Article

Coral record of increased sediment flux to the inner Great Barrier Reef since European settlement

Research School of Earth Sciences, Australian National University, Canberra 0200, Australia.
Nature (Impact Factor: 42.35). 03/2003; 421(6924):727-30. DOI: 10.1038/nature01361
Source: PubMed

ABSTRACT The effect of European settlement on water quality in the Great Barrier Reef of Australia is a long-standing and controversial issue. Erosion and sediment transport in river catchments in this region have increased substantially since European settlement, but the magnitude of these changes remains uncertain. Here we report analyses of Ba/Ca ratios in long-lived Porites coral from Havannah Reef--a site on the inner Great Barrier Reef that is influenced by flood plumes from the Burdekin river--to establish a record of sediment fluxes from about 1750 to 1998. We find that, in the early part of the record, suspended sediment from river floods reached the inner reef area only occasionally, whereas after about 1870--following the beginning of European settlement--a five- to tenfold increase in the delivery of sediments is recorded with the highest fluxes occurring during the drought-breaking floods. We conclude that, since European settlement, land-use practices such as clearing and overstocking have led to major degradation of the semi-arid river catchments, resulting in substantially increased sediment loads entering the inner Great Barrier Reef.

3 Followers
 · 
79 Views
  • Source
    • "Coral reefs in the inshore area of the Great Barrier Reef, Australia (GBR), are situated in naturally turbid waters, as fine terrigenoclastic sediment is continuously resuspended by prevailing south-easterly winds and tidal currents (Larcombe et al. 1995, 2001; Wolanski et al. 2005; Orpin and Ridd 2012). In addition, suspended solids, nutrients, pesticide residues and other contaminants are delivered by catchment runoff during seasonal flooding of adjacent rivers (Devlin and Brodie 2005; Devlin and Schaffelke 2009; Brodie et al. 2010) and reach the inshore reefs (McCulloch et al. 2003; Jupiter et al. 2008; Kennedy et al. 2012; Bainbridge et al. 2012; Devlin et al. 2012). Since European colonisation, the loads of sediment, total nitrogen and total phosphorus transported to the coastal GBR as runoff are estimated to have increased by factors of 5.5, 5.7 and 8.9, respectively (Kroon et al. 2012). "
    [Show abstract] [Hide abstract]
    ABSTRACT: A five-year period (2002–2006) of below-median rainfall followed by a six-year period (2007–2012) of above-median rainfall and seasonal flooding allowed a natural experiment into the effects of runoff on the water quality and subsequent coral community responses in the Whitsunday Islands, Great Barrier Reef (Australia). Satellite-derived water quality estimates of total suspended solids (TSS) and chlorophyll-a (Chl) concentration showed marked seasonal variability that was exaggerated during years with high river discharge. During above-median rainfall years, Chl was aseasonally high for a period of 3 months during the wet season (February–April), while TSS was elevated for four months, extending into the dry season (March–June). Coinciding with these extremes in water quality was a reduction in the abundance and shift in the community composition, of juvenile corals. The incidence of coral disease was at a maximum during the transition from years of below-median to years of above-median river discharge. In contrast to juvenile corals, the cover of larger corals remained stable, although the composition of communities varied along environmental gradients. In combination, these results suggest opportunistic recruitment of corals during periods of relatively low environmental stress with selection for more tolerant species occurring during periods of environmental extremes.
    Coral Reefs 08/2014; 33(4). DOI:10.1007/s00338-014-1201-y · 3.62 Impact Factor
  • Source
    • "However, it is currently unknown whether adverse effects of salinity on coral reefs have become more frequent or extensive with alteration of freshwater flow regimes to tropical coastal waters. Cores of reef sediment and corals have indicated both increases (McCulloch et al., 2003) and decreases (Hungspreugs et al., 2002) in terrestrial sediment fluxes to coral reefs since the 1900s. Increases in sediment fluxes can result in smothering of coral reef organisms due to the settling of suspended sediment (sedimentation ), as well as in reduced light availability for photosynthesis due to turbidity caused by suspended sediment in the water column (Fabricius, 2011). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The continuing degradation of coral reefs has serious consequences for the provision of ecosystem goods and services to local and regional communities. While climate change is considered the most serious risk to coral reefs, agricultural pollution threatens approximately 25% of the total global reef area with further increases in sediment and nutrient fluxes projected over the next 50 years. Here, we aim to inform coral reef management using insights learned from management examples that were successful in reducing agricultural pollution to coastal ecosystems. We identify multiple examples reporting reduced fluxes of sediment and nutrients at end-of-river, and associated declines in nutrient concentrations and algal biomass in receiving coastal waters. Based on the insights obtained, we recommend that future protection of coral reef ecosystems demands policy focused on desired ecosystem outcomes, targeted regulatory approaches, up-scaling of watershed management, and long-term maintenance of scientifically robust monitoring programs linked with adaptive management.
    Marine Pollution Bulletin 08/2014; 85(1). DOI:10.1016/j.marpolbul.2014.06.003 · 2.79 Impact Factor
  • Source
    • "river catchments that affect the turtle Island group and Lizard Island are much smaller than those that influence Orpheus Island (neil et al. 2002). In addition, of all the rivers along the Queensland coast, the Burdekin river produces the highest volume of suspended sediments to the GBr lagoon, emitting an estimated 3 × 10 8 kg year −1 (neil et al. 2002; McCulloch et al. 2003; Kroon et al. 2012). Although Orpheus Island is not in the direct path of the flood plume stemming from the Burdekin river, excessive nutrients and (to a lesser extent) suspended sediments from the Burdekin river have been documented at considerable distances that easily extend past, and encompass, Orpheus Island (Devlin and Brodie 2005; Devlin et al. 2008; Bainbridge et al. 2012). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Spatial variation in the epilithic algal matrix (eAM) cryptofauna was investigated at three locations on the Great Barrier reef: two inner shelf—Orpheus Island and the turtle Island group—and a mid-shelf location, Lizard Island. Although the EAM appears to be a relatively simple and consistent habitat, significant differences in cryptofaunal assemblages were found between locations. EAM assemblages from Orpheus Island were markedly different. this appears to be a function of the sediment profile characteristics (grain size >60 μm) at Orpheus Island, as many cryptofaunal taxa displayed posi- tive relationships with sediment volume. however, sediment volumes did not differ significantly between the three locations, highlighting the possibility of cyclonic activ- ity affecting the sediment profile at Orpheus Island in the months preceding the study, in addition to the nutrient input from major terrigenous sources. the results of this study show that EAM cryptofaunal assemblages are not uniform across the Great Barrier reef and suggest that dissolved nutrients, sediment loads and distance from river systems may be significant drivers of cryptobenthic faunal compositions.
    Marine Biology 07/2014; 1(161):2183-2190. DOI:10.1007/s00227-014-2495-6 · 2.39 Impact Factor
Show more