David Neil

Sediment yield and impacts from river catchments to the Great Barrier Reef lagoon

Land use intensification is estimated to result in an overall increase in sediment delivery to the Great Barrier Reef lagoon by a factor of approximately four. Modelling suggests that, following land use intensification, croplands cause the greatest increase of sediment yield and sediment concentration, whereas erosion of grazing land is the main contemporary source of sediments, primarily owing to the large spatial extent of this land use. The spatial pattern of sediment yield to the coast after land use intensification is strongly correlated with the pattern under natural conditions, although the greatest increase is estimated to have occurred in the wet-dry catchments. Sediment transport and resuspension processes have led to the development of a strongly sediment-partitioned shelf, with modern mud-rich sediments almost exclusively restricted to the inner and inner-middle shelf, northward-facing embayments and in the lee of headlands. Elevated sediment concentrations increase the potential transport rates of nutrients and other pollutants. Whether increased sediment supply to the coastal zone has impacted on reefs remains a point of contention. More sediment load data need to be collected and analysed in order to make detailed estimates of catchment yields and establish the possible sediment impact on the Great Barrier Reef.

Instability in a marginal coral reef: the shift from natural variability to a human‐dominated seascape

As global climate change drives the demise of tropical reef ecosystems, attention is turning to the suitability of refuge habitat. For the Great Barrier Reef, are there historically stable southern refugia where corals from the north might migrate as climate changes? To address this question, we present a precise chronology of marginal coral reef development from Moreton Bay, southeast Queensland, Australia. Our chronology shows that reef growth was episodic, responding to natural environmental variation throughout the Holocene, and that Moreton Bay was inhospitable to corals for about half of the past 7000 years. The only significant change in coral species composition occurred between ~200 and ~50 years ago, following anthropogenic alterations of the bay and its catchments. Natural historical instability of reefs, coupled with environmental degradation since European colonization, suggests that Moreton Bay offers limited potential as refuge habitat for reef species on human time scales.

Measurements of the local energy balance over a coral reef flat, Heron Island, southern Great Barrier Reef, Australia

Coral reefs are thought to face significant threat from global warming due to increased water temperatures and ocean acidity. However, research into the surface energy balance of coral reefs and their associated micrometeorology is rare. Here we present, through a case study approach, the first direct in situ measurements of the surface energy balance of Heron Reef, a small platform coral reef in the southern Great Barrier Reef, Australia. Surface energy exchanges were measured using the eddy covariance method and show that during winter and spring an estimated 80-98% of net radiation goes into heating of the water overlaying the reef and reef substrate. As a result, cloud cover is considered the dominant control on heating of the reef flat environment. Change in cloud cover may therefore significantly affect the thermal environment of coral reefs and their ecology. Sensible and latent heat fluxes reached their highest values during wintertime advection of dry and cool continental air blowing from mainland Australia. This resulted in a net loss of energy from the reef flat and a decreasing trend in water temperature. Turbulent fluxes otherwise remained small, with sensible heat flux often close to zero. Results indicate that coral reefs may act as heat sinks during winter and as heat sources during spring, thereby affecting local water and atmosphere heat budgets and associated thermodynamics. Copyright 2010 by the American Geophysical Union.

Moreton Bay and its estuaries: a sub-tropical system under pressure from rapid population growth

Moreton Bay and its associated estuaries are an example of a complex aquatic system that is under increasing pressure from rapid population growth and urbanisation. Although the extent of decline in ecosystem health within Moreton Bay and its associated estuaries is significant and well documented, a range of innovative management responses have been implemented to reverse current declines. An overview of the development of Moreton Bay is provided, highlighting the dynamic and resilient nature of the system over geological time. The ecological responses that occur at decadal timeframes are presented along with a summary of the current state of the Bay’s ecology. The future challenges that are posed by predicted population increases, urbanisation and changes to the region’s climate are also discussed. The highly variable nature of the system over relatively short timeframes (i.e. flood vs non-flood conditions) as well as the ability of the system to adapt to long term changes (i.e. past morphological and ecosystem shifts) suggests that Moreton Bay and its associated estuaries have significant capacity to adapt to change. Whether the current rate of anthropogenically induced change is too rapid for the system to adapt, or whether such adaptions will be undesirable, is unable to be ascertained in any detail at this stage. Notwithstanding the above, the combination of a science-based management framework and the collaborative decision making processes that have been implemented to halt the decline of Moreton Bay have shown remarkable progress in a relatively short period of time.

Cooperative fishing interactions between Aboriginal Australians and dolphins in eastern Australia

Abstract Published eyewitness accounts and stories from Aboriginal Australians are used to provide an overview of the geographical extent and characteristics of cooperative fishing between Aboriginal Australians and dolphins in eastern Australia. These sources indicate that cooperative fishing was geographically widespread in eastern Australia, involved both bottlenose dolphins and orcas, and had a significance (emotional and spiritual) to Aboriginal people beyond the acquisition of food. These fishing interactions represent both context and precedent for the economic and emotional objectives of contemporary human–dolphin interactions such as dolphin provisioning.

Polar Eolian Sand Transport: Grain Characteristics Determined by an Automated Scanning Electron Microscope (QEMSCAN®)

QEMSCAN®, an automated scanning electron microscope, is used to provide a high-resolution analysis of eolian sands collected from Victoria Valley, McMurdo Dry Valleys, Antarctica. This technique provides a rapid, digital, quantitative morphological and mineralogical analysis of sediments, originally developed for the mining industry, which we apply for the first time to the study of eolian sand transport. Results show fine to medium-sized sands (<300 µm) are similar in shape and mineralogy throughout the hyper-arid landscape of the Victoria Valley. We relate this to the almost continuous mixing of fine-grained sediments in the mostly snow- and ice-free valley by frequent thermally induced easterly winds and less common but stronger topographically channeled southwesterly foehn winds. Analysis of local dune sands transported during easterly winds, which typically just exceed the local threshold entrainment velocity of 5.3 m s−1 (at 0.4 m), indicate preferential transport of quartz grains by these winds. Surface type was found to exhibit considerable influence over the characteristics of eolian sand transport with much larger grains carried in saltation and modified suspension above fluvio-glacial outwash surfaces than above sand dunes. Results illustrate the potential of QEMSCAN as an effective tool for multi-parameter analysis of eolian sands allowing greater insight into the controls on eolian sand transport in settings such as the Victoria Valley, Antarctica.

Towards environmental management of water turbidity within open coastal waters of the Great Barrier Reef

Water turbidity and suspended sediment concentration (SSC) are commonly used as part of marine monitoring and water quality plans. Current management plans utilise threshold SSC values derived from mean-annual turbidity concentrations. Little published work documents typical ranges of turbidity for reefs within open coastal waters. Here, time-series turbidity measurements from 61 sites in the Great Barrier Reef (GBR) and Moreton Bay, Australia, are presented as turbidity exceedance curves and derivatives. This contributes to the understanding of turbidity and SSC in the context of environmental management in open-coastal reef environments. Exceedance results indicate strong spatial and temporal variability in water turbidity across inter/intraregional scales. The highest turbidity across 61 sites, at 50% exceedance (T50) is 15.3 NTU and at 90% exceedance (T90) 4.1 NTU. Mean/median turbidity comparisons show strong differences between the two, consistent with a strongly skewed turbidity regime. Results may contribute towards promoting refinement of water quality management protocols.

Spatial Variation of CO2- and SO3- Radicals in Massive Coral as Environmental Indicator

Electron spin resonance (ESR) signal intensities of a massive coral colony from the Great Barrier Reef are measured-along the growth direction with a microwave scanning ESR imaging system. The annual high intensity regions of CO2- radicals are the same as the skeletal high density regions. Those of SO3- radicals are the same as the yellow-green fluorescent bands which correlate with summer. A long-range fluctuation which has a 12-year cycle is also observed in the intensities of these two radicals. Thus, the ESR signal intensities of coral can be used as an indicator of past environmental changes.

Effect of high sedimentation rates on surface sediment dynamics and mangrove growth in the Porong River, Indonesia.

Large quantities of mud from the LUSI (Lumpur Sidoarjo) volcano in northeastern Java have been channeled to the sea causing high rates of sediment delivery to the mouth of the Porong River, which has a cover of natural and planted mangroves. This study investigated how the high rates of sediment delivery affected vertical accretion, surface elevation change and the growth of Avicennia sp., the dominant mangrove species in the region. During our observations in 2010-2011 (4-5years after the initial volcanic eruption), very high rates of sedimentation in the forests at the mouth of the river gave rise to high vertical accretion of over 10cmy(-1). The high sedimentation rates not only resulted in reduced growth of Avicennia sp. mangrove trees at the two study sites at the Porong River mouth, but also gave rise to high soil surface elevation gains.

Gift giving by wild bottle-nose dolphins (Tursiops sp.) to humans at a wild dolphin provisioning program, Tangalooma, Australia

ABSTRACT Since 1992, wild dolphin provisioning has occurred on a nightly basis at Tangalooma, a resort located on Moreton Island, Australia. Each evening at dusk up to 12 bottlenose dolphins (Tursiops sp.) are provided with fish in a regulated provisioning program. Since July 1998, biologists managing the program have documented 23 occurrences of “gift giving,” when several of the provisioned dolphins have offered wild-caught cephalopod or fin fish species to staff members. The characteristics of each of these events are presented, and we explore the relationships between these events and their temporal patterns, and the age and sex of the dolphins involved. We also consider the behavioral explanations for the “gift giving,” including prey sharing, play, and teaching behaviors, which have previously been described for cetaceans and other higher mammals. Gift giving may occur either as a discreet behavior (that may be a sequel to one or more other behaviors such as play or food preparation), or as a part of other behaviors, such as play and/or food sharing. It is most likely a manifestation of the particular relationship between the provisioned dolphins and the human participants in the provisioning. Gift giving has become an established but infrequent part of the culture of the provisioned dolphins at Tangalooma.