Marine Habitat Mapping Research Articles

Integrating indigenous ecological knowledge and multi-spectral image classification for marine habitat mapping in Oceania

This paper evaluates the usefulness of integrating indigenous ecological knowledge and remote sensing analyses to produce tropical marine habitat maps. Fishers from Roviana Lagoon, Solomon Islands, visually interpreted a Landsat-7 Enhanced Thematic Mapper (ETM+) multi-spectral satellite image to identify shallow-water marine environments. Their assessments were used to direct a supervised classification of the image and create habitat maps with indigenously defined habitat classes. Results show that these participatory remote sensing techniques produce accurate broad-scale marine habitat maps that can be useful to managers and decision makers. Participatory methods that draw from indigenous habitat definitions also have the potential benefit of generating new insights about socio-ecological processes and enhancing local acceptance and understanding of conservation projects by allowing stakeholders to actively contribute in management planning.

Thematic accuracy assessment of acoustic seabed data for shallow benthic habitat mapping

A single beam acoustic ground discrimination system (AGDS) was used to survey 1.25 km2 of shallow (< 20 m depth) seabed on the northeast coast of Tasmania, Australia. This paper investigates the uncertainties associated with the qualitative interpretation of real time and post‐processed acoustic signal, and the effect of track spacing on the mapping of rocky reef distribution. The survey was repeated with different track spacing (50 m, 100 m, 200 m and 50 × 200 m shore normal) to investigate the influence of data density and ‘knowledge based interpolation’ validated against direct measurements made with an underwater video camera. Habitat area calculations varied substantially only with the 50 × 200 m transect. These results have important implications for the qualitative assessment and application of AGDS technology in shallow water marine habitat mapping.

La situation des récifs coralliens des îles Éparses françaises de l’océan Indien

The status of the coral reefs of French Scattered Islands in the Indian Ocean. — Together with La Réunion and Mayotte Islands, Scattered Islands make up French Indian Ocean Territories (FIOT) which all possess highly ecologically sensitive natural habitats of major value for migrant species (turtles, seabirds, mammals). As a contribution to the national action plan of IFRECOR (French initiative on coral reefs) we set up during the period 2002-2005 a survey and monitoring program in order to increase the knowledge of the still poorly known coral reefs of these islands scattered from North to South in the Mozambique Channel and in central Indian Ocean. Results were particularly focused on the geomorphological mapping of shallow marine habitats and on a structural and functional approach of fish, coral and mollusc communities. Additional approaches with rapid assessment methods remained non exhaustive but nevertheless allow a first integrated diagnosis of the patrimonial value of the coral sanctuaries of Scattered Islands and to propose decision-making tools for identifying applied and fundamental axes of research as well as actions of monitoring adapted particularly to vulnerability factors and global warming.

Acquisition of Through-water Aerial Survey Images

The behavior of light at the air/water interface has substantial effects on the quality of vertical, or nadir-looking imagery used to interpret subsurface features for purposes such as marine habitat mapping. Reflection of the direct solar beam into the sensor by waves on the surface of the water creates bright glints, which obscure bottom features of interest. Sun angle, refraction, and reflection of the direct solar beam affect the amount of subsurface illumination and shadowing of bottom features. Simple interpretations of these sea surface effects are made with sufficient accuracy to improve planning for airborne, vertical image capture, particularly aerial photography or video imagery. The time available for image capture over shallow water is typically limited to a short period in the morning. The start time is controlled by subsurface illumination levels, which are determined by sun angle and locally variable factors, such as light attenuation by the water column, rather than surface reflection or subsurface shadowing. The end time is determined by sun glitter effects, which in this case study, are predictable from sun angle, camera field of view, and wind speed with an R 2 value of 0.9554.

Recent Advances in Automated Genus-specific Marine Habitat Mapping Enabled by High-resolution Multibeam Bathymetry

There is a great need for accurate, comprehensive maps of seafloor habitat for use in fish stock assessments, marine protected area design, and other resource management pursuits. Recent advances in acoustic remote sensing technology have made it possible to obtain high-resolution (meter to sub-meter) digital elevation models (DEMs) of seafloor bathymetry that can rival or surpass those available for the terrestrial environment. The acquisition and processing of these data are expensive, however, requiring specialized equipment, expertise, and large amounts of both field and laboratory effort per unit area mapped. Further, the interpretation and classification of these data into maps of habitat type is typically (and appropriately) performed only by trained experts that are familiar with both seafloor geomorphology and the nature and limitations of the data sources. Because it is done visually, this interpretation can be very time-consuming and may yield subjective results that are not comparable from site-to-site or between individual interpreters.We applied an algorithmic terrain analysis approach to efficiently and objectively classify seafloor habitats using the quantifiable landscape metric Topographic Position Index (TPI). We used high-resolution multibeam bathymetry, together with precisely geolocated (± 5 m) ROV observations of fish distribution, to produce a preliminary genus-specific habitat suitability model for eight rockfish (Sebastes) species in the Del Monte shale beds of Monterey Bay, California. A high-resolution (2 m) multibeam bathymetry Digital Elevation Model (DEM) was generated and used to produce a derived TPI surface model using repeatable, algorithmic methods. This data layer, together with the positions and counts by species from 229 rockfish observations (2892 total fish) was then used to create preliminary predictive models of habitat suitability and fish distribution, as well as stock estimates for the study area. A second, independent fish observation data set was used to validate the models.

Testing the utility of abiotic surrogates for marine habitat mapping at scales relevant to management

Habitat mapping at the scale at which marine protected areas are designed and managed is essential for assessment of, and design for, representation. Most habitat mapping studies rely solely or in part on abiotic surrogates for patterns of biodiversity. The utility of abiotic variables in predicting biological distributions at the local scale (10 s of km) was tested in a remote video survey of macrobenthos in Moreton Bay, Australia. Habitat classifications of the same set of 41 sites based on 6 abiotic variables and abundances of 89 taxa and bioturbation indicators were compared using correlation, regression and ordination analyses. The concepts of false homogeneity (abiotically similar but biologically distinct) and false heterogeneity (abiotically distinct but biologically similar) were defined to describe types of errors associated with using abiotic surrogates to construct habitat maps, and quantified using two separate methods. Overall, the best prediction by abiotic surrogates explained less than 30% of the pattern of biological similarity. Errors of false homogeneity were between 20% and 62%, depending on the methods of estimation. Predictive capability of abiotic surrogates at the taxon level was poor, with only 6% of taxon/surrogate correlations significant. Abiotic variables did not discriminate sufficiently between different soft bottom communities to be a reliable basis for mapping. These results have implications for the widespread use of abiotic surrogates in marine habitat mapping to plan for, or assess, representation in marine protected areas. Little confidence can be placed in marine habitat classifications based solely or largely on abiotic surrogates without calibration by rigorous biological surveys at the appropriate scale. Therefore, it is questionable whether marine protected areas designed on this basis can have measurable benefits for conservation.

Mapping marine environments with IKONOS imagery: enhanced spatial resolution can deliver greater thematic accuracy

The IKONOS 2 satellite was launched in late 1999 and carries the first commercial multispectral instrument to achieve 4 m spatial resolution. The cost and accuracy of using IKONOS imagery to map shallow-water marine environments is evaluated and compared directly to that using a suite of satellite and airborne instruments including Landsat Multispectral Scanner (MSS) and Thematic Mapper (TM), Satellite Pour l'Observation de la Terre (SPOT) High-Resolution Visible (HRV) multispectral and panchromatic, and Compact Airborne Spectrographic Imager (CASI). Evaluations were conducted in the Turks and Caicos Islands which are ideally suited to aquatic remote sensing because of the large areas of clear, shallow water containing a range of different habitats. Over 600 field sites were surveyed and used to define habitat categories, supervise image classification, and make an independent assessment of thematic map accuracy. For the high-resolution IKONOS imagery, pixel sizes were small enough to allow within-habitat textural information to be added to the classification. Making full use of this textural information in supervised classifications significantly improved ( P<.01) thematic map accuracy for fine-level habitat discrimination (13 classes). Although significantly ( P<.001) and almost 20% more accurate than Landsat TM, like other satellite-borne sensors, IKONOS data were unable adequately to discriminate 13 categories of coral, algal, and seagrass habitats (overall accuracy 50%). Comparison with CASI in a restricted area where only nine of these habitats were represented indicated that CASI (81% user accuracy) was significantly ( P<.01) more accurate than IKONOS (64% user accuracy). Comparisons of IKONOS, Landsat TM, and CASI along a transect in the maximally penetrating blue part of the spectrum suggest that the poor descriptive resolution of satellite sensors is partly due to loss of radiance contrast, presumably as a result of atmospheric Rayleigh scattering. Problems of scattering, coupled with the relatively poor spectral resolution of satellite sensors such as IKONOS, currently constrain their use for fine-level marine habitat mapping. IKONOS data enabled significantly more accurate mapping at a geomorphological scale (e.g., coral vs. seagrass) than other satellite sensors except Landsat TM. While reasonably high accuracies (75%) were obtained for such coarse-level habitat mapping, Landsat TM was more cost-effective than IKONOS, even for small (50 km 2) areas. IKONOS may only be a cost-effective option if (i) independent field data are available to identify habitat patches, (ii) the area to be mapped is fairly small (<500 km 2), and (iii) small-scale (<10 m) habitat dynamics are to be monitored. IKONOS data are unlikely to identify deterioration in coral reefs directly because changes in community structure cannot be resolved spectrally from the satellite.

Technologies and their influence on future UK marine resource development and management

This paper attempts to predict changes and trends in future UK marine resource development and management. It does this by asserting that our presumptions about marine resources and the way in which they should be used are changing. Some emerging presumptions may not only preclude the use of existing technologies in some cases (e.g. dumping at sea), but may also act as drivers to the development of new technologies, such as offshore wave and wind power generation devices. A variety of maritime industries exploiting both living and non-living resources are examined individually. Attention is paid to marine conservation and the technologies that are important to providing generally for the protection of the marine environment. The authors conclude that major drivers will be ones for cleaner seas, for the development of renewable marine energy sources, and for the innovative management of the consequences of sea-level rise. With regard to the exploitation of living resources the finite limits to fisheries are stressed, and the present importance of industrial fishmeal supplies for salmon farming are highlighted. One of the greatest potential technological advances is predicted to be in marine habitat mapping. Given the changes in presumptions about our use of the seas, one over-riding conclusion is that the sustainable development of marine resources, and the conservation of priority habitats and species (for both the local seas and global oceans), must involve sustainable mechanisms for conflict resolution and decision-making.

The application of satellite remote sensing to coastal management in Singapore.

This paper reviews the application of satellite remote sensing to management of Singapore's coastal environment. Remotely sensed data have been used for marine habitat mapping, water quality monitoring, ship and ship-wake detection, oil spill detection, red tide monitoring, and mapping of reclamation activities. While these applications clearly cover most of the range of opportunities for use of remotely sensed data in the coastal zone, there is still a need for more complete baseline studies of natural resources and habitats, and monitoring of the impacts of development on the coastal and marine environment. There is also a requirement for more management-oriented research and continued development and revision of the available datasets. Integration and exchange of information between management agencies and research groups is also an important aspect of sustainable management of Singapore's coastal environment and marine resources.

A review of remote sensing for the assessment and management of tropical coastal resources

This article reviews applications of remote sensing to the assessment of tropical coastal resources. These applications are discussed in the context of specific management objectives and sensors used. Remote sensing remains the only way to obtain synoptic data for large coastal areas uniformly in time and space, repeatedly and nonintrusively. Routine applications to tropical coastal management include the mapping of littoral and shallow marine habitats, change detection, bathymetry mapping, and the study of suspended sediment plumes and coastal currents. The case studies reviewed suggest that wider use of remote sensing in tropical coastal zone management is limited by (1) factors that affect data availability, such as cloud cover and sensor specification; and (2) the problems that decision makers face in selecting a remote sensing technique suitable to their project objectives. These problems arise from the difficulty in comparing the capabilities of different sensors and the limited amount of published ...

Habitat mapping in the Caribbean for management and conservation: Use and assessment of aerial photography

Abstract The nature and distribution of the coastal and shallow marine habitats of Anguilla in the Caribbean were examined using aerial photography coupled with extensive ground truth information. The objective was to develop an accurate method of marine habitat mapping for the analysis of the marine ecosystem in order to develop a procedure for marine and coastal resource management. This paper describes the method which was adopted as well as the biological results. It is concluded that the management and sustainable use of the natural resources may be improved as a result of accurate habitat mapping.