Melanie Emmajade Roberts

Sun Cable posed several questions related to the bio-fouling of submarine transmission cablesfor their installation between Darwin and Singapore. The group considered growth factors,hydrodynamic effects and heating and insulation impact on the cables across the range ofdifferent conditions over the proposed path. The Coral Triangle as it is known has a greatbio-diversity and a range of different seabed and physical conditions, leading to highly variableconditions.

Diazotrophic cyanobacteria, including those responsible for harmful algal blooms, fix atmospheric dinitrogen (N ₂ ) to sustain growth when they are limited by dissolved inorganic nitrogen (DIN) supply. Conventional models fail to accurately predict the timing and magnitude of N ₂ fixation, partly because of oversimplified assumptions about diazotrophic species responses to N. We hypothesized that cellular carbon (C) and N would co‐vary with DIN availability, and cellular N quota reduced below a critical threshold would trigger heterocyst differentiation and N ₂ fixation. Conversely, we hypothesized that heterocysts would be discarded, and N ₂ fixation would cease at another higher cellular N quota threshold. To test this hypothesis, we undertook experiments to provide data to calibrate a model of cellular C and N of N ₂ fixation in the cyanobacterium Raphidiopsis raciborskii . The model incorporated internal N quotas, external DIN supply and a time lag for N ₂ fixation as key regulators of heterocyst production and N ₂ fixation, explaining > 70% of the variation in measured cellular N and C : N molar ratios. Heterocysts were predicted to form at a cellular N quota of 0.085 mg N mg ⁻¹ C and were discarded from filaments at 0.275 mg N mg ⁻¹ C. There was a 5‐d time lag between DIN deprivation and initiation of N ₂ fixation. Continuous DIN supply was predicted to enhance N ₂ fixation more than an equivalent one‐off pulse. Our study highlighted the need to consider cellular N and N supply regimes in driving N ₂ fixation to provide more accurate predictions of the response of cyanobacteria to DIN availability.

Introduction: Optimizing investment strategies for nature‐based solutions is critical for addressing climate change and biodiversity loss while ensuring financial viability. Scaling restoration requires funding beyond public and philanthropic sources; nature markets can generate conservation‐linked revenues. However, climate‐related risks, such as cyclones, threaten ecological outcomes and financial sustainability. Despite progress in conservation planning and environmental finance, few tools integrate both perspectives under uncertainty. Objectives: We develop and test an investment framework that optimizes financial returns from restoration projects that are exposed to climate risks. Investment returns are generated through a carbon market. We evaluate whether introducing flexibility in the timing and scale of investment improves financial and ecological outcomes. Methods: We developed a value iteration model optimized using stochastic dynamic programming to identify year‐by‐year investment decisions for mangrove restoration over a 25‐year horizon. The model incorporates carbon market returns, ecological vulnerability, and probabilistic cyclone disturbance. We compared the adaptive strategy to a traditional, upfront investment approach across different restoration unit sizes, disturbance frequencies, and discount rates. Results: Adaptive investment strategies outperformed traditional approaches. On average, the optimized approach achieved approximately 15% greater financial return, reflected by a higher profitability index (1.21 vs. 1.03) and 7% higher environmental effectiveness. It also achieved a positive or zero net present value in 77% of cases compared to 47% under a traditional approach by enabling adaptive investment responses to extreme events. Investment was not recommended at discount rates above 11%, highlighting the importance of financing conditions in determining project feasibility. Conclusions: Financial adaptability can improve both ecological outcomes and long‐term viability of restoration projects. Adaptive strategies offer a more robust response to climate uncertainty than fixed approaches.

Context: Gully erosion is a significant socioeconomic and environmental issue that affects agricultural productivity, infrastructure, and water quality of receiving waters. Despite a variety of interventions to prevent gully formation and rehabilitate existing gullies, cost-effective interventions are specific to individual gullies. Aims: The aim of this study was to assess the performance of a suite of gully management interventions across three different classical gullies. Methods: A one-dimensional process-based model, MERGE (modelling erosion resistance for gully erosion), was used to quantify the sediment yield exiting the gullies, in response to various management interventions. Key results: The net decrease in sediment yield was 2.5–57.4% for each of four interventions applied in isolation and 51.2–78.7% in combination. Reductions in sediment yield for each intervention varied markedly among sites, by a factor of 2.6–78.3 in absolute terms. This resulted in a unique ranking of the interventions by their effectiveness for a given site. Overall, interventions applied in combination were most effective, outperforming those applied in isolation by a factor of 1.24–1.37, but the effect of applying interventions in combination was not additive. Conclusions: This study demonstrates the ability of the gully erosion model MERGE to be a useful tool to identify and tailor effective intervention strategies for individual gullies, and be a useful guide for decision making for erosion management. Implications: Analysis of expected benefits of gully remediation using tools such as MERGE is important for assessing options at gully sites due to their widely varying response.

The production and emission of fugitive dust is a topic ofconcern that Concrush brought to the MISG, 2020. Concrushis recycled concrete manufacturing company in the Hunterregion of New South Wales. Concrush's operations producefugitive dust, fine particles that can escape the site. Fugitive dust can travel long distances from the site ofemission, and can have negative health impacts includingrespiratory illnesses. Presently, concrete recyclingfacilities are managed by the Environmental ProtectionAgency using guidelines initially developed for the coalindustry. Concrush seeks to understand the appropriatenessof these guidelines, and how they can reduce and managefugitive dust on their Teralba site. Mathematical modellingof dust emission and transport, together with a review ofsimilar processes in the literature, identified a number ofpractical options for Concrush to reduce their dustemissions. In addition, opportunities for improved datacollection are identified.