Glacial Bay Research Articles

Primary production in the bays of the novaya zemlya archipelago (Kara Sea) in the contrasting glacial and non-glacial environmental conditions

Ongoing warming is leading to the accelerated shrinkage of glaciers located on Arctic islands. Consequently, the influence of glacial meltwater on phytoplankton primary production in Arctic bays becomes critically important in an era of warming. This work studies the spatiotemporal variation of primary production and chlorophyll a concentration in the bays along the eastern coast of the Novaya Zemlya archipelago. Data were collected during nine cruises performed from July to October (2013–2022). The effect of underwater photosynthetically available radiation (PAR) and nutrients on primary production was assessed separately for bays influenced by glacial meltwater (glacial bays) and those without such influence (non-glacial bays). The median value of water column-integrated primary production (IPP) for all bays was 38 mgC m−2 d−1, characterizing them as oligotrophic areas. IPP in non-glacial bays was found to be 2.3-fold and 1.4-fold higher than that in glacial bays during summer and autumn, respectively. Underwater PAR was the main abiotic factor determining IPP during the ice-free period. In the entire bays nutrient concentrations were high, exceeding the limiting values for growth and photosynthesis of phytoplankton. It was concluded that the high turbidity from glacial meltwater runoff leads to decreased underwater PAR and, consequently, to a decline in IPP. This study demonstrates that rapid warming could have a negative impact on the productivity of high Arctic bays and their adjacent areas.

Influence of glacial influx on the hydrodynamics of Admiralty Bay, Antarctica - study based on combined hydrographic measurements and numerical modeling

This study investigates the impact of glacial water discharges on the hydrodynamics of a glacial bay in Antarctica, comparing it to well-studied northern hemisphere fjords. The research was carried out in Admiralty Bay (AB) in the South Shetland Islands, a wide bay adjacent to twenty marine-terminating glaciers. From December 2018 until February 2023, AB water properties were measured on 136 days. This dataset showed that a maximally two-layered stratification occurs in AB and that glacial water is always the most buoyant water mass. Using the Delft3D Flow, a three-dimensional hydrodynamical model of AB was developed. During tests, the vertical position and initial velocity of glacial discharges have been shown to be insignificant for the overall bay circulation. Fourteen model scenarios have been calculated with an increasing glacial influx added. The AB general circulation pattern consists of two cyclonic cells. Even in scenarios with significant glacial input, water level shifts and circulation are predominantly controlled by the ocean. Glacial freshwater is carried out of AB along its eastern boundary in a surface layer. Freshwater thickness in this outflow current is maximally 0.27-0.35 m. Within the inner AB inlets, significant glacial influx produces buoyancy-driven vertical circulation. Using an approach combining hydrographic and modeling data, a four-year timeseries of glacial influx volumes into AB has been produced. On average, glacial influx in summer is 10 times greater than in spring and winter and 3 times higher than in autumn. The annual glacial influx into AB was estimated at 0.434-0.632 Gt. Overall, the study demonstrated the unique characteristics of the topography and forcings that influence the hydrodynamics of an Antarctic glacial bay.

Characterization of suspended particles at different glacial bays at Spitsbergen

Particle size distribution (PSD) and concentration of mineral-suspended sediment released from melting glaciers are important factors affecting the local marine ecosystem, e.g. affecting the light availability in water columns, thus changing underwater light climate for photosynthetic organisms. We examined the characteristics of various samples of natural mineral assemblages suspended in different glacial bays in Hornsund and Kongsfjord at Spitsbergen. The concentrations of the total mass of particles (TSM) in suspended sediment as well as particular organic matter (POM) and particular inorganic matter mass (PIM) together with mineralogical composition and particular size distribution (PSD) were determined.In this study, we investigated the PSD properties and variability in the front of different tidewater glaciers based, laser diffractometer measurements (LISST-100x), and XRD – techniques to obtain the mineralogical composition of the particles. The sampled sites are under the strong influence of freshwater discharge from the glacier. At each station, inorganic particulate matter contributed up to 98% to total suspended matter with the particle concentration of the particle reaches up to 111 mg/l with mean surface PSD slopes ranging from 3.24 to 3.85. The result provides valuable baseline information on the observed range of variability of the size of suspended particles due to glacial runoff and the presence of particles of different mineral origin in the glacial bays.

Enhanced heavy metal discharges to marine deposits in glacial bays of two Arctic fjords (Hornsund and Kongsfjorden)

Climate change is transforming Arctic ecosystems in ways that are influencing the transport and accumulation of contaminants. The spatial and temporal variability of heavy metal distribution was studied in two Spitsbergen fjords – Kongsfjorden and Hornsund. Sediment cores from five stations in Kongsfjorden and six in Hornsund were collected in 2018–2019 and used for measurement of heavy metal concentrations (Hg, Pb, Cd, Cu, and Zn). Sediment layers were dated by the 210Pb method to reveal the history of contamination. Isotopic lead composition was used to study sources of Pb. Loads of heavy metals to fjord deposits were calculated based on mass sediment accumulation rates. The heavy metal loads varied spatially and reached ranged 0.3 mg m−2 yr−1 for Hg, 57.6 mg m−2 yr−1 for Pb, 0.5 mg m−2 yr−1 for Cd, 101 mg m−2 yr−1 for Cu, and 117 mg m−2 yr−1 for Zn. Heavy metal discharge from the glaciers to the glacial bays were much higher compared to discharge in central and outer fjord parts. This may suggest that glaciers can be important secondary sources of pollutants to fjords.

Tidewater glaciers as “climate refugia” for zooplankton-dependent food web in Kongsfjorden, Svalbard

With climate warming, many tidewater glaciers are retreating. Fresh, sediment-rich sub-glacial meltwater is discharged at the glacier grounding line, where it mixes with deep marine water resulting in an upwelling of a plume visible in front of the glacial wall. Zooplankton may suffer increased mortality within the plume due to osmotic shock when brought in contact with the rising meltwater. The constant replenishment of zooplankton and juvenile fish to the surface areas attracts surface-foraging seabirds. Because access to other feeding areas, such as the marginal ice zone, has become energetically costly due to reduced sea-ice extent, glacial plumes may become increasingly important as “climate refugia” providing enhanced prey availability. Here, we investigated zooplankton concentrations within the plume and adjacent waters of four tidewater glaciers in Kongsfjorden, Svalbard, in early August 2016 and late July 2017. Our aim was to compare the zooplankton composition, abundance, and isotopic signatures within the plumes to those in adjacent fjord and shelf waters. Our hypothesis was that the plumes resulted in increased zooplankton mortality through osmotic shock and increased prey availability to predators. The mortality due to osmotic shock in the glacial plume was low (<5% dead organisms in samples), although slightly higher than in surrounding waters. This indicates that plumes are inefficient “death traps” for zooplankton. However, the high abundance and biomass of zooplankton within plume areas suggest that the “elevator effect” of rising glacial water supplies zooplankton to the sea surface, thereby enhancing prey availability for surface-feeding seabirds. Thus, our study provides evidence that glacial plumes are important as “climate refugia” for foraging seabirds. Stable isotope signatures showed that the glacial bay zooplankton and fish community represent a distinct isotopic niche. Additionally, zooplankton mortality associated with the plume estimated over 100-days of melt season supports a flux of 12.8 tonnes of organic carbon to benthic communities in the glacial bays. Benthic scavengers, such as Onisimus caricus and Anonyx nugax, were abundant in the glacial bay, where they feed on sinking organic matter.

Depth-dependence of the underwater noise emission from melting glacier ice.

Submarine-melting of ice at the glacier-ocean interface accounts for a large portion of the ice-loss at tidewater glaciers and produces sound via bubble-release. The sound production is dominant in the sub-surface region near the glacier-ocean interface. This depth-dependence of the sound is studied by melting ice blocks in a glacial bay at various depths up to 20 m and recording their acoustics over a large frequency range. The acoustic energy decreases with depth in line with expectations from the physics of the phenomenon and is fit to an exponentially decaying curve. The estimated variation will be useful for interpreting the sound in marine-terminating glaciers bays in terms of the submarine-melting activity.

Spatial variation in acoustic field due to submarine melting in glacial bays

Climate-change induced melting is leading to accelerating ice loss at tidewater glaciers worldwide. A significant component of the freshwater flux from these glaciers arises from submarine melting at the glacier-ocean interface. This melting causes a distinct acoustic signature due to the release of pressurized bubbles underwater, opening up the possibility of monitoring this phenomenon on a large scale using passive acoustic systems. To evaluate the use of sound in monitoring submarine glacier melting, we made acoustic measurements using vertical hydrophone arrays in four glacial bays in Svalbard in 2019. As the recording array was moved away from the glacier, the variation in the recorded acoustic level due to melting ice did not follow a uniformly decreasing trend as one might expect. Moreover, the acoustic intensities at different glaciers were clustered at different levels. These observations indicate that the geometry of the glacier-ocean interface, thermohaline structure of the underwater channel and presence of floating ice in the bay played a role in determining the acoustic field. Most of this variation can be explained through propagation modeling. Moving forward, this model-based interpretation of the field will play an integral part in inverting the sound to estimate the submarine melt rate.

Vertical directionality and spatial coherence of the sound field in glacial bays in Hornsund Fjord.

Arctic glacial bays are among the loudest natural environments in the ocean, owing to heavy submarine melting, calving, freshwater discharge, and ice-wave interactions. Understanding the coherence and vertical directionality of the ambient sound there can provide insights about the mechanisms behind the ice loss in these regions. It can also provide key information for operating technologies such as sonar, communication, and navigation systems. To study the unexplored sound coherence and vertical directionality in glacial bays, a vertical hydrophone array was deployed, and acoustic measurements were made at four glacier termini in Hornsund Fjord, Spitsbergen, in June and July 2019. The measurements show that the sound generated by melting glacier ice is more dominant in the upper portion of the water column near the glacier terminus. The melt water from the submarine melting and the freshwater discharge from the glacier create a glacially modified water duct near the sea surface. This disrupts the inter-sensor vertical coherence in the channel. However, some coherence across the duct is preserved for sound arising from spatially localized events at low frequencies. Overall, the observations in this study can help improve the understanding of the submarine melting phenomenon in glacial bays.

Spatial Patterns of Particles and Plankton in the Warming Arctic Fjord (Isfjorden, West Spitsbergen) in Seven Consecutive Mid-Summers (2013–2019)

The restructuring of planktonic communities towards an increasing share of small individuals is not only expected, but also already observed consequence of warming in the rapidly changing Arctic. Here we demonstrate a simultaneous study on the nano-, micro- and mesoplankton (divided into small and large), and corresponding size fractions of particles along a hydrographical gradient in the Isfjorden – the largest Spitsbergen fjord system. The sampling was performed in 7 following summers (2013-2019) from the main basin under the influence of Atlantic Waters (ISA station), up to Billefjorden – the innermost part affected by meltwaters from Nordenskioldbreen (BAB station). Our objective was to elucidate the composition and spatial patterns in distribution of plankton and particles (P&P) under various hydrographical regimes. Combining two laser-based measurements (LOPC and LISST) with standard plankton analysis allowed us to conclude that vertical hydrographical stratification and eddy activity were forcing either layered or patchy distribution of P&P. The concentrations of P&P measured by LISST (nano- and micro-) were lower than the abundance of the corresponding size fractions of protists, but they did not differ significantly among the stations due to different origin of P&P. Nevertheless, the decreasing trend in the abundance of both investigated mesoplankton fractions could be observed between the ISA and BAB stations, whereas the opposite tendency was noted for P&P. Moreover, the abundance of mesoplankton was equal to the concentrations of the corresponding size fractions of P&P at the ISA station and much lower than the LOPC counts at the BAB station, which points towards notable amount of marine aggregates in the glacial bay. Even if some observations alluded to P&P susceptibility to the local processes, the inter-annual variability in P&P distribution surpassed the differences between the sampling stations. It suggests that both the large-scale processes (i.e. intensified inflow of Atlantic Waters) and natural seasonal changes associated with subtle differences in sampling timing had a stronger influence on investigated plankton than local factors. This pioneering study, which links traditional and advanced methods, clearly demonstrated that such approach is convenient for tracking small-scale spatial patterns and inter-annual variability of P&P in the Arctic pelagial.

Underwater noise from glacier calving: Field observations and pool experiment.

The underwater noise emission from glacier calving is investigated by integrating acoustic and photographic observations made in a glacial bay and model pool. Similarities in the impact noise in these two settings are identified. Distinct fluid-dynamics processes are involved in sound generation: iceberg detachment, water entry, entrainment and collective oscillation of a bubble cloud, secondary impacts due to splashes, and calving-induced wave action. The lag between initial impact and bubble plume pinch-off from the subsurface cavity depends on ice block dimensions and drop height and may be useful in reducing errors in estimates of calving fluxes made using underwater sound.

Benthic fauna of the Oga Bay (Novaya Zemlya, Kara Sea)

Benthic fauna of the Oga Bay (the Kara Sea, Novaya Zemlya) was studied in 20152016 during the IO RAS expeditions on RV "Akademik Mstislav Keldysh". 5 grab stations (15 samples) at depths of 70140 m were sampled. Three macrobenthic communities consecutively replaced each others from the inner near-glacier part of the gulf towards the outher slope. The main factor determining the distribution of macrobenthic communities in the Oga Bay is the concentration of suspended matter in the water column and in the near-bottom layer, that caused by a very powerful level of sedimentation from the Goluboy (Oga) glacier. The depletion of benthic communities (qualitative and quantitative) which is typical for Arctic fjords with glacial inflow was shown. The specific community with the dominance of bivalve Portlandia arctica inhabits the main part of the bay. The peculiarities of the benthos of Arctic glacial bays are discussed.

Benthic Fauna of Oga Bay (Novaya Zemlya, Kara Sea)

The benthic fauna of Oga Bay (Kara Sea, Novaya Zemlya archipelago) was studied in 2015–2016 during the R/V Akademik Mstislav Keldysh expeditions. Five grab stations at depths of 70–140 m were sampled (three grabs per station). Three macrobenthic communities consecutively replacing each other from the inner near-glacier part of the bay toward the outer slope were revealed. Concentration of suspended matter in the water column and in the near-bottom layer, caused by powerful sedimentation from the Goluboi (Oga) glacier was the main factor determining the macrobenthic communities distribution. An overall decrease in abundance, biomass and diversity of macrofauna was found in the area of glacier discharge. The community dominated by bivalve Portlandia arctica inhabits the main part of the bay. The peculiarities of the benthic communities of the Arctic glacial bays and fjords are discussed.

Plankton or benthos: where krill belongs in Spitsbergen fjords? (Svalbard Archipelago, Arctic)

This study couples observations of krill (Thysanoessa inermis, Thysanoessa longicaudata, Thysanoessa rashii) from Tucker trawl nets and cameras, trying to test hypothesis that in the glaciated fjords of Svalbard most of the euphausiids biomass is located in near-bottom habitat and explains why in this region there are a substantial part of the krill population near the sea floor. Photographic material from the summers of 2013–2017 shows large numbers of near-bottom euphausiids (39% of the total krill biomass in Hornsund and 41% in Kongsfjorden), which reached a maximum density of 751 ± 224 indiv. m−3 in Kongsfjorden, 731 ± 198 indiv. m−3 in Hornsund, and 426 ± 124 indiv. m−3 in Adventfjorden. Regional distribution of near-bottom aggregations of krill seem to be associated with close proximity to the glacier front rather than with depth. The highest densities were located in the glacial bays. Where and why these aggregations occur is probably complicated and dependent on many environmental factors acting together. However, the dominant factors seem to be sedimentation and estuarine circulation. No krill aggregations were found during the winter cruise. The dominating species was T. inermis which made up 90% of the community. Other krill species—T. rashii and T. longicaudata, made up 6% and 4%, respectively. In the summer, aggregations of other macrozooplankton were also observed: amphipods of the genus Themisto and chaetognaths of the genera Eukrohnia and Parasagitta. Euphausiid densities in the water column (from Tucker trawl hauls) were an order of magnitude lower (0.33 indiv. m−3 for Kongsfjorden and 0.61 indiv. m−3 for Hornsund) than those of the near-bottom aggregations observed on cameras system. At most stations, the krill exhibited a behaviour, known as “nose diving” in the sediment, which is likely related to feeding. Observation of this phenomenon may indicate that krill (mostly T. inermis), found near the bottom of Spitsbergen fjords, is looking for food there. Near-bottom aggregations of zooplankton, mainly krill, are common in glacial bays and can be important in the function of the fjord ecosystem. Our research proves that the zooplankton biomass can be highly underestimated if only Tucker trawl sampling is done, due to neglecting the near-bottom layer in this type of method.

Is the trophic diversity of marine benthic consumers decoupled from taxonomic and functional trait diversity? Isotopic niches of Arctic communities

AbstractIt is predicted that a diverse array of functional traits in species‐rich assemblages can lead to strong resource partitioning among coexisting species and moderate a wider spectrum of resource use. We compared two benthic communities in an Arctic fjord: a species‐rich community (in an outer basin) and an impoverished community (in a glacially impacted bay) and explored (1) if high species richness was translated into high functional trait richness and (2) if high taxonomic and functional diversity promoted high trophic diversity in terms of resource use (indicated by isotopic niche measures). We documented higher functional trait richness in the outer basin (computed based on traits describing feeding mode, mobility, food source, body size and life habit), but the area occupied by consumers in the δ15N vs. δ13C iso‐space (a proxy for total trophic resource use) did not differ between the two sites. A wide array of functional traits used to acquire food may extend the benthic community trophic niche spatially (where and how animals forage) without impacting the isotopic niche breadth (in this system, mostly reflecting “what animals feed on”) due to the relatively homogenous distribution of isotopic characteristics of detritus pool across vertical scales in marine sediments. Moreover, this trend could indicate that a species‐poor community tends to exploit all the available food items, possibly due to the low food availability for primary consumers in a glacially impacted environment. Communities in glacial bays could therefore be particularly sensitive to future changes in glacial inputs and associated organic matter fluxes.

Spatiotemporal changes in the concentration and composition of suspended particulate matter in front of Hansbreen, a tidewater glacier in Svalbard

Summary Tidewater glaciers supply large amounts of suspended particulate matter (SPM) and freshwater to fjords and affect oceanographic, sedimentological and biological processes. Our understanding of these processes, is usually limited to the short summer season. Here, we present the results of a one-year-long monitoring of the spatial variability in SPM characteristics in a context of oceanographic and meteorological conditions of a glacial bay next to Hansbreen, a tidewater glacier in Hornsund (southern Spitsbergen). The observed range of SPM concentrations was similar to ranges measured in other sub-polar glaciated fjords, especially in Svalbard. The major source of SPM is the meltwater discharge from the glacier. The maximum water column-averaged SPM concentrations did not correlate with peaks in freshwater discharge and were observed at the beginning of the autumn season, when the fjord water transitioned from stratified to fully mixed. The observed spatiotemporal variations in the total SPM, particulate organic matter (POM) and particulate inorganic matter (PIM) are likely controlled by a combination of factors including freshwater supply, water stratification and circulation, bathymetry, the presence of sea ice, biological productivity and sediment resuspension. During the ablation season, the SPM maximum concentrations were located within the upper water layer, whereas during the winter and spring, the greatest amounts of SPM were concentrated in deeper part. Thus, typical remote sensing-based studies that focus on SPM distributions may not reflect the real SPM levels. POM and PIM concentrations were correlated with each other, during most of the time suggesting that they may have a common source.

Studying melting icebergs with ambient noise oceanography

Marine-terminating glaciers are retreating at an unprecedented pace, largely as a result of enhanced submarine melting. However, studying ice-ocean interactions is complicated due to both harsh conditions prevailing in glacial bays and lack of scientific methods enabling continuous measurements. Recent studies have shown that high underwater noise levels measured in the Arctic are related to glacier melt, but quantitative research requires proper separation of individual noise sources, including icebergs and glacier fronts. Therefore, we show results of field experiments carried out in 2013, 2015, and 2016 in Hornsund fjord, Svalbard, to present directionality and statistics of the noise produced by melting icebergs. Measurements of noise directionality were conducted with 3-hydrophone acoustic array. Calculated angles of arrivals for the noise at the frequency range of 1–10 kHz correspond well to locations of individual, grounded icebergs. The amplitude of sound emitted by these sources has a symmetric α-stable distribution, with parameters depending on separation between iceberg and receiver. These findings demonstrate that ambient noise oceanography is an efficient tool to detect and track icebergs using natural noise they produce during melting. [Work funded by the Polish National Science Centre, Grant No. 2013/11/N/ST10/01729 and by ONR, Grant No. N00014-17-1-2633.]

Sources of 137Cs to an Arctic fjord (Hornsund, Svalbard)

Although primary sources of anthropogenic 137Cs have decreased nowadays, the Arctic is exposed to a variety of secondary sources. These include riverine run-off, oceanic currents, drifting sea ice, melting glaciers and permafrost. Recent reports underline the role of glaciers, specifically cryoconite holes, in radionuclide accumulation. Therefore, this study investigates the hypothesis that melting glaciers are an important means of delivering 137Cs for Arctic fjord (Hornsund, Svalbard). As marine sediments are the final sink for most contaminants, seven 30–40 cm long sediment cores collected in 2016 were investigated for 137Cs activity concentration. Five were collected in a transect from the central to the outer part of the fjord while two were collected within one km of the different melting tidewater glaciers. Sediment layers were dated using 210Pb to reveal the history of 137Cs accumulation. The measured 137Cs activity concentrations ranged from <0.1 to 7.7 Bq kg−1. The activity concentrations ranging from 0.3 to 3.1 Bq kg−1 were measured in surface (0–2 cm) sediments. The total 137Cs inventories were calculated for five station and ranged from 322 to 908 Bq m−2, of which 29–34 Bq m−2 were deposited within the last decade. At two stations characterized by largest sediment accumulation rates only the last decade inventories were calculated and they ranged from 13 to 444 Bq·m−2. The mean of 137Cs fluxes calculated for last decade ranged from 2.7 to 44.1 Bq m−2yr−1. The history of 137Cs environmental inputs was well revealed in the sediments as the 137Cs penetration depth agreed with the time of its introduction to the Arctic and the most pronounced 137Cs activity concentration peak was found in sediments dated for circa 1963. Although 137Cs fluxes and inventories were largest in the glacial bay (Brepollen), the 137Cs was diluted in a large amount of sedimenting material. Based on the results in this study, the glaciers do not appear to act as important sources of 137Cs to the marine environment in the Hornsund fjord.

The malacostracan fauna of two Arctic fjords (west Spitsbergen): the diversity and distribution patterns of its pelagic and benthic components

Summary This study examines the performance of pelagic and benthic Malacostraca in two glacial fjords of west Spitsbergen: Kongsfjorden, strongly influenced by warm Atlantic waters, and Hornsund which, because of the strong impact of the cold Sorkapp Current, has more of an Arctic character. The material was collected during 12 summer expeditions organized from 1997 to 2013. In all, 24 pelagic and 116 benthic taxa were recorded, most of them widely distributed Arctic-boreal species. The advection of different water masses from the shelf had a direct impact on the structure of the pelagic Malacostraca communities, resulting in the clear dominance of the sub-arctic hyperiid amphipod Themisto abyssorum in Kongsfjorden and the great abundance of Decapoda larvae in Hornsund. The taxonomic, functional and size compositions of the benthic malacostracan assemblages varied between the two fjords, and also between the glacier-proximate inner bays and the main fjord basins, as a result of the varying dominance patterns of the same assemblage of species. There was a significant drop in species richness in the strongly disturbed glacial bays of both fjords, but only in Hornsund was this accompanied by a significant decrease in density and diversity, probably due to greater isolation and poorer quality of sediment organic matter in its innermost basin. Our results suggest that the diversity and distribution of benthic malacostracans in these two fjords are only distantly related to the different hydrological regimes; rather, they are governed by locally acting factors, such as depth, sediment type, the variety of microhabitats and the availability and quality of food.

The impact of glacier meltwater on the underwater noise field in a glacial bay

Ambient noise oceanography is proving to be an efficient and effective tool for the study of ice-ocean interactions in the bays of marine-terminating glaciers. However, obtaining quantitative estimates of ice melting or calving processes from ambient noise requires an understanding of how sound propagation through the bay attenuates and filters the noise spectrum. Measurements of the vertical structure in sound speed in the vicinity of the Hans Glacier in Hornsund Fjord, Spitsbergen, made with O(130) CTD casts between May and November 2015, reveal high-gradient, upward-refracting sound speed profiles created by cold, fresh meltwater during summer months. Simultaneous recordings of underwater ambient noise made at depths of 1, 10 and 20 meters in combination with propagation model calculations using the model Bellhop illustrate the dominant role these surface ducts play in shaping the underwater soundscape. The surface ducts lead to a higher intensity and greater variability of acoustic energy in the near-surface layer covered by glacially-modified waters relative to deeper waters, indicating deeper zones as most appropriate for inter-seasonal acoustic monitoring of the glacial melt. Surface waveguides in Hornsund are relatively shallow and trap sound above O(1 kHz). Deeper waveguides observed elsewhere will also trap low-frequency sounds, such as those generated by calving events for example. Finally, the ambient noise field in Hornsund is shown to be strongly dependent on the distribution of ice throughout the bay, stressing the importance of performing complementary environmental measurements when interpreting the results of acoustic surveys. This article is protected by copyright. All rights reserved.

Distribution of macroalgae in Kongsfjorden, Svalbard

Macroalgal distribution varies with prevailing environmental gradients in fjords, particularly in glacial fjords such as Kongsfjorden, Svalbard. This survey by scuba-diving in 1996 and 1998 was the first to determine species composition, dominance and distribution of macroalgae along the entire length axis of a fjord in the Arctic. Macroalgal distribution was determined quantitatively by frame sampling and with digital video along transects at five hard-bottom locations from outer to inner fjord and interpreted against environmental gradients of depth (0–30 m), substratum, wave exposure and distance from inner glacial front. Most species identified (>70%) belonged to the Arctic and Arctic-temperate biogeographic groups, often with limited distribution to inner or outer part of the fjord. Dominant species or species with wide geographic distribution were typically widely distributed along the fjord axis. Peaks in biomass varied from 5 to 10 m at the middle-to-outer fjord, whereas in the inner bay it peaked at <5 m. The biomass distribution of macroalgae was mainly related to depth and distance from the inner glacial bay, and varied with wave exposure and sediment cover. Climate-related changes, after our study, indicate that the macroalgal belt has become shallower at Hansneset in middle fjord, with increased biomass in the upper sublittoral zone because of higher temperature and less sea ice. Distribution and production of macroalgae and fauna in shallow regions of the Arctic are likely to increase in the future, particularly in areas subjected to ocean warming, such as Kongsfjorden and other fjords and coastal areas in Svalbard.