Vurdering av sårbare bunnhabitater i det nordlige Barentshavet; trålfangete bunndyr fra det årlige «øko-toktet»

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Responding to global warming: New fisheries management measures in the Arctic

The northernmost commercial fisheries in the world take place in the northern Barents Sea up to around 80° N. This is an area where global warming is particularly intense and where large, previously ice-covered areas are now more accessible to fishing vessels. This raised questions whether existing conservation and management measures are adequate. In this paper, we discuss the process of developing new regulatory measures, including four large preliminary closed areas covering 442,022 km2 and an additional ten closed areas covering more than 3260 km2 that protects sites with biodiversity, specific to the region. The new measures, an amendment to an old regulation related to the management of impacts from bottom fisheries on ecosystems, is based on knowledge derived from more than 10 years of scientific surveys of the seabed ecology. A key finding here is that cost-efficient, large-scale mapping and monitoring of seabed ecosystems is important for the development of area-based regulations of fishing activities. In the process of developing the regulation the Directorate of Fisheries made its own analysis of the data from the scientific surveys by a novel approach using commercially available software. Such area-based measures also contribute to the achievement of Aichi target 11 and UN Sustainable Development Goal 14.5 on protecting maritime areas.acceptedVersio

Weak seasonality in benthic food web structure within an Arctic inflow shelf region

The Arctic Ocean is characterized by pronounced seasonality in the quantity and quality of organic matter exported from the surface ocean. While it is well established that changes in food availability can alter the abundance, biomass and function of benthic organisms, the impact on food web structure is not well studied. We used bulk carbon and nitrogen stable isotope analysis to assess the quantity and quality of sediment organic matter and structure of the benthic food web in four seasons within the Northern Barents Sea (76°N − 82 °C). Despite a highly seasonal vertical flux, we found that the organic carbon and chlorophyll-a content of surface sediments was seasonally stable, suggesting a lack of seasonality in food availability at the seafloor. However, organic biomarkers indicate that the quality of sediment organic matter increased to a maximum in August and December, up to 6 months after the spring bloom. The seasonal stability of food quantity was mirrored in food-web structure (e.g., total isotopic range, number of trophic levels) which did not change significantly across sampling periods. We expected that suspension and deposit feeders would respond more readily to seasonal changes in food quality compared to predators. However, we observed no significant seasonal changes in the trophic levels or isotopic niche areas of benthic functional groups. The centroids of isotopic niches of all benthic functional groups shifted seasonally by <2 ‰ along the δ13C-axis, suggesting minimal shifts in carbon resource use. Because the northern Barents Sea experiences significant changes in seasonal sea ice cover, we expected that stable-isotope ratios of benthic organisms would show an increased consumption of sympagic-derived organic matter through less negative δ13C values in early spring and summer. However, only two taxa (the soft coral Gersemia spp. and bivalves in the family Yoldiidae) showed 13C-enrichment in spring or summer consistent with the assimilation of sympagic-derived organic matter, despite previous evidence suggesting widespread use of this carbon source. Overall, our results show that there is an apparent de-coupling in time between pelagic processes and benthic food-webs in which the accumulation and assimilation of high-quality organic matter occurs for benthos during the fall and early winter months when there is little to no fresh organic matter generated at the surface. This temporal mismatch highlights the importance of considering the timescales over which components of the marine ecosystem respond to short-term environmental changes and the methods employed to assess seasonality.Weak seasonality in benthic food web structure within an Arctic inflow shelf regionpublishedVersio

Isotopic turnover of polar cod (Boreogadus saida) muscle determined through a controlled feeding experiment

Polar cod (Boreogadus saida) is an important trophic link within Arctic marine food webs and is likely to experience diet shifts in response to climate change. One important tool for assessing organism diet is bulk stable isotope analysis. However, key parameters necessary for interpreting the temporal context of stable isotope values are lacking, especially for Arctic species. This study provides the first experimental determination of isotopic turnover (as half-life) and trophic discrimination factors (TDFs) of both δ13C and δ15N in adult polar cod muscle. Using a diet enriched in both 13C and 15N, we measured isotopic turnover times of 61 and 49 days for δ13C and δ15N, respectively, with metabolism accounting for >94% of the total turnover. These half-life estimates are valid for adult polar cod (>3 years) experiencing little somatic growth. We measured TDFs in our control of 2.6‰ and 3.9‰ for δ13C and δ15N, respectively, and we conclude that applying the commonly used TDF of ~1‰ for δ13C for adult polar cod may lead to misrepresentation of dietary carbon source, while the use of 3.8‰ for δ15N is appropriate. Based on these results, we recommend that studies investigating seasonal shifts in the diet of adult polar cod sample at temporal intervals of at least 60 days to account for isotopic turnover in polar cod muscle. Although isotopic equilibrium was reached by the fish in this study, it was at substantially lower isotope values than the diet. Additionally, the use of highly enriched algae in the experimental feed caused very high variability in diet isotope values which precluded accurate calculation of TDFs from the enriched fish. As a result of the challenges faced in this study, we discourage the use of highly enriched diets for similar experiments and provide recommendations to guide the design of future isotopic turnover experiments.publishedVersio

Fauna analyses of a possible electrical cable corridor in the Hardanger fjord

In relation to a possible cable pathway on the sea floor through the inner half of the Hardanger fjord, the Institute for Marine Research has carried out ROV inspections of the benthic faunal communities along 17 selected bottom transects. The surveyed area was restricted to the inner half of the Hardanger fjord – from Sima to Norheimsund in the period 9–29 November 2010. The deep horizontal seabed along the midline of the investigated part of the fjord was dominated by the crustacean Munida sp and its borrow, the sea cucumbers Bathyplotes sp and Stichopous sp, sea-pens, and the echiuran Bonellia sp. The steep walls along the sides of the investigated fjord were populated with less abundant but still relatively frequently-occurring taxa such the sea star Brisingia sp, the large bivalve Acesta sp, and several species of sponges. Though any local recovery time is unknown, we do not consider these populations to be threatened by the possible cable-laying activities. These are not listed in the Norwegian redlist and are not considered as threatened by the OSPAR Convention. However, in the outer part of the investigated area (transects named Kvamsøy cliff wall and Øystese), the vulnerable corals Lophelia pertusa and Anthomastus grandiflorus (redlisted) and Primnoa sp were observed. To avoid threatening impacts to these groups of corals, we therefore recommend using video monitoring during any cable-laying activities

Fauna analyses of a possible electrical cable corridor in the Hardanger fjord

In relation to a possible cable pathway on the sea floor through the inner half of the Hardanger fjord, the Institute for Marine Research has carried out ROV inspections of the benthic faunal communities along 17 selected bottom transects. The surveyed area was restricted to the inner half of the Hardanger fjord – from Sima to Norheimsund in the period 9–29 November 2010. The deep horizontal seabed along the midline of the investigated part of the fjord was dominated by the crustacean Munida sp and its borrow, the sea cucumbers Bathyplotes sp and Stichopous sp, sea-pens, and the echiuran Bonellia sp. The steep walls along the sides of the investigated fjord were populated with less abundant but still relatively frequently-occurring taxa such the sea star Brisingia sp, the large bivalve Acesta sp, and several species of sponges. Though any local recovery time is unknown, we do not consider these populations to be threatened by the possible cable-laying activities. These are not listed in the Norwegian redlist and are not considered as threatened by the OSPAR Convention. However, in the outer part of the investigated area (transects named Kvamsøy cliff wall and Øystese), the vulnerable corals Lophelia pertusa and Anthomastus grandiflorus (redlisted) and Primnoa sp were observed. To avoid threatening impacts to these groups of corals, we therefore recommend using video monitoring during any cable-laying activities

Fish Assemblages of a Sub-Arctic Fjord Show Early Signals of Climate Change Response Contrary to the Benthic Assemblages

Arctic benthic ecosystems are facing high-speed environmental changes, such as decreased sea ice coverage, increased temperature and precipitations, as well as the invasion by non-indigenous species. Few sub-arctic fjords have the particularity to have an inner-most part forming a basin in which water remains very cold. Those fjords may offer a refugee for cold-water arctic species as well as a small-scale “laboratory” of the changes that arctic assemblages located at higher latitudes might face soon. The Porsangerfjord in Northern Norway is a sub-arctic fjord with an inner arctic part and face red king crabs Paralithodes camtchasticus invasion since the end of the 1990s. It offers a case study of the dynamics of arctic ecosystems facing multiple stressors, i.e., climate change and invasive species. Based on a time series of megabenthic invertebrates and bentho-demersal fishes over 2007–2019, a complex multivariate analysis (STATICO) was used to identify the trends in the relationship between taxa and the environment. We showed the main environmental changes in the fjord were the freshening of the water, the increase of the seabed current, and the decrease of the maximum sea ice extent. A strong along-fjord gradient was visible for both benthic and fish assemblages. Species richness and Shannon diversity of fishes significantly increased into the fjord, due to the arrival of warm-water species over time that overlapped with cold-water species that have seen their biomass significantly reduced. No significant decrease in the biomass of the cold-water benthic species was visible, which could indicate an efficient refugee effect of the inner fjord. Yet, this refugee effect could be unbalanced by the red king crab invasion as it is a predator of several arctic species. In the Porsangerfjord, fish species thus respond to climate change while megabenthic assemblages are more threatened by invasive species.publishedVersio

Fish Assemblages of a Sub-Arctic Fjord Show Early Signals of Climate Change Response Contrary to the Benthic Assemblages

Arctic benthic ecosystems are facing high-speed environmental changes, such as decreased sea ice coverage, increased temperature and precipitations, as well as the invasion by non-indigenous species. Few sub-arctic fjords have the particularity to have an inner-most part forming a basin in which water remains very cold. Those fjords may offer a refugee for cold-water arctic species as well as a small-scale “laboratory” of the changes that arctic assemblages located at higher latitudes might face soon. The Porsangerfjord in Northern Norway is a sub-arctic fjord with an inner arctic part and face red king crabs Paralithodes camtchasticus invasion since the end of the 1990s. It offers a case study of the dynamics of arctic ecosystems facing multiple stressors, i.e., climate change and invasive species. Based on a time series of megabenthic invertebrates and bentho-demersal fishes over 2007–2019, a complex multivariate analysis (STATICO) was used to identify the trends in the relationship between taxa and the environment. We showed the main environmental changes in the fjord were the freshening of the water, the increase of the seabed current, and the decrease of the maximum sea ice extent. A strong along-fjord gradient was visible for both benthic and fish assemblages. Species richness and Shannon diversity of fishes significantly increased into the fjord, due to the arrival of warm-water species over time that overlapped with cold-water species that have seen their biomass significantly reduced. No significant decrease in the biomass of the cold-water benthic species was visible, which could indicate an efficient refugee effect of the inner fjord. Yet, this refugee effect could be unbalanced by the red king crab invasion as it is a predator of several arctic species. In the Porsangerfjord, fish species thus respond to climate change while megabenthic assemblages are more threatened by invasive species.publishedVersio

Utvidet oppfølgingsundersøkelse av PL393 NUCULA august 2007 – april 2008

I forbindelse med boring av letebrønn 7125/4-1 Nucola har Havforskningsinstituttet gjennomført den lovpålagte grunnlagsundersøkelsen i august 2006 samt en utvidet oppfølgingsundersøkelse i september 2007. I begge undersøkelsene ble brønnlokaliteten undersøkt med CTD, zooplankton-nett, fisketrål (bunn og pelagisk) og visuelle observasjoner for å kartlegge havoverflaten, vannsøylen og havbunnen. Sedimentoverflaten ble kartlagt i et 5 5 km stort område rundt brønnlokaliteten med fem videotransekter og 8 trekk (stasjoner) med en 2 m bred epibentisk bomtrål. Resultatene fra oppfølgningsundersøkelsen viser at Nucula har et rikt og variert dyreliv, og at effekten fra boringen er så begrenset i geografisk omfang at den ikke kan registreres i de kvantitative og kvalitative undersøkelsene. Med dette vurderer Havforskningsinstituttet at gjengroing av de påvirkete områdene vil skje over tid, og at det ikke vil være langtidseffekter på havbunnen fra boringen som foregikk i årsskiftet 2006 til 2007

Origin of marine invertebrate larvae on an Arctic inflow shelf

Many benthic invertebrate taxa possess planktonic early life stages which drift with water currents and contribute to dispersal of the species, sometimes reaching areas beyond the current ranges of the adults. Until recently, it had been difficult to identify planktonic larvae to species level due to lack of distinguishing features, preventing detection of expatriate species. Here, we used DNA metabarcoding of the COI gene to obtain species-level identification of early life stages of benthic invertebrates in zooplankton samples from the Barents Sea and around Svalbard, where, regionally, large volumes of warm Atlantic Water enter the Arctic from the south. We compared the larval community in the water column to the adult community on the seafloor to identify mismatches. In addition, we implemented particle tracking analysis to identify the possible areas of origin of larvae. Our results show that 30-45% of larval taxa—largely polychaetes and nudibranchs—were not local to the sampling area, though most were found nearby in the Barents Sea. In the particle tracking analysis, some larvae originating along the Norwegian coast were capable of reaching the northwest coast of Svalbard within 3 mo, but larvae found east of Svalbard had a more constrained possible area of origin which did not extend to the Norwegian coast. This study highlights largely regional-scale larval connectivity in the Barents Sea but demonstrates the potential for some long-lived larval taxa to travel to Svalbard and the Barents Sea from further south