Physical constrains and productivity in the future Arctic Ocean

Published version. Also available at http://dx.doi.org/10.3389/fmars.2015.00085Today's physical oceanography and primary and secondary production was investigated for the entire Arctic Ocean (AO) with the physical-biologically coupled SINMOD model. To obtain indications on the effect of climate change in the twenty-first century the magnitude of change, and where and when these may take place SINMOD was forced with down-scaled climate trajectories of the International Panel of Climate Change with the A1B climate scenario which appears to predict an average global atmospheric temperature increase of 3.5–4°C at the end of this century. It is projected that some surface water features of the physical oceanography in the AO and adjacent regions will change considerably. The largest changes will occur along the continuous domains of Pacific and in particular regarding Atlantic Water (AW) advection and the inflow shelves. Withdrawal of ice will increase primary production, but stratification will persist or, for the most, get stronger as a function of ice-melt and thermal warming along the inflow shelves. Thus, the nutrient dependent new and harvestable production will not increase proportionally with increasing photosynthetic active radiation (PAR). The greatest increases in primary production are found along the Eurasian perimeter of the AO (up to 40 g C m−2 y−1) and in particular in the northern Barents and Kara Seas (40–80 g C m−2 y−1) where less ice-cover implies less Arctic Water (ArW) and thus less stratification. Along the shelf break engirdling the AO upwelling and vertical mixing supplies nutrients to the euphotic zone when ice-cover withdraws northwards. The production of Arctic copepods along the Eurasian perimeter of the AO will increase significantly by the end of this century (2–4 g C m−2 y−1). Primary and secondary production will decrease along the southern sections of the continuous advection domains of Pacific and AW due to increasing thermal stratification. In the central AO primary production will not increase much due to stratification-induced nutrient limitation

Phytoplankton community succession and dynamics using optical approaches

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 traditional microscopic or pigment methods can be a solution for detecting rapid responses of community dynamics and succession. In this study, we combined in situ high-frequency (every 30 min from May to September 2017) optical and hydrographic data from a moored buoy and weekly discrete samplings to track phytoplankton community dynamics and succession in Mausund Bank, a highly productive region of the coast of Norway. Three hydrographic regimes were observed: mixing period (MP) in spring, onset of stratification (transient period, TP) in summer and a stratified period (SP) in fall, with occasional strong winds that disrupted the surface stratification in the beginning of September. A bloom dominated by the diatom Skeletonema costatum was observed in the MP due to intense mixing and nutrient availability, while flagellates prevailed in nutrient-poor waters during the TP, followed by a bloom dominated by rhizosolenid diatoms (Proboscia alata and Guinardia delicatula), when stratification peaked. A mixed assemblage of diatoms (e.g. Pseudo-nitzschia), coccolithophores and dinoflagellates occurred during the SP, as strong winds reintroduced nutrients to surface waters. Through pigment (chemotaxonomy) and microscopic observations, we tested, for the first time in a coastal region, whether an ‘optical community index’ derived from in situ measurements of chlorophyll a fluorescence (Fchla) and optical particulate backscattering (bbp) is suitable to differentiate between diatom versus flagellate dominance. We found a negative relationship between Fchla:bbp and diatom:flagellate, contrary to previous observations, possibly because of the influence of non-algal contribution (e.g. zooplankton, fecal pellets and detritus) to the bbp pool in highly productive systems. This finding suggests that such relationship is not universal and that other parameters are needed to refine the optical community index in coastal regions

Overexploitation, Recovery, and Warming of the Barents Sea Ecosystem During 1950–2013

The Barents Sea (BS) is a high-latitude shelf ecosystem with important fisheries, high and historically variable harvesting pressure, and ongoing high variability in climatic conditions. To quantify carbon flow pathways and assess if changes in harvesting intensity and climate variability have affected the BS ecosystem, we modeled the ecosystem for the period 1950–2013 using a highly trophically resolved mass-balanced food web model (Ecopath with Ecosim). Ecosim models were fitted to time series of biomasses and catches, and were forced by environmental variables and fisheries mortality. The effects on ecosystem dynamics by the drivers fishing mortality, primary production proxies related to open-water area and capelin-larvae mortality proxy, were evaluated. During the period 1970–1990, the ecosystem was in a phase of overexploitation with low top-predators’ biomasses and some trophic cascade effects and increases in prey stocks. Despite heavy exploitation of some groups, the basic ecosystem structure seems to have been preserved. After 1990, when the harvesting pressure was relaxed, most exploited boreal groups recovered with increased biomass, well-captured by the fitted Ecosim model. These biomass increases were likely driven by an increase in primary production resulting from warming and a decrease in ice-coverage. During the warm period that started about 1995, some unexploited Arctic groups decreased whereas krill and jellyfish groups increased. Only the latter trend was successfully predicted by the Ecosim model. The krill flow pathway was identified as especially important as it supplied both medium and high trophic level compartments, and this pathway became even more important after ca. 2000. The modeling results revealed complex interplay between fishery and variability of lower trophic level groups that differs between the boreal and arctic functional groups and has importance for ecosystem management

Reconciling behavioral, bioenergetic, and oceanographic views of bowhead whale predation on overwintering copepods at an Arctic hotspot (Disko Bay, Greenland)

Bowhead whales (Balaena mysticetus) visit Disko Bay, West Greenland in winter and early spring to feed on Calanus spp., at a time of year when the copepods are still mostly in diapause and concentrated in near-bottom patches. Combining past observations of copepod abundance and distribution with detailed observations of bowhead whale foraging behaviour from telemetry suggests that if the whales target the highest-density patches, they likely consume 26–75% of the Calanus standing stock annually. A parallel bioenergetic calculation further suggests that the whales’ patch selection must be close to optimally efficient at finding hotspots of high density copepods near the sea floor in order for foraging in Disko Bay to be a net energetic gain. Annual Calanus consumption by bowhead whales is similar to median estimates of consumption by each of three zooplankton taxa (jellies, chaetognaths, and predatory copepods), and much greater than the median estimate of consumption by fish larvae, as derived from seasonal abundance and specific ingestion rates from the literature. The copepods’ self-concentration during diapause, far from providing a refuge from predation, is the behaviour that makes this strong trophic link possible. Because the grazing impact of the whales comes 6–10 months later than the annual peak in primary production, and because Disko Bay sits at the end of rapid advective pathways (here delineated by a simple numerical particle-tracking experiment), it is likely that these Calanus populations act in part as a long-distance energetic bridge between the whales and primary production hundreds or thousands of km away

Nutrient fluxes in the Arctic in the present climate regime

The Arctic Ocean (AO) will likely become ice-free in summer within the next two decades. This will change light conditions for primary production. Parts of the AO where primary production is presently light limited will be controlled also by nutrient availability in the future. It is therefore of interest to study horizontal and vertical transports of nutrients in the AO and to assess the relative importance of the different nutrient sources. In the present study we have used the coupled system SINMOD to quantify nutrient transport and mixing in the AO. The import and export of nutrients have been calculated and compared with similar results based on analysis of observational data. Vertical transport and mixing of nutrients in different parts of the Arctic are also quantified and the relative importance of the different processes are assessed.ICE-ARCpublishedVersio

Apendix VIII Simulert lakseindusert dødelighet på virtuell smolt i produksjonsområde 2 til 7 ved bruk av SINMOD

Modellsystemet SINMOD (www.sinmod.com) inkluderer en dynamisk modell for pelagisk utvikling av lakselus og en modell for utvandring av postsmolt. Modellsystemet er brukt og resultatene analysert for å se på spredning av lus og for å estimere påvirkningen dette kan ha for dødelighet hos de ville populasjonene av laks i produksjonsområdene PO2 til PO7 for 2018 og 2019.publishedVersio

Advection of Mesozooplankton Into the Northern Svalbard Shelf Region

The northern Svalbard shelf region is part of the Atlantic advective contiguous domain along which nutrients, phyto- and mesozooplankton are advected with Atlantic Water from the Norwegian Sea along the Norwegian shelf break and into the Arctic Ocean. By applying the SINMOD model, we investigated how much mesozooplankton may be advected into the northern Svalbard shelf region. We also compared this supply with the local mesozooplankton production. To achieve this, we selected a box north of Svalbard and calculated the in- and outflux of Atlantic Calanus finmarchicus and Arctic Calanus glacialis. The average biomass inside the box ranged between 0.5 and 3.0 g C month–2 in March and August, respectively. Annually, 18.8 g C month–2 of advected (and locally produced) mesozooplankton would be available for predators inside the box before it is advected out. The advection of mesozooplankton reached 12 times more than the average biomass within the box. The model projects significance variability in mesozooplankton advection which may be explained by the hitherto non-quantified recirculation in the northern Fram Strait and differences in the geographic origin of the mesozooplankton source population. The results imply that grazing upon mesozooplankton in the Atlantic advective contiguous domain north of Svalbard is greatly advantageous for pelagic predators. It could represent an important food source for fish, birds, and whales. It is suggested that mesozooplankton encountered on the shelf north of Svalbard may derive from populations along the North Norwegian shelf break, in some years as far south as the Lofoten/Vesterålen region. This illustrates the extent and significance of the Atlantic advective contiguous domain for the European shelf of the Arctic Ocean which apparently depends on significant food supply through expatriates. Primary production on the shelf is lower than C consumption and thus the European shelf of the AO is presumably net-heterotrophic

Advection of Mesozooplankton Into the Northern Svalbard Shelf Region

The northern Svalbard shelf region is part of the Atlantic advective contiguous domain along which nutrients, phyto- and mesozooplankton are advected with Atlantic Water from the Norwegian Sea along the Norwegian shelf break and into the Arctic Ocean. By applying the SINMOD model, we investigated how much mesozooplankton may be advected into the northern Svalbard shelf region. We also compared this supply with the local mesozooplankton production. To achieve this, we selected a box north of Svalbard and calculated the in- and outflux of Atlantic Calanus finmarchicus and Arctic Calanus glacialis. The average biomass inside the box ranged between 0.5 and 3.0 g C month–2 in March and August, respectively. Annually, 18.8 g C month–2 of advected (and locally produced) mesozooplankton would be available for predators inside the box before it is advected out. The advection of mesozooplankton reached 12 times more than the average biomass within the box. The model projects significance variability in mesozooplankton advection which may be explained by the hitherto non-quantified recirculation in the northern Fram Strait and differences in the geographic origin of the mesozooplankton source population. The results imply that grazing upon mesozooplankton in the Atlantic advective contiguous domain north of Svalbard is greatly advantageous for pelagic predators. It could represent an important food source for fish, birds, and whales. It is suggested that mesozooplankton encountered on the shelf north of Svalbard may derive from populations along the North Norwegian shelf break, in some years as far south as the Lofoten/Vesterålen region. This illustrates the extent and significance of the Atlantic advective contiguous domain for the European shelf of the Arctic Ocean which apparently depends on significant food supply through expatriates. Primary production on the shelf is lower than C consumption and thus the European shelf of the AO is presumably net-heterotrophic

Dispersal and Deposition of Detritus From Kelp Cultivation

A high resolution coastal and ocean hydrodynamic model system was used to investigate the transport and deposition patterns of Particulate Organic Matter (POM) from kelp farmed at three locations of different properties: a sheltered location, an exposed location, and an offshore location. Published values on the sinking speeds of organic particles from kelp were used, spanning several orders of magnitude. Recent work on quantifying the release of particulate organic matter from farmed kelp was used to link the release of carbon to possible cultivation volumes and scenarios, and finally to link this to the potential for carbon loading on the ocean floor. The results are presented in terms of loading and distribution per unit harvested kelp, and the loading estimates are compared with estimates of natural (background) primary production. According to the simulation results, organic matter may be transported anything from a few (hundred) meters up to a hundred km away from the release site, depending on the sinking rates, time of release, and the location. The depth at which the matter settles on the sea floor likewise depends on the properties of the matter and the sites. The time until settlement varied from minutes to several hundred hours. The results underscore the importance of constraining the dispersal and deposition of detritus from kelp cultivation in order to better understand and quantify associated environmental risks posed by organic loading, and the potential for seafloor carbon sequestration by kelp farming as a nature based climate solution

Nutrient fluxes in the Arctic in the present climate regime

The Arctic Ocean (AO) will likely become ice-free in summer within the next two decades. This will change light conditions for primary production. Parts of the AO where primary production is presently light limited will be controlled also by nutrient availability in the future. It is therefore of interest to study horizontal and vertical transports of nutrients in the AO and to assess the relative importance of the different nutrient sources. In the present study we have used the coupled system SINMOD to quantify nutrient transport and mixing in the AO. The import and export of nutrients have been calculated and compared with similar results based on analysis of observational data. Vertical transport and mixing of nutrients in different parts of the Arctic are also quantified and the relative importance of the different processes are assessed