Continental Slope Off Research Articles

A dark side of cleaning symbiosis: manned submersible observations

Cleaning is a ubiquitous interspecific interaction on shallow tropical, subtropical, and temperate reefs, involving hundreds of species in all ocean basins. This remarkable mutualism encompasses fish and/or shrimp “cleaners” that remove and consume organic debris, parasites, tissue, and mucus from “client” invertebrates (e.g., anemones, crabs, octopuses) and vertebrates (e.g., sharks, bony fishes, turtles, iguanas, and cetaceans. Often regarded as a facilitative interaction, cleaning may be an important driver of reef community structure. Cleaning evolved independently in several unrelated taxa, resulting in a remarkable diversity of interaction types and behaviors. Besides the burden of epibionts, wounds, and parasites, visual and tactile signaling comprise the proximate causation of cleaning interactions. However, there are a few examples of nocturnal cleaning on marine ecosystems, which always involve shrimps acting as cleaners. Here, we report on caridean shrimps (Decapoda: Caridea) cleaning four species of carnivorous fishes in the disphotic-aphotic transition zone (280–320 m depth), based on submersible observations at the continental shelf slope off Northeastern Brazil. This is the first record of shrimp-fish cleaning interactions in deep-cold waters, and our observations support the idea that tactile signaling is of foremost importance in such interactions. We hypothesize that the complex daytime behavior and other adaptations of dedicated cleaner shrimps may have evolved from incidental cleaning by shrimps seeking food on nocturnal shelters of larger fish, or on deep water, where vision plays a minor role.

An uncommon or just an ecologically demanding species? Finding of aggregations of the brittle-star Ophiothrix maculata on the Northwest African slope

Ophiuroidea constitutes the largest class of the phylum Echinodermata. It includes families with suspension-feeder behaviour that can be found in dense aggregations in all oceans worldwide. Ophiothrix maculata was known as a rare suspension-feeder brittle star, with only four records in the Eastern Central Atlantic dating from almost 100 years ago.During the ten multidisciplinary Spanish and Norwegian surveys carried out from 2004 to 2012 off Northwest Africa, between the Gibraltar Strait and the Sierra Leone border from 19 to 1888m depth, we sampled 1298 stations. We gathered about one million individuals and 124kg of brittle stars at 501 of the stations. Eight hundred and thirty-two specimens of Ophiothrix maculata were collected at six localities on the continental slope off Mauritania, Western Sahara and Guinea Bissau, at depths between 155 and 594m. The Guinea Bissau samples represent the southernmost current record for the species. Even though Ophiothrix maculata has been previously recorded only in isolation, we discovered dense concentrations on the Mauritanian slope on the Wolof's Seamount (580 individuals) and off the Western Sahara, in a Lophelia pertusa reef (202 individuals).In this paper, we describe these findings and discuss the association of this species to hard-bottom habitats and high primary production areas, outside of the oxygen minimum zone (OMZ). We also analyse what other factors may explain the patchy distribution of O. maculata on the Northwest African slope.

Climate change and the threat of novel marine predators in Antarctica

AbstractHistorically low temperatures have severely limited skeleton‐breaking predation on the Antarctic shelf, facilitating the evolution of a benthic fauna poorly defended against durophagy. Now, rapid warming of the Southern Ocean is restructuring Antarctic marine ecosystems as conditions become favorable for range expansions. Populations of the lithodid crab Paralomis birsteini currently inhabit some areas of the continental slope off Antarctica. They could potentially expand along the slope and upward to the outer continental shelf, where temperatures are no longer prohibitively low. We identified two sites inhabited by different densities of lithodids in the slope environment along the western Antarctic Peninsula. Analysis of the gut contents of P. birsteini trapped on the slope revealed them to be opportunistic invertivores. The abundances of three commonly eaten, eurybathic taxa—ophiuroids, echinoids, and gastropods—were negatively associated with P. birsteini off Marguerite Bay, where lithodid densities averaged 4280 ind/km2 at depths of 1100–1499 m (range 3440–5010 ind/km2), but not off Anvers Island, where lithodid densities were lower, averaging 2060 ind/km2 at these depths (range 660–3270 ind/km2). Higher abundances of lithodids appear to exert a negative effect on invertebrate distribution on the slope. Lateral or vertical range expansions of P. birsteini at sufficient densities could substantially reduce populations of their benthic prey off Antarctica, potentially exacerbating the direct impacts of rising temperatures on the distribution and diversity of the contemporary shelf benthos.

Different precipitation patterns across tropical South America during Heinrich and Dansgaard-Oeschger stadials

Detailed knowledge about tropical South American precipitation patterns during Heinrich (H) and Dansgaard-Oeschger (DO) stadials provides relevant insights into the possible evolution of Amazonian hydroclimate under future climate change. Sediment core GeoB16224-1 (ca. 7°N), raised from a site in the continental slope off French Guiana in western equatorial Atlantic under the influence of the Amazon River discharge, documents the impacts of H and DO stadials on both inorganic (i.e., Fe/Ca record) and organic (i.e., alkenone C37 concentration and C37/C38 ratio) geochemistry between 41 and 13 ka BP. Our results show millennial-scale covariations of increased Fe/Ca values with decreased C37 concentration and C37/C38 ratios during H and DO stadials. Comparing our high temporal resolution data with previously published records from ca. 17°N to 4°S, we are able to differentiate the influence of H and DO stadials upon tropical South American precipitation. We find that records under the influence of the South American summer monsoon (e.g., western Amazon) and the northern edge of the Intertropical Convergence Zone (ITCZ) (e.g., northernmost South America) exhibit strong climate shifts during both H and DO stadials, but regions under the influence of the southern edge of the ITCZ (e.g., northeastern Brazil) experience a weaker reaction during DO stadials than during H stadials.

Sedimentary processes on the continental slope off Kvitøya and Albertini troughs north of Nordaustlandet, Svalbard – The importance of structural-geological setting in trough-mouth fan development

New marine-geophysical data were analyzed to investigate the sedimentary processes operating on the continental slope north of Nordaustlandet, Svalbard. Kvitøya Trough terminates in a trough-mouth fan (TMF) on the slope, whereas Albertini Trough incises the shelf edge and a TMF is notably absent. Instead, the continental slope beyond Albertini Trough is dominated by thick, acoustically stratified units likely formed by down-slope and along-slope sedimentological processes combined. The morphological and sedimentological differences between Albertini and Kvitøya troughs may partly be due to the larger dimensions of Kvitøya Trough and its associated glacial catchment area relative to Albertini, suggesting that the transport of a larger volume of glacigenic sediments potentially was a contributing factor in building Kvitøya TMF. By contrast, the downfaulted bedrock below outer Albertini Trough provided larger accommodation space for glacigenic sediments which accumulated in an outer-shelf basin, highlighting the importance of the structural-geological setting in TMF development. Debris-flow deposits and/or channel-levee deposits on the lower continental slope and rise off Kvitøya Trough indicate bypassing of glacigenic sediments from the shelf to the deep ocean, a process that is likely a result of locally steep slope gradients (<9°). The volume of the Kvitøya TMF is smaller than TMFs along the western Svalbard margin, which may be linked to the more erosion-resistant bedrock of the northern margin and/or the comparatively small drainage basin of Kvitøya Trough compared to drainage basins of ice streams that drained westwards from Barents Sea. In addition, the Kvitøya TMF is incised by gullies indicating that they formed after Last Glacial Maximum (LGM) while larger tributary canyons flanking the Kvitøya TMF likely have developed during a longer time span. High seafloor backscatter values in the tributary canyons and gullies are interpreted as coarse-grained deposits that lead down-slope to debris-flow deposits, suggesting an origin for the tributary canyons and gullies through incision by gravity flows of sediment-laden meltwater during and/or after deglaciation.

Squalus bassi sp. nov., a new long-snouted spurdog (Chondrichthyes: Squaliformes: Squalidae) from the Agulhas Bank.

The long-snouted African spurdog Squalus bassi sp. nov. is described based on material collected from the outer shelf and upper continental slope off South Africa and Mozambique. Squalus bassi shares with S. mitsukurii, S. montalbani, S. chloroculus, S. grahami, S. griffini, S. edmundsi, S. quasimodo and S. lobularis a large snout with prenarial length greater than distance between nostrils and upper labial furrows, dermal denticles tricuspidate and rhomboid and elevated number of vertebrae. Squalus bassi can be distinguished from all its congeners by a combination of body and fin colouration, external morphometrics, vertebral counts and shape of dermal denticles. Similar long-snouted congeners from the Indo-Pacific region, including S. montalbani, S. edmundsi and S. lalannei are compared in detail with the new species. This new species has been misidentified as the Japanese S. mitsukurii and the Mediterranean S. blainvillei due to the lack of comparative morphological analyses. The validity of the nominal species S. mitsukurii in the south-eastern Atlantic Ocean and western Indian Ocean is also clarified herein, indicating it has a more restricted geographical distribution in the North Pacific Ocean.

The unique deep sea-land connection: interactive 3D visualization and molecular phylogeny of Bathyhedyle boucheti n. sp. (Bathyhedylidae n. fam.)-the first panpulmonate slug from bathyal zones.

The deep sea comprises vast unexplored areas and is expected to conceal significant undescribed invertebrate species diversity. Deep waters may act as a refuge for many relictual groups, including elusive and enigmatic higher taxa, but the evolutionary pathways by which colonization of the deep sea has occurred have scarcely been investigated. Sister group relationships between shallow water and deep sea taxa have been documented in several invertebrate groups, but are unknown between amphibious/terrestrial and deep-sea species. Here we describe in full and interactive 3D morphoanatomical detail the new sea slug species Bathyhedyle boucheti n. sp., dredged from the continental slope off Mozambique. Molecular and morphological analyses reveal that it represents a novel heterobranch gastropod lineage which we establish as the new family Bathyhedylidae. The family is robustly supported as sister to the recently discovered panpulmonate acochlidian family Aitengidae, which comprises amphibious species living along the sea shore as well as fully terrestrial species. This is the first marine-epibenthic representative among hedylopsacean Acochlidiida, the first record of an acochlidian from deep waters and the first documented panpulmonate deep-sea slug. Considering a marine mesopsammic ancestor, the external morphological features of Bathyhedyle n. gen. may be interpreted as independent adaptations to a benthic life style in the deep sea, including the large body size, broad foot and propodial tentacles. Alternatively, the common ancestor of Bathyhedylidae and Aitengidae may have been a macroscopic amphibious or even terrestrial species. We hypothesize that oophagy in the common ancestor of Aitengidae and Bathyhedylidae might explain the impressive ecological and evolutionary flexibility in habitat choice in the Acochlidiida.

Bottom trawling and oxygen minimum zone influences on continental slope benthic community structure off Vancouver Island (NE Pacific)

Understanding responses of benthic ecosystems to cumulative impacts of natural stressors, long-term ocean change and increasing resource exploitation is an emerging area of interest for marine ecologists and environmental managers. Few, if any, studies have quantitatively addressed cumulative effects in the deep sea. We report here on a study from the continental slope off Vancouver Island (Canada) in the northeast Pacific Ocean, where the Oxygen Minimum Zone impinges on seabed habitats that are subjected to widespread bottom trawling, primarily by the fishery for thornyhead (Sebastolobus ssp.). We examined how the benthic megafauna in this area was influenced by varying levels of dissolved oxygen and trawling activity, along a depth gradient that was also likely to shape community composition. Continuous video and sonar records from two ROV surveys (50 linear km total; depth range 300–1400m) respectively provided data on faunal attributes (composition, abundance and diversity) and the frequency of trawl door marks on the seabed. Faunal and trawl data were compiled in a geo-referenced database along with corresponding dissolved oxygen data, and pooled into 500m segments for statistical analysis. Trawl mark occurrence peaked between 500 and 1100m, corresponding to areas of slope subjected to hypoxia (<1.4mll-1) and severe hypoxia (<0.5mll-1). A combined total of 266,251 megafauna organisms from 87 taxa were enumerated in the two transects. Significant megafaunal assemblages according to depth, trawling intensity and bottom water dissolved oxygen concentration were identified by PERMANOVA analyses, with characterizing taxa identified for all three factors. Depth, dissolved oxygen and trawl mark density accounted for 21% to 52% of the variability in benthic community structure according to multiple regression (DISTLM) models. Species richness was highest at intermediate depths and in areas subject to intermediate levels of trawling, and higher under hypoxia than under severe hypoxia. These statistically significant trends demonstrate that the structuring influences of bottom trawling on deep-sea benthic communities can be observed even where communities are being shaped by strong environmental gradients.

Observations of Seismicity and Ground Motion in the Northeast U.S. Atlantic Margin from Ocean‐Bottom Seismometer Data

ABSTRACT Earthquake data from two short‐period ocean‐bottom seismometer (OBS) networks deployed for over a year on the continental slope off New York and southern New England were used to evaluate seismicity and ground motions along the continental margin. Our OBS networks located only one earthquake of M c ∼1.5 near the shelf edge during six months of recording, suggesting that seismic activity ( M Lg >3.0) of the margin as far as 150–200 km offshore is probably successfully monitored by land stations without the need for OBS deployments. The spectral acceleration from two local earthquakes recorded by the OBS was found to be generally similar to the acceleration from these earthquakes recorded at several seismic stations on land and to hybrid empirical acceleration relationships for eastern North America. Therefore, the seismic attenuation used for eastern North America can be extended in this region at least to the continental slope. However, additional offshore studies are needed to verify these preliminary conclusions.

Time series measurements of transient tracers and tracer-derived transport in the Deep Western Boundary Current between the Labrador Sea and the subtropical Atlantic Ocean at Line W

Time series measurements of the nuclear fuel reprocessing tracer, 129I and the gas ventilation tracer, CFC-11 were undertaken on the AR7W section in the Labrador Sea (1997-2014) and on Line W (2004-2014), located over the US continental slope off Cape Cod, to determine advection and mixing time scales for the transport of Denmark Strait Overflow Water (DSOW) within the Deep Western Boundary Current (DWBC). Tracer measurements were also conducted in 2010 over the continental rise southeast of Bermuda to intercept the equator-ward flow of DSOW by interior pathways. The Labrador Sea tracer and hydrographic time series data were used as input functions in a boundary current model that employs transit time distributions to simulate the effects of mixing and advection on downstream tracer distributions. Model simulations of tracer levels in the boundary current core and adjacent interior (shoulder) region with which mixing occurs were compared with the Line W time series measurements to determine boundary current model parameters. These results indicate that DSOW is transported from the Labrador Sea to Line W via the DWBC on a time scale of 5-6 y corresponding to a mean flow velocity of 2.7 cm/s while mixing between the core and interior regions occurs with a time constant of 2.6 y. A tracer section over the southern flank of the Bermuda rise indicates that the flow of DSOW that separated from the DWBC had undergone transport through interior pathways on a time scale of 9 y with a mixing time constant of 4 y. This article is protected by copyright. All rights reserved.

Direct observations of the Antarctic Slope Current transport at 113°E

AbstractThe Antarctic Slope Current (ASC), defined here as the region of westward flow along the continental slope off Antarctica, forms the southern limb of the subpolar gyres. It regulates the exchange of water across the shelf break and provides a path for interbasin westward transport. Despite its significance, the ASC remains largely unobserved around most of the Antarctic continent. Here we present direct velocity observations from a 17 month current meter moored array deployed across the continental slope between the 1000 and the 4200 m isobaths, in the southeastern Indian Ocean near 113°E. The observed time‐mean flow consists of a surface‐intensified jet associated with the Antarctic Slope Front (ASF) and a broader bottom‐intensified westward flow that extends out to approximately the 4000 m isobath and is strongest along the upper slope. The time‐mean transport of the ASC is −29.2 Sv. Fluctuations in the transport are large, typically exceeding the mean by a factor of 2. They are mainly due to changes in the northward extent of the current over the lower slope. However, seasonal changes in the wind also drive variations in the transport of the ASF and the flow in the upper slope. Both mean and variability are largely barotropic, thus invisible to traditional geostrophic methods.

Enhanced turbulence driven by mesoscale motions and flow‐topography interaction in the Denmark Strait Overflow plume

AbstractThe Denmark Strait Overflow (DSO) contributes roughly half to the total volume transport of the Nordic overflows. The overflow increases its volume by entraining ambient water as it descends into the subpolar North Atlantic, feeding into the deep branch of the Atlantic Meridional Overturning Circulation. In June 2012, a multiplatform experiment was carried out in the DSO plume on the continental slope off Greenland (180 km downstream of the sill in Denmark Strait), to observe the variability associated with the entrainment of ambient waters into the DSO plume. In this study, we report on two high‐dissipation events captured by an autonomous underwater vehicle (AUV) by horizontal profiling in the interfacial layer between the DSO plume and the ambient water. Strong dissipation of turbulent kinetic energy of O( ) W kg−1 was associated with enhanced small‐scale temperature variance at wavelengths between 0.05 and 500 m as deduced from a fast‐response thermistor. Isotherm displacement slope spectra reveal a wave number‐dependence characteristic of turbulence in the inertial‐convective subrange ( ) at wavelengths between 0.14 and 100 m. The first event captured by the AUV was transient, and occurred near the edge of a bottom‐intensified energetic eddy. Our observations imply that both horizontal advection of warm water and vertical mixing of it into the plume are eddy‐driven and go hand in hand in entraining ambient water into the DSO plume. The second event was found to be a stationary feature on the upstream side of a topographic elevation located in the plume pathway. Flow‐topography interaction is suggested to drive the intense mixing at this site.

Detection of marine mammal vocalizations off Cape Hatteras, modulated by the Gulf Stream

To assess the ecological impact of extracting energy from the Gulf Stream, the University of North Carolina Coastal Studies Institute has deployed a mooring on the continental slope off Cape Hatteras at a depth of 230 m, equipped with an ADCP, a CTD, and a hydrophone. Analyzing data from the first deployment, we automatically detected marine mammal vocalizations. We found a strong correlation between the amount of vocalizations and the position of the Gulf Stream, with vocalizations increasing when the Gulf Stream was farther offshore. We then derived sound speed profiles for the region around the mooring using temperature and salinity profiles collected by WHOI Spray gliders. These sound speed profiles were fed into a propagation modeling tool. When the Gulf Stream was far offshore with respect to the mooring position, the model showed a set of rays that propagate down the slope in an acoustic channel along the bottom. When the Gulf Stream was nearly over the mooring, the range of angles that could propagate down the slope was reduced by a factor of six. Therefore, the propagation models suggest that the observed correlation is due to a propagation effect, resulting from the varying position of the Gulf Stream.

Intraspecific variation in the swimbladder occurrence and possibility of acoustic discrimination of the dominant mesopelagic fish Diaphus garmaniioff western Kyushu, Japan

Diaphus garmanii (Family, Mictophidae) is the most abundant mesopelagic fish in the continental slope off western Kyushu. For the application of acoustic monitoring, we have observed the swimbladder morphology of this species to estimate the target strength (TS). In this session, we show the intraspecific variation in the occurrences and shapes of swimbladder in D. garmanii, and propose the acoustic discrimination of the swimbladder morphology for accuracy improvement in biomass estimates. Acoustic data and biological samples were collected in the summer of 2012 to 2014. Both of fishes with (30% in all samples) and without (70%) swimbladder were observed by the soft X-ray method, and frequencies of the swimbladder occurrence were significantly different between male and female fishes. Theoretical scattering models showed that the TS difference between 38 kHz and 70 kHz was the most preferable parameter to discriminate the swimbladder occurrence of D. garmaniiin field acoustic data. Field acoustic data analyses implied different patterns of vertical distribution between swimbladder and swimbladderless (male and female) fishes.

Diversity and Distribution Patterns of Cetaceans in the Subtropical Southwestern Atlantic Outer Continental Shelf and Slope

Temporal and spatial patterns of cetacean diversity and distribution were investigated through eight ship-based surveys carried out during spring and autumn between 2009 and 2014 on the outer continental shelf (~150m) and slope (1500m) off southeastern and southern Brazil (~23°S to ~34°S). The survey area was divided into southeast and south areas according to their oceanographic characteristics. Twenty-one species were observed in 503 sightings. The overall number of species was similar between the two areas, though it was higher in the spring in the south area. Five species were dominant and diversity varied more seasonally than spatially. ANOVA and kernel analyses showed that overall cetacean densities were higher in spring compared to autumn. Physeter macrocephalus, the most frequent species, concentrated throughout the south area at depths over 1000m in both seasons. Despite the overlapped occurrence at a broader scale, small delphinids presented latitudinal and in-offshore gradients as well as seasonal variation in distribution patterns, which could indicate habitat partitioning between some species. Delphinus delphis was only recorded in the south and its density decreased in areas where the presence of Stenella frontalis increased, mainly beyond the 250m isobath. Densities of S. longirostris and S. attenuata increased in lower latitudes and beyond the shelf break. The large delphinids Tursiops truncatus and Globicephala melas formed mixed groups in many occasions and were observed along the study area around depths of 500m. Grampus griseus was twice as frequent in the south area and densities increased in waters deeper than 600m. As expected, densities of both small and large migratory whales were higher during spring, over the continental slope, in the southeast area. The results presented here provided strong evidence on the importance of the outer continental shelf and slope to a diverse community of cetaceans occurring in the subtropical Southwestern Atlantic.

Observed internal tides and near-inertial waves on the continental shelf and slope off Jaigarh, central west coast of India

The characteristics of internal tides (ITs) and near-inertial waves (NIWs) on the continental shelf and slope off Jaigarh (17∘N), central west coast of India were studied. Eight-month (March–October) long Acoustic Doppler Current Profiler (ADCP) measurements made in the year 2008 were used in the present study. Analysis of sea surface heights from satellite altimeter data, where the tracks of the satellites are oriented nearly in the direction of the semimajor axis of barotropic tides, reveals the presence of diurnal and semidiurnal internal tides with surface amplitudes of about 2cm. Baroclinic current spectra of horizontal velocities show peaks in IT frequencies of M2, S2, K1 and O1 and in inertial frequency (f). The observed current spectra show higher energies than those in Garrett–Munk reference spectra by about 2–3 times. Based on the estimates of “critical topography” (where the topographic slope is equal to the slope of IT) and computed barotropic body force (Baines, 1982), the shelf-edge, mid-slope and deep part of the slope region are found to be the possible generation sites of internal tides in the region. Over the period of observation, the IT on the slope is found to be energetic, with a strong IT during March to mid-April (pre-monsoon period). Whereas, on the shelf, IT is weak during the pre-monsoon and found to be strong in the southwest monsoon. The available hydrographic data and model simulated hydrography suggest that this difference is linked with the stratification changes on the shelf and slope during these seasons, where the stratification is found to be weak on the shelf and strong on the slope during pre-monsoon. Strong low-mode NIW is observed on the shelf associated with the storm events while the NIW is found to be less energetic on the slope.

Effects of seismic surveys on New Zealand fur seals during daylight hours: Do fur seals respond to obstacles rather than airgun noise?

The responses of New Zealand fur seals (Arctocephalus forsteri) during a three-dimensional marine seismic survey were recorded in the first quantified investigation of the effects of seismic exploration operations on otariid seals. The survey was over the continental slope off southern New Zealand, where fur seals dive to forage at night and rest on the surface during daylight hours. Data were restricted to daylight sightings from the source vessel while towed seismic gear was fully deployed, with comparisons made between fur seal responses when airguns were off and when airguns were operating at full power. Results were inconclusive. Comparisons were confounded because both sighting rate and distance first seen decreased with deteriorating sea state. The key finding of this study was that the source vessel and towed gear created physical obstacles that often generated responses from fur seals. A more thorough investigation is recommended in order to differentiate between responses to airgun noise and responses to physical obstacles, and improvements are suggested to rectify shortfalls in data collection that should generate conclusive outcomes.

The Kongsfjorden Channel System offshore NW Svalbard: downslope sedimentary processes in a contour-current-dominated setting

Submarine channel systems on and off glaciated continental margins can be up to hundreds of kilometres long, tens of kilometres wide and hundreds of metres deep. They result from repeated erosion and various downslope processes predominantly during glacial periods and can, therefore, provide valuable tools for the reconstruction of past ice-sheet dynamics. The Kongsfjorden Channel System (KCS) on the continental slope off northwest Svalbard provides evidence that downslope sedimentary processes are locally more dominant than regional along-slope sedimentation. It is a relatively short channel system (~120 km) that occurs at a large range of water depths (~250–4000 m) with slope gradients varying between 0° and 20°. Multiple gullies on the Kongsfjorden Trough Mouth Fan merge to small channels that further merge to a main channel. The overall location of the channel system is controlled by variations in slope gradients and the ambient regional bathymetry. The widest and deepest incisions occur in areas of the steepest slope gradients. The KCS has probably been active since ~1 Ma when glacial activity on Svalbard increased and grounded ice expanded to the shelf break off Kongsfjorden repeatedly. Activity within the system was probably highest during glacials. However, reduced activity presumably took place also during interglacials.

Breaking Internal Tides Keep the Ocean in Balance

By studying how underwater waves strike the continental slope off Tasmania, researchers seek to uncover the mechanisms that keep the circulation of the global ocean in balance.

A new species of Dolicholana Bruce, 1986 (Isopoda, Cymothoidea, Cirolanidae), the first record of the genus from the Atlantic Ocean.

The isopod genus Dolicholana Bruce, 1986, previously known only from the Indo-West Pacific, is recorded for the first time from the Atlantic Ocean. A new species, Dolicholana brucei sp. nov., is described from the northeastern Brazilian coast, and is the first record of the genus Dolicholana Bruce, 1986 for the Atlantic Ocean. The material was collected from the upper part of the continental slope off Rio Grande do Norte (150 m depth). The new species is characterized by pereopod 1 propodal palm being crenulate, ischium of pereopod 1 and 2 with a plumose seta on the anterior margin, peduncle of pleopods 3-5 bearing an accessory lobe acute on the distolateral angle, pleotelson posterior margin being rounded, and the uropodal endopod and the exopod apices distally being rounded. A revised key to the genus is provided.