Distribution and drivers of coral disease at Ningaloo reef, Indian Ocean

Abstract

We investigated the prevalence and potential drivers of coral disease across Ningaloo Reef on the Western Australian coast. Coral disease assessment surveys were undertaken at 2 spatial scales, the first over a small area of reef (Bill's Bay, 2.5 × 5.0 km), where human use is high and where several anoxic events have caused significant coral mortality, and the second over a broader area (spanning ~200 km of the Ningaloo coast). Throughout Ningaloo, 2.3% of coral colonies showed signs of disease, although disease prevalence varied at both broad and local scales, ranging from 1.1 to 7% along the coast, and from 0.1 to 3.1% locally -all within the range of values recorded in other Indo-Pacific regions. Seven diseases were identified, the most common being 'skeletal eroding band' (which affected ~1% of colonies). At a broad spatial scale, prevalence of skeletal eroding band was positively related to the number of coral colonies exhibiting Drupella spp. feeding scars, whilst blackband disease (BBD) was positively associated with density of coral colonies. At the local scale, severity of anoxic events and occurrence of Drupella spp. feeding scars were positively related to prevalence of BBD, whilst other cyanobacterial bands were associated only with Drupella spp. scars. We saw no strong indication that human activities, measured as density of people or vessels in the water, were related to disease prevalence. Positive relationships amongst disease, anoxic events and Drupella spp. feeding suggest that natural stressors are potential drivers of disease at Ningaloo. KEY WORDS: Ningaloo Marine Park · Coral Bay · Drupella · Climate change · Coral disease Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 433: [75][76][77][78][79][80][81][82][83][84] 2011 Islands (Hobbs & Frisch 2010), and observations of disease off the Pilbara coast (Page & Stoddart 2010). Unpublished records of disease also exist for the Abrohlos Islands south of Ningaloo Reef (L. Smith pers. comm.) and the Rowley Shoals (S. Long pers. comm.). Clearly, greater efforts are required to understand the diseases impacting corals in the eastern Indian Ocean and in Western Australia.Ningaloo Reef, which stretches over 300 km along the Western Australian coast, is Australia's largest fringing coral reef (Department of Conservation and Land Management 2005). The reef, while reserved as a marine park, is subject to natural pressures, including outbreaks of corallivorous Drupella spp. gastropods and anoxic water events. Densities of D. cornus, for example, have been unusually high at Ningaloo and, in the 1980s, caused a reduction in coral cover of up to 85% at some sites (Ayling & Ayling 1987). Bill's Bay, in the southern section of the reef, has been subject to several natural anoxic events associated with coral 76 Since the intensity of both natural and anthropogenic stressors varies along Ningaloo Reef, this region is optimal for investigating the impacts of these factors on coral disease levels. The pr...

Sediment and Turbidity Associated with Offshore Dredging Increase Coral Disease Prevalence on Nearby Reefs

“…Prevalence levels of black band disease, skeletal eroding band disease and growth anomalies did not differ significantly among sediment plume exposure groups and all were consistent with levels reported from Ningaloo Reef [44].…”

The corallivorous invertebrate Drupella aids in transmission of brown band disease on the Great Barrier Reef

“…The ciliate band clearly started from the feeding scar and then progressed rapidly to cause nubbin death within 48-60 h. The substantial impact that aggregations of these gastropods have inflicted on Indo-Pacific reefs is well known, reducing live coral by up to 75 % on Ningaloo Reef in Western Australia (Ayling and Ayling 1987), and leading to mortality of all corals on parts of Eilat reefs within 2 years (Shafir et al 2008). It is generally assumed that such impacts are a direct consequence of coral tissue removal through feeding, but the capacity of Drupella to transmit BrB in association with its feeding activity, as shown here, highlights an additional mechanism that is likely to significantly contribute to the ecological impact of Drupella outbreaks (also see Onton et al 2011). Identification of Drupella as a disease vector adds to the mounting evidence that a range of invertebrates play important roles in coral disease dynamics, including the fireworm Hermodice caranculata, a winter reservoir and summer vector of Vibrio shiloi (Sussman et al 2003); the mollusk Coralliophila abbreviata, a vector and interepizootic reservoir of the white pox pathogen (Sutherland et al 2011); and the crown-of-thorns starfish, A. planci, also a potential BrB vector (Nugues and Bak 2009).…”

“…For example, large numbers of Drupella cornus led to mortality of all corals within 2 years on parts of reefs in Eilat (Shafir et al 2008). Furthermore, the abundance of Drupella has been correlated with various diseases, including white syndromes (Antonius and Riegl 1998), skeletal eroding band and black band disease (Onton et al 2011). It is not clear, however, whether coral mortality resulting from disease attracts Drupella, or whether Drupella outbreaks promote coral disease.…”

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

“…are raising concerns not only for their direct predatory effects on their preys, but also for their feared involvement as vector in some infectious diseases (e.g., Turner, 1994; Antonius & Riegl, 1998; Onton et al, 2011; Nicolet et al, 2013). Luckily, cases of Drupella around the island are still relatively few yet we recommend they should still be monitored over time.…”