Why map benthic habitats?

CHAPTER 1

Why map benthic habitats? Peter T. Harris1 and Elaine K. Baker2 1

UNEP/GRID-Arendal, Arendal, Norway 2UNEP/GRID-Arendal, School of Geoscience, University of Sydney, Sydney, NSW, Australia

Abstract This introductory chapter provides an overview of the book’s contents and definitions of key concepts including benthic habitat, potential habitat, and seafloor geomorphology. The chapter concludes with a summary of commonly used habitat mapping technologies. Benthic (seafloor) habitats are physically distinct areas of seabed that are associated with particular species, communities, or assemblages that consistently occur together. Benthic habitat maps are spatial representations of physically distinct areas of seabed that are associated with particular groups of plants and animals. Habitat maps can illustrate the nature, distribution, and extent of distinct physical environments present and importantly they can predict the distribution of the associated species and communities. The data sets collected for constructing habitat maps provide fundamental information that can be used for a range of management and industry applications, including the management of fisheries, spatial marine environmental management, design of marine reserves, supporting offshore oil and gas infrastructure development, port and shipping channel construction, maintenance dredging, tourism, and seabed aggregate mining. Seafloor habitat mapping provides fundamental baseline information for decision-makers working in these sectors. GeoHab (www.geohab.org) is an international association of marine scientists conducting research using a range of mapping technologies into the use of biophysical (i.e., geologic and oceanographic) indicators of benthic habitats and ecosystems as proxies for biological communities and species diversity. Using this approach, combinations of physical attributes of the seabed identify habitats that have been demonstrated to be effective as surrogates for the benthic communities that they typically support. Thus management priorities can be identified using seabed habitat maps as a guide. The work of GeoHab demonstrates how knowledge of seabed properties can be employed to guide marine environmental management, marine resource management, and conservation efforts. Seafloor geomorphology is one of the more useful of the physical attributes of the seabed mapped and measured by GeoHab scientists. Different geomorphic features (e.g., submarine canyons, seamounts, atolls, fjords, etc.) are commonly associated with particular suites of habitats. Knowledge of the geomorphology and biogeography of the seafloor has improved markedly over the past 15 years. Using multibeam sonar, submarine features such as fjords, sand banks, coral reefs, seamounts, canyons, and spreading ridges have been revealed in unprecedented detail. The case studies presented in this book represent a range of seabed geomorphic features where detailed bathymetric maps have been combined with seabed video and sampling to yield an integrated picture of the benthic communities that are associated with different types of benthic habitat.

Seafloor Geomorphology as Benthic Habitat. DOI: https://doi.org/10.1016/B978-0-12-814960-7.00001-4 © 2020 Elsevier Inc. All rights reserved.

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Chapter 1 Keywords: Benthic habitat; potential habitat; seafloor geomorphology; biogeography; benthic communities

Habitat is the property that inherently integrates many ecosystem features, including higher and lower trophic level species, water quality, oceanographic conditions and many types of anthropogenic pressures. Thus, strengthening assessments of status and trends in habitat quality and extent will be an important priority in the development of a global marine assessment. Assessment of Assessments Report, UNEP and IOC-UNESCO (2009)

General outline of the content of this book This book provides a synthesis of seabed geomorphology and benthic habitats based on the most recent, up-to-date information contained in 53 case studies. Part I (Chapters 1 6) of the book provides an introduction in which the drivers that underpin the need for benthic habitat maps are examined, including threats to benthic habitats. The habitat mapping approach and classification schemes, based on principles of biogeography and benthic ecology, are reviewed and the use of biophysical surrogates for habitats and benthic biodiversity are surveyed. Part I ends with a brief summary of seafloor geomorphology and geomorphic features that are the subject of the case studies. The case studies are crossreferenced throughout Part I, to provide the reader with a broad overview and context for the detailed information they contain. Part II (Chapters 7 59) of this book includes 53 separate case studies representing a diverse range of geomorphic features and their associated habitats from the coast to the abyss around the world (Fig. 1.1). The spatial content of the case studies, combined with the review of information provided in Part I, warrants the description of this book as an “Atlas” in the sense that it comprises a collection of maps that represent a range of different geomorphic features and habitats. Spatial mapping is one of the most important tools used by GeoHab scientists to convey information and demonstrate relationships among different variables. To be accepted, case studies had to conform to a template. Case studies are required to contain both geomorphic and biologic data, provide a clear description of at least one geomorphic feature type, describe the oceanographic setting, and provide an assessment of the naturalness (state and trend) of the environment. The spatial comparison of biological data with spatial physical data is a key element of every case study and authors were given the opportunity to describe surrogacy relationships and the methods used to identify and quantify them. A glossary is included with this book to provide definitions of key terms used in habitat mapping, description, and classification.

Why map benthic habitats? 5

Figure 1.1 Distribution of 57 case studies presented in Part II of this book. Chapter numbers are indicated for each case study.

Part III (Chapter 60) provides a synthesis of the content of the case studies and is partly based on responses to a questionnaire that was completed by case study authors; responses to the questionnaire are also considered in the introductory chapters (Part I). The synthesis (Part III) includes headings such as attributes of the case study areas (depth range, naturalness, geomorphic feature types), surrogates and classification systems used, the socioeconomic aspects underpinning habitat mapping (main clients for habitat maps and funding sources), gap analysis (i.e., geographic areas, geomorphic features, and environmental variables not included in the case studies), and finally what constitutes best practices for habitat mapping.

What are the main purposes of habitat mapping? When asked this question the case study authors nominated a number of purposes for mapping benthic habitats (Table 1.1), but among these four stand out as being preeminent:

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Chapter 1 Table 1.1: List of different purposes of habitat mapping in relation to case studies included in this volume (purpose nominated by case study authors).

Purpose of study Spatial marine planning and management (n 5 28) MPA design (n 5 18) Resource assessment (n 5 16) Fisheries reserve design and management (n 5 10) Scientific research and knowledge (n 5 7) Monitoring MPAs and environments (n 5 3) Exploration (n 5 2) Hazard assessment (n 5 2) Method development (n 5 1) Oil spill monitoring (n 5 1) Geological mapping (n 5 1) Coral reef detection by satellite (n 5 1) Site selection for aquaculture and wave energy (n 5 1) Guideline for seafloor mapping (n 5 1) Tectonic characterization (n 5 1)

Chapter numbers 7, 8, 9, 10, 11, 17, 18, 19, 20, 21, 22, 23, 27, 28, 33, 34, 36, 37, 38, 39, 40, 41, 46, 48, 49, 53, 56, 59 8, 11, 14, 17, 18, 21, 22, 24, 25, 27, 32, 37, 43, 44, 45, 48, 49, 52 7, 8, 16, 26, 27, 29, 32, 35, 39, 43, 46, 47, 48, 49, 51, 58 8, 14, 22, 26, 27, 29, 32, 36, 37, 43 12, 22, 25, 31, 37, 42, 59 36, 41, 48 55, 57 50, 54 36 35 13 31 46 25 55

Many authors nominated more than one purpose for their study. See Fig. 1.1 for location of case studies.

(1) to support government spatial marine planning, management, and decision-making; (2) to support and underpin the design of marine protected areas (MPAs); (3) to conduct scientific research programs aimed at generating knowledge of benthic ecosystems and seafloor geology; and (4) to conduct living and nonliving seabed resource assessments for economic and management purposes, including the design of fishing reserves. An important point is that many authors nominated more than one purpose for their case study (Table 1.1). This highlights another particular benefit of habitat mapping: the data collected to manage one sector can be applied to others, since most of the information required about habitats is essentially the same for all applications. The goal to “map once— use many ways” underpins and justifies most government-funded seafloor mapping programs as well as the creation of national and regional databases and information systems containing essential marine environmental data.

What are benthic habitats? A habitat (which is Latin for “it inhabits”) is an ecological or environmental area that is inhabited by a particular species of animal, plant, or other type of organism. Benthic habitats are physically distinct areas of seabed that are associated with the occurrence of a particular species. More broadly, habitats are often utilized by communities or assemblages

Why map benthic habitats? 7 that consistently occur together (e.g., shallow, wave-influenced rocky seabed, kelps, mollusks, and fish occur in a kelp forest habitat; Connor et al., 2004). The collective term biotope is commonly used with reference to both the abiotic and biotic elements (physical habitats and their associated biota). The benthic habitat includes the natural environment in which an organism or community lives, or the physical environment that surrounds (influences and is utilized by) a species or community. The classification of habitats may be structured in a hierarchy to reflect degrees of similarity (e.g., biotopes, biotope complexes, broad habitats). Seascapes (the marine version of “landscapes”) comprise suites of habitats that consistently occur together. Chapter 4, Biogeography, benthic ecology, and habitat classification schemes, of this book contains more detailed descriptions of the fundamental concepts of biogeography and habitat classifications arising throughout this book.

Potential habitat mapping In order to truly understand the spatial relationships between the occurrence of organisms and their preferred habitats, information should be collected about both. However, the available mapping technologies generally reveal only the physical aspects of the marine environment and, at broad spatial scales, they do not provide much information about the occurrence of individual organisms. In other words, our ability to map the physical spaces that organisms might utilize far exceeds our ability to measure the extent to which those spaces are actually occupied. Mapping the physical habitats is commonly known as the “potential habitat mapping” approach (Greene et al., 2007). The data contained in the Ocean Biogeographic Information System (Fig. 1.2) makes a clear point. Although the database is already extensive and contains over 30 million records, there are still large gaps in the registration of species and we will never possess perfect knowledge of the existence of species or of their spatial distribution. It is impossible to map the ocean’s true species biodiversity. However, using potential habitat maps based on relationships that have been tested in different settings, we can at least estimate biodiversity and make predictions about its spatial distribution. The underlying tenet of potential habitat mapping is that mapping the spatial distribution of habitats provides a means of estimating the occurrence of biota which commonly utilize that habitat type (Greene et al., 2007). From the perspective of management and conservation, if the potential habitats are protected then the biodiversity associated with those habitats will also be protected (at least to some extent). Furthermore, it follows that an area that supports a high diversity of habitats (high habitat heterogeneity) can be expected to support a greater biodiversity than an area which contains only a few (or one)

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Figure 1.2 Map showing the nearly 30 million Ocean Biogeographic Information System (OBIS) records of 120,000 species. Colors represent data collected prior to the Census of Marine Life (in blue) and data collected during the program (yellow and red). This database provides global coverage with an average of one data point per every 12 km2. The map also illustrates the broad areas of seafloor where no samples have been collected (Ausubel et al., 2010).

habitat types; this is the so-called habitat heterogeneity hypothesis and it is a cornerstone of ecological theory (Tews et al., 2004). Habitats are a shorthand way of describing and integrating other biophysical and ecosystem information. To nominate tropical coral reef habitat, temperate kelp forest habitat or abyssal seamount habitat (e.g.,) immediately specifies particular associated biota plus the accompanying environmental attributes. It follows that there is a clear role for using environmental attributes that we can map and which exert control over biodiversity. In other words, we study and map habitats and other surrogates for biodiversity and use these to design our marine environmental management measures. The objective for marine scientists tasked with conserving biodiversity is therefore to identify and make use of measurable attributes or indicators of biodiversity (e.g., Levinton, 2001). Understanding the different measurable environmental parameters that exert control over marine biodiversity underlies much of the content of this book.

Geomorphology and habitats Among the physical attributes mapped and measured in detail in recent times using multibeam sonar equipment is the geomorphology of the seafloor. Temperate rocky reefs on

Why map benthic habitats? 9 the continental shelf, seamounts, submarine canyons, rocky ridges, pinnacles, ledges, escarpments, and muddy basins; these are examples of different geomorphic features that might each be expected to be associated with particular types of benthic habitat. The organization of this book (in terms of geomorphic features) is designed to advance our understanding of the different habitats associated with particular geomorphic features, and to allow examples to be compared and contrasted between different regions of the earth. It might also be argued that the diversity of seabed geomorphic features has an intrinsic value of its own. The natural diversity of geological features has been termed geodiversity by some scientists, and the conservation of such diversity can be included as a criterion in making management decisions (Gray, 2004). This concept is not unfamiliar to conservationists, because many iconic terrestrial parks are defined on the basis of a prominent physical feature (e.g., the Grand Canyon and Mount Rainier in the United States or Uluru in Australia) and similarly some MPAs are defined by the presence of a particular reef, island, or rocky promontory. However, biological aspects of habitats are emphasized by most government agencies and nature conservation organizations and in many cases there is little if any acknowledgment of the geological aspects of habitats (Gray, 2004).

Habitat mapping technologies and approaches The case studies in this book present examples of habitat maps that have been produced using a range of technologies, including satellite, airborne, and remotely operated drones. Multibeam swath sonar, sidescan sonar, ship-deployed remotely operated vehicles (ROVs), ship-deployed underwater cameras and videos, autonomous underwater vehicles (AUV), manned submersibles, and direct sampling of the seafloor are also commonly employed technologies (Table 1.2). A key point is that habitat mapping surveys will use several complementary technologies to map and sample the environment; determining the optimal combination of technologies to be deployed on a survey is a challenging task for habitat mapping scientists. The different systems have different applications for mapping different habitats at different spatial scales and the terminology may be confusing for some readers, which is why they are briefly reviewed here. In essence, seabed mapping technologies can be divided into four broad groups: (1) acoustic, sonar technology; (2) remote sensing based on natural or transmitted light; (3) underwater photography and video; and (4) direct sampling of sediment and biota.

Sonar systems Measuring the water depth using acoustic (sonar) technology is based upon measuring the time taken for sound waves to travel between the vessel and the seafloor and back again. Transducers are the devices used to transmit and receive sound pulses from a vessel. The

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Chapter 1

Table 1.2: List of seafloor mapping technologies used in the case studies presented in this book, in relation to mapping effort (area mapped per hour), typical data resolution, and remarks about applications (based partly on Kenny et al., 2003).

Technology

Mapping effort (km2/h)

Resolution (m) 10

Satellite remote sensing

Aircraft or drone remote sensing (LIDAR, hyperspectral, CASI, etc.) 12 , 30 kHz Multibeam sonar

Examples case study chapters (this volume)

3

21

1

3

3

7, 8, 11, 15, 20, 22, 31, 34, 35

.10

3

3

3

7, 8, 28

.100

3

3

10

22, 57, 58

30 100 kHz Multibeam sonar

B30

.200 kHz Multibeam sonar

B2

3

3

9, 14, 15 16, 18, 21, 23, 24, 49

Sidescan sonar (B100 300 kHz) Single-beam echo sounder

B3

3

3

24, 25, 30, 39, 42 34, 35

B1

3

10

3

3

3

Remarks

23

10

3

10

22

3

.1000

10

2

13, 14, 16, 22, 29, 49

Restricted to operational coverage, mainly shallow seas ,10 m Generally restricted to depths ,30 m

Backscatter plus depth data, low mapping effort trade-off with lower resolution, expensive system Backscatter plus depth data, intermediate mapping effort and resolution Backscatter plus depth data, greater mapping effort required but finer resolution data collected. Moderate cost for (semiportable) system. Backscatter data only, inexpensive Can use seabed classification software (QTC, Roxann, etc.), inexpensive (Continued)

Why map benthic habitats? 11 Table 1.2: (Continued)

Technology

Mapping effort (km2/h)

Resolution (m) 10

Subbottom profiler, shallow seismic profiler

B1

Towed video, ROV, and other ship-deployed underwater cameras Autonomous underwater vehicles (AUV)

0.001

Manned submersible

Grab and core samples

Examples case study chapters (this volume)

3

3

2

10

10

1

21

10

22

10

10

3

15, 17, 25, 40, 49, 50, 54 3

19, 37, 38, 39, 46, 53, 58, 59

0.001

3

3

3

18, 28

0.0001

3

3

3

37, 54, 57

,1 3 1026

3

Remarks

23

3

10, 14, 15, 16, 21, 24, 25, 27, 32, 33, 34, 35, 39, 41, 42, 43, 46, 50, 51, 52, 54, 58

Able to quantify thickness of unconsolidated sediments Megabenthos and geological feature identification

Able to replicate exact survey line for habitat monitoring ID and limited sampling of benthos and geology, expensive Quantitative data on fauna and sediments

Note that most case studies employed multiple technologies; 35 studies used multibeam sonar at some frequency and 43 specified that some form of vessel-deployed camera or video system was used. Examples of technology listed here featured as a unique and major part of the case study.

most advanced technology is called “multibeam sonar” that uses multiple ( . 100) sound beams to map the depth of water in a swath of the seabed across the track of the ship (Fig. 1.3), in contrast to a single-beam sonar which only maps a single row of points located directly below the ship. Modern multibeam systems are coupled with the Global Positioning System (GPS) to create accurate bathymetric maps (seabed topographic maps) that are presented in many of the case studies in this book. Different frequencies (measured in kilohertz; kHz) are used to map different water depths: higher frequencies ( . 100 kHz) are used in water depths of 10 100 m, frequencies of less than around 30 kHz are used in water depths 100 2000 m, and a frequency of around 12 kHz is used to map the abyssal depths of the ocean. Lower frequency (,30 kHz) systems utilize large (expensive) arrays of transducers that must be mounted on the hull of a ship, whereas higher frequency

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Figure 1.3 Multibeam sonar is used to map the depth of water in a swath across the ship’s track, allowing a map of the seafloor to be constructed. Source: Used with permission from the New Zealand Institute of Water and Atmospheric Sciences.

( . 100 kHz) systems are smaller in size and can be deployed from smaller research vessels (often as portable systems). For different frequencies there is also a trade-off between area mapped and resolution: higher frequency, shallow water systems provide finer spatial resolution than lower frequency, deepwater systems, whereas lower frequency systems map larger areas of seabed in a single sweep of seafloor mapping compared with higher frequency systems (Table 1.2). When the sound pulses bounce off the seafloor, the strength of the echo depends on the roughness and hardness of the seafloor; rougher and/or harder surfaces produce a stronger echo. Because of this, the strength of the sonar reflection (the backscatter) provides information on the seafloor topography and the presence of rock or sediment on the bottom. An older technology employing transducers located in a “fish” towed behind the survey vessel is known as sidescan sonar and it collects only acoustic backscatter data. Sidescan sonars are still used mainly because the technology is easy to deploy from small vessels and is less expensive than multibeam sonar. The resolution of towed sidescan sonar systems can

Why map benthic habitats? 13 exceed that of multibeam systems, but the exact location of the towfish behind the vessel is difficult to measure. This means that the data cannot easily be accurately located, which introduces errors when the backscatter data are combined with existing bathymetric data. A significant advantage of multibeam sonar is that it generates both accurate (georeferenced) water depth and backscatter data simultaneously. Continuous seismic reflection profiling (“seismic profiling”) is another acoustic method used in some case studies (Table 1.2). This method is based on a sound source which generates acoustic pulses generally of a low frequency (usually ,3 4 kHz, depending on the source) and having much higher energy compared with conventional echo sounders. Some of the energy from a seismic acoustic pulse is reflected from the seafloor directly back to the ship (as in an echo sounder), but part of the energy is able to penetrate into the seabed and reflect back off different rock layers beneath the seafloor. In this way a single vertical profile, showing the thicknesses of different rock and sediment layers, is created as the vessel traverses an area. Large (more powerful) seismic systems commonly use a separate sound source in which the sound pulses are generated by high-pressure “air guns” or electric “sparkers” or “boomers,” and the return signal is received by a second towed array of receivers (contained in a “seismic eel”). Smaller, less powerful subbottom profiler systems (basically large echo sounders) have transducers that send and receive the acoustic pulse from a single unit. Most modern research vessels have such subbottom profilers built in. Smaller portable systems can be towed behind, or deployed over the side of, smaller research vessels.

Remote sensing based on natural or transmitted light Remotely sensed images of the shallow marine environment can be collected from satellites or aircraft to generate snapshots and time series of chlorophyll, ocean temperature (McClain, 2009), wave climate (Hemer et al., 2009), and a number of other properties (Dankers et al., 2011). Satellite passive sensors rely on natural solar radiation reflected from the surface of the earth. Systems deployed from aircraft can use natural light but also use active radar sensors or laser sources to create images and gather information. Light imaging, detection, and ranging (LIDAR) technology utilizes the reflective and transmissive properties of water and the seafloor to measure water depth using a laser, usually deployed from an aircraft. When an airborne laser beam is aimed vertically at the sea surface, the infrared is reflected while the blue-green light is transmitted through the water column. The blue-green light reflects off the seafloor (in shallow water) and water depth is calculated from the time difference between the surface and bottom returns. LIDAR systems are useful for mapping shallow water areas, to a maximum depth of around 30 m (depending on the clarity of the water).

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Underwater cameras In order to map the occurrence of plants and animals on the seafloor, scientists collect underwater images using still and video cameras. Video data can be overlain on acoustic data, such as multibeam bathymetry and backscatter, to examine the relationships between seafloor depth, shape, composition, and plant and animal distributions. Directly observing the seafloor geology, plants, and animals not only allows for rapid characterization (Anderson et al., 2007) but it also provides the foundation to monitor future changes. Cameras can be lowered on a wire to the seabed, towed behind the vessel on a sled, deployed from submersibles, or mounted in ROVs and AUVs. In most ship-deployed systems the digital camera images are sent via a cable to a recorder and TV screen on the ship, allowing biota and habitats to be viewed and assessed in real time (Anderson et al., 2007). Multiple passes over an object on the seafloor (or viewed from multiple camera lenses mounted on an underwater vehicle) can be used to create digital 3D models of the object for study and analysis (see Chapter 13: Seabed habitats of the Bay of Fundy, Atlantic Canada, for example). Another use of cameras is to mount them with some kind of bait in the field of view to obtain insights into the mobile animals that inhabit a particular location that come to feed on the food provided (see Chapter 28: Temperate rocky reef on the southeast Australian continental shelf, Chapter 37: Substrate mapping to inform ecosystem science and marine spatial planning around the Main Hawaiian Islands, and Chapter 59: Geomorphology and benthic habitats of the Kermadec Trench, SW Pacific Ocean).

Seafloor sampling In order to build our understanding of habitats, all imagery and mapping data must be correlated with samples obtained from the seabed. In particular, sediment properties (grain size, mineralogy, etc.) and the taxonomy of most species can only be accurately determined from physical samples. To lower on a wire some device to the seafloor in order to obtain a sediment sample or biological specimen involves technologies that have been developed since the Challenger expedition in 1872 76, and there are literally hundreds of different kinds of seafloor sampling devices in existence. Different devices have been used in many of the case studies presented in this book. Some good textbooks describing different marine geological and biological sampling methods and techniques are Seibold and Berger (1996), Ericson (2003), and Levinton (2001). A drawback of these older seabed sampling technologies is that the samples are collected from random locations on the seabed—the spatial context of the biological specimen returned is poorly constrained. Using modern satellite navigation systems coupled with acoustic telemetry the location of sampling devices can now be accurately calculated, but even this technology has its limitations in depths of more than a few hundred meters. One alternative is to use manned submersibles or ROVs, which allow scientists to collect

Why map benthic habitats? 15 samples using a robotic arm, with the advantage that the samples are collected from known locations and in the context of the surrounding environment that can be imaged and measured at the same time as the samples are collected (see Chapter 37: Substrate mapping to inform ecosystem science and marine spatial planning around the Main Hawaiian Islands, or Chapter 54: Chemosynthetic seep communities triggered by seabed slumping off of northern Papua New Guinea, for example). The trade-off is that manned submersibles are expensive to build and operate and they can cover only small areas of seabed during each deployment (Table 1.2).

Acknowledgments This chapter is updated from the version published in the 2012 volume with minor additions to references and text as needed. The authors acknowledge the financial assistance of UN Environment/GRID-Arendal.

References Anderson, T.J., Chochrane, G.R., Roberts, D.A., Chezar, H., Hatcher, G., 2007. A rapid method to characterise seabed habitats and associated macro-organisms. In: Greene, G., Todd, B.J. (Eds.), Mapping the Seafloor for Habitat Characterisation. Geological Association of Canada, pp. 75 83. Ausubel, J.H., Crist, D.T., Waggoner, P.E. (Eds.), 2010. First Census of Marine Life 2010: Highlights of a Decade of Discovery. Census of Marine Life, Washington, DC. Available from: http://www.coml.org/. Connor, D.W., Allen, J.H., Golding, N., Howell, K.L., Lieberknecht, L.M., Northen, K.O., et al., 2004. Marine Habitat Classification for Britain and Ireland Version 04.05. Joint Nature Conservation Committee, Peterborough. Dankers, N., van Duin, W., Baptist, M., Dijkman, E., Cremer, J., 2011. Ch. 11: The Wadden Sea in the Netherlands: ecotopes in a World Heritage barrier island system. In: Harris, P.T., Baker, E.K. (Eds.), Seafloor Geomorphology as Benthic Habitat: GeoHab Atlas of Seafloor Geomorphic Features and Benthic Habitats. Elsevier, Amsterdam. Ericson, J., 2003. Marine Geology: Exploring the New Frontiers of the Ocean. Facts on File, New York. Gray, M., 2004. Geodiversity - Valuing and Conserving Abiotic Nature. John Wiley & Sons, Chichester. Greene, H.G., Bizzarro, J.J., O’Connell, V.M., Brylinsky, C.K., 2007. Construction of digital potential benthic habitat maps using a coded classification scheme and its application. In: Todd, B.J., Greene, H.G. (Eds.), Mapping the Seafloor for Habitat Characterisation. Geological Association of Canada Special Paper 47, St. Johns, Newfoundland, pp. 141 156. Hemer, M.A., Church, J.A., Hunter, J.R., 2009. Variability and trends in the directional wave climate of the Southern Hemisphere. Int. J. Climatol. 30, 475 491. IOC-UNESCO, 2009. An assessment of assessments, findings of the group of experts. Start-Up Phase of a Regular Process for Global Reporting and Assessment of the State of the Marine Environment, Including Socio-economic Aspects. United Nations, UNEP and IOC-UNESCO, Valetta, Malta, p. 208. Kenny, A.J., Cato, I., Desprez, M., Fader, G., Schu¨ttenhelm, R.T.E., Side, J., 2003. An overview of seabedmapping technologies in the context of marine habitat classification. ICES J. Marine Sci. 60, 411 418. Levinton, J.S., 2001. Marine Biology: Function, Biodiversity, Ecology. Oxford University Press, New York. McClain, C.R., 2009. A decade of satellite ocean color observations. Ann. Rev. Mar. Sci. 1, 19 42. Seibold, E., Berger, W.H., 1996. The Sea Floor: An Introduction to Marine Geology. Springer-Verlag, Berlin. Tews, J., Brose, U., Grimm, V., Tielbo¨rger, K., Wichmann, M.C., Schwager, M., et al., 2004. Animal species diversity driven by habitat heterogeneity/diversity: the importance of keystone structures. J. Biogeogr. 31, 79 92.