Geir Johnsen

• Professor at Norwegian University of Science and Technology

We present the first record of a wood-boring, deep-sea mollusk belonging to the genus Xyloredo from the high Arctic. Wood-boring mollusks of the genus Teredo have previously sporadically been documented in the Arctic, but only in shallow waters strongly affected by relative warm Atlantic waters. Our finding not only identifies a new and until now u...

The push broom design of an underwater hyperspectral imaging (UHI) instrument makes it possible to measure angle-resolved spectral radiance ${ L}(\lambda)$ in a plane. We describe the characterization of a commercial UHI instrument (UHI-4, Ecotone AS, Norway) and the spectral, geometric, and radiometric calibration transfer for measuring ${L}(\lamb...

In situ spectral reflectance initially captured at high spatial resolution with underwater hyperspectral imaging (UHI) is effective for classification and quantification in oceanic biogeochemical studies; however, the measured spectral radiance is rarely used as an absolute quantity due to challenges in calibration of UHI instruments. In this paper...

Expanding spatial presentation from two-dimensional profile transects to three-dimensional ocean mapping is key for a better understanding of ocean processes. Phytoplankton distributions can be highly patchy and the accurate identification of these patches with the context, variability, and uncertainty of measurements on relevant scales is difficul...

Seaweed farming is the fastest-growing aquaculture sector worldwide. As farms continue to expand, automated methods for monitoring growth and biomass become increasingly important. Imaging techniques, such as Computer Vision (CV), which allow automatic object detection and segmentation can be used for rapid estimation of underwater kelp size. Here,...

The spring phytoplankton bloom plays a major role in pelagic ecosystems; however, its dynamics are not well understood due to insufficient, highly resolved observational data. Here we investigate the start, peak, and decline of a 2‐week phytoplankton spring bloom in Frohavet located in a biological hotspot of the coast of mid‐Norway. We used observ...

The Barents Sea is one of the Polar regions where current climate and ecosystem change is most pronounced. Here we review the current state of knowledge of the physical, chemical and biological systems in the Barents Sea. Physical conditions in this area are characterized by large seasonal contrasts between partial sea-ice cover in winter and sprin...

The optical chain and logger (OptiCAL) is an autonomous ice-tethered observatory equipped with multiple light sensors for mapping the variation of light with depth. We describe the instrument and present an ensemble calibration for downwelling irradiance ${{\rm E}_{{\rm PAR}}}$ in [ $\unicode{x00B5}{\rm mol}\;{\rm m^{- 2}}{\rm s^{- 1}}$ ]. Results...

Arctic macroalgae species have developed different growth strategies to survive extreme seasonal changes in irradiance in polar regions. We compared photophysiological parameters such as the light saturation parameter (Ek) and pigment composition of green, red, and brown macroalgae collected in January (Polar Night) and October 2020 (end of the lig...

The spring phytoplankton bloom plays a major role in pelagic ecosystems; however, its dynamics is overlooked due to insufficient, highly-resolved observational data. Here we investigate the start, peak and decline of a two-week phytoplankton spring bloom in Frohavet, located at the coast of mid-Norway. We used observations from an uncrewed surface...

The ArcLight observatory provides an hourly continuous time series of all-sky images providing light climate data (intensity, spectral composition, and photoperiod) from the Arctic (Svalbard at 79°N). Until recently, no complete annual time series of light climate relevant for biological processes has been provided from the high Arctic because of i...

The HYPSO-1 satellite, a 6U CubeSat carrying a hyperspectral imager, was launched on 13 January 2022, with the Goal of imaging ocean color in support of marine research. This article describes the development and current status of the mission and payload operations, including examples of agile planning, captures with low revisit time and time serie...

Climate change, and other human-induced impacts, are severely increasing the intensity and occurrences of algal blooms in coastal regions (IPCC, 2022). Ocean warming, marine heatwaves, and eutrophication promote suitable conditions for rapid phytoplankton growth and biomass accumulation. An increase in such primary producers provides food for marin...

Arctic marine ecosystems are strongly influenced by the extreme seasonality of light in the region. Accurate determination of light is essential for building a comprehensive understanding of the dynamics of animal and aquatic algae populations. Current approaches to underwater light field parameterisations rely upon shortwave radiation (300–3000 nm...

The high photosynthetic productivity of the Mausund bank on the coast of mid-Norway has given the area important economic and ecologic value. Monitoring chlorophyll-a (chl-a) production can assist in managing the local aquaculture and ecosystem. Hyperspectral imagers (HSIs), with frequent revisit times when used on a small satellite, have the poten...

Plankton distributions are remarkably ‘patchy’ in the ocean. In this study, we investigated the contrasting phytoplankton-zooplankton distributions in relation to wind mixing events in waters around a biodiversity-rich island (Runde) located off the western coast of Norway. We used adaptive sampling from AUV and shipboard profiles of in-situ phytop...

On the Tautra Ridge – a 39-100 m deep morainic sill located in the middle of the Trondheimsfjord, Norway – some of the world’s shallowest known occurrences of the scleractinian cold-water coral (CWC) Desmophyllum pertusum can be found. The earliest D. pertusum records from the Tautra Ridge date back to the 18th century, and since then, the location...

We describe an Underwater Hyperspectral Imager (UHI) deployed on an instrument-carrying platform consisting of two interconnected mini-ROVs (Remotely Operated Vehicle) for the mapping and monitoring of Arctic macroalgal habitats in Kongsfjorden (Svalbard) during the Polar Night. The mini-ROV-UHI system is easy to transport, assemble and deploy from...

The sacoglossan sea slug Plakobranchus ocellatus is a pantropical gastropod that pilfers and incorporates algal chloroplasts (kleptoplasts) into its digestive cells and benefits from the production of photosynthate. It is a mobile, reef forager with mottled, wing-like parapodia that provide good camouflage in sand and are typically observed closed...

This article proposes a novel methodology for precise georegistration in underwater hyperspectral imaging (UHI) using a red–green–blue (RGB) camera to build a photogrammetry model that estimates the pose and a 3-D seabed model. The two main scientific contributions are: 1) the development of two methods for geometric calibration of the hyperspectra...

Light plays a fundamental role in the ecology of organisms in nearly all habitats on Earth and is central for processes such as vision and the entrainment of the circadian clock. The poles represent extreme light regimes with an annual light cycle including periods of Midnight Sun and Polar Night. The Arctic Ocean extends to the North Pole, and mar...

A central challenge in microplastics (MP, diameter < 5 mm) research is the analysis of small plastic particles in an efficient manner. This review focuses on the recent application of infrared hyperspectral imaging (HSI) to analyze MP. We provide a narrative context for understanding technical principles of HSI followed by a systematic review and d...

The ArcLight observatory provides hourly continuous time series of light regime data (intensity, spectral composition, and photoperiod) from the Arctic, Svalbard at 79° N. Until now, no complete annual time series of biologically relevant light has been provided from the high Arctic due to insufficient sensitivity of commercial light sensors during...

In situ observations of pelagic fish and zooplankton with optical instruments usually rely on external light sources. However, artificial light may attract or repulse marine organisms, which results in biased measurements. It is often assumed that most pelagic organisms do not perceive the red part of the visible spectrum and that red light can be...

In total, 90 gelatinous spheres, averaging one meter in diameter, have been recorded from ~1985 to 2019 from the NE Atlantic Ocean, including the Mediterranean Sea, using citizen science. More than 50% had a dark streak through center. They were recorded from the surface to ~60-70 m depth, mainly neutrally buoyant, in temperatures between 8-24⁰C....

A R T I C L E I N F O Keywords: Phytoplankton community succession Pigments In situ optical sensors (fluorescence and backscattering) Hydrography A B S T R A C T The phytoplankton in coastal regions are responding to constant environmental changes, thus the use of proxies derived from in situ frequent time-series observations and validated from tra...

Review protocol

The Mohn’s Treasure, described as an inactive sulfide mound, was discovered at 2,600-m depth on the Arctic Mid-Ocean Ridge (AMOR) in 2002. In 2015, we conducted the first biological survey of Mohn’s Treasure using remotely operated vehicle (ROV) photo transects and sampling. This site is covered by a thick layer of fine sediments, where hard substr...

The Polar Night has long been regarded as a period of no biological activity. As a logical consequence, environmental management has mainly been neglected in this period. We will use the Northguider accident in December 2018 as a case study for the need to prioritize operative habitat mapping and monitoring to provide a sufficiently knowledge-based...

The Polar Night has a unique beauty. The aurora borealis, the moonlight, the faint glow of the sun behind white mountains, and, not the least, the mysteries of the living creatures that we have found in the Polar Night – this, in addition to the many scientific discoveries that have radically changed our perception of what the Polar Night is, inspi...

How much light is available for biological processes during Polar Night? This question appears simple enough. But the reality is that conventional light sensors for measuring visible light (~350 to ~700 nm) have not been sensitive enough to answer it. Beyond this technical challenge, “light” is a general term that must be qualified in terms of “lig...

Microalgae have unique adaptions including low metabolic activity, utilization of lipid storage, and resting stage formation to survive the Polar Night. Some species are mixotrophic or heterotrophic and do survive periods that are not favorable for photosynthetic (autotrophic) growth, such as the Polar Night. In addition, the autotrophic and mixotr...

In 2007, a possible wreck site was discovered in Trygghamna, Isfjorden, Svalbard by the Norwegian Hydrographic Service. Using (1) a REMUS 100 autonomous underwater vehicle (AUV) equipped with a sidescan sonar (SSS) and (2) a Seabotix LBV 200 mini-remotely operated vehicle (ROV) with a high-definition (HD) camera, the wreck was in 2015 identified as...

For organisms that remain active in one of the last undisturbed and pristine dark environments on the planet—the Arctic Polar Night—the moon, stars and aurora borealis may provide important cues to guide distribution and behaviours, including predator-prey interactions. With a changing climate and increased human activities in the Arctic, such natu...

Until recently, the prevailing view of marine life at high latitudes has been that organisms enter a general resting state during the dark Polar Night and that the system only awakens with the return of the sun. Recent research, however, with coordinated, multidisciplinary field campaigns based on the high Arctic Archipelago of Svalbard, have provi...

Due to its Arctic location at 79°N, Kongsfjorden in Svalbard experiences strong seasonality in light climate, changing from polar night to midnight sun. Sea ice conditions and the optical properties of seawater further modify the amount and the spectral composition of solar radiation penetrating into the water column, thus defining the underwater l...

Plankton are an extremely diverse and polyphyletic group, exhibiting a large range in morphological and physiological traits. Here, we apply automated optical techniques, provided by the pulse‐shape recording automated flow cytometer—CytoSense—to investigate trait variability of phytoplankton and plastidic ciliates in Arctic and Atlantic waters of...

The impacts of human activity on coastal ecosystems are becoming increasingly evident across the world. Consequently, there is a growing need to map, monitor, and manage these regions in a sustainable manner. In this pilot study, we present what we believe to be a novel mapping technique for shallow-water seafloor habitats: Underwater hyperspectral...

Recent reports on Arctic underice phytoplankton blooms have directed attention to primary production below the sea ice cover. Such underice blooms cannot be detected from space; thus, methods for autonomous underice measurements are critically needed to extend observations beyond ship‐based surveys. One central aspect of the ecology of these blooms...

Trace metal or Rare Earth Element (REE) content of marine macroalgae are underexamined and there is a great need for further understanding since macroalgae are used for food and may also be bioindicators of environmental changes. This study, by using High Resolution Inductive Coupled Plasma Spectrometer (HR‐ICP‐MS) in a clean lab (Class 1000), inve...

Currents, wind, bathymetry, and freshwater runoff are some of the factors that make coastal waters heterogeneous, patchy, and scientifically interesting—where it is challenging to resolve the spatiotemporal variation within the water column. We present methods and results from field experiments using an autonomous underwater vehicle (AUV) with embe...

Underwater hyperspectral imaging is a relatively new method for characterizing seafloor composition. To date, it has been deployed from moving underwater vehicles, such as remotely operated vehicles and autonomous underwater vehicles. While moving vehicles allow relatively rapid surveying of several 10-1000 m², they are subjected to short-term vari...

Diatoms are a keystone algal group, with diverse cell morphology and a global distribution. The biogeography of morphological, functional, and life-history traits of marine diatoms were investigated in Arctic and Atlantic waters of the Labrador Sea during the spring bloom (2013-2014). In this study, trait-based analysis using community-weighted mea...

Abstract Identification of benthic megafauna is commonly based on analysis of physical samples or imagery acquired by cameras mounted on underwater platforms. Physical collection of samples is difficult, particularly from the deep sea, and identification of taxonomic morphotypes from imagery depends on resolution and investigator experience. Here,...

Efficient sampling of coastal ocean processes, especially mechanisms such as upwelling and internal waves and their influence on primary production, is critical for understanding our changing oceans. Coupling robotic sampling with ocean models provides an effective approach to adaptively sample such features. We present methods that capitalize on i...

The jellyfish Periphylla periphylla, which can have strong ecological impacts on its environment, is ubiquitous in the Norwegian Sea and its range was predicted to extend northwards. The occurrence of P. periphylla in the northern Barents Sea increased since 2014 and, for the first time, several individuals were collected within a high Arctic fjord...

The importance of newly formed sea ice in spring is likely to increase with formation of leads in a more dynamic Arctic icescape. We followed the ice algal species succession in young ice (≤0.27 m) in spring at high temporal resolution (sampling every second day for 1 month in May-June 2015) in the Arctic Ocean north of Svalbard. We document the ea...

Under-ice blooms of phytoplankton in the Chukchi Sea have been observed, with strong implications for our understanding of the production regimes in the Arctic Ocean. Using a combination of satellite remote sensing of phytoplankton biomass, in situ observations under sea ice from an autonomous underwater vehicle (AUV), and in vivo photophysiology,...

Hyperspectral seafloor surveys using airborne or spaceborne sensors are generally limited to shallow coastal areas, due to the requirement for target illumination by sunlight. Deeper marine environments devoid of sunlight cannot be imaged by conventional hyperspectral imagers. Instead, a close-range, sunlight-independent hyperspectral survey approa...

Anthropogenic disturbances in the marine environment, such as excessive sedimentation produced by mine tailing deposition, can affect the physiology and behavior of benthic fauna. Mine tailing particles are sharper than natural occurring sediments and could therefore cause more harmful effects. Cold-water coral ecosystems are among the habitats in...

By applying an underwater hyperspectral imager (UHI) to a selection of archaeological artifacts, we have found spectral signatures that are representative of materials likely to be present at wreck sites. By successfully using the signatures to classify a subset of said artifacts placed on the seabed at 61 m depth, we demonstrate that it is possibl...

Light is a major cue for nearly all life on Earth. However, most of our knowledge concerning the importance of light is based on organisms’ response to light during daytime, including the dusk and dawn phase. When it is dark, light is most often considered as pollution, with increasing appreciation of its negative ecological effects. Using an Auton...

Coralline algae constitute a cosmopolitan group of calcifying rhodophytes (red algae) that display characteristic optical fingerprints due to light absorption by specific light-harvesting pigments. The spectrally conspicuous nature of coralline algae makes them potential candidates for optical remote sensing surveys. Recently, underwater hyperspect...

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Visually-oriented predators, such as seabirds, are highly light dependent, and thus their presence and activity under continuously dark conditions of Arctic polar night pose a number of questions about the strategies and mechanisms they use to find prey. Here, opportunistic observations of the behaviors of Thick-billed Murres (Uria lomvia; n = 4) a...

The Arctic Ocean is rapidly changing from thicker multiyear to thinner first-year ice cover, with significant consequences for radiative transfer through the ice pack and light availability for algal growth. A thinner, more dynamic ice cover will possibly result in more frequent leads, covered by newly formed ice with little snow cover. We studied...

The Arctic icescape is rapidly transforming from a thicker multiyear ice cover to a thinner and largely seasonal first-year ice cover with significant consequences for Arctic primary production. One critical challenge is to understand how productivity will change within the next decades. Recent studies have reported extensive phytoplankton blooms b...

The Arctic Ocean faces rapid climate change, which impacts both physical and biological components of the marine ecosystem. Due to complicated and costly logistics inherent to sampling ice-covered areas, most studies conducted in the Arctic are based on relatively short-term sampling (weeks to months) centered around the minimum ice season. Given t...

Currently a new underwater hyperspectral imager (UHI) have been deployed on Remotely Operated Vehicles (ROV) for a more automated identification, mapping and monitoring of bio-geo-chemical objects of interest (OOI). Sea floor maps based on UHI can be used to classify 001 based on specific optical fingerprints providing spectral upwelling radiance o...

Bioluminescence commonly influences pelagic trophic interactions at mesopelagic depths. Here we characterize a vertical gradient in structure of a generally low species diversity bioluminescent community at shallower epipelagic depths during the polar night period in a high Arctic fjord with in situ bathyphotometric sampling. Bioluminescence potent...

Based on humans shared cognitive capabilities in detecting and classifying objects and movement, imaging technology should contribute to a general understanding of the marine environment. However, images are complex and interdisciplinary collaborations are required to exploit the images inherent potential by identifying solutions dealing with human...

The current understanding of Arctic ecosystems is deeply rooted in the classical view of a bottom-up controlled system with strong physical forcing and seasonality in primary-production regimes. Consequently, the Arctic polar night is commonly disregarded as a time of year when biological activities are reduced to a minimum due to a reduced food su...

Here it is reported the first detection of DV-chl a together with the usual chl a in the marine dinoflagellate Alexandrium ostenfeldii from the Baltic Sea. Growth response and photosynthetic parameters were examined at two irradiances (80 and 240 μmol photons ·m(-2 ·) s(-1) ) and temperatures (15° and 19 °C) in a divinylic strain (AOTV-OS20) vs a m...

Several recent lines of evidence indicate that the polar night is key to understanding Arctic marine ecosystems. First, the polar night is not a period void of biological activity even though primary production is close to zero, but is rather characterized by a number of processes and interactions yet to be fully understood, including unanticipated...

The light regime is an ecologically important factor in pelagic habitats, influencing a range of biological processes. However, the availability and importance of light to these processes in high Arctic zooplankton communities during periods of 'complete' darkness (polar night) are poorly studied. Here we characterized the ambient light regime thro...

Biofouling on cultivated kelp in open sea conditions is a challenge when fouling species such as the encrusting bryozoans Membranipora membranacea and Electra pilosa develop colonies that cover the surface of the kelp lamina. The bryozoan colonies make the flexible lamina brittle and susceptible to breakage and reduce the commercial value of the bi...

New technology has led to new opportunities for a holistic environmental monitoring approach adjusted to purpose and object of interest. The proposed integrated environmental mapping and monitoring (IEMM) concept, presented in this paper, describes the different steps in such a system from mission of survey to selection of parameters, sensors, sens...