High-latitude Fjord Research Articles

Short-term sedimentary evidence for increasing diatoms in Arctic fjords in a warming world

Arctic fjords are hotspots of marine carbon burial, with diatoms playing an essential role in the biological carbon pump. Under the background of global warming, the proportion of diatoms in total phytoplankton communities has been declining in many high-latitude fjords due to increased turbidity and oligotrophication resulting from glacier melting. However, due to the habitat heterogeneity among Svalbard fjords, diatom responses to glacier melting are also expected to be complex, which will further lead to changes in the biological carbon pumping and carbon sequestration. To address the complexity, three short sediment cores were collected from three contrasting fjords in Svalbard (Krossfjorden, Kongsfjorden, Gronfjorden), recording the history of fjord changes in recent decades during significant glacier melting. The amino acid molecular indicators in cores K4 and KF1 suggested similar organic matter degradation states between these two sites. In contrast to the turbid Kongsfjorden and Gronfjorden, preserved fucoxanthin in Krossfjorden indicated a continuous increase in diatoms since the mid-1980s, corresponding to a 59 % increase in biological carbon pumping, as quantified by the δ13C of sedimentary organic carbon. The increasing biological carbon pumping in Krossfjorden is further attributed to its hard rock types in the glacier basin, compared to Kongsfjorden and Gronfjorden, which are instead covered by soft rocks, as confirmed by a one-dimensional model. Given the distribution of rock types among basins in Svalbard, we extrapolate our findings and propose that approximately one-fifth of Svalbard's fjords, especially those with hard rock basins and persistent marine-terminated glaciers, still have the potential for an increase in diatom fractions and efficient biological carbon pumping. Our findings reveal the complexity of fjord phytoplankton responses and biological carbon pumping to increasing glacier melting, and underscore the necessity of modifying Arctic marine carbon feedback to climate change based on results from fjords underlain by hard rocks.

Rock avalanches in northeastern Baffin Island, Canada: understanding low occurrence amid high hazard potential

Rock avalanches in fjord environments can cause direct catastrophic damage and trigger secondary submarine landslides and tsunamis. These are well-documented in Greenland, Norway, and Alaska but have gone largely unreported in the extensive fjord terrain of the eastern Canadian Arctic. We provide the first inventory of rock avalanche deposits in northeastern Baffin Island—a region characterized by moderate to high seismic hazard, steep and high-walled fjords and glacial valleys, active deglaciation, and observed climate warming. Over a broad study area of ~60,000 km2, one sixth of the terrain had sufficient slope height and gradient to potentially generate rock avalanches. Within that hazard zone, we identified eight rock avalanche deposits at six locations. Only three rock avalanche deposits at two locations are dated, using aerial imagery (1958-present), to the last century while five deposits at four locations are inferred as syn- to post-glacial, likely occurring shortly after local debuttressing. These total numbers fall well below documented inventories from Greenland, Norway, and Alaska. We hypothesize that (1) continuous permafrost persists throughout this region and continues to act as a stabilizing factor and (2) rock mass quality is high in areas of most extreme relief contrast within the study region relative to analogous high-latitude fjord systems such as those in southwestern Greenland. We suggest that Baffin Island is currently in a period of quasi-stability that follows the intense instability during initial deglaciation, yet precedes the higher anticipated slope instability that may occur during permafrost degradation.

Late Holocene echinoderm assemblages can serve as paleoenvironmental tracers in an Antarctic fjord

High Latitude fjords can serve as sediment trap, bearing different type of proxies, from geochemical to micropaleontological ones, making them exceptional tools for paleoenvironmental reconstruction. However, some unconventional proxies can be present and can be used to depict a comprehensive and exhaustive interpretation of past changes. Here, studying a sediment core in Edisto Inlet (Ross Sea, Antarctica) we used irregular echinoid spines and ophiuroids (Ophionotus victoriae) ossicles to trace environmental changes throughout the last 3.6 kyrs BP. Irregular echinoids can serve as proxy for the organic matter content, while O. victoriae ossicles can be used as proxy for steady sea-ice cycle along with organic deposition events. O. victoriae release a high number of ossicles, making estimation about the population quite challenging; still, presence data, can be easily collected. By applying Generative Additive Models to the stratigraphical distribution of these data, we detected an environmental phase that was previously unnoticed by other traditional proxies: the Ophiuroid Optimum (2–1.5 kyrs BP). In conclusion, here we demonstrate how echinoderm presence can be used as a valuable source of information, while proving the potential of modelling binary data to detect long-term trend in Holocene stratigraphical records.

High rates of marine organic carbon burial on the southwest Greenland margin induced by Neoglacial advances

Marine sediments in glacially-carved fjords at high latitudes feature high organic carbon (OC) burial rates, but there are fewer data on the role of glacial activity on high-latitude OC burial rates outside of fjords. Here, we investigate the relationship between sediment OC burial rates in the deep troughs and basins of the southwest Greenland shelf and Holocene glacial dynamics. Since the onset of prominent Neoglacial advances ~2500 years ago, the nature of the OC buried in the deep troughs and basins of the shelf was influenced by the glacier-driven increase in sediment accumulation rates (SAR), reactive iron (oxyhydr)oxide concentrations and fine-grain sediment, while OC burial rates were primarily enhanced by increasing SAR. Peak OC burial rates (~18.5 ± 5.7 g m−2 a−1) in the deep troughs and basins of the shelf during the past ~1300 years are comparable to those of many high-latitude fjords, and the inferred total annual OC burial in these trough and basin areas is equivalent to ~5% of the annual CO2 uptake by the Labrador Sea deep convection.

Environmental controls on the generation of submarine landslides in Arctic fjords: Insight from Pangnirtung Fjord, Baffin Island, Nunavut

High-latitude fjords are susceptible to hazardous subaerial and submarine mass movements such as rock avalanches and landslides. Geophysical surveys in the fjords of Baffin Island (Nunavut) have shown widespread evidence of submarine landslides, but their timing and triggers remain relatively unconstrained, limiting our ability to understand the environmental controls on the wide range of landslides occurring in high latitude fjords. Using bathymetric, sub-bottom, and sediment core data, this study seeks to generate a comprehensive understanding of the distribution, morphology, lithology, and timing of submarine landslides in Pangnirtung Fjord (SE Baffin Island, Nunavut). These results are used to evaluate the influence of different environmental controls on the generation of submarine landslides in Arctic fjords. We identified 180 near-surface submarine landslides, most of which are relatively small (∼ 0.13 km2), with elongated depletion zones and wide deposits dispersed along the basin floor of the fjord. Landslide ages, calculated from radiocarbon dating and 210Pb/137Cs activities, indicate that 8 of the 11 dated landslides occurred in the last 200 years. Four types of environmental controls were identified, which are believed to have preconditioned or triggered the observed landslides: 1) 51% of landslides, by area, are associated with subaerial sources and extend offshore of debris flow channels and fans; 2) 23% are initiated in shallow-water (< 40 m), are non-subaerially influenced, and may have been triggered by nearshore processes and sea-ice loading; 3) 13% are located in deeper waters (>40 m) and associated with sills and moraines, suggesting they are older deposits associated with the retreat of the ice sheet in the fjord; and 4) 13% are offshore of river deltas, likely associated with delta progradation; they form the largest landslide deposits in the fjord. This research suggests that the main triggers for submarine landslides in high-latitude fjords are climatically influenced (rainfall, floods, subaerial debris flows, and sea ice loading). Consequently, the predicted increase in the frequency of subaerial debris flows and river floods due to anthropogenic climate change will likely result in an increase in the recurrence of these types of submarine landslides. Additional monitoring efforts will be then needed to fully evaluate how future climate will impact the submarine landslide hazard across the Arctic.

Movement diversity and partial sympatry of coastal and Northeast Arctic cod ecotypes at high latitudes.

Movement diversity within species represent an important but often neglected, component of biodiversity that affects ecological and genetic interactions, as well as the productivity of exploited systems. By combining individual tracking data from acoustic telemetry with novel genetic analyses, we describe the movement diversity of two Atlantic cod Gadus morhua ecotypes in two high-latitude fjord systems: the highly migratory Northeast Arctic cod (NEA cod) that supports the largest cod fishery in the world, and the more sedentary Norwegian coastal cod, which is currently in a depleted state. As predicted, coastal cod displayed a higher level of fjord residency than NEA cod. Of the cod tagged during the spawning season, NEA cod left the fjords permanently to a greater extent and earlier compared to coastal cod, which to a greater extent remained resident and left the fjords temporarily. Despite this overall pattern, horizontal movements atypical for the ecotypes were common with some NEA cod remaining within the fjords year-round and some coastal cod displaying a low fjord fidelity. Fjord residency and exit timing also differed with spawning status and body size, with spawning cod and large individuals tagged during the feeding season more prone to leave the fjords and earlier than non-spawning and smaller individuals. While our results confirm a lower fjord dependency for NEA cod, they highlight a movement diversity within each ecotype and sympatric residency between ecotypes, previously undetected by population-level monitoring. This new knowledge is relevant for the management, which should base their fisheries advice for these interacting ecotypes on their habitat use and seasonal movements.

Distribution of particulate and dissolved organic carbon in surface waters of northern scottish fjords

Coastal waters can act concurrently as a source and sink of carbon (C), with coastal sediments trapping and storing significant quantities of C, while C is simultaneously released to the atmosphere through biogeochemical processes in the water column. The mid-to high-latitude fjords are recognised as hotspots for the burial and storage of OC in their sediments and for their potential to provide a long-term climate regulation service. Yet the distribution of particulate (POC) and dissolved organic carbon (DOC) in fjord water columns remains a significant knowledge gap, that is particularly acute in temperate vegetated systems such as those in the North Atlantic. Here we present POC and DOC data from surface waters across four Scottish fjords with differing meteorological, catchment and submarine geomorphological characteristics to both quantify and understand the factors governing the spatial distribution of POC and DOC in fjords. The measured POC and DOC concentrations in the surface waters of the four fjords are broadly analogous to other temperate vegetated fjord systems around the world. Within these systems, local factors such as submarine geomorphology is the primary factor driving POC and DOC dispersal in fjord surface waters. The data highlights that fjords are important pathways for the transport and storage of POC and DOC in the coastal ocean and that a greater focus is required on the water column OC to allow the role fjords play in near- (water column) and long-term (sediment) climate regulation to be quantified.

Sources and Fate of Organic Carbon in West Spitsbergen Fjord Systems: A Review

Abstract Fjord margins in the high latitude regions are the hotspots for long term carbon burial. Studying the source and fate of organic carbon in high latitude fjords would help assess the sedimentary processes and burial. With the unprecedented warming, the marine productivity patterns are changing, leading to changes in the sources of organic carbon and its eventual burial in marine sediments. In the present study, high latitude fjords in the West Spitsbergen region has been reviewed, subjected to competing effects of large freshwater influx from the glacial melts, enhanced West Spitsbergen Current and its control on marine productivity. The West Spitsbergen Current advects warm North Atlantic waters enriched in nutrients to the fjords in the West Spitsbergen region. The increased freshwater from the glacial melts also dominates the fjords. Thus, the composition of organic matter in the fjord is mainly controlled by the inflow of freshwater from the glaciers and intrusion of oceanic waters to the fjords influencing the organic matter stability and carbon burial efficiency in the fjord sediments. The ongoing rapid warming in the Arctic changes the hydrographic settings, and changes in the strength of West Spitsbergen Current may also influence the long-term organic carbon burial in the West Spitsbergen fjords.

The Interplay of Mycosporine-like Amino Acids between Phytoplankton Groups and Northern Krill (Thysanoessa sp.) in a High-Latitude Fjord (Kongsfjorden, Svalbard).

We investigated pigment and mycosporine-like amino acid (MAA) concentrations of phytoplankton and Northern krill (Thysanoessa sp.) in sub-Arctic Kongsfjorden. Chlorophyll a (Chl-a) concentrations in the surface and middle-layer water were 0.44 μg L−1 (±0.17 μg L−1) and 0.63 μg L−1 (±0.25 μg L−1), respectively. Alloxanthin (Allo, a marker of cryptophytes) was observed at all stations, and its mean values for surface and middle-layer water were 0.09 μg L−1 (±0.05 μg L−1) and 0.05 (±0.02 μg L−1), respectively. The mean MAA-to-Chl-a ratios at the surface (3.31 ± 2.58 μg (μg Chl-a)−1) were significantly higher than those in the middle-layer water (0.88 ± 0.49 μg (μg Chl-a)−1), suggesting that these compounds play an important role in reducing UV photodamage. In gut pigment levels of Northern krill, the most abundant accessory pigment was Allo (2.79 ± 0.33 μg g−1 dry weight; d.w.), as was the accumulation of Chl-a (8.29 ± 1.13 μg g−1 d.w.). The average concentration of MAAs was 1.87 mg g−1 d.w. (±0.88 mg g−1 d.w.) in krill eyes, which was higher than that in all other body parts (0.99 ± 0.41 mg g−1 d.w.), except for the gut. Thysanoessa sp. was found to contain five identified MAAs (shinorine, palythine, porphyra-334, mycosporine-glycine, and M-332) in the krill eye, whereas shinorine and porphyra-334 were only observed in the krill body, not the eyes and gut. These findings suggest that Northern krill accumulate MAAs of various compositions through the diet (mainly cryptophytes) and translocate them among their body parts as an adaptation for photoprotection and physiological demands.

Could Norwegian fjords serve as an analogue for the future of the Svalbard fjords? State and fate of high latitude fjords in the face of progressive \u201catlantification\u201d

Benthic foraminifera are one of the most widely and abundantly distributed organisms in the fjords of Svalbard and Norway. Due to their short life span and quick reactivity to environmental changes they can be used as indicators of the “atlantification” process. Here, we compare the benthic foraminifera assemblages along the latitudinal gradient, from the fjords of northern Svalbard to southern Norway to assess whether the “atlantification” process may homogenise the foraminiferal assemblages in terms of their abundance and species composition. Furthermore, the previously published data on benthic foraminiferal faunas was updated to identify changes in distribution that have occurred over the last few decades. For this purpose, fjord mouths in western and northern Svalbard (Isfjorden, Wijdefjorden and Rijpfjorden) and northern and southern Norway (Balsfjorden, Raunefjorden and Hjeltefjorden) were resampled. The analysis revealed similarities between the Svalbard and Norwegian foraminiferal assemblages of up to 30%; however, there were essential differences in terms of abundance and biodiversity. These results suggest that Svalbard fjords will remain distinct in the future, even under conditions of further warming or “atlantification”. Svalbard fjords may be dominated by Atlantic Water- preferring species, whereas, in Norwegian fjords, pressure from human activity will probably be the main driver of environmental changes, leading to changes in the foraminiferal assemblages with the increasing dominance of opportunistic, hypoxia-tolerant species.

Drivers of Atmosphere-Ocean CO2 Flux in Northern Norwegian Fjords

High-latitude fjords and continental shelves are shown to be sinks for atmospheric CO2, yet large spatial-temporal variability and poor regional coverage of sea-air CO2 flux data, especially from fjord systems, makes it difficult to scale our knowledge on how they contribute to atmospheric carbon regulation. The magnitude and seasonal variability of atmosphere-sea CO2 flux was investigated in high-latitude northern Norwegian coastal areas over 2018 and 2019, including four fjords and one coastal bay. The aim was to assess the physical and biogeochemical factors controlling CO2 flux and partial pressure of CO2 in surface water via correlation to physical oceanographic and biological measurements. The results show that the study region acts as an overall atmospheric CO2 sink throughout the year, largely due to the strong undersaturation of CO2 relative to atmospheric concentrations. Wind speed exerted the strongest influence on the instantaneous rate of sea-air CO2 exchange, while exhibiting high variability. We concluded that the northernmost fjords (Altafjord and Porsangerfjord) showed stronger potential for instantaneous CO2 uptake due to higher wind speeds. We also found that fixation of CO2 was likely a significant factor controlling ΔpCO2 from April to June, which followed phenology of spring phytoplankton blooms at each location. Decreased ΔpCO2 and the resulting sea-air CO2 flux was observed in autumn due to a combined reduction of the mixed layer with entrain of high CO2 subsurface water, damped biological activity and higher surface water temperatures. This study provides the first measurements of atmospheric CO2 flux in these fjord systems and therefore an important new baseline for gaining a better understanding on how the northern Norwegian coast and characteristic fjord systems participate in atmosphere carbon regulation.

Occurrence and Habitat Characteristics of Aurelia sp. Polyps in a High-Latitude Fjord

Causes and consequences of jellyfish bloom formation are subject to controversial discussions worldwide. While medusae have been studied to a broader extent, the knowledge on polyp stages of scyphozoans is limited thus hampering reliable prediction of jellyfish bloom formation. This study describes the occurrence, abundance, habitat characteristics and interactions of scyphozoan Aurelia sp. polyp colonies with other fouling organisms in intertidal and subtidal sectors of Trondheimsfjorden (Norway). In total, 982 polyps were found on 70 substrata of varying material types during a field survey in spring-summer 2018 along a longitudinal gradient within and outside Trondheimsfjorden. The polyps were identified as Aurelia sp. based on molecular species identification. Most polyps were found in bays with macroalgae canopy on the down facing side of artificial and natural substrata (rocks, concrete, iron) and inside rock cracks. Polyp microhabitats included the surface of Ascidia mentula (solitary ascidian), increments of Pomatoceros triqueter (polychete) tubes and dead Balanus balanoides (barnacle) shells. Based on the deployment of settling plates, abundance of Aurelia sp. polyps ranged from 1.2 (± 0.7) to 0.12 (± 0.07) polyps cm–2. Settlement occurred either directly on the PVC settling plates or as epibionts on the ascidian Ascidia mentula and on barnacle shells of Balanus balanoides. This study provides insights into the potential of local Aurelia sp. polyps contributing to the seasonal occurrence and abundance of Aurelia sp. in fjord systems, where intensive blooms occur annually.

Eat or Sleep: Availability of Winter Prey Explains Mid-Winter and Spring Activity in an Arctic Calanus Population

Copepods of the genus Calanus have adapted to high levels of seasonality in prey availability by entering a period of hibernation during winter known as diapause, but repeated observations of active Calanus spp. have been made in January in high latitude fjords which suggests plasticity in over-wintering strategies. During the last decade, the period of Polar Night has been studied intensively in the Arctic. A continuous presence of an active microbial food web suggests the prevalence of low-level alternative copepod prey (such as microzooplankton) throughout this period of darkness. Here we provide further evidence of mid-winter zooplankton activity using a decadal record of moored acoustics from Kongsfjorden, Svalbard. We apply an individual based life-history model to investigate the fitness consequences of a range of over-wintering strategies (in terms of diapause timing and duration) under a variety of prey availability scenarios. In scenarios of no winter prey availability (Pwin = 0 g C L&#x100000;1), the optimal time to exit diapause is in March. However, as Pwin increases (up to 40 g C L&#x100000;1), there is little fitness difference in copepods exiting diapause in January compared to March. From this, we suggest that Calanus are able (in energetic terms) to either i) exit diapause early to deal with uncertainty in spring bloom timing, or ii) remain active throughout winter if diapause is not possible (i.e. environment not deep enough, or not enough lipid reserves built up over the previous summer). The range of viable overwintering strategies increases with increasing Pwin, suggesting that there is more flexibility for Calanus spp. in a scenario of non-zero Pwin.

Seasonal and spatial patterns of primary production in a high-latitude fjord affected by Greenland Ice Sheet run-off

Abstract. Primary production on the coast and in Greenland fjords sustains important local and sustenance fisheries. However, unprecedented melting of the Greenland Ice Sheet (GrIS) is impacting the coastal ocean, and its effects on fjord ecology remain understudied. It has been suggested that as glaciers retreat, primary production regimes may be altered, rendering fjords less productive. Here we investigate patterns of primary productivity in a northeast Greenland fjord (Young Sound, 74∘ N), which receives run-off from the GrIS via land-terminating glaciers. We measured size fractioned primary production during the ice- free season along a spatial gradient of meltwater influence. We found that, apart from a brief under-ice bloom during summer, primary production remains low (between 50 and 200 mg C m−2 d−1) but steady throughout the ice-free season, even into the fall. Low productivity is due to freshwater run-off from land-terminating glaciers causing low light availability and strong vertical stratification limiting nutrient availability. The former is caused by turbid river inputs in the summer restricting phytoplankton biomass to the surface and away from the nitracline. In the outer fjord where turbidity plays less of a role in light limitation, phytoplankton biomass moves higher in the water column in the fall due to the short day length as the sun angle decreases. Despite this, plankton communities in this study were shown to be well adapted to low-light conditions, as evidenced by the low values of saturating irradiance for primary production (5.8–67 µmol photons m−2 s−1). With its low but consistent production across the growing season, Young Sound offers an alternative picture to other more productive fjords which have highly productive spring and late summer blooms and limited fall production. However, patterns of primary productivity observed in Young Sound are not only due to the influence from land-terminating glaciers but are also consequences of the nutrient-depleted coastal boundary currents and the shallow entrance sill, features which should also be considered when generalizing about how primary production will be affected by glacier retreat in the future.

Tidal Conversion and Dissipation at Steep Topography in a Channel Poleward of the Critical Latitude

AbstractIn high-latitude fjords and channels in the Canadian Arctic Archipelago, walls support radiating internal tides as Kelvin waves. Such waves allow for significant barotropic to baroclinic tidal energy conversion, which is otherwise small or negligible when poleward of the critical latitude. This fundamentally three-dimensional system of a subinertial channel is investigated with a suite of numerical simulations in rectangular channels of varying width featuring idealized, isolated ridges. Even in channels as wide as 5 times the internal Rossby radius, tidal conversion can remain as high as predicted by an equivalent two-dimensional, nonrotating system. Curves of tidal conversion as a function of channel width, however, do not vary monotonically. Instead, they display peaks and nulls owing to interference between the Kelvin waves along the wall and similar waves that propagate along the ridge flanks, the wavelengths of which can be estimated from linear theory to guide prediction. Because the wavelengths are comparable to width scales of Arctic channels and fjords, the interference will play a first-order role in tidal energy budgets and may consequently influence the stability of glaciers, the ventilation of deep layers, the locations of sediment deposition, and the fate of freshwater exiting the Arctic Ocean.

Death in southern Patagonian fjords: Copepod community structure and mortality in land- and marine-terminating glacier-fjord systems

Glacial retreat at high latitudes has increased significantly in recent decades associated with global warming. Along Chile's Patagonian fjords, this has promoted increases in freshwater discharge, vertical stratification, and the input of organic and inorganic particles to fjords. In addition, it has modified the water chemistry [i. e. nutrient stoichiometry] and its associated biota. This study evaluates the effect of deglaciation in high-latitude fjords (54°S) on copepod survival and how this might affect the export of particulate organic carbon to the benthos. We selected two contrasting fjord systems in terms of their geomorphology and the quality and quantity of freshwater contributions: (a) Pia Fjord, with marine-terminating glaciers, and (b) Yendegaia Fjord, with land-terminating-glaciers. Both are located along the Beagle Channel (54°S), southern Chilean Patagonia.These two fjords differed significantly in phytoplankton and copepod biomass. Whereas Pia Fjord showed high chlorophyll-a concentration (7 mg Chl-a m−3) and copepod abundance (970 ind. m−3), in Yendegaia Fjord, the biomass was very low for both autotrophs (<0.3 Chl-a m−3) and copepods (470 ind. m−3). Conversely, a greater proportion of copepod carcasses was recorded in Pia (22%) versus Yendegaia (18%), with small copepods (600–1000 µm prosome length) being less affected than large ones (>1000 µm). The presence of carcasses was better explained by the amount of suspended particulate inorganic matter in the water column than by salinity. The contribution of dead copepods to the vertical carbon flux was <3.5% of the total carbon exported down to 50 m depth, with contributions of 9.5 ± 9.9 mgC m−2 d−1 in Yendegaia and 10.8 ± 10.8 mgC m−2 d−1 in Pia. Our results suggest that heavy deglaciation processes in high-latitude fjords may reduce phytoplankton biomass, causing the copepod abundance to decrease and non-predatory mortality in filter-feeding copepods to decline.

Seasonal succession, distribution, and diversity of planktonic protists in relation to hydrography of the Godthåbsfjord system (SW Greenland)

High-latitude fjord environments are undergoing dynamic seasonal changes, affecting spatio-temporal patterns in planktonic abundances. To investigate how physical gradients impact sub-Arctic planktonic protists (> 20 μm), a seasonal transect study was performed in 2013 during three periods of planktonic succession: spring, summer, and autumn. The samples were collected from the glacier-fjord-ocean transect in SW Greenland using two complementary sampling methods, i.e. net hauls (20-μm net) and Niskin bottles. The key drivers of the distribution of planktonic groups and dominant taxa were hydrographic properties (defined as ‘time’, salinity, and temperature) reflecting the area’s seasonally changing circulation system. Cold and relatively saline waters in spring favoured the single haptophyte species Phaeocystis cf. pouchetii, while in summer, fresher waters influenced by glacial discharge favoured diatoms, followed by dinoflagellates and predatory ciliates in autumn. Our findings reveal a monodominant structure among the planktonic protists observed in each key sub-region and in each season. (1) Gedaniella boltonii (spring) was associated with inner fjord upwelling, (2) Chaetoceros sp. (summer) and Chaetoceros cf. socialis (autumn) were linked to ‘glacial meltwater’ circulation in the main fjord, and (3) Thalassiosira poroseriata (summer) and Skeletonema sp. (autumn) characterized warm and relatively saline offshore waters influenced by the West Greenland Current. The observed spatio-temporal patterns were linked to changes in hydrographic regimes driven by the interplay between the melting of the Greenland Ice Sheet and inflows of offshore, Atlantic-sourced waters.

Deposition, return flux, and burial rates of nitrogen and phosphorus in the sediments of two high-Arctic fjords

Summary The aim of this study was to determine the burial rates of nitrogen (N) and phosphorus (P) in the sediments of two high-latitude fjords: Hornsund and Kongsfjorden (Spitsbergen). Both deposition to sediments and the return flux from sediments to the water column of the various species of these elements were, therefore, quantified. The burial rate was then calculated as the difference between deposition and return flux. The required concentrations of N and P species were measured in surface sediments, in pore water extracted from the sediments, and in the above-bottom water at sampling stations situated along the axes of the fjords. Annual deposition to sediments ranged between 2.3–8.3 g m−2 for N and 0.9–2.8 g m−2 for P. The nitrogen return fluxes ranged from 0.12 to 1.46 g m−2 y−1. At most stations, the N flux was predominantly of dissolved organic (about 60–70%) rather than inorganic N. The P return flux varied between 0.01 and 0.11 g m−2 y−1, with organic species constituting 60–97%. The N and P burial rates differed between fjords: 2.3–7.9 g N m−2 y−1 and 0.9–2.8 g P m−2 y−1 in Hornsund vs. 0.9–1.3 N g m−2 y−1 and 1.0–1.2 g P m−2 y−1 in Kongsfjorden. This was accompanied by a different efficiency of N and P burial – higher in Hornsund than in Kongsfjorden, in both cases. This suggests differences in the quality and quantity of N and P organic species deposited to sediments and therefore differences in the intensity of their mineralization and/or decomposition.

Comparison of the burial rate estimation methods of organic and inorganic carbon and quantification of carbon burial in two high Arctic fjords

Summary Quantifying the burial of organic carbon (OC) and inorganic carbon (IC) species in marine sediments contribute to a better understanding of carbon cycle. This is especially important in the Arctic, where carbon deposition is relatively high and expected to change with climate warming. This study aimed to quantify the burial rates of OC and IC in the sediments of two high-latitude fjords – Hornsund and Kongsfjorden (European Arctic). Comparison of the results from three methods quantifying carbon burial in marine sediments was carried out. Sediment cores, pore water, and over-bottom water samples were analyzed for OC and IC. The burial rates were established by considering: carbon deposition to sediments minus carbon return flux, carbon deposited to sediments 80–100 years ago and carbon deposited to sediments recently. The radiolead method was employed for sediment dating. Carbon return flux was obtained using dissolved carbon species concentrations in pore water and over-bottom water. Sediment linear and mass accumulation rates in the fjords were 0.12–0.20 cm y−1 and 1160–2330 g m−2 y−1. The OC burial rates were 19.3–30.3 g OC m−2 y−1 in Hornsund and 5.7–10.0 g OC m−2 y−1 in Kongsfjorden. IC burial was taken as equal to IC deposition and ranged from 10.7 to 20.8 g IC m−2 y−1 in Hornsund and 19.4–45.7 g IC m−2 y−1 in Kongsfjorden. The “return flux” model seems most appropriate for carbon burial rate studies. The data demonstrated that OC burial dominates in Hornsund, while in Kongsfjorden, IC burial is more important.

Total suspended particulate matter in the Porsanger fjord (Norway) in the summers of 2014 and 2015

Summary High-latitude fjords, very vulnerable to global change, are impacted by their land and ocean boundaries, and they may be influenced by terrestrial water discharges and oceanic water inputs into them. This may be reflected by temporal and spatial patterns in concentrations of biogeochemically important constituents. This paper analyses information relating to the total suspended matter (TSM) concentration in the Porsanger fjord (Porsangerfjorden), which is situated in the coastal waters of the Barents Sea. Water samples and a set of physical data (water temperature, salinity, inherent optical properties) were obtained during two field expeditions in the spring and summer of 2014 and 2015. Bio-optical relationships were derived from these measurements, enabling optical data to be interpreted in terms of TSM concentrations. The results revealed significant temporal variability of TSM concentration, which was strongly influenced by precipitation, terrestrial water discharge and tidal phase. Spatial distribution of TSM concentration was related to the bathymetry of the fjord, dividing this basin into three subregions. TSM concentrations ranged from 0.72 to 0.132 g m−3 at the surface (0–2 m) and from 0.5 to 0.67 g m−3 at 40 m depth. The average mineral fraction was estimated to be 44% at surface and 53% at 40 m.