University of Tasmania

New research has revealed the importance of mineral forms of iron in regulating the cycling of this bio-essential nutrient in the ocean. The findings pave the way for new work on the relationship between the iron and carbon cycles and how changing ocean oxygen levels may interact. New research published today in Nature has revealed the importance of mineral forms of iron in regulating the cycling of this bio-essential nutrient in the ocean. The findings pave the way for new work on the relationship between the iron and carbon cycles and how changing ocean oxygen levels may interact. The study, led by the University of Liverpool and involving collaborators in the United States, Australia and France, addresses a knowledge gap in ocean research. Principal Investigator Professor Alessandro Tagliabue said: "To date we have not fully appreciated the role that mineral forms of iron have played in driving the distributions and temporal dynamics of iron in the ocean" The ocean of the early earth was low in oxygen and rich in iron, which was incorporated as a catalyst in many biological reactions. These include photosynthesis, which via its proliferation oxygenated the earth system. As iron is less soluble in well oxygenated seawater, precipitation and sinking of iron oxides led to iron levels declining. Consequently, iron now plays a critical role in regulating ocean productivity and hence ecosystems across the contemporary ocean. It is thought that iron levels are largely regulated above their soluble thresholds by organic molecules called ligands, which bind iron. This view has underpinned the representation of the marine iron cycle in global models used to explore how changes in climate affect levels of biological productivity in the future. However, oceanographers have been puzzled as to why there seemed to be a much larger loss of iron due to insolubility from the ocean than expected from the measured high levels of ligands. The ocean models built according to the expected pattern have generally performed poorly in reproducing observations. This project, which was a process study contribution to the international GEOTRACES effort  was jointly funded by the US National Science Foundation and the UK Natural Environment Research Council and examined the processes driving the cycling of iron over an annual cycle for the first time. It revealed that iron was largely cycling independently of ligands in the upper ocean and instead controlled by the clustering of iron oxide colloids to form so-called 'authigenic' particles that are lost from the upper ocean. The authors developed a new numerical model to both explain their results and extrapolate their findings across the ocean. The new model performed markedly better in reproducing other independent observations and highlighted that this new process was important in around 40% of upper ocean waters. A key implication is that this process occurs via the co-aggregation of iron oxides and carbon, which has implications for the global carbon cycle and may be sensitive to future trends of ocean oxygen loss. "These findings will cause us to reassess our understanding of the iron cycle and its sensitivity to changing environmental conditions," said Professor Tagliabue. The University of Liverpool-led study also involved researchers from the University of South Florida, Oregon State University, Bigelow Laboratory for Ocean Sciences, Sorbonne Université, University of Tasmania, University of Leeds, the Bermuda Institute of Ocean Sciences, University of Georgia, and Old Dominion University. Professor Tagliabue said: "Our work was only possible thanks to the efforts to measure multiple different forms of iron in seawater over the annual cycle at the Bermuda Atlantic Time Series site."

WEDNESDAY, July 12, 2023 -- A greater number of chronic pain sites is associated with an increased risk for incident all-cause dementia and Alzheimer disease, according to a study recently published in BMC Medicine . Jing Tian, from the University of Tasmania in Hobart, Australia, and colleagues examined whether a greater number of chronic pain sites is associated with a higher risk for dementia and its subtypes in a prospective cohort study involving 356,383 participants in the U.K. Biobank. Participants were categorized as having no chronic pain; chronic pain in one, two, three, and four sites; and pain "all over the body." The researchers found that 4,959 participants developed dementia during a median follow-up of 13 years. A greater number of chronic pain sites was associated with an increased risk for incident all-cause dementia and Alzheimer disease in a dose-response manner (hazard ratios, 1.08 and 1.09 per one-site increase, respectively), but not vascular and frontotemporal dementia, after adjustment for sociodemographic factors, lifestyle, comorbidities, pain medications, psychological problems, and sleep factors. In a subsample of patients who underwent a fluid intelligence test, there was no significant association observed between the number of chronic pain sites and the risk for incident all-cause dementia. "These findings suggest that chronic pain in multiple sites may represent an accessible marker to assess an individual's dementia risk and identify 'at-risk' individuals at early stages," the authors write. Abstract/Full Text Posted July 2023

The diet quality of fish across large parts of the world's oceans could decline by up to 10 per cent as climate change impacts an integral part of marine food chains, a major study has found. The diet quality of fish across large parts of the world's oceans could decline by up to 10 per cent as climate change impacts an integral part of marine food chains, a major study has found. QUT School of Mathematical Sciences researcher Dr Ryan Heneghan led the study published in Nature Climate Change that included researchers from the University of Queensland, University of Tasmania, University of NSW and CSIRO. They modelled the impact of climate change on zooplankton, an abundant and extremely diverse group of microscopic animals accounting for about 40 per cent of the world's marine biomass. Zooplankton are the primary link between phytoplankton -- which convert sunlight and nutrients into energy like plants do on land -- and fish. Zooplankton include groups such as Antarctic krill -- a major food source for whales -- and even jellyfish. "Despite their abundance, diversity and critical importance in transferring energy from phytoplankton to fish, knowledge about what shapes the composition of zooplankton communities across the world's oceans is relatively limited," Dr Heneghan said. "This is a challenge, since if zooplankton are affected by climate change, this could have important implications for the ocean's ability to sequester carbon emissions, and the productivity of fisheries." The research team used a global marine ecosystem model to look at the impact of climate change on the major zooplankton groups, from single-cell zooplankton, to krill, and all the way up to jellyfish. "We used the model to project changes in the zooplankton community in response to climate change, and then assess how these changes could affect the diet quality of small fish -- the primary predators of zooplankton beyond the zooplankton themselves," Dr Heneghan said. "We found future climate change drives shifts in the composition of zooplankton communities across most of the world's oceans. These changes were mostly caused by decreases in the size of phytoplankton under climate change." The researchers found future zooplankton communities will be increasingly dominated by carnivorous groups, such as chaetognaths, and gelatinous groups, such as salps and larvaceans, at the expense of small crustacean omnivores such as krill and copepods. "In the oceans, energy is transferred from microscopic plankton up to fish and whales by size-based predation -- big things eating small things," Dr Heneghan said. Like blue whales, which eat krill, gelatinous salps and larvaceans eat prey millions of times smaller than themselves, which means unlike other larger zooplankton eaten by fish, they can directly access smaller phytoplankton for food. As a result, salps and larvaceans provide an effective shortcut for the transfer of energy from increasingly dominant small phytoplankton to fish. "This shortcut partially offsets the increase in the number of steps from phytoplankton to fish from shrinking phytoplankton and increases in carnivorous zooplankton," Dr Heneghan said. "But, it comes at a cost: these groups are gelatinous, having about five per cent of the carbon contained in omnivorous zooplankton such as krill and copepods. "In terms of nutrition, this would be like replacing a rib-eye steak with a bowl of jelly. "As a result, our model projects that the diet quality of small fish could decline across large areas of the world's oceans, which would exacerbate declines in fish biomass from climate change by up to 10 per cent." Dr Heneghan said shifts to more gelatinous fish diets had already been observed during a recent marine heatwave in the North Pacific, commonly called "the Blob." "The higher temperatures drove declines in phytoplankton production, which in turn drove decreases in the prevalence of carbon-dense krill, which were replaced by gelatinous zooplankton," he said. "As a result, small fish in the region shifted to more gelatinous diets, which drove declines in their weight and abundance. "Our model results indicate the shift to more gelatinous diets for small fish could become more common in the future under ocean warming. "For human societies, the this could have far-reaching implications globally, since according to the United Nations Food and Agriculture Organization fisheries are a key ecosystem service worth US$150 billion a year and providing more than 20 per cent of dietary animal protein for 3.3 billion people, and supporting 60 million livelihoods." The research team included Dr Heneghan, Dr Jason Everett, Professor Julia Blanchard, Patrick Sykes and Professor Anthony Richardson.