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Seagrass systems of the Western Pacific region are biodiverse habitats, providing vital services to ecosystems and humans over a vast geographic range. SeagrassNet is a worldwide monitoring program that collects data on seagrass habitats, including the ten locations across the Western Pacific reported here where change at various scales was rapidly detected. Three sites remote from human influence were stable. Seagrasses declined largely due to increased nutrient loading (4 sites) and increased sedimentation (3 sites), the two most common stressors of seagrass worldwide. Two sites experienced near-total loss from of excess sedimentation, followed by partial recovery once sedimentation was reduced. Species shifts were observed at every site with recovering sites colonized by pioneer species. Regulation of watersheds is essential if marine protected areas are to preserve seagrass meadows. Seagrasses in the Western Pacific experience stress due to human impacts despite the vastness of the ocean area and low development pressures.

Atmospheric concentrations of the greenhouse gas nitrous oxide (N(2)O) have increased significantly since pre-industrial times owing to anthropogenic perturbation of the global nitrogen cycle, with animal production being one of the main contributors. Grasslands cover about 20 per cent of the temperate land surface of the Earth and are widely used as pasture. It has been suggested that high animal stocking rates and the resulting elevated nitrogen input increase N(2)O emissions. Internationally agreed methods to upscale the effect of increased livestock numbers on N(2)O emissions are based directly on per capita nitrogen inputs. However, measurements of grassland N(2)O fluxes are often performed over short time periods, with low time resolution and mostly during the growing season. In consequence, our understanding of the daily and seasonal dynamics of grassland N(2)O fluxes remains limited. Here we report year-round N(2)O flux measurements with high and low temporal resolution at ten steppe grassland sites in Inner Mongolia, China. We show that short-lived pulses of N(2)O emission during spring thaw dominate the annual N(2)O budget at our study sites. The N(2)O emission pulses are highest in ungrazed steppe and decrease with increasing stocking rate, suggesting that grazing decreases rather than increases N(2)O emissions. Our results show that the stimulatory effect of higher stocking rates on nitrogen cycling and, hence, on N(2)O emission is more than offset by the effects of a parallel reduction in microbial biomass, inorganic nitrogen production and wintertime water retention. By neglecting these freeze-thaw interactions, existing approaches may have systematically overestimated N(2)O emissions over the last century for semi-arid, cool temperate grasslands by up to 72 per cent.

A field study was conducted on two texturally different soils to determine the influences of biosolids application on selected soil chemical properties and carbon dioxide fluxes. Two sites, located in Manildra (clay loam) and Grenfell (sandy loam), in Australia, were treated at a single level of 70 Mg ha-1 biosolids. Soil samples were analyzed for SOC fractions, including total organic carbon (TOC), labile, and non-labile carbon contents. The natural abundances of soil δ13C and δ15N were measured as isotopic tracers to fingerprint carbon derived from biosolids. An automated soil respirometer was used to measure in-situ diurnal CO2 fluxes, soil moisture, and temperature. Application of biosolids increased the surface (0-15 cm) soil TOC by > 45% at both sites, which was attributed to the direct contribution from residual carbon in the biosolids and also from the increased biomass production. At both sites application of biosolids increased the non-labile carbon fraction that is stable against microbial decomposition, which indicated the soil carbon sequestration potential of biosolids. Soils amended with biosolids showed depleted δ13C, and enriched δ15N indicating the accumulation of biosolids residual carbon in soils. The in-situ respirometer data demonstrated enhanced CO2 fluxes at the sites treated with biosolids, indicating limited carbon sequestration potential. However, addition of biosolids on both the clay loam and sandy loam soils found to be effective in building SOC than reducing it. Soil temperature and CO2 fluxes, indicating that temperature was more important for microbial degradation of carbon in biosolids than soil moisture.

Much of New South Wales and southern Queensland suffered from extreme drought from 2017 to 2019. This study models drought and bushfires impacts using VU‐TERM, a multi‐regional, dynamic CGE model. Prolonged drought pushed national real GDP to 0.7 per cent or more below base in 2018–2019 and 2019–2020. NSW’s real GDP fell relative to forecast by 1.1 per cent or $6.9 billion in 2018–2019 and 1.6 per cent or $10.2 billion in 2019–2020. These impacts reflect a severe diminution of farm output, given that agriculture accounts for around 1.6 per cent of NSW’s income. Bushfires exacerbated 2019–2020 losses. We assume that there is a full recovery in seasonal conditions in 2020. However, prolonged drought and bushfire destruction deplete farm capital through depressed investment and diminished herd numbers. Consequently, the income earning capacity of farms in recovery remains below that of a no drought base. The net present value of the national welfare loss is $63 billion, split between $53 billion in losses from drought and $10 billion from bushfires. The latter excludes any valuation of human lives lost, flora, fauna or forestry destruction. In the longer term, adaptation and policy responses will need to reflect the expectation of increased frequency of adverse climatic events.

This study examined the potential use of macroalgae epiphytic on mangrove aerial roots as indicators of estuarine contamination. The distribution and abundance of macroalgae was investigated in four estuaries in the vicinity of Sydney, Australia, and compared to water and sediment metal concentrations, nutrient concentrations and physicochemical parameters over four seasonal surveys. Macroalgal diversity and distribution appeared to be highly influenced by the ambient contaminant concentrations, while biomass appeared to be linked with nutrient concentrations. The distribution of the Rhodophyta species, Catenella nipae Zanardini significantly decreased as metal concentrations increased among the estuaries during all seasonal surveys. This species showed strong potential for use as a bioindicator of estuarine contamination.

AbstractWarming of freshwaters as a result of climate change is expected to have complex interactions with the toxicity of contaminants to aquatic organisms. The present study evaluated the effects of temperature on the acute toxicity of endosulfan, chlorpyrifos, and phenol to 3 warm water species of fish—silver perch, rainbowfish, and western carp gudgeon—and 1 cold water species, rainbow trout. Endosulfan was more toxic to silver perch at 30 °C and 35 °C than at 15 °C, 20 °C and 25 °C during short exposures of 24 h, but at 96 h, temperature had no effect on toxicity. Toxicity to rainbow trout increased with increasing temperature, whereas warm water species exhibited maximum toxicity at around 30 °C, decreasing again toward 35 °C. Chlorpyrifos became more toxic to all species with increasing temperature. Phenol toxicity to all species decreased at low to intermediate temperatures; but as temperatures increased further toward the upper thermal limit, phenol became more toxic. Increasing toxicity in the upper thermal range of cold water species may contribute to upstream range contraction in rivers with high toxicant loads. In contrast, warm water species may not exhibit a range shift within rivers as a result of interactions between temperature and toxicity. Catchment management to offset global warming at local scales may present opportunities to mitigate increased toxicity of contaminants to fish. Environ Toxicol Chem 2015;34:1809–1817. © 2015 SETAC

Two chickpea genotypes viz. Bhakar-2011 (desi) and Noor-2013 (kabuli) were sown in soil filled pots supplied with low (0.3 mg kg-1) and high (3 mg kg-1 soil) zinc (Zn) under control (70% water holding capacity and 25/20 °C day/night temperature), drought (35% water holding capacity) and heat (35/30 °C day/night temperature) stresses. Drought and heat stresses reduced rate of photosynthesis, photosystem II efficiency, plant growth and Zn uptake in chickpea. Low Zn supply exacerbated adverse effects of drought and heat stresses in chickpea, and caused reduction in plant biomass, carbon assimilation, antioxidant activity, impeded Zn uptake and enhanced oxidative damage. However, adequate Zn supply ameliorated adverse effect of drought and heat stresses in both chickpea types. The improvements were more in desi than kabuli type. Adequate Zn nutrition is crucial to augment growth of chickpea plants under high temperature and arid climatic conditions.

Vegetated coastal ecosystems, in particular mangroves, tidal marshes and seagrasses are highly efficient at sequestering and storing carbon, making them valuable assets for climate change mitigation and adaptation. The state of Queensland, in northeastern Australia, contains almost half of the total area of these blue carbon ecosystems in the country, yet there are few detailed regional or state-wide assessments of their total sedimentary organic carbon (SOC) stocks. We compiled existing SOC data and used boosted regression tree models to evaluate the influence of environmental variables in explaining the variability in SOC stocks, and to produce spatially explicit blue carbon estimates. The final models explained 75 % (for mangroves and tidal marshes) and 65 % (for seagrasses) of the variability in SOC stocks. Total SOC stocks in the state of Queensland were estimated at 569 ± 98 Tg C (173 ± 32 Tg C, 232 ± 50 Tg C, and 164 ± 16 Tg C from mangroves, tidal marshes and seagrasses, respectively). Regional predictions for each of Queensland's eleven Natural Resource Management regions revealed that 60 % of the state's SOC stocks occurred within three regions (Cape York, Torres Strait and Southern Gulf Natural Resource Management regions) due to a combination of high values of SOC stocks and large areas of coastal wetlands. Protected areas in Queensland play an important role in conserving SOC assets in Queensland's coastal wetlands. For example, ~19 Tg C within terrestrial protected areas, ~27 Tg C within marine protected areas and ~ 40 Tg C within areas of matters of State Environmental Significance. Using multi-decadal (1987-2020) mapped distributions of mangroves in Queensland; we found that mangrove area increased by approximately 30,000 ha from 1987 to 2020, which led to temporal fluctuations in mangrove plant and SOC stocks. We estimated that plant stocks decreased from ~45 Tg C in 1987 to ~34.2 Tg C in 2020, while SOC stocks remained relatively constant from ~107.9 Tg C in 1987 to 108.0 Tg C in 2020. Considering the level of current protection, emissions from mangrove deforestation are potentially very low; therefore, representing minor opportunities for mangrove blue carbon projects in the region. Our study provides much needed information on current trends in carbon stocks and their conservation in Queensland's coastal wetlands, while also contributing to guide future management actions, including blue carbon restoration projects.