Coral Disease Prevalence of Coconut Island: a Temporal Study between 2007-08 and 2011 Stephan Bitterwolf1, Greta Aeby Ph.D.2 & Marilyn Brandt Ph.D.1 1University of the Virgin Islands 2Hawai’i Institute of Marine Biology
Introduction Lesion Types Results: Change in Host Abundance Disease Prevalence vs. Size Conclusions
Montipora capitata: lesion prevalence vs. size class Community change in relationship to disease • Coral reefs cover less than 0.1% of the ocean surface area • PTLS and PorTrem lesion prevalence showed significant 1 and harbor up to 25% of all marine fish species. This effects of Year and Site (Fig 4). • Due to the low coral species diversity in Hawaii, 0.9 ecosystem provides humans services valued at • MC and PC showed significant effects of site, year and disease can have great implications for benthic approximately $US375 billion worldwide (NOAA, 2010) . interaction between site and year (Table 1, Fig 5 & 6). At 0.8 composition/community structure, consequently sites H & I a decrease in MC and corresponding increase in 0.7 affecting the* productivity of the coral reef • Coral disease occurrence is on the rise and, working in PC relative abundance was observed between 2007 & ecosystem. synergism with other stressors, has caused an estimated 0.6 2011. 27% coral cover loss worldwide (Sutherland et al., 2004) 0.5 • Montipora capitata is structurally more complex • For all other species, abundances were low and no obvious than Porites compressa. At two of the sites with Hawaii exhibits low coral species diversity. Thus its coral Prevalence 0.4 • temporal trends were observed between site or year. the highest starting M. capitata abundances, M. ecosystem could be severely impacted by coral disease. 0.3 capitata declined while P. compressa increased. • In 2007-2008 Williams et al. (2010) conducted a disease Temporal Lesion Prevalence 0.2 0.5 • Disease may have affected these sites more abundance survey on the reefs of Coconut Island, Oahu, 0.45 0.1 0.4 significantly because of higher starting host Hawaii. The area has since been subjected to many disease * 0 0.35 densities. The observed change in species outbreaks including a recent outbreak of Montipora white 0 20 40 60 80 100 120 140 160 180 0.3 composition could mean a decrease in rugosity or syndrome. In 2011, we conducted an identical survey to 0.25 2011 Average Size (cm) habitat space necessary for other species’ survival. 0.2 2007 Fig 7: MWS prevalence vs. average colony size with 1st order that of Williams et al. to determine whether community 0.15 structure has changed and what community factors may be Prevalence regression fit. Disease levels as a function of site and time 0.1 * related to disease. 0.05 0 Porites compressa: lesion prevalence vs. size class • PorTrem and PTLS showed significant effect of STUDY HYPOTHESIS: Coral community structure has MWS PTLS PGA Bleaching PorTrem 1 site and time. This may indicate an epizootic lesion changed in response to increased disease outbreaks and Lesion 0.9 outbreak and is not conclusive for lesion ± coral disease is associated with community factors Fig 4: Lesion prevalence ( SEM) by year of survey. 0.8 prevalence* at other times of the year. * indicates significant difference including coral cover and size structure. 0.7 Relationships between community factors and disease 0.6 * Table 1: F Ratio and P value by Species, Site, Year and • PTLS prevalence vs. abundance showed increasing Methods Interaction between Site & Year 0.5 * 0.4 trend with Porites compressa abundance indicating Prevalence that it may be a population dynamic lesion. • 8 sites within an 800 m2 area were surveyed around 0.3 Coconut Island (Fig 1). 0.2 • Lesion prevalence was found to increase with size 0.1 for all diseases except BLwTL. This may Each site was surveyed with 5 transects, 2x10m each. • 0 correspond to a greater surface area of contact and • Transects were surveyed for Colony Size/Species & Lesion 0 20 40 60 80 100 120 140 160 180 increased exposure time to factors leading to lesion Average Size (cm) Presence/Type. development (e.g., predation, pathogens, PTLS PGA PorTrem bleaching, parasitism). • Lesions documented included predation, Porites tissue Results: Relationship to Community Factors Fig 8: Prevalence of PTLS, PGA and PorTrem on Poritids vs. average Overall Conclusions loss, Montipora white syndrome, Porites and Montiporid st nd Fig 2: Coral lesions colony size with corresponding 1 and 2 order regression fits. growth anomalies, Porites bleaching with tissue loss, and • PTLS prevalence was significantly related to P. compressa • Results from this study will aid in the A: Montipora Growth Anomaly B: Montipora White Syndrome Porites trematodiasis (Fig 2: A-G). abundances (F = 6.109, p < 0.05, arcsin-root transformation All Species: lesion prevalence vs. size class identification of important factors influencing C: Bleaching with Tissue Loss D: Porites Tissue Loss 1 • Species abundance/disease prevalence was statistically applied). No other relationships were found between coral disease and community change in coral reef E: Porites Trematodiasis F: Predation 0.9 analyzed using 2 way-ANOVAs investigating the effect of disease prevalence and host abundances. communities. Understanding the dynamics of G: Porites Growth Anomaly 0.8 site and time. • All lesions, except BlwTL, exhibited significant disease among* heterogeneous coral reef habitats relationships between size class and prevalence (Table 2, 0.7 can provide insight into how disease acts within • Lesion vs. abundance (density and cover) and lesion vs. Figures 7-9). 0.6 complex communities. size class were analyzed with linear or polynomial Results: Frequency of Disease 0.5 regressions to investigate relationships. 0.4 Prevalence References * • In all, 6189 coral colonies of 4 species (Fungia scutaria Table 2: Regression formulas for lesions as a function of 0.3 NOAA. NOAA: Heat Stress to Caribbean Corals in 2005 (FC), Montipora capitata (MC), Pocillopora damicornis colony size. * significant regression,** low sample size Worst on Record. 15 11 2010. 10 09 2011 Coconut Island, Oahu, Hawaii 0.2
Disease Prevalence Montipora capitata Densities Between Survey Years Porites compressa Densities Between Survey Years 0.6 1 1 0.5 0.8 * * 0.8 0.4
0.3 0.6 0.6 * * 0.2 Prevalence 0.4 2007 0.4 2007 0.1 2011 2011 0.2 0.2 0.0 % % Abundance Coral 0 % Abundance Coral 0 A B C D G H I J A B C D G H I J Site Site Fig 3: Average disease prevalence (± SEM) for all sites Fig 1: Site locations around Coconut Island, Oahu, Hawaii. combined in 2011 Fig 5 & 6: Relative abundnaces (± SEM) of Montipora capitata and Porites compressa by site in 2007 and 2011. * Indicates significant difference determined by post-hoc tests.