Scientific articles
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2004
Coral Cover: The Cover of Living and Dead Corals from Airborne Remote Sensing
Trends in coral cover are widely used to indicate the health of coral reefs but are costly to obtain from field survey over large areas. In situ studies of reflected spectra at the coral surface show that living and recently dead colonies can be distinguished. Here, we investigate whether such spectral differences can be detected using an airborne remote sensing instrument. The Compact Airborne Spectrographic Imager (Itres Research Ltd, Canada) was flown in two configurations: 10 spectral bands with 1-m2 pixels and 6 spectral bands with 0.25-m2 pixels. First, we show that an instrument with 10 spectral bands possesses...
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2003
Seaweed Resistance to Microbial Attack: A Targeted Chemical Defense Against Marine Fungi
Pathogenic microbes can devastate populations of marine plants and animals. Yet, many sessile organisms such as seaweeds and sponges suffer remarkably low levels of microbial infection, despite lacking cell-based immune systems. Antimicrobial defenses of marine organisms are largely uncharacterized, although from a small number of studies it appears that chemical defenses may improve host resistance. In this study, we asked whether the common seaweed Lobophora variegata is chemically defended against potentially deleterious microorganisms. Using bioassayguided fractionation, we isolated and characterized a 22-membered cyclic lactone, lobophorolide (1), of presumed polyketide origin, with sub-M activity against pathogenic and...
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2002
Widespread and Persistent Populations of a Major New Marine Actinomycete Taxon in Ocean Sediments
A major taxon of obligate marine bacteria within the order Actinomycetales has been discovered from ocean sediments. Populations of these bacteria (designated MAR 1) are persistent and widespread, spanning at least three distinct ocean systems. In this study, 212 actinomycete isolates possessing MAR 1 morphologies were examined and all but two displayed an obligate requirement of seawater for growth. Forty-five of these isolates, representing all observed seawater-requiring morphotypes, were partially sequenced and found to share characteristic small-subunit rRNA signature nucleotides between positions 207 and 468 (Escherichia coli numbering). Phylogenetic characterization of seven representative isolates based on almost...
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2001
In April–May 1998, mass coral bleaching was observed in the lagoon of Rangiroa Atoll, Tuamotu Archipelago, French Polynesia. Six months later, the extent of bleaching-induced coral mortality was assessed at three sites. Corals in the fast-growing genus Pocillopora had experienced >99% mortality. Many large colonies of the slow-growing genus Porites (mean horizontal cross-sectional area 5.8 m2) had also died – a phenomenon not previously observed in French Polynesia and virtually unprecedented world-wide. At one site, 25% of colonies, or 44% of the pre-bleaching cover of living Porites, experienced whole-colony mortality. At the two...
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2001
A bird’s-eye view of the health of coral reefs. Nature 413:36
Almost three-quarters of the world's coral reefs are thought to be deteriorating as a consequence of environmental stress. Until now, it has been possible to evaluate reef health only by field survey, which is labour-intensive and time-consuming. Here we map live coral cover from the air by remote imaging, a technique that will enable the state of shallow reefs to be monitored swiftly and over large areas.
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2001
Cloudy Weather May Have Saved Society Island Reef Corals During the 1998 ENSO Event
During the 1998 El Niño-Southern Oscillation (ENSO) event, mass coral bleaching in French Polynesia was patchy at a scale of 100s of km. Bleaching was extensive in parts of the Tuamotu archipelago (creating up to 99% coral mortality) but extremely mild in the Society Islands (Tahiti, Moorea), ca 350 km to the south-west, despite sea surface temperature (SST) anomalies being of similar magnitude to previous years in which mass bleaching occurred. We examine whether environmental variables account for this unexpected paucity of bleaching using a 50 yr record of SST, a 17 yr record of daily wind and...
