Seafloor Geomorphology—Coast, Shelf, and Abyss (original) (raw)
Related papers
GeoHab Atlas of Seafloor Geomorphic Features and Benthic Habitats
Seafloor Geomorphology as Benthic Habitat, 2012
This chapter presents a broad synthesis and overview based on the 57 case studies included in Part 2 of this book and on questionnaires completed by the authors. The case studies covered areas of seafloor ranging from 0.15 km 2 to over 1,000,000 km 2 (average of 26,600 km 2) and a broad range of geomorphic feature types. The mean depths of the study areas ranged from 8 to 2,375 m, with about half of the studies on the shelf (depth Ͻ 120 m) and half on the slope and at greater depths. Mapping resolution ranged from 0.1 to 170 m (mean of 13 m). There is a relatively equal distribution of studies across the four naturalness categories: near pristine (n ϭ 17), largely unmodified (n ϭ 16), modified (n ϭ 13), and extensively modified (n ϭ 10). In terms of threats to habitats, most authors identified fishing (n ϭ 46) as the most significant threat, followed by pollution (n ϭ 12), oil and gas development (n ϭ 7), and aggregate mining (n ϭ 7). Anthropogenic climate change was viewed as an immediate threat to benthic habitats by only three authors (n ϭ 3). Water depth was found to be the most useful surrogate for benthic communities in the most studies (n ϭ 17), followed by substrate/sediment type (n ϭ 14), acoustic backscatter (n ϭ 12), wave-current exposure (n ϭ 10), grain size (n ϭ 10), seabed rugosity (n ϭ 9), and bathymetric/topographic position index (BPI/TPI) (n ϭ 8). Water properties (temperature, salinity) and seabed slope are less useful surrogates. Multiple analytical methods were used to identify surrogates, with ARC GIS being by far the most popular method (23 out of 44 studies that specified a methodology). Of the many purposes for mapping benthic habitats, four stand out as preeminent: (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. Out of 57 case studies, habitat mapping was intended to be part of an ongoing monitoring program in 24 cases, whereas the continents of Africa, Asia, and South America were not represented in any case study. Given the intense pressures facing benthic habitats and broad regional differences in ecosystems, species, and habitats, future case studies from these regions should be specifically sought for future editions of the Atlas.
GIS analysis of seafloor geomorphology exposes conservation concerns
2007
While there is increasing support for the conservation of high-seas biodiversity through declaring high-seas marine reserves, there is a lack of information on deep-sea benthic communities. An alternative that offers a quantitative and systematic approach to identifying conservation priority areas is Geographic Information System (GIS) analysis of seafloor geomorphic features as a substitute for biodiversity. There are currently around 4600 marine protected areas (MPAs), covering 2.2 million square kilometres or about 0.6% of the ocean area. Most MPAs (62%) are within 12 miles of coastal areas, and none is on the high seas (The Sea Around Us 2006). A geomorphic province map covering the whole of the world’s oceans, originally published by Agapova et al (1979), has been scanned, geo-referenced and digitised at Geoscience Australia (figure 1). This map classifies the seafloor into 23 separate geomorphic categories. It shows that the features least common within national EEZs are hilly...
Seafloor Geomorphology as Benthic Habitat: GeoHab Atlas of seafloor geomorphic features and benthic habitats., 2012
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 (eg. 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 10 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 57 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.
Zenodo (CERN European Organization for Nuclear Research), 2023
This report updates the 'Two-part Seabed Geomorphology classification scheme' of Dove et al. (2016) and presents a new glossary (Part 1) of Seabed Morphology features. This Morphology glossary is intended to provide marine scientists with a robust and consistent way to characterise the seabed. Each glossary entry includes a feature definition and a representative schematic diagram to support clear and accurate classification. Feature terms and definitions are primarily drawn from the International Hydrographic Organization (IHO) guide for undersea feature names, which are herein modified and augmented with additional terms to ensure the final feature catalogue and glossary encompasses the diversity of morphologies observed at the seabed, while also minimising duplication and/or ambiguity. This updated classification system and new glossary are the result of a collaboration between marine geoscientists from marine mapping programmes/networks in Norway (MAREANO), Ireland (INFOMAR), UK (MAREMAP), and Australia (Geoscience Australia) (MIM-GA). A subsequent report will present the (Part 2) Geomorphology feature glossary.
We present the first digital seafloor geomorphic features map (GSFM) of the global ocean. The GSFM includes 131,192 separate polygons in 29 geomorphic feature categories, used here to assess differences between passive and active continental margins as well as between 8 major ocean regions (the Arctic, Indian, North Atlantic, North Pacific, South Atlantic, South Pacific and the Southern Oceans and the Mediterranean and Black Seas). The GSFM provides quantitative assessments of differences between passive and active margins: continental shelf width of passive margins (88 km) is nearly three times that of active margins (31 km); the average width of active slopes (36 km) is less than the average width of passive margin slopes (46 km); active margin slopes contain an area of 3.4 million km2 where the gradient exceeds 5o, compared with 1.3 million km2 on passive margin slopes; the continental rise covers 27 million km2 adjacent to passive margins and less than 2.3 million km2 adjacent to active margins. Examples of specific applications of the GSFM are presented to show that: 1) larger rift valley segments are generally associated with slow-spreading rates and smaller rift valley segments are associated with fast spreading; 2) polar submarine canyons are twice the average size of non-polar canyons and abyssal polar regions exhibit lower seafloor roughness than non-polar regions, expressed as spatially extensive fan, rise and abyssal plain sediment deposits – all of which are attributed here to the effects of continental glaciations; and 3) recognition of seamounts as a separate category of feature from ridges results in a lower estimate of seamount number compared with estimates of previous workers.
Geo-marine Letters, 2019
Marine habitat mapping provides essential information for environmental management and design of marine reserves. In tropical regions, particularly along the Brazilian coast, the spatial variability of marine habitats is poorly known. The aim of this study is to evaluate the geodiversity of the region as an indicator to benthic habitat distribution, applying an integrative approach utilizing existing broad-scale bathymetric and seafloor geological data sets. A digital bathymetric model (DBM) of the Pernambuco Continental shelf (PCS) was generated at 80 m resolution from available bathymetric data. Through the benthic terrain model (BTM), DBM derivatives and the benthic structures were generated. These structures were combined with the textural seabed classification using tools in ArcGIS™ 10.5 Spatial Analyst to identify 22 seabed geomorphic features, including a submarine canyon confirmed around 8°20′S. These geomorphological features describe the surficial characteristics of the seafloor, providing the baseline for subsequent habitat-mapping studies, and can therefore be considered a potential habitat map. Three profiles taken to describe the cross-shelf seafloor environment (North, Center, and South) extracted from interpolated seabed geomorphological map revealed that sediment grain size becomes coarser from inshore to offshore, with predominantly sand and gravel sediment grain sizes. Overall, these results indicated a great potential for PCS due to the geodiversity present in the area, which leads to a higher biodiversity as well. Based on that, the central portion of PCS is suggested as a priority area for conservation because it was the most geomorphologically diverse. These terrain features influence the environmental conditions, such as currents, waves, nutrients, and other oceanographic parameters, which results in high diversity of benthic habitats in the region. This study presents a first step in characterizing the geomorphology of PCS by using reliable, standardized data.
PLOS ONE, 2015
In 2009 the NW and SE flanks of Anton Dohrn Seamount were surveyed using multibeam echosounder and video ground-truthing to characterise megabenthic biological assemblages (biotopes) and assess those which clearly adhere to the definition of Vulnerable Marine Ecosystems, for use in habitat mapping. A combination of multivariate analysis of still imagery and video ground-truthing defined 13 comprehensive descriptions of biotopes that function as mapping units in an applied context. The data reveals that the NW and SE sides of Anton Dohrn Seamount (ADS) are topographically complex and harbour diverse biological assemblages, some of which agree with current definitions of 'listed' habitats of conservation concern. Ten of these biotopes could easily be considered Vulnerable Marine Ecosystems; three coral gardens, four cold-water coral reefs, two xenophyophore communities and one sponge dominated community, with remaining biotopes requiring more detailed assessment. Coral gardens were only found on positive geomorphic features, namely parasitic cones and radial ridges, found both sides of the seamount over a depth of 1311-1740 m. Two cold-water coral reefs (equivalent to summit reef) were mapped on the NW side of the seamount; Lophelia pertusa reef associated with the cliff top mounds at a depth of 747-791 m and Solenosmilia variabilis reef on a radial ridge at a depth of 1318-1351 m. Xenophyophore communities were mapped from both sides of the seamount at a depth of 1099-1770 m and were either associated with geomorphic features or were in close proximity (< 100 m) to them. The sponge dominated community was found on the steep escarpment either side of the seamount over at a depth of 854-1345 m. Multivariate diversity PLOS ONE |
Condor seamount is a linear volcano located in the Azores (northeast Atlantic), 35km in length, 2–6km wide, and of varied seafloor morphology. A scientific observatory devoted to research on seamount ecosystem structure and functioning has been established on Condor, secured by a temporary fishing closure. Multiple projects have contributed to this observatory by targeting the seamount with snapshots and long-term deployments of moored, satellite-based, and shipborne technologies. This chapter presents a brief characterization of the seamount’s seafloor environment by focusing on the multibeam bathymetry data and a series of video, oceanographic, and fishery surveys. A classification based upon the bathymetric position index is presented to characterize the landscape composition of the seamount. Habitats of conservation importance, such as coral gardens and deep-sea sponge aggregations, are documented. A qualitative zonation of the benthic assemblages based on the video surveys is presented along with dominant fish and crustacean catch data for comparable depth strata.