Review: Sediment‐Related Controls on the Health of the Great Barrier Reef

Abstract

Linking terrestrial soil erosion to the degradation of marine ecosystems relies on a long chain of evidence. Here, this chain of evidence is reviewed for Australia's Great Barrier Reef and its catchments. Excessive sediment delivery to the marine environment is one component of an interlinked group of stressors that include coral bleaching, damage by storms, and plagues of crown-of-thorns starfish. Sediment and the pollutants they carry are one of the drivers of marine ecosystem decline and adversely impact recovery following disturbance by other stressors. Significantly, a portion of the N species carried by fine sediment in the freshwater system is released in the marine environment, thereby perturbing marine ecology. Available controls on sediment and pollutant delivery are hillslope erosion rates, gully and streambank erosion rates, sediment deposition rates in sediment sinks including footslopes, floodplains, and water reservoirs, and the application rates of pesticides and fertilizers. By reducing sediment fluxes through the combined strategies of erosion control and deposition enhancement, near-and offshore impacts can be reduced. Gully and streambank erosion are more significant sources of fine sediment than hillslope erosion. Fertilizer and non-fertilizer N and pesticides carried by sediment play an important role in coral reef degradation. A graphic summary of the spatial configuration the sources and sinks is provided to guide the prioritization of interventions. The scale of intervention required to achieve the desired marine outcome is so large that a combined voluntary and regulatory approach is needed.Abbreviations: COTS, crown-of-thorns starfish; DIN, dissolved inorganic nitrogen; GBR, Great Barrier Reef; OSL, optically stimulated luminescence.Coral reef ecosystems are in global decline (Bellwood et al., 2004). The quality of runoff from non-urban land is one of the stressors impacting the world's marine systems (Halpern et al., 2008). There are many examples of concern about this relationship and responses from governments, organizations, and communities (Lotze et al., 2006). Knowledge concerning this relationship and its controls is extensive but appears primarily as fragments of a long chain of links in the land-stream-estuary-marine-reef continuum.In this review, I have structured the knowledge concerning this chain, drawing on the extensive peer-reviewed publications concerning the Great Barrier Reef (GBR) and its contributing catchments. First I address the foundation question: Does excess land-derived sediment impact on the health of the GBR? Using the accumulated assessments of the sediment budgets and its components, I have constructed a description of the fluxes of sediment and sediment-bound nutrients through the catchment-estuary system. Finally, I have identified and comment on the available management controls on sediment delivery within this system. Does Excess Land-Derived Sediment Impact the Great Barrier Reef?A causal relationship between elevated river sediment loads and degrad...

Pre-development denudation rates for the Great Barrier Reef catchments derived using 10Be

“…Concerns about accelerated erosion rates in catchments adjacent to the GBR have increased in recent years due to the growing evidence for declining reef health (De'ath et al, 2012, Hairsine, 2017. Due to the size of these catchments, previous attempts to quantify the relative variability of erosion within, and between catchments, relied heavily on localised monitoring studies (Caitcheon et al, 2012, Bartley et al, 2007Nichols et al, 2014) and large-scale process-based modelling that are often underpinned by sparse locally measured data (McCloskey et al, 2021, Hughes andCroke, 2011).…”

Modelling Hydrological Processes and Identifying Soil Erosion Sources in a Tropical Catchment of the Great Barrier Reef Using SWAT

“…In tropical regions of Queensland, where there is a potential for high soil erosion, it is estimated that around half of its primary rainforests (6700 km 2 of 13,000 km 2 ) have been destroyed since the beginning of European colonisation [3,4]. These anthropogenic changes in GBR catchments have amplified soil erosion, increased sediment concentrations in the reef and consequently resulted in the degradation of the coral and seagrass ecosystems, which provide food and shelter for variety of marine species [5][6][7][8][9]. Specifically, the increased build-up of sediment in downstream waterbodies of GBR tropical catchments is likely to bring more ecological issues such as shrinking habitat and interstitial spaces, hence, disturbing the behaviour and lowering the survival rate of freshwater species [10].…”

Oceanography and Marine Biology

“…Some also review specific ecological processes on coral reefs, such as bioerosion (Hutchings & Kiene 1986, Sammarco 1996, Tribollet 2008, calcification and carbonate accretion (Allemand et al 2011, Bertucci et al 2013, Kennedy et al 2013, herbivory (Cvitanovic et al 2007, Mumby 2009a, Bonaldo et al 2014, Puk et al 2016, foraging associations (Lukoschek & McCormick 2000), cleaning symbioses (Cote 2000, Vaughan et al 2017) and certain modes of predation like corallivory (Cole et al 2008, Rotjan & Lewis 2008, Konow et al 2017, Rice et al 2019. As coral reefs degrade, a growing body of literature also draws focus on the environmental stressors threatening biological processes and reef functioning, including climate change (Hoegh-Guldberg et al 2007, Atkinson & Cuet 2008, Pratchett et al 2008b, Przeslawski et al 2008, Graham et al 2011b, Andersson & Gledhill 2013, Munday et al 2013b, Albright et al 2016a, Anthony 2016, Hoey et al 2016a, Camp et al 2018a, Espinel-Velasco et al 2018, storms and cyclones (Harmelin-Vivien 1994), water quality (Fabricius 2005, McKinley & Johnston 2010, Erftemeijer et al 2012, Wear & Thurber 2015, Hairsine 2017) and anthropogenic stressors more generally…”