H. J. T. Hoving

GEOMAR Helmholtz Centre for Ocean Research Kiel · Division of Marine Ecology

Many benthic deep‐sea animals rely on carcasses from the overlying water column that sink to the seafloor and form local organic enrichments known as food falls. This flux of organic carbon from the shallow pelagic to the deep sea is part of the biological carbon pump (BCP) and as such contributes to carbon sequestration. For a complete understandi...

Background Assessing the historical dynamics of key food web components is crucial to understand how climate change impacts the structure of Arctic marine ecosystems. Most retrospective stable isotopic studies to date assessed potential ecosystem shifts in the Arctic using vertebrate top predators and filter-feeding invertebrates as proxies. Howeve...

Climate change is threatening marine ecosystems on a global scale but particularly so in the Arctic. As a result of warming, species are shifting their distributions, altering marine communities and predator-prey interactions. This is known as the Atlantification of the Arctic. Warming may favor short-lived, opportunistic species such as cephalopod...

The deep pelagic ocean is increasingly subjected to human-induced environmental change. While pelagic animals provide important ecosystem functions including climate regulation, species-specific responses to stressors remain poorly documented. Here, we investigate the effects of simulated ocean warming and sediment plumes on the cosmopolitan deep-s...

A summary of latest research from the iAtlantic project. https://www.iatlantic.eu/wp-content/uploads/2023/11/iAtlantic_Jellyfish_DSM_brief_webversion.pdf The full study is available as an open access publication: Stenvers, V.I., Hauss, H., Bayer, T., Havermans, C., Hentschel, U., Schmittmann, L., Sweetman, A. & Hoving, H.J.T. (2023) Experimental...

Life in the deep ocean (200 meters or more below the surface) plays a central role in the marine carbon cycle by fixing, transferring, storing, and sequestering carbon from surface waters, forming the largest carbon reservoir on the planet. These processes have allowed the ocean to absorb 90% of excess heat and 25% of CO2 released into the atmosphe...

Climate change is expected to have major negative effects on marine life across phylogenetic groups. Cephalopods, however, have life history characteristics that suggest they may benefit from certain climate change scenarios. Of all cephalopods, squids reach the greatest biomasses; as a result, they are of substantial importance for human and preda...

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...

Abyssal plain communities rely on the overlying water column for a settling flux of organic matter. The origin and rate of this flux as well as the controls on its fine-scale spatial distribution following seafloor settlement are largely unquantified. This is particularly true across regions where anthropogenically-induced seafloor disturbance has...

Deep-sea cephalopods are diverse, abundant, and poorly understood. The Cirrata are gelatinous finned octopods and among the deepest-living cephalopods ever recorded. Their natural feeding behaviour remains undocumented. During deep-sea surveys in the Arctic, we observed Cirroteuthis muelleri. Octopods were encountered with their web spread wide, mo...

Supplementary material for ‘Miles down for lunch: deep-sea in situ observations of Arctic finned octopods Cirroteuthis muelleri suggest pelagic-benthic feeding migration’

Global warming causes profound environmental shifts in the Arctic Ocean, altering the composition and structure of communities. In the Fram Strait, a transitional zone between the North-Atlantic and Arctic Ocean, climate change effects are particularly pronounced and accelerated due to an increased inflow of warm Atlantic water. Gelatinous zooplank...

The Arctic Ocean is home to a unique fauna that is disproportionately affected by global warming but that remains under‐studied. Due to their high mobility and responsiveness to global warming, cephalopods and fishes are good indicators of the reshuffling of Arctic communities. Here, we established a nekton biodiversity baseline for the Fram Strait...

Ocean manipulation to mitigate climate change may harm deep-sea ecosystems.

Climate change is expected to produce major effects across marine life, and cephalopods seem to benefit from these effects. Of these animals, squids exhibit the greatest levels of biomass and of a substantial importance for human consumption. To test the hypothesis that effects of climate change are beneficial for commercial squid, we used species...

Massive swarms of the red crab, Pleuroncodes planipes (Stimpson 1860), a species of squat lobster, are a dominant functional component of the upwelling ecosystem in the eastern Pacific Ocean. These swarms can wash ashore on the coast creating mass depositions of crustacean carcasses, a striking phenomenon that has been long documented in Baja Calif...

At depths below 200 m, the pelagic deep sea comprises the largest, but least explored, part of the ocean. In this vast environment, animals are hard to find, and interactions among them are even harder to investigate (Robison, 2009). Climate change and industrial exploitation simultaneously impose increasing pressure on deep-sea ecosystems, leading...

Cephalopods are important in Arctic marine ecosystems as predators and prey, but knowledge of their life cycles is poor. Consequently, they are under-represented in the Arctic ecosystems assessment models. One important parameter is the change in ecological role (habitat and diet) associated with individual ontogenies. Here, the life history of Gon...

Supplementary file for the following paper: https://www.mdpi.com/2076-2615/12/24/3548

When pelagic organisms die and fall onto the deep-sea floor they create food falls, i.e., parcels of organic enrichment that subsidize deep benthic scavenging communities. The diversity and quantities of food falls remain unstudied for many ocean regions since they are stochastically deposited and rapidly scavenged. The Southern Ocean habitat suppo...

The Southern Ocean is a challenging study site due to its remoteness and climate. Octopods have an important trophic role as both predator and prey in this extreme habitat and belong to the diverse, endemic megafauna of the benthic communities found in Antarctica. Yet, major parts of their lifestyle, diversity and distribution are unknown for most...

Underwater images are used to explore and monitor ocean habitats, generating huge datasets with unusual data characteristics that preclude traditional data management strategies. Due to the lack of universally adopted data standards, image data collected from the marine environment are increasing in heterogeneity, preventing objective comparison. T...

Deep-sea benthic communities depend on food that reaches the seafloor from the overlying water column as well as from in-situ autotrophic production. Sinking carcasses (food falls) from jellyfish and squid contribute to this nutrient flux, but natural medium-sized food falls are rarely observed. Consequently, little is known about scavenging commun...

Cephalopods are abundant predator mollusks in the ocean, with squids being the most prominent in human consumption. In the last sixty years, commercial cephalopod populations have increased and expanded poleward, due to their high flexibility. However, physiological and modelling studies have shown impairments and declines for these animals in futu...

Calcifying plankton in the upper ocean produce calcium carbonate (CaCO3) shells that sink to the seafloor after death resulting in the vertical transport of inorganic carbon in shells and organic carbon in carcasses. In situ observations of pelagic detritus on the abyssal plain are very scarce. Carcasses are rapidly scavenged and shells may dissolv...

During pelagic video transects off Santo Antão, Cabo Verde, we encountered the midwater scorpionfish Ectreposebastes imus in midwater between 300 and 800 m over a bottom depth of about 1000 m. The fish were typically positioned vertically with their heads pointing upwards. These first midwater observations of E. imus suggest migratory (potentially...

The distributions of marine ectotherms are governed by physiological sensitivities to long-term trends in seawater temperature and dissolved oxygen. Short-term variability in these parameters has the potential to facilitate rapid range expansions, and the resulting ecological and socioeconomic consequences may portend those of future marine communi...

The deep sea is among the largest, most biologically diverse, yet least-explored ecosystems on Earth. Baseline information on deep-sea biodiversity is crucial for understanding ecosystem functioning and for detecting community changes. Here, we established a baseline of cephalopod community composition and distribution off Cabo Verde, an archipelag...

Cruise report of the FramJelly project on the RV Polarstern expedition PS126 to Fram Strait

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...

Octopods are dominant players of the benthic megafauna of the Weddell Sea over large depth ranges • Largest database of Southern Ocean Octopods in situ observations allows distribution, behavioural and diversity studies • The slopes of the Weddell Sea receive organic input by various types of food falls • Differences in octopod abundance and specie...

Holopelagic animals were long assumed to have widespread geographic distributions due to the failure to recognize hydrographic species' barriers in the open ocean. As molecular genetic tools are more commonly used to study the ocean's inhabitants, diversity is found to be substantially higher than when inferred from morphological taxonomies alone....

Observations of the diversity, distribution and abundance of pelagic fauna are absent for many ocean regions in the Atlantic, but baseline data are required to detect changes in communities as a result of climate change. Gelatinous fauna are increasingly recognized as vital players in oceanic food webs, but sampling these delicate organisms in nets...

Gelatinous zooplankton are increasingly acknowledged to contribute significantly to the carbon cycle worldwide, yet many taxa within this diverse group remain poorly studied. Here, we investigate the pelagic tunicate Pyrosoma atlanticum in the waters surrounding the Cabo Verde Archipelago. By using a combination of pelagic and benthic in situ obser...

Nervous systems across Animalia not only share a common blueprint at the biophysical and molecular level, but even between diverse groups of animals the structure and neuronal organization of several brain regions are strikingly conserved. Despite variation in the morphology and complexity of eyes across malacostracan crustaceans, many studies have...

Cephalopod fisheries have expanded over the last decade. They are characterised by annual uncertainty in yield quantity and quality. This is attributed to changes in environmental conditions such as temperature combined with the semelparous life strategy (one reproductive cycle during life) of the majority of squid species. We determined the effect...

Gonatus fabricii (Lichtenstein, 1818) is an ecologically important squid that spends its entire life cycle within the Arctic where it is the most abundant cephalopod. Due to the rarity of mature and reproducing females, it is unknown how many eggs females spawn (actual fecundity). Among 47,000 specimens studied between 2005 and 2019 one spent, dege...

Fundamental insight on predator-prey dynamics in the deep sea is hampered by a lack of combined data on hunting behavior and prey spectra. Deep-sea niche segregation may evolve when predators target specific prey communities, but this hypothesis remains untested. We combined environmental DNA (eDNA) metabarcoding with biologging to assess cephalopo...

Cephalopods are pivotal components of marine food webs, but biodiversity studies are hampered by challenges to sample these agile marine molluscs. Metabarcoding of environmental DNA (eDNA) is a potentially powerful technique to study oceanic cephalopod biodiversity and distribution but has not been applied thus far. We present a novel universal pri...

In the deep sea, benthic communities largely depend on organic material from the overlying water column for food. The remains of organisms on the seafloor (food falls) create areas of organic enrichment that attract scavengers. The scavenging rates and communities of food falls of medium-sized squid, fish and jellyfish (1-100 cm) are poorly known....

Distribution patterns of fragile gelatinous fauna in the open ocean remain scarcely documented. Using epi-and mesopelagic video transects in the eastern tropical North Atlantic, which features a mild but intensifying midwater oxygen minimum zone (OMZ), we established one of the first regional observations of diversity and abundance of large gelatin...

Gelatinous zooplankton can be present in high biomass and taxonomic diversity in planktonic oceanic food webs, yet the trophic structuring and importance of this “jelly web” remain incompletely understood. To address this knowledge gap, we provide a holistic trophic characterization of a jelly web in the eastern tropical Atlantic, based on δ13C and...

Despite the ecological and economic importance of oceanic squids of the order Oegopsida Orbigny 1845, they are among the most mysterious groups of pelagic organisms. Starting in October 2019, the 2-year postdoc project GOIPD/2019/460 “Genome and specific biodiversity of oceanic squids assessed through Next Generation Sequencing”, funded by the Iris...

The pelagic cephalopods Japetella diaphana and Vampyroteuthis infernalis are charismatic and widely distributed members of deep pelagic ecosystems. Their habitat temperatures, metabolic rates, feeding and reproductive strategies all together suggest that the pace of life in these species is reduced when compared to neritic octopod species, but info...

I'm interested in cephalopod phylogenetics, systematics, taxonomy, natural history, reproductive biology and trophic ecology of cephalopods, especially oceanic squids. Currently, as an Irish Research Council postdoc fellow, my research is focussed on the phylogenetics of oegopsid squids, assessed through shallow whole genome sequencing (Genome Skim...

The ecology of vertically migrating mesopelagic micronekton is affected by physical properties of their environment. Increased light attenuation in particle-rich productive waters, as well as low oxygen conditions decrease the migration amplitude. This likely has implications on the trophic organisation of micronekton communities, which are predomi...

Background The giant squid (Architeuthis dux; Steenstrup, 1857) is an enigmatic giant mollusc with a circumglobal distribution in the deep ocean, except in the high Arctic and Antarctic waters. The elusiveness of the species makes it difficult to study. Thus, having a genome assembled for this deep-sea–dwelling species will allow several pending ev...

Vampyroteuthis infernalis Chun, 1903, is a widely distributed deepwater cephalopod with unique morphology and phylogenetic position. We assessed its habitat and trophic ecology on a global scale via stable isotope analyses of a unique collection of beaks from 104 specimens from the Atlantic, Pacific and Indian Oceans. Cephalopods typically are acti...

There is a need for cost-efficient tools to explore deep-ocean ecosystems to collect baseline biological observations on pelagic fauna (zooplankton and nekton) and establish the vertical ecological zonation in the deep sea. The Pelagic In situ Observation System (PELAGIOS) is a 3000 m rated slowly (0.5 m s-1) towed camera system with LED illuminati...

The jumbo squid Dosidicus gigas was recently claimed to be an iteroparous species with ovaries returning to an immature, resting stage after spawning. Analysis of the data and figures presented in two recent articles revealed that this claim was based on misinterpretation of histological information and that Dosidicus is not iteroparous. Having con...

As a general trend in the life history of marine organisms, species inhabiting cold waters have reduced growth rates and increased lifespans. Studies based on egg sizes and brooding times of deep-sea and polar octopods support this hypothesis, but empirical data on growth are still scarce. To test the hypothesis that octopods inhabiting cold waters...

Reproductive systems of rare adult specimens of the deep-sea squid genera Chiroteuthis, Mastigoteuthis, Liocranchia, and Bathoteuthis were collected in 2006 and 2015 in the different research surveys in the Atlantic Ocean between 46°40′S and 17°11′N. Whole squids were preserved in 4% buffered formaldehyde solution, subsequently transferred into 70%...

Dosidicus gigas (the Humboldt squid) is a widely distributed and ecologically important predator in the eastern Pacific Ocean, but its mating behaviour is poorly understood. Individuals of this species have undergone a drastic change in size at maturity in the last years. We investigated mating activity of Humboldt squid in the Gulf of California i...

There is a need for cost-efficient tools to explore deep ocean ecosystems to collect baseline biological observations on pelagic fauna (zooplankton and nekton) and establish the vertical ecological zonation in the deep sea. The Pelagic In situ Observation System (PELAGIOS) is a 3000m-rated slowly (0.5m/s) towed camera system with LED illumination,...

We report on the first records of Kiyohimea usagi Matsumoto & Robison 1992 (Ctenophora; Eurhamphaeidae) in the Atlantic Ocean. This large, fragile ctenophore cannot be captured by nets, and can only be studied in its natural habitat, the pelagic ocean. In the eastern Atlantic, in the Cape Verde region, in situ observations were obtained using the m...

ICES CM 2016/+H Title of abstract: Assessing life-cycle and longevity of cold water octopods (Cephalopoda: Octopoda) using growth marks on hard body structures. Name(s) of authors: Richard Schwarz, Hendrik Jan T. Hoving, Uwe Piatkowski, Thorsten Reusch Life cycle studies on cephalopods have focused mostly on the near shore forms of squid and octop...

Recent studies on the life history of cephalopods have challenged the paradigm that all coleoid cephalopods have a single reproductive cycle and a short lifespan. Although lifespan has been investigated in several octopod species, few studies have considered their life-history traits in relation to environmental conditions via a comparative approac...

In recent decades the Cabo Verde ichthyofauna has been studied more extensively, and nowadays photo-recording is employed as a valuable asset under special caution and consideration. Four species reported here are new records for Cabo Verde: Carlarius sp., sea catfish; Serranus cabrilla, comber; Branchiostegus semifasciatus, African tilefish and Lu...

The orange-back flying squid, Sthenoteuthis pteropus, plays an important role in the eastern tropical Atlantic Ocean (ETA) pelagic food web, as both predator and prey. Specimens of S. pteropus were caught off the Cape Verde Islands and concentrations of Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V, and Zn were measured in the digestive gland....

Gelatinous zooplankton hold key functions in the ocean and have been shown to significantly influence the transport of organic carbon to the deep sea. We discovered a gelatinous, flux‐feeding polychaete of the genus Poeobius in very high abundances in a mesoscale eddy in the tropical Atlantic Ocean, where it co‐occurred with extremely low particle...