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Remote Sensing for Understanding Coral Reef Dynamics and Processes: Photo-Systems to Coral Reef Systems

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A special issue of Remote Sensing (ISSN 2072-4292).

Deadline for manuscript submissions: closed (30 September 2012) | Viewed by 67787

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Special Issue Editors

Prof. Dr. Stuart Phinn

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Guest Editor

School of SEES, University of Queensland, St Lucia, Brisbane, QLD 4072, Australia
Interests: ecological remote sensing; earth observation
Special Issues, Collections and Topics in MDPI journals

Dr. Chris Roelfsema

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Guest Editor

Remote Sensing Research Centre, School of Geography, Planning and Environmental Management, The University of Queensland, Brisbane, QLD 4072, Australia
Interests: remote sensing of coastal and marine environments; conservation and management of coral reef and seagrass ecosystems; improving marine field calibration and validation approaches of remote sensing imagery
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Although numerous past and current special issues of remote sensing and coral reef journals, along with summary books, have focussed on mapping of coral reefs, few if any have focussed on using remotely sensed data to estimate and understand the dynamics or processes occurring on coral reefs. Measurements of how sun-light is absorbed, scattered and transmitted provides information fundamental to understanding the biophysical structures and processes of coral reefs from molecular (10^-6m) and global (10⁸km) scales. “Remote sensing” covers a range of scales and disciplines from microscopy/micro-analysis to satellite image analysis, and the finer scale knowledge is essential for “scaling up” or mapping and monitoring over large areas. There is a need to improve interactions between coral/algal physiologists and scientists mapping, modelling and monitoring reefs, to link knowledge and applications to provide the same level of operational mapping and monitoring as terrestrial plant ecology.

Papers in the special issue will move on from the starting point of reef mapping and focus on the use of time series or specific field and image data and processing models to estimate and understand biological and physical (hydrodynamic, geomorphic) processes acting on reefs. This will include applications from a range of sensors and scales, spectrometry and fluorometry in laboratory and field; hydro-optical measurements; multi- and hyper-spectral imaging. These may cover a range of environmental variables, including photosynthetic efficiency and concentrations of pigments in corals and algae;; benthic community types; primary production, concentrations of organic in inorganic material in coral reef waters, along with bathymetry, hydrodynamics and geomorphic zones. Select papers will cover integration of variables across scales, as these are essential to enable larger scale measurement and monitoring of processes on coral reefs and their surrounding environments.

Prof. Dr. Stuart Phinn
Dr. Chris Roelfsema
Guest Editors

Keywords

coral reefs
time series
models
ecosystem processes
hydrodynamics
primary production
calibration and validation
(bio)physical processes
scaling

Published Papers (6 papers)

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2019 KiB

Open AccessArticle

Image-Based Coral Reef Classification and Thematic Mapping

by A.S.M. Shihavuddin, Nuno Gracias, Rafael Garcia, Arthur C. R. Gleason and Brooke Gintert

Remote Sens. 2013, 5(4), 1809-1841; https://doi.org/10.3390/rs5041809 - 15 Apr 2013

Cited by 87 | Viewed by 13298

Abstract

This paper presents a novel image classification scheme for benthic coral reef images that can be applied to both single image and composite mosaic datasets. The proposed method can be configured to the characteristics (e.g., the size of the dataset, number of classes, resolution of the samples, color information availability, class types, etc.) of individual datasets. The proposed method uses completed local binary pattern (CLBP), grey level co-occurrence matrix (GLCM), Gabor filter response, and opponent angle and hue channel color histograms as feature descriptors. For classification, either k-nearest neighbor (KNN), neural network (NN), support vector machine (SVM) or probability density weighted mean distance (PDWMD) is used. The combination of features and classifiers that attains the best results is presented together with the guidelines for selection. The accuracy and efficiency of our proposed method are compared with other state-of-the-art techniques using three benthic and three texture datasets. The proposed method achieves the highest overall classification accuracy of any of the tested methods and has moderate execution time. Finally, the proposed classification scheme is applied to a large-scale image mosaic of the Red Sea to create a completely classified thematic map of the reef benthos. Full article

(This article belongs to the Special Issue Remote Sensing for Understanding Coral Reef Dynamics and Processes: Photo-Systems to Coral Reef Systems)

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1042 KiB

Open AccessArticle

Mapping Coral Reef Resilience Indicators Using Field and Remotely Sensed Data

by Anders Knudby, Stacy Jupiter, Chris Roelfsema, Mitchell Lyons and Stuart Phinn

Remote Sens. 2013, 5(3), 1311-1334; https://doi.org/10.3390/rs5031311 - 14 Mar 2013

Cited by 40 | Viewed by 12888

Abstract

In the face of increasing climate-related impacts on coral reefs, the integration of ecosystem resilience into marine conservation planning has become a priority. One strategy, including resilient areas in marine protected area (MPA) networks, relies on information on the spatial distribution of resilience. We assess the ability to model and map six indicators of coral reef resilience—stress-tolerant coral taxa, coral generic diversity, fish herbivore biomass, fish herbivore functional group richness, density of juvenile corals and the cover of live coral and crustose coralline algae. We use high spatial resolution satellite data to derive environmental predictors and use these in random forest models, with field observations, to predict resilience indicator values at unsampled locations. Predictions are compared with those obtained from universal kriging and from a baseline model. Prediction errors are estimated using cross-validation, and the ability to map each resilience indicator is quantified as the percentage reduction in prediction error compared to the baseline model. Results are most promising (percentage reduction = 18.3%) for mapping the cover of live coral and crustose coralline algae and least promising (percentage reduction = 0%) for coral diversity. Our study has demonstrated one approach to map indicators of coral reef resilience. In the context of MPA network planning, the potential to consider reef resilience in addition to habitat and feature representation in decision-support software now exists, allowing planners to integrate aspects of reef resilience in MPA network development. Full article

(This article belongs to the Special Issue Remote Sensing for Understanding Coral Reef Dynamics and Processes: Photo-Systems to Coral Reef Systems)

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1476 KiB

Open AccessArticle

Evolution of Coral Rubble Deposits on a Reef Platform as Detected by Remote Sensing

by Amelia M. Shannon, Hannah E. Power, Jody M. Webster and Ana Vila-Concejo

Remote Sens. 2013, 5(1), 1-18; https://doi.org/10.3390/rs5010001 - 21 Dec 2012

Cited by 25 | Viewed by 9028 | Correction

Abstract

An investigation into the evolution of coral rubble deposits on a coral reef platform is assessed using high-resolution remote sensing data and geospatial analysis. Digital change detection analysis techniques are applied to One Tree Reef in the southern Great Barrier Reef by analysing aerial photographs and satellite images captured between 1964 and 2009. Two main types of rubble deposits were identified: (1) rubble flats that are featureless mass accumulations of coral rubble; and, (2) rubble spits that are shore-normal linear features. While both deposits prograde in a lagoon-ward direction, rubble spits move faster (~2 m/yr) than rubble flats (~0.5 m/yr). The volume of rubble, the underlying substrate, the energy regime, and storm frequency control the rate of progradation. Rubble flat occurrence is restricted to the high-energy (windward) margin of the coral reef platform, while rubble spits are distributed reef wide, both in modal high energy and modal low energy regions of the reef. Rubble spit deposition is considered to be a result of enlarged spur and groove morphology of the forereef, whereby wave energy is focused through the enlarged groove formations causing the preferential deposition of coral rubble in particular zones of the adjacent reef flat. One last control is thought to be the elevation of the reef crest whereby lower areas are more prone to rubble flat development. A vertical and ocean-ward accumulation of rubble is occurring on the windward margin of the reef leading to a build-up and build-out of the reef, governing the expansion of the reef footprint. This study shows for the first time the evolution of a coral reef rubble flat and rubble spits over decadal time scales as detected through remotely sensed images spanning 45 years. Full article

(This article belongs to the Special Issue Remote Sensing for Understanding Coral Reef Dynamics and Processes: Photo-Systems to Coral Reef Systems)

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2040 KiB

Open AccessArticle

Satellite-Derived Photic Depth on the Great Barrier Reef: Spatio-Temporal Patterns of Water Clarity

by Scarla Weeks, P. Jeremy Werdell, Britta Schaffelke, Marites Canto, Zhongping Lee, John G. Wilding and Gene C. Feldman

Remote Sens. 2012, 4(12), 3781-3795; https://doi.org/10.3390/rs4123781 - 27 Nov 2012

Cited by 35 | Viewed by 9819

Abstract

Detecting changes to the transparency of the water column is critical for understanding the responses of marine organisms, such as corals, to light availability. Long-term patterns in water transparency determine geographical and depth distributions, while acute reductions cause short-term stress, potentially mortality and may increase the organisms’ vulnerability to other environmental stressors. Here, we investigated the optimal, operational algorithm for light attenuation through the water column across the scale of the Great Barrier Reef (GBR), Australia. We implemented and tested a quasi-analytical algorithm to determine the photic depth in GBR waters and matched regional Secchi depth (Z_SD) data to MODIS-Aqua (2002–2010) and SeaWiFS (1997–2010) satellite data. The results of the in situ Z_SD/satellite data matchup showed a simple bias offset between the in situ and satellite retrievals. Using a Type II linear regression of log-transformed satellite and in situ data, we estimated Z_SD and implemented the validated Z_SD algorithm to generate a decadal satellite time series (2002–2012) for the GBR. Water clarity varied significantly in space and time. Seasonal effects were distinct, with lower values during the austral summer, most likely due to river runoff and increased vertical mixing, and a decline in water clarity between 2008–2012, reflecting a prevailing La Niña weather pattern. The decline in water clarity was most pronounced in the inshore area, where a significant decrease in mean inner shelf Z_SD of 2.1 m (from 8.3 m to 6.2 m) occurred over the decade. Empirical Orthogonal Function Analysis determined the dominance of Mode 1 (51.3%), with the greatest variation in water clarity along the mid-shelf, reflecting the strong influence of oceanic intrusions on the spatio-temporal patterns of water clarity. The newly developed photic depth product has many potential applications for the GBR from water quality monitoring to analyses of ecosystem responses to changes in water clarity. Full article

(This article belongs to the Special Issue Remote Sensing for Understanding Coral Reef Dynamics and Processes: Photo-Systems to Coral Reef Systems)

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1278 KiB

Open AccessArticle

A Geospatial Appraisal of Ecological and Geomorphic Change on Diego Garcia Atoll, Chagos Islands (British Indian OceanTerritory)

by Sarah Hamylton and Holly East

Remote Sens. 2012, 4(11), 3444-3461; https://doi.org/10.3390/rs4113444 - 12 Nov 2012

Cited by 27 | Viewed by 12329

Abstract

This study compiled a wide range of modern and historic geospatial datasets to examine ecological and geomorphic change at Diego Garcia Atoll across a 38-year period (1967–2005). This remarkable collection of spatially referenced information offered an opportunity to advance our understanding of the nature and extent of environmental change that has taken place with the construction of the military airbase at Diego Garcia. Changes assessed included movements of the lagoon rim shorelines, changes in the terrestrial vegetation on the lagoon rim and amendments to the bathymetry of the lagoon basin through dredging activities. Data compiled included detailed shoreline and vegetation maps produced as part of the H.M.S. Vidal Indian Ocean Expedition (1967), three Ikonos satellite images acquired in 2005 that collectively covered the complete Atoll area, a ground truthing field dataset collected in the northern section of the lagoon for the purpose of seafloor mapping (2005), observational evidence of shoreline erosion including photographs and descriptions of seawater inundations and bathymetric soundings from five independent surveys of the lagoon floor (1967, 1985, 1987, 1988 and 1997). Results indicated that much of the change along the lagoon rim is associated with the expansion of the inner lagoon shoreline as a result of the construction of the military airbase, with an estimated increase in land area of 3.01 km² in this portion of the atoll rim. Comparisons of 69 rim width transects measured from 1967 and 2005 indicated that shorelines are both eroding (26 transects) and accreting (43 transects). Within a total vegetated area of 24 km², there was a notable transition from Cocos Woodland to Broadleaf Woodland for a land area of 5.6 km². From the hydrographic surveys, it was estimated that approximately 0.55 km³of carbonate sediment material has been removed from the northwest quadrant of the lagoon, particularly in the vicinity of the Main Passage. As no previous record of benthic character exists, a complete benthic habitat map of the atoll was derived through classification of the three IKONOS satellite images. Management implications arising from this overall appraisal of geomorphic and ecological change at Diego Garcia included the need for ongoing monitoring of shoreline change at a representative set of sites around the atoll rim, monitoring of the water flow regime through the northern channels between the open ocean and the lagoon basin and an ongoing mapping campaign to record periodic changes in the character of the benthic surface ecology. Full article

(This article belongs to the Special Issue Remote Sensing for Understanding Coral Reef Dynamics and Processes: Photo-Systems to Coral Reef Systems)

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613 KiB

Open AccessArticle

Coral Reef Surveillance: Infrared-Sensitive Video Surveillance Technology as a New Tool for Diurnal and Nocturnal Long-Term Field Observations

by Markus Dirnwoeber, Rudolf Machan and Juergen Herler

Remote Sens. 2012, 4(11), 3346-3362; https://doi.org/10.3390/rs4113346 - 31 Oct 2012

Cited by 9 | Viewed by 9217

Abstract

Direct field observations of fine-scaled biological processes and interactions of the benthic community of corals and associated reef organisms (e.g., feeding, reproduction, mutualistic or agonistic behavior, behavioral responses to changing abiotic factors) usually involve a disturbing intervention. Modern digital camcorders (without inflexible land-or ship-based cable connection) such as the GoPro camera enable undisturbed and unmanned, stationary close-up observations. Such observations, however, are also very time-limited (~3 h) and full 24 h-recordings throughout day and night, including nocturnal observations without artificial daylight illumination, are not possible. Herein we introduce the application of modern standard video surveillance technology with the main objective of providing a tool for monitoring coral reef or other sessile and mobile organisms for periods of 24 h and longer. This system includes nocturnal close-up observations with miniature infrared (IR)-sensitive cameras and separate high-power IR-LEDs. Integrating this easy-to-set up and portable remote-sensing equipment into coral reef research is expected to significantly advance our understanding of fine-scaled biotic processes on coral reefs. Rare events and long-lasting processes can easily be recorded, in situ-experiments can be monitored live on land, and nocturnal IR-observations reveal undisturbed behavior. The options and equipment choices in IR-sensitive surveillance technology are numerous and subject to a steadily increasing technical supply and quality at decreasing prices. Accompanied by short video examples, this report introduces a radio-transmission system for simultaneous recordings and real-time monitoring of multiple cameras with synchronized timestamps, and a surface-independent underwater-recording system. Full article

(This article belongs to the Special Issue Remote Sensing for Understanding Coral Reef Dynamics and Processes: Photo-Systems to Coral Reef Systems)

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