Shorebird population decreases are increasingly evident worldwide, especially in the East Asian-Australasian Flyway (EAAF). To arrest these declines, it is important to understand the scale of both the problem and the solution. We analysed an expansive Australian citizen science data set spanning the years from 1973 to 2014 to explore factors related to differences in trends among shorebird populations in wetlands throughout Australia. Of seven resident Australian shorebird species, the four inland species exhibited continental decreases, while the three coastal species did not. Decreases in inland resident shorebirds were related to changes in water availability at nontidal wetlands, suggesting that degradation of wetlands in Australia's interior is playing a role in these declines. The analyses also revealed continental decreases in abundance in 12 of 19 migratory shorebird species, and decreases in 17 of 19 migratory species in the southern half of Australia over the past 15 years. Many trends were most strongly associated with continental gradients in latitude 2 or longitude, suggesting some large-scale patterns in the decreases with steeper declines often evident in the south of Australia. After accounting for this effect, local variables did not explain variation in migratory shorebird trends between sites. Our results are consistent with other studies indicating that migratory shorebird population decreases in the EAAF are most likely being driven primarily by factors outside Australia. This reinforces the need for urgent overseas conservation actions. However, substantially heterogeneous trends within Australia, combined with inland resident shorebird declines indicate effective management of Australian shorebird habitat remains important.
We review and develop conceptual models for the bio-transfer of ciguatoxins in food chains for Platypus Bay and the Great Barrier Reef on the east coast of Australia. Platypus Bay is unique in repeatedly producing ciguateric fishes in Australia, with ciguatoxins produced by benthic dinoflagellates (Gambierdiscus spp.) growing epiphytically on free-living, benthic macroalgae. The Gambierdiscus are consumed by invertebrates living within the macroalgae, which are preyed upon by small carnivorous fishes, which are then preyed upon by Spanish mackerel (Scomberomorus commerson). We hypothesise that Gambierdiscus and/or Fukuyoa species growing on turf algae are the main source of ciguatoxins entering marine food chains to cause ciguatera on the Great Barrier Reef. The abundance of surgeonfish that feed on turf algae may act as a feedback mechanism controlling the flow of ciguatoxins through this marine food chain. If this hypothesis is broadly applicable, then a reduction in herbivory from overharvesting of herbivores could lead to increases in ciguatera by concentrating ciguatoxins through the remaining, smaller population of herbivores. Modelling the dilution of ciguatoxins by somatic growth in Spanish mackerel and coral trout (Plectropomus leopardus) revealed that growth could not significantly reduce the toxicity of fish flesh, except in young fast-growing fishes or legal-sized fishes contaminated with low levels of ciguatoxins. If Spanish mackerel along the east coast of Australia can depurate ciguatoxins, it is most likely with a half-life of ≤1-year. Our review and conceptual models can aid management and research of ciguatera in Australia, and globally.
In many wetlands the timing and duration of inundation determine ecological characteristics and the provision of ecosystem services; however, wetland conservation decisions often rely on static maps of wetland boundaries that do not capture their dynamic hydrological variability and connectivity. The Amazon River basin contains some of the world's most extensive wetlands, many of which are floodplains where seasonal flood pulses result in a temporally varying inundation area and hydrological connectivity with river systems. This study classified Amazon wetlands according to the timing and duration (months per year) of inundation detected by remote sensing, and also investigated the contribution of precipitation regimes in affecting wetland distribution and hydrological dynamics. Permanently inundated wetlands account for the largest area and are mainly floodplains located in the lowlands of the catchment. Seasonally inundated wetlands varied greatly in the duration of inundation over the course of the year, ranging from 1 to 9 months. Distinct seasonal timing was detected among the large wetland complexes, reflecting rainfall regimes as well as time lags for drainage and drying. For example, inundation in the extensive Llanos de Moxos region of the southern Amazon was protracted and lasted well after the rainy season, compared with the Roraima region of the northern Amazon, where inundation was shorter and tracked the rainy season. The integration of inundation dynamics into wetland classification captures regional differences in timing and duration of inundation in the major wetlands of the basin that should be considered for conservation planning and other ecological applications. This information can aid regional wetland management and planning, especially with regards to minimizing the effects of dam and waterway construction that can directly affect the natural wetland dynamics. The use of global remotely sensed inundation data makes this approach easily transferable to other large tropical wetlands.
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