Response of a hypersaline salt marsh to a large flood and rainfall event along the west coast of southern Africa

The Orange Estuary lost 27% (276 ha) of its wetland area near the mouth as a result of bad management practices during the 1980s. The salt marsh has been unable to recover over the last 20 years because of the persistently high soil and groundwater salinity. In 2006, a 1 in 5 year flood occurred that completely covered the desertified salt marsh and floodplain with freshwater. The flood was followed by an above average (>45 mm) winter rainfall. Soil and groundwater sampled in April and August 2004 were compared with 2006 data to quantify the impact of the flood and rainfall event. It was hypothesised that the two freshwater events would significantly reduce the soil and groundwater salinity. However, the results showed no significant difference in sediment electrical conductivity throughout the soil profile over the four sampling periods. Soil moisture and organic content however increased significantly after these events in the surface soil layer. The flood deposited silt and scoured sand from the surface layers in significant quantities. The depth to groundwater in the desertified marsh retained a similar pattern after the flood despite 15 cm changes in depth in places. In 2004 a clear groundwater electrical conductivity gradient was present extending from the less saline north part of the marsh (0–15 mS cm⁻¹) to the central part (120–135 mS cm⁻¹) and decreasing again towards the south (60–75 mS cm⁻¹). The flood served to even out the groundwater salinity across the desertified marsh (60–90 mS cm⁻¹). The flood and high rainfall had a limited impact on the soil and groundwater characteristics. The few significant changes that were recorded were mostly restricted to the surface soil layers and on a small spatial scale. The rainfall did however create numerous pools of low salinity (<60 mS cm⁻¹) water on the marsh surface that provided a brief opportunity for salt marsh seeds to germinate. A further benefit of the flood was the increased tidal reach into the desertified marsh importing freshwater from the river mouth and exporting salt. Despite these responses it is unlikely that the hypersaline salt marsh will revegetate naturally. Human intervention is needed to ensure the rehabilitation of this important Ramsar site.     

Estimating the carbon transfer between the ocean, atmosphere and the terrestrial biosphere since the last glacial maximum

Carbon dioxide records from polar ice cores and marine ocean sediments indicate that the last glacial maximum (LGM) atmosphere CO₂ content was 80–90 ppm lower than the mid-Holocene. This represents a transfer of over 160 GtC into the atmosphere since the LGM. Palaeovegetation studies suggest that up to 1350 GtC was transferred from the oceans to the terrestrial biosphere at the end of the last glacial. Evidence from carbon isotopes in deep sea sediments, however, indicates a smaller shift of between 400 and 700 GtC. To understand the functioning of the carbon cycle this apparent discrepancy needs to be resolved. Thus, older data have been reassessed, new data provided and the potential errors of both methods estimated. New estimates of the expansion of terrestrial biomass between the LGM and mid-Holocene are 700 GtC ± > 300 GtC, using the ocean carbon isotope-based method, compared with of 1100 GtC ± > 500 GtC using the palaeovegetation estimate. If these estimates of the carbon shift to the terrestrial biosphere are equilibrated with the dissolved carbon in the oceans, and the CaCO₃ compensation of the ocean is taken into account, then the glacial atmospheric CO₂ would have been between 50 (± 30) ppm and 95 (± 50) ppm higher. The glacial atmosphere therefore should have had a CO₂ partial pressure of between 330 and 375 μatm. Hence, a rise of between 130 and 175 μatm in atmospheric CO₂, rather than 80 μatm, at the end of the last glacial must be accounted for.     

Efficacy of PIT tags and an autonomous antenna system to study the juvenile life stage of an estuarine-dependent fish

Many marine fishes use spatially distinct habitats as juveniles and adults. Determining which juvenile habitats are most important to sustaining adult populations (i.e., which habitats are nurseries) has proven difficult, in part due to challenges in estimating survival of juveniles in putative nursery habitats. Recent technological advances have made largescale tagging efforts a viable approach to estimating survival of juvenile fishes by increasing recapture rates and enabling the use of individual-identification tags. These techniques, using Passive Integrated transponder (PIT) tags and autonomous antenna detection systems (antenna), have been successfully applied in freshwater environments. This paper reports the adaptation of these techniques to estuarine mangrove creeks (salinity: 2–28‰) for research of the juvenile life stage on an estuarine-dependent marine fish,Centropomus undecimalis. Retention rate of PIT tags in juveniles >120 mm standard length was 100%, with no mortality. The antenna detection field covered 48% of the creek water column, and the antenna was experimentally determined to detect approximately 67% of tagged fish that swam through. Overall recapture rate of tagged fish by the antenna was >40%. This recapture rate is higher than the sparse data typical of traditional tag-recapture studies. A time-dependent Jolly-Seber model was fit to the data, providing estimates of capture probability (0.8) and weekly apparent survival (0.41) that will be invaluable in comparing juvenile habitats of different quality (e.g., natural versus anthropogenically degraded). This research demonstrates the viability of this approach to fish research in estuarine habitats.     

Conflict in Common: Heritage-making in Cape York

The outstanding natural and cultural values of Cape York have been acknowledged for decades, but those decades have been characterised by deep conflict. Non-government organisation intervention in local politics has seen a forceful push for nominating some or all of the Cape York Peninsula as a World Heritage Site. We illuminate the authorised heritage discourse at work in heritage-making, and highlight contested issues of ownership, governance, authenticity, and value. These themes contribute to the possibility of marginalising the voices of local people who wish to contribute to heritage-making in Cape York. Politics infuses all aspects of heritage-making in Cape York, and the specific experiences on Cape York reflect larger political processes occurring in World Heritage discourse. The paper draws on interviews undertaken in May and June 2012.     

Emerging Geographies of Conservation and Indigenous Land in Australia

International examples of interactions between Indigenous peoples and the new conservation paradigm come mainly from developing countries and suggest divisions over priorities. As a Western settler society, Australia is at a critical time in conservation and Indigenous peoples' rights. Innovative approaches to conservation are promoted. The role and influence of non-governmental organisations is increasing. Indigenous peoples' rights to land are recognised and Indigenous involvement in conservation is growing. Yet, despite Australia being considered a leader in these arenas, particularly the latter, there has been little analysis of the relationship between innovative approaches to conservation and Indigenous Australians under the new paradigm. This paper describes how the spatial manifestations of approaches under the new conservation paradigm and Indigenous land in Australia are creating new geographies. We identify geographies of overlap, dichotomy and absence. The paper identifies research needs into these geographies, including: examining the influence of ‘recognition’ in engagements between conservation and Indigenous Australians; investigating the impacts of approaches under the new paradigm such as scaling-up, territorialism and differing governance structures on Indigenous Australians; and questioning the social responsibilities of the non-governmental organisations towards Indigenous Australians.     

Land use and the spatial distribution of perfluoroalkyl compounds as measured in the plasma of bottlenose dolphins (Tursiops truncatus)

The distribution of perfluoroalkyl compounds (PFCs) in the environment is well documented with higher concentrations observed in wildlife located in industrial and urban areas. This study examined the distribution of PFCs in relation to land use using blood samples collected from bottlenose dolphins during capture-release health assessment surveys conducted in Charleston, SC. The study area was partitioned into three subareas (ACW, CHS, and SRE) based upon habitat and land use characteristics. The ACW and CHS subareas are characterized by high degrees of industrial and urban land uses, while the SRE subarea is more residential and characterized by a lower degree of developed land use. Long-term monitoring data from photo-identification surveys were used to group bottlenose dolphins based on their proportions of sightings in the different subareas. Dolphins affiliated with both the ACW and CHS subareas were observed to have significantly higher mean plasma concentrations of perfluorooctane sulfonate (PFOS), perfluorodecanoic acid (PFDA) and perfluoroundecanoic acid (PFUnA) than those affiliated with the SRE subarea. Dolphins affiliated with the ACW subarea were found to have a significantly higher mean plasma concentration of PFUnA than those affiliated with the CHS subarea. Further examination of the distribution of the PFCs revealed positive correlations with developed land uses and negative correlations with wetland/marsh land cover. A positive correlation was also observed between PFUnA and agricultural land use. The variability and scale of the observed contaminant burdens have important implications for the conservation and management of living marine resources and illustrates the importance of long-term monitoring of free-ranging wildlife species.