Biochemical responses to ocean acidification contrast between tropical corals with high and low abundances at volcanic carbon dioxide seeps

At two natural volcanic seeps in Papua New Guinea, the partial pressure of carbon dioxide (pCO2) in the seawater is consistent with projections for 2100. Here, the cover of massive scleractinian corals Porites spp. is twice as high at elevated compared with ambient pCO2, while that of branching corals such as Acropora millepora is greater than twofold reduced. To assess the underlying mechanisms for such community shifts under long-term exposure to elevated pCO2, biochemical parameters related to tissue biomass, energy storage, pigmentation, cell protection, and cell damage were compared between Porites spp. and A. millepora from control (mean pHtotal = 8.1, pCO2 = 323 µatm) and CO2 seep sites (mean pHtotal = 7.8, pCO2 = 803 µatm) each at two reefs. In Porites spp., only one of the biochemical parameters investigated (the ratio of photoprotective to light-harvesting pigments) responded to pCO2, while tissue biomass, total lipids, total proteins, and some pigments differed between the two reefs, possibly reflecting differences in food availability. Furthermore, some fatty acids showed pCO2 –reef interactions. In A. millepora, most pigments investigated were reduced at elevated pCO2, while other parameters (e.g. tissue biomass, total proteins, total lipids, protein carbonyls, some fatty acids and pigments) differed between reefs or showed pCO2–reef interactions. Tissue biomass, total lipids, and cell-protective capacities were distinctly higher in Porites spp. than in A. millepora, indicating higher resistance to environmental stress in massive Porites. However, our data suggest that important biochemical measures remain relatively unaffected in these two coral species in response to elevated pCO2 up to 800 µatm, with most responses being smaller than differences between species and locations, and also when compared with responses to other environmental stressors such as ocean warming.

Sperm immobilizing properties of lemon juice

The aim of this study was to evaluate the sperm-immobilizing properties of lemon juice to determine if they are consistent with its traditional contraceptive use. It was found that lemon juice supernatant (LJS) has high osmolality (550–60 mOsm) and low pH (2.2–2.6) and that addition of LJS to semen to give a final concentration of 20% v/v reduced the pH from around 8.4 to 4.1. This acidification was associated with irreversible cessation of all sperm movements within 1 minute. In conclusion, lemon juice should be further evaluated for acceptability, safety, and efficacy as a topical vaginal contraceptive agent.

Using omeprazole to link the components of the post-prandial alkaline tide in the spiny dogfish, Squalus acanthias

After a meal, dogfish exhibit a metabolic alkalosis in the bloodstream and a marked excretion of basic equivalents across the gills to the external seawater. We used the H⁺, K⁺-ATPase pump inhibitor omeprazole to determine whether these post-prandial alkaline tide events were linked to secretion of H⁺ (accompanied by Cl^–) in the stomach. Sharks were fitted with indwelling stomach tubes for pretreatment with omeprazole (five doses of 5mg omeprazole per kilogram over 48 h) or comparable volumes of vehicle (saline containing 2% DMSO) and for sampling of gastric chyme. Fish were then fed an involuntary meal by means of the stomach tube consisting of minced flatfish muscle (2% of body mass) suspended in saline (4% of body mass total volume). Omeprazole pretreatment delayed the post-prandial acidification of the gastric chyme, slowed the rise in Cl^– concentration of the chyme and altered the patterns of other ions, indicating inhibition of H⁺ and accompanying Cl^– secretion. Omeprazole also greatly attenuated the rise in arterial pH and bicarbonate concentrations and reduced the net excretion of basic equivalents to the water by 56% over 48h. Arterial blood CO₂ pressure and plasma ions were not substantially altered. These results indicate that elevated gastric H⁺ secretion (as HCl) in the digestive process is the major cause of the systemic metabolic alkalosis and the accompanying rise in base excretion across the gills that constitute the alkaline tide in the dogfish.

A Ramsar wetland in crisis the Coorong, Lower Lakes and Murray Mouth, Australia

The state of global freshwater ecosystems is increasingly parlous with water resource development degrading high-conservation wetlands. Rehabilitation is challenging because necessary increases in environmental flows have concomitant social impacts, complicated because many rivers flow between jurisdictions or countries. Australia's MurrayDarling Basin is a large river basin with such problems encapsulated in the crisis of its Ramsar-listed terminal wetland, the Coorong, Lower Lakes and Murray Mouth. Prolonged drought and upstream diversion of water dropped water levels in the Lakes below sea level (20092010), exposing hazardous acid sulfate soils. Salinities increased dramatically (e.g. South Lagoon of Coorong>200gL-1, cf. modelled natural 80gL-1), reducing populations of waterbirds, fish, macroinvertebrates and littoral plants. Calcareous masses of estuarine tubeworms (Ficopomatus enigmaticus) killed freshwater turtles (Chelidae) and other fauna. Management primarily focussed on treating symptoms (e.g. acidification), rather than reduced flows, at considerable expense (≥AU$2 billion). We modelled a scenario that increased annual flows during low-flow periods from current levels up to one-third of what the natural flow would have been, potentially delivering substantial environmental benefits and avoiding future crises. Realisation of this outcome depends on increasing environmental flows and implementing sophisticated river management during dry periods, both highly contentious options.

Implications of future climate for marine fish

Climate change has already been linked to significant impacts on Earth's ocean ecosystems including shifts in species geographic ranges, changes in population abundance, shits in timing of seasonal events, and establishment of introduced species (Walter et al. 2002, Parmesan and Yohe 2003). Global climate modelling for the Australian region has identified south-eastern Australia as the area that will be subject to the greatest impacts from climatic change (Lough 2009). The major changes predicted include warming of air and water, changes to wind patterns, changes to the strength and southerly extent of dominant oceanic currents flowing down the east and west coasts of Australia, changes to rainfall and run-off (distribution, timing and intensity), increasing ocean acidification, increasing exposure to UV light and sea level rise (Lough and Hobday 2011). Victorian species may be at greater risk than species in other areas of Australia, because Victorian marine waters are in a zone of predicted high climate change (Johnson et al. 2011, Wernberg et al. 2011).

Mitochondrial dysfunction has divergent, cell type-dependent effects on insulin action

The contribution of mitochondrial dysfunction to insulin resistance is a contentious issue in metabolic research. Recent evidence implicates mitochondrial dysfunction as contributing to multiple forms of insulin resistance. However, some models of mitochondrial dysfunction fail to induce insulin resistance, suggesting greater complexity describes mitochondrial regulation of insulin action. We report that mitochondrial dysfunction is not necessary for cellular models of insulin resistance. However, impairment of mitochondrial function is sufficient for insulin resistance in a cell type-dependent manner, with impaired mitochondrial function inducing insulin resistance in adipocytes, but having no effect, or insulin sensitising effects in hepatocytes. The mechanism of mitochondrial impairment was important in determining the impact on insulin action, but was independent of mitochondrial ROS production. These data can account for opposing findings on this issue and highlight the complexity of mitochondrial regulation of cell type-specific insulin action, which is not described by current reductionist paradigms.

Detecting range shifts among Australian fishes in response to climate change

One of the most obvious and expected impacts of climate change is a shift in the distributional range of organisms, which could have considerable ecological and economic consequences. Australian waters are hotspots for climate-induced environmental changes; here, we review these potential changes and their apparent and potential implications for freshwater, estuarine and marine fish. Our meta-analysis detected 300 papers globally on 'fish' and 'range shifts', with ∼7% being from Australia. Of the Australian papers, only one study exhibited definitive evidence of climate-induced range shifts, with most studies focussing instead on future predictions. There was little consensus in the literature regarding the definition of 'range', largely because of populations having distributions that fluctuate regularly. For example, many marine populations have broad dispersal of offspring (causing vagrancy). Similarly, in freshwater and estuarine systems, regular environmental changes (e.g. seasonal, ENSO cycles not related to climate change) cause expansion and contraction of populations, which confounds efforts to detect range 'shifts'. We found that increases in water temperature, reduced freshwater flows and changes in ocean currents are likely to be the key drivers of climate-induced range shifts in Australian fishes. Although large-scale frequent and rigorous direct surveys of fishes across their entire distributional ranges, especially at range edges, will be essential to detect range shifts of fishes in response to climate change, we suggest careful co-opting of fisheries, museum and other regional databases as a potential, but imperfect alternative. © 2011 CSIRO Open Access.

Can macroalgae contribute to blue carbon? An Australian perspective

Macroalgal communities in Australia and around the world store vast quantities of carbon in their living biomass, but their prevalence of growing on hard substrata means that they have limited capacity to act as long-term carbon sinks. Unlike other coastal blue carbon habitats such as seagrasses, saltmarshes and mangroves, they do not develop their own organic-rich sediments, but may instead act as a rich carbon source and make significant contributions in the form of detritus to sedimentary habitats by acting as a “carbon donor” to “receiver sites” where organic material accumulates. The potential for storage of this donated carbon however, is dependent on the decay rate during transport and the burial efficiency at receiver sites. To better understand the potential contribution of macroalgal communities to coastal blue carbon budgets, a comprehensive literature search was conducted using key words, including carbon sequestration, macroalgal distribution, abundance and productivity to provide an estimation of the total amount of carbon stored in temperate Australian macroalgae. Our most conservative calculations estimate 109.9 Tg C is stored in living macroalgal biomass of temperate Australia, using a coastal area covering 249,697 km2. Estimates derived for tropical and subtropical regions contributed an additional 23.2 Tg C. By extending the search to include global studies we provide a broader context and rationale for the study, contributing to the global aspects of the review. In addition, we discuss the potential role of calcium carbonate-containing macroalgae, consider the dynamic nature of macroalgal populations in the context of climate change, and identify the knowledge gaps that once addressed will enable robust quantification of macroalgae in marine biogeochemical cycling of carbon. We conclude that macroalgal communities have the potential to make ecologically meaningful contributions toward global blue carbon sequestration, as donors, but given that the fate of detached macroalgal biomass remains unclear, further research is needed to quantify this contribution.

Human threats to sandy beaches: a meta-analysis of ghost crabs illustrates global anthropogenic impacts

Beach and coastal dune systems are increasingly subjected to a broad range of anthropogenic pressures that on many shorelines require significant conservation and mitigation interventions. But these interventions require reliable data on the severity and frequency of adverse ecological impacts. Such evidence is often obtained by measuring the response of 'indicator species'.Ghost crabs are the largest invertebrates inhabiting tropical and subtropical sandy shores and are frequently used to assess human impacts on ocean beaches. Here we present the first global meta-analysis of these impacts, and analyse the design properties and metrics of studies using ghost-crabs in their assessment. This was complemented by a gap analysis to identify thematic areas of anthropogenic pressures on sandy beach ecosystems that are under-represented in the published literature.Our meta-analysis demonstrates a broad geographic reach, encompassing studies on shores of the Pacific, Indian, and Atlantic Oceans, as well as the South China Sea. It also reveals what are, arguably, two major limitations: i) the near-universal use of proxies (i.e. burrow counts to estimate abundance) at the cost of directly measuring biological traits and bio-markers in the organism itself; and ii) descriptive or correlative study designs that rarely extend beyond a simple 'compare and contrast approach', and hence fail to identify the mechanistic cause(s) of observed contrasts.Evidence for a historically narrow range of assessed pressures (i.e., chiefly urbanisation, vehicles, beach nourishment, and recreation) is juxtaposed with rich opportunities for the broader integration of ghost crabs as a model taxon in studies of disturbance and impact assessments on ocean beaches. Tangible advances will most likely occur where ghost crabs provide foci for experiments that test specific hypotheses associated with effects of chemical, light and acoustic pollution, as well as the consequences of climate change (e.g. species range shifts).