Implementing a light-based seagrass management approach for a large scale dredging program

Seagrass has been highlighted as a key ecosystem component at risk from port developments and associated dredging activities on the central east coast of Queensland Australia. Fisheries Queensland has developed a light-based approach to manage impacts on seagrasses from turbidity plumes associated with a large-scale port dredging program. In situ and laboratory seagrass shading tolerance studies were conducted to simulate the effects of a dredge plume-related reduction in light from increased turbidity. A review of historical seagrass trends at permanent transect monitoring sites throughout the region and associated Photosynthetically Active Radiation (PAR) data refined species-specific light requirements to develop a working light trigger value for a management intervention that would protect seagrasses from dredge plume impacts. This light-based approach is being trialed in parallel with turbidity management plans. The development, implementation and outcomes of this Light-Based Seagrass Management Approach will be presented

Implementing a light-based seagrass management approach for a large scale dredging program

Seagrass has been highlighted as a key ecosystem component at risk from port developments and associated dredging activities on the central east coast of Queensland Australia. Fisheries Queensland has developed a light-based approach to manage impacts on seagrasses from turbidity plumes associated with a large-scale port dredging program. In situ and laboratory seagrass shading tolerance studies were conducted to simulate the effects of a dredge plume-related reduction in light from increased turbidity. A review of historical seagrass trends at permanent transect monitoring sites throughout the region and associated Photosynthetically Active Radiation (PAR) data refined species-specific light requirements to develop a working light trigger value for a management intervention that would protect seagrasses from dredge plume impacts. This light-based approach is being trialed in parallel with turbidity management plans. The development, implementation and outcomes of this Light-Based Seagrass Management Approach will be presented

Impacts of a large-scale flood event on sub-tropical intertidal seagrass meadows

Long term monitoring of coastal seagrasses in the Port of Gladstone has provided the opportunity to better understand the impacts of extreme weather events on these marine plant communities. We studied the effects of a large-scale flood event in the summer of 2010-2011on seven intertidal seagrass meadows at Gladstone Harbour on the central east coast of Queensland. Significant declines in percent cover and above-ground biomass were recorded at several meadows following the weather event with some meadows yet to recover to pre-flood levels by early 2012. Seagrass condition, assessed quarterly and more recently monthly from November 2009 (and biannually from 2005 for some locations), was tested against potential drivers (rainfall, river flow, PAR, temperature and tidal exposure) using multiple linear regression analysis. We present the results from this analysis. We also present results of an investigation of the capacity for meadow recovery from a below ground seed bank

Under pressure...how to succeed as a deepwater seagrass

As a functional group seagrasses are ubiquitous throughout the Great Barrier Reef World Heritage Area (GBRWHA), from offshore coral reefs to inshore estuaries and embayments. Mounting concern for acute and chronic anthropogenic pressures on seagrasses have steered efforts to develop indicators of light attenuation stress. Developing a “one-size-fits-all” model for the 15 species found in the GBRWHA is ineffective without accounting for functional differences in their life history traits. We investigated the growth attributes and adaptation of deepwater (>10m) seagrass communities with a goal to improve coastal management strategies impacting this functional group. We explored what role density and stratification of a seed bank plays in meadow resilience, and how the optical challenges of growing at depth may affect seed germination in these ephemeral meadows. Sediment cores were collected over three years from three Halophila spp. meadows within the GBRWHA. Seed densities varied over time and with depth (≤ 10cm) but followed similar trends among meadows. Collections of mature fruits afforded fresh seeds to establish the first successful seed viability test known for this genus. Fresh seeds were also used to examine the role spectrally-refined light at depth has on germination success. While strategically Halophila spp. are known to rely on seeds, having a more intimate understanding of the functionality of their seed banks and how they respond to environmental cues, bridges a science gap for effectively mitigating light-driven loss of tropical deepwater seagrasses

Using Alphafold2 to Predict the Structure of the Gp5/M Dimer of Porcine Respiratory and Reproductive Syndrome Virus

Porcine reproductive and respiratory syndrome virus is a positive-stranded RNA virus of the family Arteriviridae. The Gp5/M dimer, the major component of the viral envelope, is required for virus budding and is an antibody target. We used alphafold2, an artificial-intelligence-based system, to predict a credible structure of Gp5/M. The short disulfide-linked ectodomains lie flat on the membrane, with the exception of the erected N-terminal helix of Gp5, which contains the antibody epitopes and a hypervariable region with a changing number of carbohydrates. The core of the dimer consists of six curved and tilted transmembrane helices, and three are from each protein. The third transmembrane regions extend into the cytoplasm as amphiphilic helices containing the acylation sites. The endodomains of Gp5 and M are composed of seven β-strands from each protein, which interact via β-strand seven. The area under the membrane forms an open cavity with a positive surface charge. The M and Orf3a proteins of coronaviruses have a similar structure, suggesting that all four proteins are derived from the same ancestral gene. Orf3a, like Gp5/M, is acylated at membrane-proximal cysteines. The role of Gp5/M during virus replication is discussed, in particular the mechanisms of virus budding and models of antibody-dependent virus neutralization

Heterogeneity in brain metastases – advanced MRI at the brain-tumour interface predicts aggressive growth patterns.

Background Brain metastases are increasingly common tumours treated as a homogenous group with SRS, surgery and whole brain radiotherapy. However, there are significant rates of local recurrence. We prospectively investigated intra- and inter-tumour heterogeneity in a series of brain metastases undergoing advanced MRI followed by image guided neurosurgical sampling from the leading edge in the course of resection. Method Pre-surgery 3T-MRI was obtained using 32 direction DTI and T1 with gadolinium. Image guided sampling was performed at the leading edge of the tumour as it was removed with reference samples from the core. Histogram analysis of regions of interest were matched to tissue locations. Growth pattern was assessed by a pathologist using a previously described classification and CD34, Ki67, necrosis and cellularity were scored semi-automatically using NIH ImageJ software. Survival and brain recurrence were recorded. Results Twenty-six cases were included. The mean diffusivity (MD) values recorded at the edge of metastases were significantly different in distribution, median and mean from those at the core (Wilcoxon matched pairs, p=.001). There was significantly higher necrosis (p=.026) and a trend to higher CD34 density at the leading edge versus the core. MD and the change in MD across the leading edge correlated with cellularity (r=-.41, p=.047) but did not predict clinical outcomes nor pathological growth pattern. Metastases which appeared more diffusely invasive pathologically had a significantly lower peritumoral fractional anisotropy (FA) (p=.039) suggesting more tract white matter disruption. These tumours also had more dense CD34 staining (r=-.55, p=.041) at their leading edge and a trend to lower survival and more rapid intracranial recurrence. Conclusion There is significant intra-tumoral heterogeneity among brain metastases and assessment of the brain-tumour interface radiologically and biologically may yield more useful information about behaviour and prognosis than assessing the whole metastasis

Surgical management of posterior fossa metastases

The diagnosis of brain metastases is associated with a poor prognosis reflecting uncontrolled primary disease that has spread to the relative sanctuary of the central nervous system. 20 % of brain metastases occur in the posterior fossa and are associated with significant morbidity. The risk of acute hydrocephalus and potential for sudden death means these metastases are often dealt with as emergency cases. This approach means a full pre-operative assessment and staging of underlying disease may be neglected and a proportion of patients undergo comparatively high risk surgery with little or no survival benefit. This study aimed to assess outcomes in patients to identify factors that may assist in case selection. We report a retrospective case series of 92 consecutive patients operated for posterior fossa metastases between 2007 and 2012. Routine demographic data was collected plus data on performance status, primary cancer site, details of surgery, adjuvant treatment and survival. The only independent positive prognostic factors identified on multivariate analysis were good performance status (if Karnofsky performance score >70, hazard ratio (HR) for death 0.36, 95 % confidence interval (CI) 0.18–0.69), adjuvant whole brain radiotherapy (HR 0.37, 95 % CI 0.21–0.65) and adjuvant chemotherapy where there was extracranial disease and non-synchronous presentation (HR 0.51, 95 % CI 0.31–0.82). Patients presenting with posterior fossa metastases may not be investigated as thoroughly as those with supratentorial tumours. Staging and assessment is essential however, and in the meantime emergencies related to tumour mass effect should be managed with steroids and cerebrospinal fluid diversion as required

Spatial Risk Assessment for Coastal Seagrass Habitats in the Great Barrier Reef World Heritage Area: a case study of the dry and wet tropics

[Extract] Seagrasses are specialised marine flowering plants that grow in the estuary and nearshore environments of most of the world’s continents. There are relatively few species globally (about 60) and these are grouped into just 13 Genera and 5 Families. Most are entirely marine although some species (such as Enhalus acoroides) cannot reproduce unless emergent at low tide. There are 15 species of seagrass in the GBRWHA. The high diversity of seagrass reflects the variety of habitats, the extensive bays, estuaries, coasts, lagoons and reefs that are available for seagrass colonization. More than 5,000 km2 of coastal seagrass meadows are in eastern Queensland waters shallower than 15 m and it is expected that approximately 40,000km2 of the seafloor in the GBRWHA deeper than 15 m has some seagrass (Coles et al. 2007). This represents about 36% of the total recorded area of seagrass in Australia

How can herbivores modify ecosystem service delivery in seagrass meadows?

Seagrasses provide important habitat that delivers ecosystem services such as the provision of food to a wide diversity of herbivores globally. In the Great Barrier Reef (GBR) we find the full size spectrum of herbivores; from small mesograzers such as amphipods, to macrograzers such as fish and large megagrazers such as turtles and dugongs. These herbivores can structurally alter seagrass beds in either positive or negative ways depending on their size, feeding preferences and methods and grazing intensity. These structural changes can subsequently interact with the delivery of other ecosystem services, or the benefits to humans, provided by the seagrass meadow. Multiple ecosystem services have the potential to interact with each other in non-linear relationships. Interactions between herbivory and the provision of other ecosystem services may be additive, synergistic or antagonistic. For example where seagrass growth is stimulated by mesograzers controlling epiphytic algal loads, or light cropping by fish or turtles there may be an additive or synergistic association with carbon sequestration, sediment stabilisation and habitat provision while heavy grazing by dugong may interact with these services in an antagonistic relationship, but have an additive or synergistic relationship with ecotourism. An understanding of these interactions will be important to ecosystem mangers seeking to maximise delivery of ecosystem services and will help them to understand what trade-offs need to be considered when managing for the conservation of megaherbivores. The GBR not only has one of the highest diversities of herbivores, but also highly diverse seagrass species which cover more than 35 000 km 2. This makes the GBR an ideal place to study seagrass herbivore interactions and their impact on ecosystem service provision across a range of seagrass species and community types. This presentation will outline the current knowledge about herbivore impacts on seagrass ecosystem service provision and provide a conceptual framework to illustrate how herbivory may interact with other ecosystem services. It will also identify how research from temperate seagrass beds may apply to a tropical setting and suggest how the current research gap can be addressed

The role of herbivores as ecosystem engineers in tropical seagrass meadows

Seagrasses provide important habitat that delivers ecosystem services and provides food to a wide diversity of herbivores globally. In the Great Barrier Reef we find large seagrass meadows that are grazed on by a diverse herbivore community. This presents a challenge for managers trying to conserve herbivores, the habitats they rely on, and maintain ecosystem service delivery in coastal ecosystems. Herbivore communities can structurally alter seagrass meadows in positive or negative ways depending on their size, feeding methods and grazing intensity. These structural changes can alter the ecosystem services provided by the seagrass meadow. We carried out exclusion and seagrass tethering experiments targeting in tropical and subtropical seagrass meadows in Queensland, Australia to understand how herbivores can structure meadows and the interactions between herbivore groups. Our results show different feeding strategies of herbivores in each habitat, especially megaherbivores, which impact the meadow in different ways. The effects on biomass, shoot density and shoot height depended on the type of grazing observed. Grazer mediated changes in meadow structure will have important implications for the ecosystem services delivered by tropical seagrass ecosystems and the management of these ecosystems, including incorporating grazing dynamics into monitoring projects