Depth Off Research Articles

Do cold water corals provide an essential habitat for Helicolenus dactylopterus (Delaroche, 1809) in the Northwest Africa?

Cold water corals (CWC) provide habitats for many organisms including demersal fish. Bottom trawl observations have indicated a co-occurrence of the fish Helicolenus dactylopterus with CWC reefs, but a detailed understanding of this relation is lacking. To better understand the nature of this relation we have analyzed 85 video-lines from ROV dives conducted at 25–1700 m depth off Morocco, Mauritania, and Senegal in 2020 and 2021. We annotated abundance, size, and behavior of the 552 specimens observed (32% juveniles and 68% adults), of these 82% occurred in CWC habitats at 400–600 m depth. Both juveniles and adults were observed standing on the seafloor. Our observations are discussed considering available knowledge on feeding ecology and life cycle of H. dactylopterus. Our findings show that CWC provides an essential habitat for this species at least during parts of its lifecycle, however, more behavioral studies are needed for an in-depth understanding of this association.

First observation of a skate egg case nursery in the Ross Sea.

Areas of importance to Southern Ocean skates are poorly defined. Here, we identify a deepwater skate egg case nursery in a discrete location at ~460 m depth off Cape Adare in the Southern Ocean. This is the first confirmed observation of a skate nursery area in the Ross Sea and only the second observation for the Southern Ocean. The morphology and size of the egg cases were consistent with the genus Bathyraja and most likely belong to the Bathyraja sp. (cf. eatonii). The nursery occurs within the "no take" General Protection Zone of the Ross Sea region marine protected area, where commercial fishing is prohibited.

New species and records of Heterospio (Annelida, Longosomatidae) from continental shelf, slope and abyssal depths of the Atlantic Ocean, Pacific Ocean, Indian Ocean and adjacent seas.

Nineteen species of the rare polychaete genus Heterospio are reported, 15 of which are new to science. The status of H. longissima Ehlers, 1874, the type-species, is reviewed. The specimens examined are from several locations in the North Atlantic Ocean, Gulf of Mexico, Caribbean Sea, off Br azil, the Indian Ocean, the Pacific Ocean off California, New Zealand, Australia, and the South China Sea. Deep-water samples from the western North Atlantic Ocean collected by the late Drs. H.L. Sanders and R.R. Hessler that were reported by Hartman as H. longissima were re-examined and referred to two new species, H. hartmanae n. sp. (abyssal depths, New England to Bermuda transect) and H. guiana n. sp. (bathyal depths off Suriname). Other materials from the Sanders/Hessler North Atlantic collections were also examined and referred to two additional species, H. canariensis n. sp. (deep water off Canary Islands) and H. southwardorum n. sp. (Bay of Biscay) as well as H. cf. reducta from off SW Ireland in bathyal depths. New collections from the North Atlantic region include additional materials of H. hartmanae n. sp. (deep water off the Mid-Atlantic and SE USA), H. aruba n. sp. (Caribbean Sea), H. bathyala n. sp. (deep water off SE USA), and H. dibranchiata n. sp. (deep water, Gulf of Mexico). Heterospio paulolanai n. sp. is from shelf depths off southeastern Brazil. Heterospio knoxi n. sp. is from the North Island of New Zealand, H. ehlersi n. sp. is from the Gulf of Thailand, in the South China Sea, H. bidentata n. sp. is described from deep water in the Coral Sea off eastern Australia, and H. alata n. sp. and H. brunei n. sp. are described from deep water off the Island of Borneo in the South China Sea. Heterospio africana n. sp. and H. antonbruunae n. sp. are described from off east Africa in the Mozambique Channel. New records and descriptions of H. catalinensis, H. indica, and H. peruana are presented. The 15 new species reported here nearly triple the number of previously known species of Heterospio, with 23 species now recognized. All known species are tabulated and compared.

Osedax (Siboglinidae: Annelida) utilizes shark teeth for nutrition

Abstract We deployed jaws of the common thresher shark (Alopias vulpinus) on the seafloor at ~1000 m depth off Monterey California for 8 months. The jaws disintegrated, with all the hyaline cartilage disappearing, leaving some fragments of tessellated cartilage and the teeth. Two different Osedax species, O. packardorum and O. talkovici were found to have bored into the roots of some of the teeth, and were using the dentin pulp, which is rich in collagen, as a food source. The enameloid crowns of the shark teeth and the tessellated cartilage showed no signs of Osedax activity. This is the first demonstration of Osedax exploiting a source of food that is not bone. This raises questions as to the original food source of Osedax ‘bone worms'. Examination for the presence of Osedax in the skeletons and teeth of Mesozoic and possibly even Palaeozoic fossil sharks, bony fish and reptiles is warranted.

Gorgonophilus canadensis (Copepoda: Lamippidae) a parasite in the octocoral Paragorgia arborea – relation to host, reproduction, and morphology

The family Lamippidae (Cyclopoida) are endosymbionts mainly occurring in shallow water octocorals and records from deep-sea corals are few. Here we investigated the relationship between the lamippid Gorgonophilus canadensis Buhl-Mortensen & Mortensen, 2004 and its host the deep-sea coral Paragorgia arborea. Twenty-one specimens of G. canadensis was found inside eight gall-like structures on a P. arborea colony collected in 2010 at 318 m depth off Norway. The galls contained on average 1.6 females, 1.0 males, and 7.5 egg sacs estimated to contain 400 eggs each. Females were larger than males (4.6 mm compared to 2.0 mm). The gall volume increased with the number of egg sacs, females, and the length of females inside, the latter correlation was significant (p < 0.05). The number of egg sacs in galls was positively correlated with the abundance and length of females (p < 0.05), and by adding Canadian data from 17 galls the relation between egg sacs and numbers of females and males in galls became stronger (p < 0.01 and p < 0.05, respectively). Scanning electron microscopy revealed that this highly modified endoparasite has thoracic appendages with non-segmented flexible spines with a specialized structure at their tips through which threads are excreted. We speculate that this adaptation could relate to feeding or attachment of egg sacs inside the galls. Thread production has rarely been reported for copepods and we explore its function in the group as well as other crustaceans. The age and size of the parasite, and the introduction to and release from the host is also discussed.

Cheilostomatida (Bryozoa) from the Ionian Apulian coast (Italy) with the description of new species

The mesophotic zone is a relatively poorly studied area of the Mediterranean Sea, drawing great interest by the scientific community in the last years. This zone represents a connection between the shallow water and the deep-sea communities, in which photophilic framework builders (e.g. coralline red algae) are gradually replaced by heterotrophic ones, such as ahermatypic corals and the bivalve Neopycnodonte cochlear. In this habitat the framework-forming organisms produce a hard substrate with a high topographic complexity, hosting a great biodiversity of secondary structuring taxa like bryozoans. During a survey on coralligenous banks in the mesophotic zone in c. 60 m depth off Gallipoli (southern Apulia), epibiotic aggregations of N. cochlear were found on the fans of the hexacoral Savalia savaglia. In the present paper the diversity of cheilostomatid bryozoans hosted by these bivalve aggregations is described and compared with published information on similar nearby habitats. A total of 48 taxa were found, six of which are newly described: Crassimarginatella matildae sp. nov., Micropora biopesiula sp. nov., Haplopoma celeste sp. nov., Schizomavella (Schizomavella) cerranoi sp. nov., Schizomavella (Calvetomavella) biancae sp. nov., and Schizoporella adelaide sp. nov. The species richness known from the southern Apulian shelf at this depth (47 species) is hereby raised to 83 cheilostomatid bryozoans. Moreover, only 12 species are shared with the other localities studied previously, while 36 are restricted to Gallipoli, supporting the hypothesis of a high rate of exclusivity among Apulian sites in terms of species composition. The differences in faunal composition, and particularly the presence of several new species discovered at Gallipoli, show once more that our knowledge of the bryozoan fauna in certain Mediterranean habitats is still incomplete and warrants further studies. https://doi.org/urn:lsid:zoobank.org:pub:DDC82039-EF44-4169-8198-C67F60B14BA0

First Record of Elasmobranch Hosts for the Gnathiid Isopod Crustacean Thaumastognathia: Description of Thaumastognathia bicorniger sp. nov.

Gnathiid larvae (Crustacea; Isopoda; Gnathiidae) infesting elasmobranch and holocephalan fishes from mainly bathyal depths off Suruga Bay, off Kume-jima Island, and five sites from off Tokyo Bay to Shimoda City, Japan were examined. A total of 1460 gnathiid larvae were sampled from 87 host individuals belonging to seven families and 10 species. The morphology of these larvae was distinguishable from other gnathiid species by the head appendages. These larvae presented two pigmentation patterns, stripes or spots, on their dorsal thoraxes in live specimens. Furthermore, they were determined as the second and third stage praniza larvae on the basis of allometric variance of maximum head and abdomen widths. A third stage praniza with stripe pigmentation metamorphosed into an adult male and could be identified as a new species of the genus Thaumastognathia Monod, 1926. The duration between detachment from the host and metamorphosis into male adult required 204 days. This paper describes Thaumastognathia bicorniger sp. nov. on the basis of P3/stripe larvae and the male adult. This report is the first record of the larva and host information for a species of Thaumastognathia.

Observations of surface wave fields in the Arabian Sea under tropical cyclone Tauktae

The characteristics of surface wave fields in the eastern Arabian Sea under tropical cyclone Tauktae were investigated using buoy data. On May 16, 2021, the cyclone passed within 96 km of the buoy location, and a maximum wave height of 9.7 m with a significant wave height of 5.6 m was recorded by the buoy, moored at 23.5 m water depth off Goa. As the cyclone approached the buoy location, a shift in the frequency caused waves to turn into unimodal spectra with high wave energy and spectral peak parameter. Further, the evolution of cyclone-induced waves and their spatial variation have been investigated using the ERA5 reanalysis data. The results suggest that for distances of ∼400 km spatial extend from the cyclone's eyewall, the cyclone induced waves to have a high impact with significant wave height above 3 m for a cyclone sustained wind speed of around 100–120 knots. The dominance of wind-seas over swells and the directional shift are noticeable, specifically along the west coast of India during the tropical cyclone passage.

Complete mitochondrial genomes of two species of Stichopathes Brook, 1889 (Hexacorallia: Antipatharia: Antipathidae) from Rapa Nui (Easter Island)

We report the complete mitochondrial genomes of two antipatharian species, Stichopathes sp. SCBUCN-8849 and Stichopathes sp. SCBUCN-8850, collected between 120 and 180 m depth off Rapa Nui (∼ −27.1°, −109.4°). The size of the two mitogenomes are 20,389 bp (29.0% A, 15.2% C, 19.9% G, and 35.9% T) and 20,463 bp (29.0% A, 15.3% C, 19.9% G, and 35.8% T), respectively. Both mitogenomes have the classic Hexacorallia gene content of 13 protein-coding, two rRNA, and two tRNA genes plus a COX1 intron with embedded HEG as found in the Antipathidae and other antipatharian families.

Baseline soundscapes of deep‐sea habitats reveal heterogeneity among ecosystems and sensitivity to anthropogenic impacts

AbstractUnderwater soundscapes, though invisible, are crucial in shaping the biodiversity of marine ecosystems by acting as habitat‐specific settlement cues for larvae. The deep sea has received little attention in soundscape research, but it is being targeted for mineral extraction to feed the ever‐growing needs of our society. Anthropogenic impacts on soundscapes influence the resilience of key shallow‐water habitats, and the same likely applies to the deep. Japan is a forerunner in deep‐sea mining, but virtually no deep soundscape baselines exist for Japanese waters. Here, we report baseline soundscapes from four deep‐sea locations in Japan, including the Suiyo Seamount hydrothermal vent, the abyssal plain around the Minamitorishima Island home to manganese nodule fields and muds rich in rare‐earth elements, twilight depths off Sanriku, as well as a typical bathyal system in Suruga Bay. Long‐duration audio recordings were visualized and factorized by an unsupervised machine learning model, revealing differing characteristics among the habitats. Two locations near the coast are highly influenced by shipping noise. The Suiyo vent is characterized by low‐frequency sounds from venting, and the abyssal Minamitorishima is quiet with a flat spectral shape. Noise from observation platforms is likely sufficient to alter soundscape characteristics, especially in offshore locations, suggesting offshore mining‐targeted areas are susceptible to impacts from anthropogenic noise. We argue that the monitoring of soundscapes is an indispensable component for assessing potential mining impacts on deep‐sea ecosystems. Our results establish reference points for future soundscape monitoring and assessment in Japanese waters as well as similar ecosystems globally.

A new species of Gymnelus (Perciformes, Zoarcidae) from Greenland, similar to G. viridis

Zoarcid fishes of the genus Gymnelus Reinhardt inhabit the shelves of the North Pacific Ocean and the Arctic. A new species, G. pseudosquamatus sp. nov., is described from trawl samples taken at depths off South-West Greenland. It is most similar to the type species of the genus, Common Fish Doctor G. viridis, inhabiting the coastal waters of Greenland. The characters of the latter are specified on materials from the type locality, including the neotype and specimens of J.C.H. Reinhardt. Both species are in the group of Gymnelus with an interrupted supratemporal commissura, two supratemporal sensory pores (1+0+1), and a dorsal fin originating above the pectoral fin. The two species differ in a complex of characters, including habitus. In G. viridis, the trunk is roundish in cross section, highest above the beginning of the anal fin; the anterior rays of the dorsal fin are shortened, and covered with a thick and somewhat fleshy skin. In G. pseudosquamatus, the body is compressed and deeper anteriorly, the dorsal-fin rays are evenly elongated, and the fin membrane is thin. Differences in counts and measurements are statistically significant, including the number of vertebrae and rays in the dorsal, anal and pectoral fins, the number of teeth on the jaws, as well as the length and depth of the head, predorsal length, the length of pectoral fins, eye diameter and length of the gill slit. The color of G. pseudosquamatus, with 8–16 wide brown mottled bands, is also unusual, as the skin is dotted with light speckles that create the illusion of tiny scales, which is the reason for the name “pseudosquamatus”, the Deceptive Fish Doctor. While G. viridis is found inshore in a zone of macroalgae, the new species is found in deeper waters (100–457 m) along the shelf edge of South-West Greenland. The name Ophidium stigma Lay et Bennett, 1839 (=Gymnelus stigma) should be excluded from the synonymy of G. viridis, since the original description mentions the presence of scales on the body, which are absent in Gymnelus.

Baleenopelta rotunda, a newly discovered limpet from decaying baleen from New Zealand

ABSTRACT A new genus and species of the Osteopeltidae that is restricted to decaying baleen is described from 377 to 1042 m depth off mainland New Zealand, the Chatham Islands and the Auckland Islands. ZooBank registration: urn:lsid:zoobank.org:pub:4CD02E01-9B34-405B-B6CC-D4306C81A690

Performance Evaluation of MQL with Graphene Mixed Nano Fluids prepared at different Concentrations in Turning of Pure Titanium (TI6Al4V) Alloy

This paper presents an investigation into the minimum quantity lubrication mode with Nano fluid during turning of titanium (TI6AL4V) alloy. In heavy cutting conditions, minimum quantity lubrication (MQL) has been observed, that, Nano-cutting fluids which have enrich thermal conductivity than base fluid, are begun to be used in MQL system. The addition of the required nano particle ratio to the base liquid is one of the most important issues that arise in this method. Therefore, this study aimed to find the optimum distribution rate of graphene nano particles having excellent properties and machining parameters. To do this, graphene nano particles were added to a vegetable-based cutting solution. Nano-cutting fluids were prepared in different volumetric concentrations. When turning of titanium (TI6AL4V) alloy, these Nano fluids were used in the MQL system. Three different parameters were added to the experimental design to study the performance of Nano fluids under several cutting conditions. i.e., speed, feed rate and depth off cut. Apart from this experimental design, three tests were carried out at each concentration ratio while keeping the machining parameters constant to clearly see the impact of concentration rates on surface roughness, flank wear. And crater wear. In addition, while chipping/fracture, were observed under all cutting conditions

A new species of Egglestonichthys (Teleostei, Gobiiformes, Gobiidae) from Okinawa Island, Japan.

Egglestonichthys fulmensp. nov. (Teleostei: Gobiidae) is described on the basis of a single specimen (21.7 mm in standard length) collected from 250 m depth off Okinawa Island, Ryukyu Islands, Japan. The new species is characterized by the following combination of characters: anal-fin rays I, 9; pectoral-fin rays 17, lower rays not free from membrane; longitudinal scale series 25; transverse scales 8; pre-dorsal-fin scale rows 8; cheek and opercle naked; pelvic frenum absent; caudal fin lanceolate, its length 32.2% of SL; interorbital width very narrow, 1.2% of HL (much narrower than pupil diameter); no spicules or odontoid processes on outer surface of gill arches; and body whitish, upper half with broken zigzag pattern of bright yellow patches and associated scattered black melanophores in fresh specimens (melanophores retained in preserved specimens). Several characters, including pectoral-fin ray count, interorbital width, and coloration uniquely distinguish the new species from congeners.

Bioluminescence in an Undescribed Species of Carnivorous Sponge (Cladorhizidae) From the Deep Sea

One dominant ecological trait in the dimly-lit deep-sea is the ability of organisms to emit bioluminescence. Despite its many ecological roles in deep-sea ecosystems, the presence of inherent bioluminescence in marine sponges has been debated for more than a century. This work reports repeated observations of luminescence from six individuals of an undescribed carnivorous sponge species (Cladorhizidae) sampled near 4,000 m depth off Monterey Bay (CA, United States). These are the first fully documented records of bioluminescence in the phylum Porifera. Videos and photographs of the sponges’ bioluminescence were recorded on board after collection and in vitro bioluminescence assays indicate that the bioluminescence system is a coelenterazine-based luciferase. Coelenterazine luciferin is already described in various organisms such as cnidarians, chaetognaths, copepods, cephalopods, ctenophores, ostracods, and some mysid or decapod shrimps. Based on these observations we discuss new ecological hypotheses of functional traits such as bioluminescence and carnivory in deep sea organisms.

Joint Ecological and Archeological Shipwreck Surveys Using Submersible Video and Laser‐Line Scanning

Archeological and ecological studies of shipwrecks are often conducted separately. We provide a proof of concept for a cross-disciplinary approach. Here, we extract ecological metrics from archeological surveys on two World War II shipwrecks that rest at ~200 m depth off North Carolina, USA. We used two advanced technologies (video and laser-line scanning), both from human-occupied submersibles to assess fish communities from imagery and models intended for archeological investigations. Combining video and laser technologies allowed us to identify fish and pinpoint their locations. The resulting fish data revealed that both shipwrecks hosted high densities of groupers, primarily concentrated around tall shipwreck features. These photographs illustrate the article “Extracting ecological metrics from archaeological surveys of shipwrecks using submersible video and laser-line scanning” by Katrina H. Johnson, Avery B. Paxton, J. Christopher Taylor, Joseph Hoyt, John McCord, and William Hoffman Ecosphere. https://doi.org/10.1002/ecs2.3210.

A new genus and species of Sternaspidae (Annelida: Polychaeta) from the deep eastern Atlantic

Based on specimens recently collected in sediments from 2700 m depth off Mauritania (Northwest Africa; type locality) and from 2700–4400 m depth off Angola (Southwest Africa), a new genus and species, Mauretanaspis longichaeta gen. et spec. nov., is described. The new genus and species are characterized by a unique combination of characters: ventro-caudal shield covered by firmly adhering sediment, lateral margins strongly bent and merging into integument; introvert hooks tapering; eight pre-shield segments; absence of peg chaetae; exceptionally long posteriormost lateral chaetae equaling body length; posterior shield chaetae equaling shield length. A comparative table of characters for all currently recognised sternaspid genera and a key to all species with ventro-caudal shield covered by firmly adhering sediment are provided.

&lt;em&gt;Atlantiphoxus wajapi&lt;/em&gt; n. gen., n. sp. (Crustacea: Amphipoda: Phoxocephalidae), a new deep-sea amphipod from the southwestern Atlantic

A new genus and species of the family Phoxocephalidae is here described with material collected during the Mini Biological Trawl Project at 224 and 500 m depth off Brazil’s southeastern coast in the states of Rio de Janeiro and São Paulo. Atlantiphoxus wajapi n. gen., n. sp. can be grouped in the subfamily Phoxocephalinae and seems to be morphologically close to Fuegiphoxus Barnard and Barnard, 1980 and Parharpinia Stebbing, 1899. However it can be easily distinguished within the phoxocephalids by the following characters: deep pereonites with small coxae; rostrum unconstricted; eyes absent; man­dible molar not triturative, but as a small hump with 3 multicuspidate stout setae; pereopods 3-4 with stout dactylus; pereopod 5 basis strongly tapering distally; pereopod 7 basis anterodistal corner with a row of long plumose setae; dactylus elongate. Epimeral plate 3 posteroventral margin strongly produced.

Calcification depths and temperatures of planktonic foraminifera off southwest Hainan Island and their paleoceanographic implications

Abstract The East Asian monsoon system influences the local oceanographic and climatic conditions of South China Sea (SCS), making the habitat depths of planktonic foraminifera (PF) specific for this region.The previous paleo-ocean reconstructions of SCS have been based on calcification habitat depths derived from other oceans, which may have affected the accuracy of interpretations. In this study, the calcification depths of Globigerinoides ruber, Globigerinoides sacculifer, and Neogloboquadrina dutertrei from sediment traps deployed at 1000 m depth off southwest Hainan Island from July 2012 to April 2013 were analyzed with regard to the stable isotopes of oxygen (δ18O) and carbon (δ13C) to calculate their regional apparent calcification depths (ACDs) with the overall aim to improve the reconstruction of the upper ocean thermal structure. ACDs and temperature estimated from foraminifera δ18O ranged from 0 to 42 m and 25°C for G. ruber, 30-65 m and 23.3°C for G. sacculifer, and 75-100 m and 20.3°C for N. dutertrei, respectively. The difference between the thermocline-species (N. dutertrei) and mixed-layer species (G. ruber and G. sacculifer) δ18O (∆δ18OTh–ML) and the temperature (∆T) shows water column stratification. The periods of lower and higher ∆T and ∆δ18O were in phase with the changes in regional overlying wind speed. Additionally, this study reveals that N. dutertrei lives and calcifies its shells within the base of the mixed-layer depth (MLD) and upper thermocline depth in SCS. Overall, the results from this study provide a new insight to understand the mixed-layer and thermocline depth in the northern SCS.

Deep sea floor observations of typhoon driven enhanced ocean turbulence

The impact of large atmospheric disturbances on deep benthic communities is not well known quantitatively. Observations are scarce but may reveal specific processes leading to turbulent disturbances. Here, we present high-resolution deep-ocean observations to study potential turbulent mixing by a large atmospheric disturbance. We deployed an array of 100-Hz sampling-rate geophysical broadband Ocean Bottom Seismometers (OBSs) on the seafloor. Within the footprint of this array we also deployed an oceanographic 0.5-Hz sampling-rate vertical temperature sensor string covering the water phase between 7 and 207 m above the seafloor at about 3000 m depth off eastern Taiwan between June 2017 and April 2018. In September 2017, all instruments recorded Category 4 cyclone Typhoon Talim’s passage northeast of the array one day ahead of the cyclone’s closest approach when the cyclone’s eye was more than 1,000 km away. For 10 days, a group of near-inertial motions appeared most clearly in temperature. The group contained the largest inertial amplitudes in the ten month time series, and which led to turbulence dissipation rates O(10−7 m2 s−3). The observation reflects the importance of barotropic response to a cyclone and the propagation of inertio-gravity waves in weak density stratification. In addition to internal tides, these waves drove turbulent overturns larger than 200 m that were concurrently recorded by OBSs. The turbulent signals were neither due to seismic activity nor to ocean-surface wave action. Cyclones can generate not only microseisms and earth hums, as well as turbulence in the water column, producing additional ground motions. Quantified turbulence processes may help constrain models on sediment resuspension and its effect on deep-sea benthic life.