Article

Documenting hurricane impacts on coral reefs using two‐dimensional video‐mosaic technology

Marine Ecology (Impact Factor: 1.84). 05/2007; 28(2):254 - 258. DOI: 10.1111/j.1439-0485.2006.00140.x

ABSTRACT Four hurricanes impacted the reefs of Florida in 2005. In this study, we evaluate the combined impacts of hurricanes Dennis, Katrina, Rita, and Wilma on a population of Acropora palmata using a newly developed video-mosaic methodology that provides a high-resolution, spatially accurate landscape view of the reef benthos. Storm damage to A. palmata was surprisingly limited; only 2 out of 19 colonies were removed from the study plot at Molasses Reef. The net tissue losses for those colonies that remained were only 10% and mean diameter of colonies decreased slightly from 88.4 to 79.6 cm. In contrast, the damage to the reef framework was more severe, and a large section (6 m in diameter) was dislodged, overturned, and transported to the bottom of the reef spur. The data presented here show that two-dimensional video-mosaic technology is well-suited to assess the impacts of physical disturbance on coral reefs and can be used to complement existing survey methodologies.

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Available from: R. Pamela Reid, Sep 01, 2015
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    • "In aerial or underwater mapping, when a robot is equipped with a down-looking camera, it is often of interest to obtain a global view of the area in the form of a photo-mosaic. Mosaics can support different science applications such as geological [1] [2] and archaeological surveys [3], ecology studies [4] [5], environmental damage assessment [6] [7] or detection of temporal changes [8]. When the seabed is mapped with a low-cost robot, the underwater medium creates several specific processing difficulties due to the attenuation and scattering of * Corresponding author. "
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    ABSTRACT: Over the past decade, several image mosaicing methods have been proposed in robotic mapping and remote sensing applications. Owing to rapid developments in obtaining optical data from areas beyond human reach, there is a high demand from different science fields for creating large-area image mosaics, often using images as the only source of information. One of the most important steps in the mosaicing process is motion estimation between overlapping images to obtain the topology, i.e., the spatial relationships between images.In this paper, we propose a generic framework for feature-based image mosaicing capable of obtaining the topology with a reduced number of matching attempts and of getting the best possible trajectory estimation. Innovative aspects include the use of a fast image similarity criterion combined with a Minimum Spanning Tree (MST) solution, to obtain a tentative topology and information theory principles to decide when to update trajectory estimation. Unlike previous approaches for large-area mosaicing, our framework is able to naturally deal with the cases where time-consecutive images cannot be matched successfully, such as completely unordered sets. This characteristic also makes our approach robust to sensor failure. The performance of the method is illustrated with experimental results obtained from different challenging underwater image sequences.
    Robotics and Autonomous Systems 02/2013; 61(2):125–136. DOI:10.1016/j.robot.2012.10.010 · 1.11 Impact Factor
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    • "Mapping acroporid populations can be accomplished on larger scales (100s km) by remote sensing techniques (e.g., satellite image analysis) (Purkis et al. 2006; Collier and Humber 2007), but these techniques are relatively expensive and may not be effective at smaller scales (10s m) due to pixel mixing, albedo effects, and image registration precision. Mapping populations at smaller scales can be accomplished in a variety of ways including side scan sonar (Collier and Humber 2007), pole-mounted video systems on boats (Lidz et al. 2008), mosaics of underwater camera footage (Gleason et al. 2007), and handheld GPS units towed by diver or snorkeler (Devine et al. 2005; Lirman et al. 2010). However, all but the last method require expensive and sometimes propriety equipment or extensive technological research and development. "
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    ABSTRACT: Western Atlantic populations of the staghorn coral Acropora cervicornis have drastically declined over the past few decades. Hence, interest in its ecology and spatial extent has increased. Acroporid corals with indeterminate arborescent growth like A. cervicornis primarily reproduce asexually by fragmentation, which can lead to extensive monotypic patches. Since fragmentation is a major component in indeterminate acroporid reproduction, these patches may expand or move over time. Periodic perimeter mapping facilitates comparison of patch areas to determine movement or expansion. A repeatable, low-cost method using a differential GPS carried by a snorkeler was employed to map the perimeter of A. cervicornis patches in southeast Florida. Perimeters were mapped over a 3-year period. Patch boundaries were dynamic, expanding in one or more directions. Patch areas increased by up to 7.5 times their original size and moved up to 51 m. Results were corroborated by spatial cluster analyses of in situ live coral cover measurements. Getis-Ord Gi* statistic and Anselin Local Moran’s I spatial cluster analyses of live coral cover within an array of in situ monitoring plots indicated that significant high cover clusters moved in the direction of mapped patch perimeter expansion. Expansion was coupled by more than 50 % decreases in total live cover. Information gained herein shows that A. cervicornis patches are spatially and temporally dynamic, having implications to long-term permanent transect monitoring studies and framework development. Results may be applicable to other shallow water indeterminate arborescent acroporid coral species.
    Coral Reefs 09/2012; 31(3). DOI:10.1007/s00338-012-0910-3 · 3.62 Impact Factor
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    • "The potential use of mesoscale, or " landscape, " mosaics has been investigated for several coral reef-related applications, including: documenting hurricane damage at both the colony and reef-framework scale [9], mapping mesophotic [26], [27] and deep-water [28] coral ecosystems, quantifying the area damaged by a ship that had run aground [10], and tracking individual colonies through time [9], [25]. Of these, the ship grounding and individual monitoring take particular advantage of the new scale of observation enabled by landscape mosaics. "
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    ABSTRACT: Owing to the rapid developments on obtaining optical data from areas beyond human reach, there is a high demand from different scientists for creating large-area image mosaics often using images as the only source of information. One of the most important steps in the mosaicing process is the motion estimation between overlapping images to obtain the topology, i.e, the spatial relationships between images. In this paper, we propose a generic framework for feature-based image mosaicing capable of obtaining the topology with a reduced number of matching attempts. It is presented an environmental application of this mosaicing approach to monitoring coral reefs.
    Signal Processing and Communications Applications (SIU), 2012 IEEE 20th Conference on; 04/2012
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