Dhugal John Lindsay

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• PhD
• Japan Agency for Marine-Earth Science Technology at Japan Agency for Marine-Earth Science and Technology

Background There been increasing interest in polymetallic nodule mining within the Clarion-Clipperton Zone (CCZ). Polymetallic nodule mining within NORI-D will release a sediment plume within the water column and a previous mining collector test within the Nauru Ocean Resources Inc. (NORI-D) contract area released surface pollution from mining tail...

Open-ocean pelagic habitats are inherently difficult to study due to their inaccessibility, which limits our ability to properly sample the dynamic nature of these environments. The biology of the pelagic habitat of the eastern Pacific Ocean remains poorly sampled. This region is characterized by the presence of an expanding oxygen minimum zone and...

Both the diffusion of turbid water (plume) and the redeposition of suspended particles associated with deep sea mining are expected to have a negative impact on the surrounding environment. In order to understand the actual conditions of the mixed environment near the seafloor, it is necessary to evaluate these environmental impacts. In a review o...

Imaging is increasingly used to capture information on the marine environment thanks to the improvements in imaging equipment, devices for carrying cameras and data storage in recent years. In that context, biologists, geologists, computer specialists and end-users must gather to discuss the methods and procedures for optimising the quality and qua...

During an ROV Hyper-Dolphin dive to bathyal depths in the Kamaishi Marine Canyon, off Tohoku District, the north Pacific, the association of a large specimen of Caprella (Crustacea: Malacostraca: Amphipoda) was observed, surrounded by juveniles, clinging to the dorsal tube feet of the deep-sea holothurian Scotoplanes globosa (Théel, 1879) at 1142 m...

Occurrence of jellyfish blooms has been known to affect fish populations, making them an important study subject. Solmaris, Phialella and Muggiaea blooms have shown to cause mass mortality of salmon. Observing jellyfish blooms in-situ as they interact with fish is essential for both science and fisheries stakeholders. However, since the exact timin...

An undescribed species of ulmarid medusa was observed in situ and captured at 812 m depth within the Sumisu Caldera, Ogasawara Islands, Japan. Morphological and molecular evidence points to it being distinct from other ulmarid medusae and a new species (pagesi), genus (Santjordia) and subfamily (Santjordiinae) are herein erected to contain it. This...

Management of deep-sea fisheries in areas beyond national jurisdiction by Regional Fisheries Management Organizations/Arrangements (RFMO/As) requires identification of areas with Vulnerable Marine Ecosystems (VMEs). Currently, fisheries data, including trawl and longline bycatch data, are used by many RFMO/As to inform the identification of VMEs. H...

In recent years, significant efforts have been dedicated to measuring and comprehending the impact of microplastics (MPs) in the ocean. Despite harmonization guidelines for MPs research, discrepancies persist in the applied methodologies and future challenges, mostly for the smaller fractions (< 100 μm). Whether intentional or accidental, ingesting...

Narcomedusae play a key role as top-down regulators in the midwater, the largest and most understudied biome on Earth. Here, we used ecological niche modeling in three-dimensions (3D), ecomorphology, and phylogeny, to answer evolutionary and ecological questions about the widespread narcomedusan genus Solmissus. Our phylogenetic analyses confirmed...

The Salas y Gómez and Nazca ridges are two adjacent seamount chains of volcanic origin located in thesoutheastern Pacific, which collectively stretch across over 2,900 km of seafloor. Ecosystems in thisregion are isolated from the South American Continent by the Atacama Trench and the Humboldt CurrentSystem. This isolation has produced a unique bio...

Orienting vertically with the head facing upward allows fish to look for the shadow of their prey against ambient light, while also making their own shadow smaller to predators beneath them. Here, we describe the in situ behavior of three midwater fish in the family Neoscopelidae, Neoscopelus macrolepidotus, Neoscopelus microchir, and Scopelengys t...

This paper aims to guide the stakeholder engagement process related to plastic pollution research in marine environments. We draw on advice identified during an online workshop (Ocean Plastic Workshop 2022) organized by Early Career Ocean Professionals (ECOPs) from 11 countries, held in April 2022. International experts and workshop participants di...

We have developed a method to combine morphological and chemical information for the accurate identification of different particle types using optical measurement techniques that require no sample preparation. A combined holographic imaging and Raman spectroscopy setup is used to gather data from six different types of marine particles suspended in...

The environmental regulation of planktonic food web structure is a key determinant for the efficiency of energy transfer through trophic levels, with direct implications for the amount of energy that is available to top-consumers and deep-sea communities. Yet, the complex trophic interplay between the different components of plankton communities un...

The observation of singleton or rare species in the deep sea is extremely valuable for gaining a census of biodiversity. At hadal depths (> 6000 m), these records provide a more complete picture of the vertical distribution of fauna. In this study, we present new in situ video records for Trachymedusae (Hydrozoa), Ascidiacea (Tunicata), and Tentacu...

Introduction Botrynema, a genus of medusozoans in the trachyline family Halicreatidae, currently contains two species: B. brucei and B. ellinorae, distinguished by the presence or absence, respectively, of an apical knob as a diagnostic character. However, no study has corroborated if these taxonomic diagnoses have a biological and evolutionary bas...

Barbeled dragonfishes (family Stomiidae) are considered rare, solitary deep-sea predators. We document the fish fauna of the Kurose Hole, a submarine caldera within Japanese waters. The area has been surveyed on three occasions: twice in 2000 during the RV ‘Natsushima’ cruise and once in 2020 during the RV ‘Kaimei’ cruise. Within the span of twenty...

In the Southern Ocean, several zooplankton taxonomic groups, euphausiids, copepods, salps and pteropods, are notable because of their biomass and abundance and their roles in maintaining food webs and ecosystem structure and function, including the provision of globally important ecosystem services. These groups are consumers of microbes, primary a...

Ecosystem services are benefits that people derive from nature. ● The deep ocean provides many critical ecosystem services, such as fish and shellfish for food; products from organisms that can be used for medicines; climate regulation; and historical, cultural, social, educational, and scientific value for people worldwide. ● Human activities can...

Freshwater jellyfish comprising the genus Craspedacusta are thought to have originated in the Yangtze River, China and have since spread to all continents except Antarctica. In this study, jellyfish were collected from Haruta-ike, an artificial pond in Chikuma City, Nagano (Japan). Medusae were identified as Craspedacusta sowerbii using morphologic...

Quantitative imaging instruments produce a large number of images of plankton and marine snow, acquired in a controlled manner, from which the visual characteristics of individual objects and their in situ concentrations can be computed. To exploit this wealth of information, machine learning is necessary to automate tasks such as taxonomic classif...

Gelatinous zooplankton (GZ) is a non-taxonomic term for jelly-like organisms that have a high proportion of water in body tissues. Advantages in being gelatinous include better buoyancy, transparency, larger sizes with lower carbon investment, rapid growth and body plasticity. Most GZ taxa have different pathways of asexual reproduction that may qu...

Digital holography is a useful tool to image microscopic particles. Reconstructed holograms give high-resolution shape information that can be used to identify the types of particles. However, the process of reconstructing holograms is computationally intensive and cannot easily keep up with the rate of data acquisition on low-power sensor platform...

Midwater marine environments are one of the largest ecosystems on earth. Collecting visual data of a quality from which identifications can be made is difficult due to limited survey opportunities. Often during dives, long video recordings are made, which need to be analyzed in real-time or in post processing for annotating observations. Although m...

The midwater is the largest continuous biome on our planet and is dominated by gelatinous zooplankton. Despite pelagic ecosystems being widely acknowledged for their ecosystem services, less than 1% of this vast habitat has been sampled. Narcomedusae are specialised in feeding on other gelatinous prey and play a key role in maintaining a well-balan...

The deep sea is categorized as a cold-water environment, typically 4°C around 800 m depth near Japan. There are warm environments in the deep sea, including hydrothermal vents and the deep Mediterranean, Red and Sulu Seas; noted as having unique faunal communities that reflect the extraordinary environmental conditions. The Kuruse Hole, located in...

Background: Southern Ocean ecosystems are currently experiencing increased environmental changes and anthropogenic pressures, urging scientists to report on their biodiversity and biogeography. Two major taxonomically diverse and trophically important gelatinous zooplankton groups that have, however, stayed largely understudied until now are the c...

Measuring the distribution, characteristics and dynamics of marine microscale plankton and other particulate matter is essential to understand the vertical flux of elements in the marine environment. Digital holographic microscopy is a powerful approach for measuring these and studying their 3-D trajectories in a relatively large observation volume...

Tracking deep ocean animals over their daily cycles will revolutionize our understanding of the largest biome on Earth.

Hydrozoan jellyfish of the genus Blackfordia currently consist of three described species: B. manhattensis, B. virginica and B. polytentaculata. These species are distinguished by combinations of the position and shape of the gonads, the number of marginal tentacles, and the presence or absence of black pigments on the bell rim. We discovered a spe...

Hyperspectral data in the near infrared range were examined for nine common types of plastic particles of 1 mm and 100-500 μm sizes on dry and wet glass fiber filters. Weaker peak intensities were detected for small particles compared to large particles, and the reflectances were weaker at longer wavelengths when the particles were measured on a we...

The Salas y Gómez and Nazca ridges are two seamount chains of volcanic origin, which include over 110 seamounts that collectively stretch across over 2,900 km in the southeastern Pacific. Ecosystems in this region are isolated by the Atacama Trench, the Humboldt Current System, and an extreme oxygen minimum zone. This isolation has produced a uniqu...

Turbidity currents are the main drivers behind the transportation of terrestrial sediments to the deep sea, and turbidite deposits from such currents have been widely used in geological studies. Nevertheless, the contribution of turbidity currents to vertical displacement of seawater has rarely been discussed. This is partly because until recently,...

The unusual holopelagic annelid Poeobius meseres Heath, 1930 (Flabelligeridae) was first collected from Monterey Bay, California and has been subsequently recorded across the northern Pacific from Japan to the Gulf of California. Rare occurrences in the eastern tropical Pacific have extended as far as 7° S off Peru. Using molecular phylogenetic ana...

The ram’s horn squid Spirula spirula (Linnaeus, 1758) is the only extant cephalopod with an internal calcareous, chambered shell that is coiled, making it the sole living representative of the once speciose order Spirulida [...]

p>A novel technique to analyse deep-sea particles using digital holography (DH) and Raman spectroscopy (RS) is currently being developed. Since RS requires long measurement periods to provide reliable results in water, a flow control system is necessary to trap particles in the instrument. One way in which this can be achieved is to control the flo...

深海性クラゲは非常に多様であるが、その全貌を把握するためには遺伝子学的なアプローチに加え、新たな採集方法の開発や深海の現場における最新撮影テクノロジーの応用が必要である。映像調査の場合には、形態が把握できるだけでなく、生物の相互作用や詳細スケールにおける個体数密度に関する情報を得ることができる。クラゲ類が深海の生態系全体にどんな影響を与えているか、多様性の維持にどう関わっているのかが少しずつ明らかになってくるのを楽しみにしている。

A noncontact method to identify sparsely distributed plastic pellets is proposed by integrating holography and Raman spectroscopy in this study. Polystyrene and poly(methyl methacrylate) resin pellets with a size of 3 mm located in a 20 cm water channel were illuminated using a collimated continuous wave laser beam with a diameter of 4 mm and wavel...

Recent advances in technology have enabled an unprecedented development of underwater research, extending from near shore to the deepest regions of the globe. However, monitoring of biodiversity is not fully implemented in political agendas and biological observations in the deep ocean have been even more limited in space and time. The Foresight W...

Optical particle measurements are emerging as an important technique for understanding the ocean carbon cycle, including contributions to estimates of their downward flux, which sequesters carbon dioxide (CO2) in the deep sea. Optical instruments can be used from ships or installed on autonomous platforms, delivering much greater spatial and tempor...

The delicate shape, elegance and vivid colors of medusae can be only captured in photographs of live specimens, since preserved they lose both color and shape. Because most jellies are slow-moving, they are relatively easy to photograph underwater or in a laboratory studio, provided that adequate equipment and a few special techniques are employed....

Separating microplastics from marine and freshwater sediments is challenging, but necessary to determine their distribution, mass, and ecological impacts in benthic environments. Density separation is commonly used to extract microplastics from sediments by using heavy salt solutions, such as zinc chloride and sodium iodide. However, current device...

Removing non-plastic materials is a mandatory process for studying microplastics in environmental samples, and non-plastic materials, both inorganic and organic matter, are often removed chemically through sequential processes. In the multiple chemical treatment processes, the samples need to be collected and the reagent removed at the end of each...

Gelatinous zooplankton can be extremely fragile, sometimes with over 95% of their mass comprised of water. Although some taxa can be sampled and observed in an aquarium, many taxa do not survive collection and can only be studied in situ. Many of these taxa are undescribed species, sometimes in new genera, families or even orders. Since holotypes o...

Gelatinous macrozooplankton can dominate many oligotrophic systems and are especially conspicuous in deep-sea and pelagic ecosystems. Due to the logistical challenges imposed by sea-ice cover, the gelatinous zooplankton fauna of the Arctic Ocean remains largely unknown, with the notable exception of the data collected during the Hidden Ocean series...

There has been very little research done in the center of the South Pacific Gyre because of the difficulties in sampling so far away from any land. However, the center of the gyre is a scientifically curious and important location due to it being a super-oligotrophic area – like a terrestrial desert. From January 27th to March 2nd 2019, the Japan A...

Ocean Networks Canada (ONC) operates large seafloor cabled observatory networks in the Arctic and NE Pacific, with some of its long-term observations nearly approaching 15 years of archived data. The seafloor network of 850+ km of backbone cables connects > 50 instrumented sites (>400 oceanographic instruments, >5,000 sensors), in habitats ranging...

Research on so-called “minor taxa” at mesophotic depths has lagged behind that of more commonly researched groups such as fish or hard corals. Exemplar taxa include species of the order Zoantharia, benthic colonial anemones that are cosmopolitan in distribution but understudied in many ecoregion and ecosystems. In this study, we examine the results...

The exploitation of deep-sea mineral resources has not yet begun. In order to realize it in the future, various issues need to be addressed. One such issue is establishing an appropriate environmental impact assessment (EIA) technique and a supporting environmental research method. At present, knowledge on the deep-sea environment is quite poor, an...

The Seven-arm Octopus, Haliphron atlanticus, was observed holding a coronate medusa, Periphyllopsis braueri, by the remotely-operated vehicle (ROV) Dolphin-3K. The jellyfish was held by the aboral surface within the arms of the octopus. Although obscured at first, the lappets and tentacles of the jellyfish became exposed as the octopus turned towar...

An individual narcomedusa assignable to Solmissus incisa sensu lato was observed having ingested a fish at 573 m depth near the southeast slope of the Kaikata seamount, Japan. Solmissus is a very common deep-sea narco-medusan genus that is widely considered to be a predator specializing on gelatinous plankton. Several cryptic species, with differen...

Loss or stark reduction of the free-swimming medusa or jellyfish stage is common in the cnidarian class Hydrozoa. In the hydrozoan clade Trachylina, however, many species do not possess a sessile polyp or hydroid stage. Trachylines inhabiting freshwater and coastal ecosystems (i.e., Limnomedusae) possess a metagenetic life cycle involving benthic,...

A new genus and species of pennellid copepod, Protosarcotretes nishikawai n. g., n. sp., is described on the basis of an ovigerous female infecting a Pacific viperfish Chauliodus macouni collected from the deep-waters of Suruga Bay, Japan. The new genus exhibits the most plesiomorphic states in the first to fourth legs of pennellids, and is differe...

Large numbers of the leptomedusa Earleria bruuni were observed inside a semi-closed deep-sea caldera during a comparative survey of the macrozooplankton fauna inside and outside the Kurose Hole, Izu-Ogasawara Islands, by the remotely operated vehicle (ROV) ‘Dolphin-3K’, on 24 September 2000. The Kurose Hole is an inactive volcanic caldera of 790 m...

Background There is growing interest in mining polymetallic nodules from the abyssal Clarion-Clipperton Zone (CCZ) in the tropical Pacific Ocean. Despite having been the focus of environmental studies for decades, the benthic megafauna of the CCZ remain poorly known. To predict and manage the environmental impacts of mining in the CCZ, baseline kno...

Online biogeographic databases are increasingly being used as data sources for scientific papers and reports, for example, to characterize global patterns and predictors of marine biodiversity and to identify areas of ecological significance in the open oceans and deep seas. However, the utility of such databases is entirely dependent on the qualit...

Marine optical imaging has become a major assessment tool in science, policy and public understanding of our seas and oceans. Methodology in this field is developing rapidly, including hardware, software and the ways of their application. The aim of the Marine Imaging Workshop (MIW) is to bring together academics, research scientists and engineers,...

Optics-based surveys for large unicellular zooplankton were carried out in five different oceanic areas. New identification criteria, in which “radiolarian-like plankton” are categorized into nine different groups, are proposed for future optics-based surveys. The autonomous visual plankton recorder (A-VPR) captured 65 images of radiolarians (three...

We have developed a global biogeographic classification of the mesopelagic zone to reflect the regional scales over which the ocean interior varies in terms of biodiversity and function. An integrated approach was necessary, as global gaps in information and variable sampling methods preclude strictly statistical approaches. A panel combining exper...

A new species of clausophyid siphonophore, Kephyes hiulcus sp. nov. is described. It can most easily be differentiated from its congener Kephyes ovata by the shape of the hydroecium in the anterior nectophore of the polygastric stage. This is open over the entire height of the nectophore in K. hiulcus sp. nov., and it is this character from which i...

A new species of “cydippid” ctenophore, Pukia ohtsukai sp. nov., is described from material collected in Nishino-omote Port, Tanegashima Island, Japan. It can be distinguished from the only other member of the genus by the presence of perradial canals, lack of bilateral diverticula beneath the comb plates, a lower number of comb plates per comb row...

A doliolid species belonging to the genus Paradoliopsis was photographed by an Autonomous Visual Plankton Recorder (AVPR) off the eastern seaboard of Japan in October 2014 at 493–512 m depth. Two Paradoliopsis gonozooids were also captured on the video record of the ROV Crambon at 372–373 m depth during the same cruise. This is the first record of...

Medusae can be conspicuous and abundant members of seafloor communities in deep-sea benthic boundary layers. The epibenthic trachymedusa, Ptychogastria polaris Allman, 1878 (Hydrozoa: Trachylina: Ptychogastriidae) occurs in the cold, high latitude systems of both the northern and southern hemispheres, with a circumpolar distribution in Arctic and s...

Juvenile specimens of the scavenging amphipod Pseudocallisoma coecum (Holmes, 1908) were recorded near the bases of the oral arms of the jellyfish Poralia rufescens Vanhöffen, 1902 in the Japan Trench. Video footage and sampling imply a high infection rate of Poralia, with one to six amphipod specimens occurring on each P. rufescens individual. The...

Here we adopt the classifications of Ctenophora proposed by Harbison (1996), updated by Mianzan (1999) and more recently by Mills (Wrobel and Mills, 1998; Mills and Haddock, 2007). The main diagnostic characters are those suggested by Mayer (1912), Liley (1958), Greve (1975), Harbison (1985, 1996), O'Sullivan (1986), and Harbison and Madin (1982)....

Here we generally adopt the classification from the World Register of Marine Species, which is the most up-to-date classification of the group. Over the years the systematics of this group has been repeatedly revised and some authors have raised the order Siphonophora to a subclass of the class Hydrozoa (e.g. Pugh, 1999; Bouillon et al., 2006). Mol...

https://www.crcpress.com/Oceanography-and-Marine-Biology-An-Annual-Review-Volume-54/Hughes-Hughes-Smith-Dale/p/book/9781498747981

Genetic barcodes of arctic medusae and meiobenthic cnidarians have uncovered a fortuitous connection between the medusa Plotocnide borealis Wagner, 1885 and the minute, mud-dwelling polyp Boreohydra simplex Westblad, 1937. Little to no sequence differences exist among independently collected samples identified as Boreohydra simplex and Plotocnide b...