Coral community responses to declining water quality: Whitsunday Islands, Great Barrier Reef, Australia

Abstract

A five-year period (2002)(2003)(2004)(2005)(2006) of belowmedian rainfall followed by a six-year period (2007)(2008)(2009)(2010)(2011)(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 abovemedian 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.

Towards protecting the Great Barrier Reef from land‐based pollution

“…Similarly, in the coastal and inshore areas of the GBR, the condition of water quality, corals and seagrasses has declined over the last decade (Fig. a, b) after a series of extreme wet seasons (Thompson et al ., ,b; Queensland Government, ). Populations of many other species such as sharks and rays, sea snakes, marine turtles, seabirds, dolphins and dugongs have declined significantly, again particularly in central and southern inshore areas, and are expected to further decrease into the future (Great Barrier Reef Marine Park Authority, ).…”

Particulate Backscattering Ratio as an Indicator of Changing Particle Composition in Coastal Waters: Observations From Great Barrier Reef Waters

“…The bio‐optical properties of inshore waters of the Great Barrier Reef (GBR) are of particularly interest due to the generally clear, shallow waters that allow extensive benthic habitats such as coral communities and seagrass meadows to exist (Collier et al, ). Further, large changes in loads of nutrients and sediments associated with both natural variations in river flows and anthropogenic catchment changes have impacted on the water clarity of the coastal habitats (Fabricius et al, ; Thompson et al, ). It is now a management priority to determine the impacts of catchment‐derived sediments and nutrients on the inshore reef waters (Baird et al, ; Brodie et al, ).…”

Baseline reef health surveys at Bangka Island (North Sulawesi, Indonesia) reveal new threats

“…These include decline in water quality, overexploitation of resources and global climate change which have all been linked with the onset of mass coral bleaching and a variety of different disease signs (Carpenter et al, 2008; Ban, Graham & Connolly, 2014; Burge et al, 2014; Thompson et al, 2014). Many environmental stressors and anthropogenic disturbances are thought to favour the onset of infectious disease, either on their own or more commonly synergistically (Sutherland, Porter & Torres, 2004; Harvell et al, 2007).…”