obtained at ∼ 42%, even in seedlings collected from higher salinities. The results of the experiment are consistent with the suggestion that the decline in seagrass biomass, area covered and productivity with increasing salinity in situ can be attributed to the response to salinity and not to other factors.

One hundred and sixty one taxa of benthic macro-algae are reported from Shark Bay, Western Australia, growing either on subtidal rock platforms, on the extensive sandflats that dominate the bay, or as epiphytes on seagrasses and other algae. In addition many species survive as drift algae amongst the seagrass beds. Tropical taxa predominate. The Rhodophyta are represented by the greatest number of taxa, but these tend to be inconspicuous epiphytes. Members of the Chlorophyta are the most conspicuous in most areas, with Penicillus nodulosus and Polyphysa peniculus the most common species. Polyphysa peniculus dominates the high salinity areas south of the Faure Sill. The brown algae Hormophysa cuneiformis and Dictyota furcellata were also common in high salinity areas. Benthic algal species richness was lower in areas of high salinity.

Background Tidal expiratory flow limitation (EFL) contributes to chronic dyspnea and exercise intolerance in COPD patients. It can be assessed with the negative expiratory pressure (NEP) technique and is expressed as either the percentage of the tidal volume over which EFL occurs (EFL%V t ) or according to more detailed three-point or five-point scoring systems. The aim of this study was to evaluate the reproducibility of the NEP technique in COPD patients. Methods Tidal EFL was evaluated with NEP in 18 subjects with stable COPD (FEV 1 range, 18 to 75% predicted) on two occasions (mean retest interval, 8.2 days) by the same rater. Agreement between testing occasions was assessed with the κ statistic for the 3-point and 5-point EFL scores, and with the coefficient of repeatability for EFL%V t . Results On the first testing occasion, nine subjects had no EFL, four subjects had EFL in the supine position, and five subjects had EFL in the sitting and the supine position. Using the 3-point score, agreement was present in 14 of 18 subjects at time 2 (κ = 0.66), indicating substantial agreement. Using the 5-point score, agreement was seen in 13 of 18 subjects (κ = 0.61), also indicating substantial agreement. The reproducibility of EFL%V t measurements was lower than that required to reliably detect clinical change in both the sitting and supine positions (coefficient of repeatability, 37% and 58%, respectively). Conclusions The 3-point and 5-point scores provide a reproducible assessment of EFL in COPD patients. The classification of EFL as a percentage of tidal volume is less reproducible, and large changes are required to be confident that real clinical change has occurred.

The distribution of seagrass beds has often been described in the literature as if these communities were naturally static components of coastal ecosystems (Larkum, 1977; McRoy and McMillan, 1977; Orth and Moore, 1983; Kirkman and Kuo, 1990), disturbed only by human influences. A paradigm of seagrass bed stability, developed for large bed-forming seagrasses such as Posidonia as in the Mediterranean Sea (Boudouresque et al., 1980), and the western and southern coasts of Australia (Larkum, 197 6; Larkum and West, 1983; Kirkman, 1978), suggested that sea level had been stable for the last 5-8,000 years and assumed that these large monospecific seagrass beds were static for that period. Immense variations have been shown in detailed studies of such beds, on a seasonal and spatial basis (e.g. Duarte et al., 1994; Alcoverro et al., 1995; Duarte et al., 2003). Change is a naturally-occurring process, which takes place in the absence of human influence (Patriquin, 1975; Hottinger and Vischer, 1983; Clarke and Kirkman, 1989; Marba and Duarte, 1995; Marba and Duarte, f998). There have also been massive declines in seagrass due to anthropogenic effects (Orth and Moore, 1983; Walker and McComb, 1992; Short and Wyllie-Echeverria, 1996), raising the possibility that such losses may be irreversible. Recent research findings suggest this is not the case (Kendrick et al., 1999, 2002). This chapter will detail aspects of more recent research demonstrating changes, both negative and positive, in seagrass distributions, as revealed by mapping and other detailed investigations. The extent of decline dominates the literature, but an increasing number of studies record the dynamic nature of seagrass meadows (Williams, 1988; Kendrick et al., 1999, 2000, 2002; Cambridge et al., 2000, 2002; Durako et al., 2002). The rates of decline and recovery will be compared. The evidence for large-scale recovery of seagrass beds, based on mapping projects, will then be described. A case study will be presented that compares and contrasts two regions on the Western Australian coast: Cockburn Sound, where seagrass loss has been dramatic and is continuing; and Success and Parmelia Banks where loss and recovery are in dynamic equilibrium or seagrasses are expanding into unvegetated sand habitats. Comparisons and contrasts in findings in Florida Bay (USA) will be explored. We will conclude by suggesting a way in which management of seagrass landscapes can be made proactive to match their dynamic nature.

Metabolic hotspots at land-water interfaces are important in supporting biogeochemical processes. Here we confirm the generality of land-aquatic interfaces as biogeochemical hot spots by extending this concept to marine beach cast materials. In situ atmospheric pCO2, from a respiration chamber (10 cm in diameter and 20 cm high) inserted into wrack deposits, was determined using a high-precision (±1 ppm) non-dispersive infrared gas analyzer (EGM-4, PP-systems) at 1 minute recording intervals. The wrack deposits supported high metabolic activities, with CO2 fluxes averaging (±SE) 6.62 ± 0.88 μmol C m-2 s-1, compared to median value of 0.98 μmol C m-2 s-1 (mean 2.21 ± 1.25 μmol C m-2 s-1) for bare sand adjacent to deposits. Wrack metabolic rates ranged 40-fold across beaches, from a minimum of 0.57 ± 0.22 μmol C m-2 s-1 to a maximum of 20.8 ± 5.04 μmol C m-2 s-1, both derived from beaches with deposits dominated by Sargassum. Rates tended to increase significantly (F test, P < 0.05) from the shoreline to reach maximum rates at about 10 m from the shoreline, declining sharply further from the shoreline, and increased with increasing thickness of the deposits (maximum about 10 cm deep), declining for thicker deposits. Wrack differing in composition had similar metabolic rates, although deposits consisting of a mixture of seagrass and algae tended to show somewhat higher rates. Our results show a meter square of wrack deposit supports a metabolic rate equivalent to that supported by 3 m2 of living seagrass or macroalgal habitat. In wrack, the marine environment provides organic material and moisture and the land environment provides oxygen to render wrack ecosystems an efficient metabolic reactor. Intense wrack metabolism should also be conducive to organismal growth by supporting the development of a cryptic, but diverse wrack-based food web. © 2007 Springer Science+Business Media, LLC.

The pattern of colonization by microorganisms on root surfaces from three species of seagrass belonging to the genus Posidonia was assessed. Microbial abundance on roots was measured by two electronic microscope techniques. Trends in microbial colonization between species and root order were defined. In addition, eutrophication status of the sampling sites and physiological status of Posidonia oceanica (L.) Delile roots have been taken into account. Our results show high microbial abundance in the Mediterranean species P. oceanica, in comparison with the low rates of colonization found in the Australian species P. australis Hook f. and P. sinuosa Cambridge et Kuo. Microbial density tended to decrease as root order increased, and living roots always showed higher microbial abundance than dead ones. Colonization of P. oceanica roots at the three sites with different environmental status follows different trends according to root order. It is suggested that root age influences the rate of microbial colonization of seagrass roots and that colonization of root surface by microorganisms is associated with organic exudates from the roots rather than with decaying root tissues. © 2005 Taylor & Francis.

Field observations, carried out as part of a hydrodynamic study on submarine pollen dispersal in dioecious Amphibolis antarctica (Labill.) Sonder et Aschers. ex Aschers., showed that pollen release and subsequent pollination events occur in stages over a period of approximately 1 mo, from late October to early December, at 32* 16' S, 115* 41' E on the coast of Western Australia. Examination of the female flowers by scanning electron microscopy, during and after pollination events, showed that the filiform pollen had adhered to the stigmas. Our field observations of a subtidal (2 m below low water) A. antarctica meadow suggest that the pollen sacs dehisce whilst still attached to the male plant. Pollen is released slowly and takes on the approximate density of the seawater, and is then carried by the local coastal currents. No surface agglomerations of pollen were observed. Preliminary qualitative observations from a dye release study at the study site implied that pollen remained within the water column, close to and amongst the canopy, thus enhancing the likelihood of collision with the nearby female plants. This is the first account of in situ pollination of fully submerged subtidal A. antarctica.

The occurrence of morpho-chronological variations was demonstrated in three Australian species of phanerogams, Posidonia australis, Posidonia coriacea and Posidonia sinuosa, which are found living around Rottnest Island (Western Australia). Three chronological parameters were identified: the thickness of dead sheaths, the internodal distance and the regular presence of floral stalk remains. The foliar primary production for these three species, as estimated using the lepidochronology method, is very high since values of 1374, 1811 and 678 mg dw shoot−1 y−1 were recorded, respectively. Rhizome production values range from 70·6 and 376·7 mg dw shoot−1 y−1 for Posidonia coriacea and Posidonia australis respectively. The results obtained are very encouraging and confirm that these morpho-chronological variations are particularly well developed for the genus Posidonia.