Mareano Leg 1 2023 Easter Cruise Report — Cruise Report 2023001005

This cruise (onboard the RV G.O. Sars, 30.03.2023 to 12.04.2023 - 13 Days long starting and ending in Bergen, Norway) was focussed on surveying the coastal belt east of “Utsira Nord” (Utsira KB) and the two multibeam mapped areas close to “Sørlige Nordsjø II” (NSJ-1 and NSJ-2). These areas are of interest due to their proximity to the named offshore wind license areas and due to their overlap with “særlig verdiful områder” (SVO) which are areas of particular scientific and management interest. The MAREANO baseline mapping method was applied, but this cruise was focussed upon completing the video lines in these areas, and testing the munin+ AUV for data uses and the integration of AUVs into the Mareano method. In addition, the Oil Directorate asked for 2 gravity cores from areas with suspected natural oil leakage, and limited physical sampling equipment was taken for contingency use. One hundred and twenty reference stations were visited including completing 112 (225m long) video lines, along with 5 AUV missions (collecting EM2040, HISAS2040, SBP, CT, photo data). Furthermore, 8 CTDs, 5 Boxcores, 4 Multicores, 2 stations with grabs for checking if the gravity corer can be used (no proposed site had suitable substrate for gravity coring), and 2 stations with 5 replicate grabs each for biology/geology were completed. Topaz subbottom profiling (SBP) data was collected along and between video lines and all gravity corer proposed sites, with additional water column multibeam echosounder (EM302) data also collected over all the proposed gravity corer sites. Note that 3 video lines, 1 AUV mission and 2 CTD sites were within the fjords near stavanger (during poor weather) in areas where FOH granted declassificaiton for AUV activities.Mareano Leg 1 2023 Easter Cruise Report — Cruise Report 2023001005publishedVersio

Gas seeps in Norwegian waters – distribution and mechanisms

Gas seeps and fluid-flow related seabed features are found over the entire Norwegian exclusive economic zone (EEZ). Multibeam water-column data from c. 136 000 km2 has revealed more than 5 000 gas seeps. Most of the gas seeps seem to have biogenic, thermogenic or mixed origin; some may be of abiotic origin. The spatial distribution of the gas seeps appears to correlate with: 1 – structural highs with associated faulting, exposing hydrocarbon reservoir rocks at or near the seabed; 2 – faults serving as conduits for fluid flow; 3 – settings where reservoir rocks overlain by less permeable cap rocks sub-crop at the seabed. Other mechanisms involve seepage around abandoned exploration wells, and possible abiotic gas generation from serpentinisation of ultramafic rocks near mid-oceanic ridges. The gas seeping from the Norwegian cold seeps is mostly methane and has, in many places, led to the formation of methane-derived authigenic carbonate crusts, which give evidence for either extensive gas seepage in the past or long-lived seepage. Chemosynthetic communities are commonly associated with cold seeps and may form special habitats together with the carbonate crusts. Methane seepage has been proposed to contribute significantly to the global carbon budget and may be associated with gas hydrates giving rise to potential geohazards. Gas seeps have been identified and spatially mapped as acoustic gas flares, using multibeam echosounder systems, which have the ability to record reflections from both the water column and the seabed. Water-column data have been recorded in the MAREANO seabed mapping program since 2010, covering an area of c. 262 000 km2 , with a data volume in the order of 210 Tb. The observations of extensive gas flares in the Norwegian EEZ are available to the scientific community and other users through a dedicated MAREANO data and web access system

Timescales of methane seepage on the Norwegian margin following collapse of the Scandinavian Ice Sheet

Gas hydrates stored on continental shelves are susceptible to dissociation triggered by environmental changes. Knowledge of the timescales of gas hydrate dissociation and subsequent methane release are critical in understanding the impact of marine gas hydrates on the ocean–atmosphere system. Here we report a methane efflux chronology from five sites, at depths of 220–400 m, in the southwest Barents and Norwegian seas where grounded ice sheets led to thickening of the gas hydrate stability zone during the last glaciation. The onset of methane release was coincident with deglaciation-induced pressure release and thinning of the hydrate stability zone. Methane efflux continued for 7–10 kyr, tracking hydrate stability changes controlled by relative sea-level rise, bottom water warming and fluid pathway evolution in response to changing stress fields. The protracted nature of seafloor methane emissions probably attenuated the impact of hydrate dissociation on the climate system

Sandbanks, sandwaves and megaripples on Spitsbergenbanken, Barents Sea

Recently acquired multibeam echosounder data from the shallowest part (26–53 m depth) of Spitsbergenbanken in the western Barents Sea reveal a variety of bedforms, including megaripples, sandwaves and sandbanks. The bedforms exhibit varying degrees of superimposition and differ in their age of formation and present depositional regime, being either active or moribund. These are the first observations of co-occurring current induced bedforms in the western Barents Sea and provide evidence of a high energy environment in the study area. The bedforms indicate both sediment erosion and transport and confirm that there is enough sand available in this area to maintain them. Such conditions are not known to be common in the western Barents Sea and reflect the unique oceanographic and benthic environment of Spitsbergenbanken.publishedVersio

Status for miljøet i norske havområder - Rapport fra Overvåkingsgruppen 2023

I denne rapporten gir Overvåkingsgruppen, for første gang, en felles vurdering av miljøtilstanden i Barentshavet og havområdene utenfor Lofoten, Norskehavet og Nordsjøen med Skagerrak. Det er også første rapport som bruker resultater fra det nylig utviklede fagsystemet for vurdering av økologisk tilstand. I denne rapporten dekkes to hovedtemaer: (1) Dominerende trekk i status og utvikling i økosystemet i alle tre havområdene, basert på vurderingene av økologisk tilstand, Overvåkingsgruppens rapport om forurensning fra 2022, indikatorer fra Overvåkingsgruppen som ikke er dekket under vurdering av økologisk tilstand, samt rapporter og annen relevant informasjon fra forskning, og (2) en vurdering av karbonbinding i marint plankton, marine vegetasjonstyper og marine sedimenter. I tillegg er det gitt en oppsummering for endringer i ytre påvirkning, vurdering av kunnskapsbehov samt en vurdering av indikatorverdier i forhold til referanseverdier og tiltaksgrenser. Vurderingen av dominerende trekk i utvikling og tilstand av miljøet som er gitt i kapittel 2, utgjør Overvåkingsgruppens bidrag til Faglig forums samlerapport om det faglige grunnlaget for revisjon og oppdatering av de helhetlige forvaltningsplanene for norske havområder.Status for miljøet i norske havområder - Rapport fra Overvåkingsgruppen 2023publishedVersio

Mapping of Cold-Water Coral Carbonate Mounds Based on Geomorphometric Features: An Object-Based Approach

Cold-water coral reefs are rich, yet fragile ecosystems found in colder oceanic waters. Knowledge of their spatial distribution on continental shelves, slopes, seamounts and ridge systems is vital for marine spatial planning and conservation. Cold-water corals frequently form conspicuous carbonate mounds of varying sizes, which are identifiable from multibeam echosounder bathymetry and derived geomorphometric attributes. However, the often-large number of mounds makes manual interpretation and mapping a tedious process. We present a methodology that combines image segmentation and random forest spatial prediction with the aim to derive maps of carbonate mounds and an associated measure of confidence. We demonstrate our method based on multibeam echosounder data from Iverryggen on the mid-Norwegian shelf. We identified the image-object mean planar curvature as the most important predictor. The presence and absence of carbonate mounds is mapped with high accuracy. Spatially-explicit confidence in the predictions is derived from the predicted probability and whether the predictions are within or outside the modelled range of values and is generally high. We plan to apply the showcased method to other areas of the Norwegian continental shelf and slope where multibeam echosounder data have been collected with the aim to provide crucial information for marine spatial planning

Physical properties of sediments in the Norwegian Trough measured on short cores taken between 1992 and 1996

Wet bulk density, dry bulk density, porosity, water content and water saturation of sediments from the Norwegian Trough were determined on short cores taken between 1992 and 1996. On the cruises 17-25 July 1992 (station 2-55) and 1-6 July 1993 (station 56-75) in the easternmost part of the Skagerrak, cores were taken with a Niemistö corer. Plastic liners (length 76 cm, outer diameter 63 mm, inner diameter 59 mm) were placed in the corer with holes drilled every five centimetres downwards. These holes were sealed with tape before sampling. After the sample was taken, the tape was removed. In most cases, there was water along the inside of the plastic liner. This water was allowed to drain before sub-samples were taken. Then plastic syringes without a tip were carefully inserted into each hole, and 10 ml of wet sediment was taken out. The sub-samples were then pressed out of the syringes into plastic bags that had been weighed in advance and stored in a refrigerator until they were measured in the laboratory. Upon arrival at the laboratory, the plastic bags with samples were weighed, the weight of the plastic bags was deducted, and the weight of 10 ml of the wet sample was noted. The weight of the dry sample was found by transferring the sample material onto a pre-weighted ceramic bowl before it was weighed again, then drying the bowl with sample in drying cabinet at 70 degrees C for 24 hours, and finally weighing the bowl with sample after drying. The weight of 10 ml of dry sample corresponds to the difference before and after drying. On the cruises 5-16 June 1994 (stations 76-133), 17-24 July 1995 (stations 135-180) and 9-19 September 1996 (stations 181-286), cores were taken with a multicorer. Plastic liners (length 61 cm, outer diameter 63 mm, inner diameter 59 mm) were placed in the corer, which after sampling was closed at both ends with rubber caps to prevent water in the core and on top of the core from leaking out or to evaporate. The cores were then transported to the laboratory in an upright position and stored as such until they were opened. After removing the rubber cap on top of the core, the water was drained by drilling holes in the plastic liner just above the top of the sediment. Lying in a rack, the core was then divided lengthwise with a circular saw by sawing through the plastic liner on both sides of the core. A thin string was then pulled in the saw gap through the sediment and the core split in two halves. Metal rings of known weight and volume were used to take sub-samples. The ring (approx. 2 cm in diameter) was gently pressed into the sediment at certain depths in the middle of one of the core halves, until the ring was full, and then gently tilted out with a spatula. The ends were levelled with a wire saw or spatula, and the excess sediment was discarded. The wet sample plus ring was weighed immediately after the sediment on the outside of the metal ring was removed. The sample was then pressed out into a pre-weighed porcelain bowl. Then the weight of bowl plus wet sample was measured, and the weight of wet sample was determined. The sample was dried in a porcelain bowl in a heating cabinet at 105 degrees C for 24 hours, before the sample plus bowl was weighed again and the dry weight was determined. More details on the methods can be found in Rise and Bøe (1995) and Bøe and Rise (1997)

Marine Habitat Mapping for the Norwegian Sea

An initiative is currently being taken by several Norwegian organizations to obtain funds to intensify ongoing investigations on marine sea-floor mapping off Norway. Led by the Geological Survey of Norway and Institute of Marine Research, planning during the last two years has led to the inception of a large-scale mapping project entitled “MAREANO - Marine Areal Database for the Norwegian Sea”. The investigation area covers 270 000 km2 of the shelf and deep sea off the central part of western Norway. It is a commercially important region for fisheries and the petroleum industry and includes the world’s largest system of cold-water coral reefs. The aim of MAREANO is to collect new as well as historical data elucidating the physical, chemical and biological characteristics of the seabed along the mid-Norwegian shelf and parts of the deeper Norwegian Sea. The project shall produce maps and/or provide information on seabed bathymetry, marine habitats, biological diversity and resources, mineralogical resources and geological features as well as habitat contamination. Stored in a GIS database, this information shall be available to environmental managers and interest groups as well as the fisheries, aquaculture and petroleum industries via a dedicated system on the intern&. A description of the MARFKNO project as well as some early results and their consequences for environmental management, e.g. establishing marine protected areas, shall be presented

Recognition of Cold-Water Corals in Synthetic Aperture Sonar Imagery

The deep-water coral Lophelia pertusa is a common reef-building scleractinian coral, or stony coral, occurring in mid to deep waters around the world. The reefs they form are regarded as hot spots for biodiversity and carbon cycling, and play a key role in benthic ecosystems in Norwegian waters. The cold-water reefs are however under increasing anthropogenic pressure due to human activities and a changing environment. Development of methods that enable time- and cost-effective monitoring of these reefs is therefore important. We propose using synthetic aperture sonar (SAS) on-board autonomous underwater vehicles (AUVs) as a means to detect the presence of assemblages of corals. Automated segmentation of areas with coral is presented using a convolutional neural network (CNN)