Pockmarks are sea-floor depressions that form when gas or liquid escapes from underlying sediments. Although they are a common feature of both glaciated and lower-latitude continental shelves, pockmarks have not been reported previously from the north-east Antarctic Peninsula margin. Here we use high-resolution geophysical data acquired using autonomous underwater vehicles to map > 240 pockmarks in three locations along the north-east Antarctic Peninsula shelf. The pockmarks are 0.4–45 m wide and 0.1–2.5 m deep, encompassing both smaller unit-pockmarks and larger normal-pockmarks. The high resolution of our data enables the identification of subdued features associated with the pockmarks, including acoustic flares within the water column, ejecta rims, intra-pockmark blocks and possibly even biological structures. The overprinting of subglacial and ice-marginal landforms by the pockmarks constrains their timing of formation to the last ~11 ka. The high density of pockmarks within the surveyed areas, together with geophysical evidence for the active seepage of gas to the sea floor, suggests that the expulsion of subsurface fluids is a widespread process on the north-east Antarctic Peninsula shelf that could have important implications for benthic biodiversity and the global carbon cycle.

In McMurdo Sound, Antarctica, fine-scale bathymetry is poorly defined, and benthic communities at water depths over 30 m have not been well described. We describe the benthic communities on two previously unknown bathymetric highs, sampled in 2012 and 2014, using scuba divers, a remotely operated vehicle, and a specially designed time-lapse camera system (SeeStar). One site (Mystery Peak) was capped by a dense thicket of the sponge Homaxinella balfourensis, a temporally variable community that likely formed in response to iceberg disturbance. Below the H. balfourensis cap (at 40 m) and at the second site (Tongue Peak, 70 m), the communities conformed to a known ecological pattern driven by food availability from benthic diatoms. Overall, mixed hydroids and bryozoans were the dominant organisms, and at greater depths the sponge Rosella podagrosa also became abundant. Over time, there were only minor changes in these communities on isolated bathymetric highs. Ice is a physical factor that interacts with depth and influences benthic communities through disturbance by icebergs and anchor ice, and through food supply by sea ice coverage. The SeeStar time-lapse camera system performed exceptionally and opens up opportunities for new winter observations in the Antarctic.

Identifying benthic substrates is important to researchers studying aquatic organisms in fresh and salt water systems. Benthic substrates are often not visible from the surface making it necessary to find another method to gather these data. Previous research has demonstrated that low cost side-scan sonar is a reliable way to identify hard substrates, such as rock and gravel, in a small, freshwater stream. In this study, the reliability of the side-scan sonar to accurately identify softer substrates such as grass and mud was tested in a large, brackish lagoon system. A total area of 11.55 km2 was surveyed with the sonar. Videos and pictures were taken at various points to groundtruth the sonar images and provide a measure of accuracy. Five substrate types were identified: dense seagrass, sparse seagrass, mangrove soil, mangrove soil with rock, and silt. Unidentifiable substrates were classified as unknown. A manually zoned benthic substrate map was created from the sonar recordings. Dense seagrass was most accurately identified. Sparse seagrass was the least accurately identified. A bathymetric map was also created from the sonar recordings.

Bathymetric Electronic Navigational Charts (bENCs) contain only bathymetry data and can be used in applications such as underwater positioning, dredging and piloting. According to International Hydrographic Organization (IHO) standard S-57, Electronic Navigational Charts (ENCs) contain depth information with pure density of depth contours. Typical depth contours encoded by Hydrographic Offices are limited to 2, 5, 10 and 20 m. Availability of more depth contours in bENCs would allow the visualisation of a safety contour which is closer to users' specific needs, especially in restricted waters such as ports, lakes and rivers. Another problem is non – Global Navigation Satellite System (GNSS) Unmanned Underwater Vehicle (UUV) navigation. bENCs could be used as reference data for UUV comparative navigation. This is called terrain reference navigation. This article presents the results from bathymetric data processing that was performed to convert data contained in bENCs into a reference for underwater comparative navigation. We use data obtained using a multibeam echo sounder to produce depth data with a horizontal spacing of 0·10 m that is suitable for use in restricted waters. The experimental data was collected in and around the Port of Gdansk, Poland.

Bathymetric data of unprecedented resolution are used to provide insights into former ice dynamics and glacial processes in a western Antarctic Peninsula embayment. An assemblage of submarine glacial landforms, which includes subglacially produced streamlined features and ice-marginal ridges, reveals the former pattern of ice flow and retreat. A group of more than 250 small (< 1–3 m high, 10–20 m wide) and relatively evenly spaced recessional moraines was identified beyond the margin of Philippa Glacier. The small recessional moraines are interpreted to have been produced during short-lived, possibly annual re-advances of a grounded ice margin during overall retreat. This is the first time that these features have been shown to be part of the assemblage of landforms produced by tidewater glaciers on the Antarctic Peninsula. Glacier-terminus changes during the last four decades, mapped from LANDSAT satellite images, were analysed to determine whether the moraines were produced during recent still-stands or re-advances of Philippa Glacier and to further investigate the short-term (annual to decadal) variability in ice-marginal position in tidewater glacier systems. The asynchronous response of individual tidewater glaciers in Darbel Bay is interpreted to be controlled mainly by local topography rather than by glacier catchment-area size.

Computer reconstructions of the bathymetry of the lake were used to quantify variations in the size and form of Lake Agassiz during its final two phases (the Nipigon and Ojibway phases), between about 9200 and 7700 14C yr B.P. (ca. 10,300–8400 cal yr B.P.). New bathymetric models for four Nipigon Phase stages (corresponding to the McCauleyville, Hillsboro, Burnside, and The Pas strandlines) indicate that Lake Agassiz ranged between about 19,200 and 4600 km3 in volume and 254,000 and 151,000 km2 in areal extent at those times. A bathymetric model of the last (Ponton) stage of the lake, corresponding to the period in which Lake Agassiz was combined with glacial Lake Ojbway to the east, shows that Lake Agassiz–Ojibway was about 163,000 km3 in volume and 841,000 km2 in areal extent prior to the final release of lake waters into the Tyrrell Sea. During the Nipigon Phase, a number of catastrophic releases of water from Lake Agassiz occurred as more northerly (lower) outlets were made available by the retreating southern margin of the Laurentide Ice Sheet; we estimate that each of the four newly investigated Nipigon Phase releases involved water volumes of between 1600 and 2300 km3. The final release of Lake Agassiz waters into the Tyrrell Sea at about 7700 14C yr B.P. is estimated to have been about 163,000 km3 in volume.

The volume and surface area of glacial Lake Agassiz varied considerably during its 4000-year history. Computer models for seven stages of Lake Agassiz were used to quantify these variations over the lake's early history, between about 11,000 and 9300 14C yr B.P. (ca. 13,000 to 10,300 cal yr B.P.). Just after formation of the Herman strandlines (ca. 11,000 14C yr B.P.), the volume of Lake Agassiz appears to have decreased by >85% as a consequence of the abrupt rerouting of overflow to its eastern outlet from its southward routing into the Mississippi River basin. This drainage released about 9500 km3 of water into the North Atlantic Ocean via the Great Lakes and Gulf of St. Lawrence. Following closure of this eastern routing of overflow, the lake reached its maximum size at about 9400 14C yr B.P. with an area of >260,000 km2 and a volume of >22,700 km3. A second major reduction in volume occurred shortly after that, when its volume decreased >10% following the opening of the Kaiashk outlet to the east into the Great Lakes, and 2500–7000 km3 of water was released into the North Atlantic Ocean. These discharges may have affected ocean circulation and North Atlantic Deep Water production.

An electronic navigational chart is a major source of information for the navigator. The component that contributes most significantly to the safety of navigation on water is the information on the depth of an area. For the purposes of this article, the authors use data obtained by the interferometric sonar GeoSwath Plus. The data were collected in the area of the Port of Szczecin. The samples constitute large sets of data. Data reduction is a procedure to reduce the size of a data set to make it easier and more effective to analyse. The main objective of the authors is the compilation of a new reduction algorithm for bathymetric data. The clustering of data is the first part of the search algorithm. The next step consists of generalisation of bathymetric data. This article presents a comparison and analysis of results of clustering bathymetric data using the following selected methods: K-means clustering algorithm, traditional hierarchical clustering algorithms and self-organising map (using artificial neural networks).

Recent advances in marine acoustic survey and land-based topographic monitoring technologies have resulted in increasingly cost-effective data acquisition in coastal areas. The DEFRA-funded National Network of Regional Coastal Monitoring Programmes of England are, for example, utilising swath bathymetry and airborne light detection and ranging (LiDAR) technology more routinely to survey the coastal zone around the coastline of England. The demand for data processing, visualisation and interpretation techniques to keep pace with such advances in data acquisition is clear. This study discusses collection and processing techniques for such data on the south coast of Dorset, England, which have enabled the production of a seamless, high spatial resolution digital elevation model across the coastal zone. Case studies demonstrate how this elevation model can be viewed and analysed using state-of-the-art digital techniques to allow geological mapping to be extended from onshore to offshore in unprecedented detail, effectively eliminating what is known as the ‘White Ribbon’ for coastal geological mapping. The potential for rolling out such techniques for wider surveying programmes across many environmental disciplines is significant, which could contribute towards improving the multi-disciplinary scientific evidence base in the complex coastal zone.

This study describes species of the genus Hymedesmia from three areas of cold-water coral reef: Mingulay Reef Complex (Scotland, UK) and Rockall and Porcupine Banks (off UK and Irish coasts). Five new species are described: Hymedesmia (Hymedesmia) gibbosa, H. stoneae, H. tendali, H. xavierae and H. valentinae. Records are provided of other poorly known Hymedesmia species: H. bocki, H. cohesibacilla, H. curvichela, H. ebria, H. gustafsoni, H. simillima, H. irregularis, H. proxima, H. hibernica and H. primitiva. Information on distribution of other Hymedesmia species occurring in Britain and Ireland is presented. The sites studied represent a variety of depth-ranges and the data collected suggest that some Hymedesmia species may be restricted to particular bathymetric zones.

Habitat preference and spatial distribution of Guiana dolphins (Sotalia guianensis) in Norte Bay, southern Brazil, was studied from 2001 to 2005. Boat surveys (N = 91) were made to evaluate the spatial distribution of the dolphins. Seven habitat variables were integrated into a geographical information system, and habitat preference was tested using the ‘Neu method’ and a habitat index. The Guiana dolphins did not use all habitat types in the same proportion as were available. Areas used more intensively included, in order of importance: (1) areas with a steep sloping sea-floor; (2) areas further from urban areas; (3) areas further from mangroves; (4) areas near the mouth of the bay; (5) shallow water areas; (6) areas of clayey-silt sediments; and (7) areas close to shore. From 2001 to 2005 there was a shift in spatial distribution and habitat use by the dolphins. The low frequency of use of areas close to urban encroachment and its related impacts to the marine environment raises concern about the coastal habitat destruction. The Guiana dolphin may be considered a habitat specialist, despite its wide latitudinal distribution in the western Atlantic Ocean. The ecological niche of the species may be defined by a narrow strip of shallow coastal waters (mostly < 30 m) bordering the coastline. The shift in the spatial use was probably linked with changes in the abundance of important prey of the species and possibly was caused by the collapse of a fish stock in the study area region. Different habitats may favour different assemblages of prey and consequently different foraging strategies by the dolphins. Human-related habitat alterations throughout the range of this species are likely to affect dolphins' ecology in many ways and, thus, must be evaluated and mitigated to conserve their critical habitats.

Magnetic, gravity and bathymetric data from Marguerite Bay are used to study the relationships between oceanic and continental tectonic evolution in the arc and fore-arc of the Antarctic Peninsula. The data are used to redefine the crustal structure of the Marguerite Bay area, providing evidence for a northward continuation of George VI Sound and the Alexander Island Mesozoic accretionary prism almost to the continental shelf edge. A two-stage model of extension, associated with changes in spreading rates and approaching ridge segments, is proposed to explain the crustal structure and Cenozoic tectonic evolution of the area. The model involves the opening of George VI trough by Tertiary dextral transtension, followed by oblique extension in an area bounded by the Tula and Adelaide fracture zones. This interpretation confirms previous work linking oceanic tectonic processes with continental arc and fore-arc structural development.

Seasonal movements and foraging areas of postbreeding (n = 9) and postmoulting (n = 3) adult southern elephant seal females from Marion Island were studied using Geolocation Time-depth Recorders. Movements were classified into three phases – an outbound transit phase, distant foraging phase, and an inbound transit phase. The longest residence time of postbreeding females during their foraging migrations was in areas at the outer edge of their feeding range (± 1460 km) both to the north and south of the island, largely within inter-frontal zones south of the Antarctic Polar Front (APF) and between the Sub-Tropical Convergence (STC) and the Sub-Antarctic Front (SAF). Postmoulting females travelled further afield (2122–3133 km distant) to the APF, to inter-frontal zones south of the APF (within the pack ice outer edge), as well as to the Antarctic Continental Shelf. This study provides additional information on the putative function of dive types in relation to the movement phases of elephant seal females from Marion Island. The relative frequency of assumed ‘foraging’, ‘exploratory’ and ‘transit’ dive types, as well as the duration and location of the different phases of movement suggest two seasonal foraging strategies. Sea floor topography could possibly cue the transit phases of both postbreeding and postmoulting females from Marion Island.

Deception Island is a large volcanic centre in Bransfield Strait, a very young marginal basin between the South Shetland Islands and Antarctic Peninsula. It has a historical record of volcanic activity, with the most recent eruption occurring in 1970. The island is a stratovolcano with a large flooded caldera forming a natural harbour known as Port Foster. It has been a focus of human activity since early last century, as a base for whaling and sealing expeditions and the locus of several scientific stations. During that period, many bathymetric surveys were carried out, the earliest in 1829 and the most recent in 1993. This study concentrates on surveys from 1948 onwards. Because Port Foster can be classified as a restless caldera, the bathymetric records were analysed for evidence of volcano-tectonic deformation, particularly caldera resurgence (uplift) which could have significant consequences for hazard and risk assessments of the volcano. The results show that a distinctive pattern of shallowing and uplift is present, correlating well with known and inferred volcanic and volcanotectonic processes on the island. In particular, bathymetric records between 1949 and 1993 show uplift rates as high as 0.3–0.5 m a−1, far exceeding normal sedimentation rates in a caldera this size. Rapid uplift in an arcuate offshore area not affected by the sedimentation of recent eruptions suggests that volcano tectonic resurgence or tectono-magmatic effects of an upward migrating magma chamber present a significant risk to the considerable human activity taking place in the region.

This study is the first to describe the winter distribution of crabeater seals (Lobodon carcinophagus) in East Antarctica. The study was conducted in the Mertz Glacier Polynya region from July to August 1999. In total 89 crabeater seals were seen in 26 groups which ranged in size from 1 to 35 animals (mean = 3.2). The mean observed haulout density along a 200 m wide strip transect was 0.108 seals per km2, or 0.042 groups per km2. Crabeater seals were not uniformly distributed in the polynya but selected areas of stable ice over shallow (< 1000 m) waters. We used a generalized linear model to assess the relationship of seal distribution to the physical attributes of sea ice concentration, thickness, and ocean depth. We found that ice thickness and ocean depth were the most important determinants of seal distribution. Crabeater seals occurred in areas where the ice affords them a stable haulout platform while allowing them access to Antarctic krill that live directly beneath the ice.

This paper describes a major calving of the Ninnis Glacier tongue in January 2000. This event, which took 10 years to complete, produced a major change in the George V Land coastline and a large iceberg (∼800 km2). By grounding or becoming “locked in” by fast ice, bergs produced locally and drifting in from afar reside for long periods (10–20 years) in the region ∼146 to 154°E to have a profound impact on sea ice distribution, both locally and 100s of kilometres up- and downstream. They are responsible for the formation of a lens of thick perennial ice to the east (∼14 000 km2 in area), and polynyas. Iceberg movement is sporadic, with intermittent ungroundings of large bergs occurring every 5–13 years. “Escaping” bergs have a temporary impact on the Mertz Glacier polynya to the west. Although public attention focuses on vast bergs, assemblages of small bergs appear to be equally important in terms of their impact on regional fast and pack ice distribution. Possible global change scenarios are discussed. The need for field observations and improved bathymetric and oceanographic data is emphasized.