Fjord Ecosystems Research Articles

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.

Hydrography-Driven Optical Domains in the Vaigat-Disko Bay and Godthabsfjord: Effects of Glacial Meltwater Discharge

We present here an assessment of in situ hyperspectral bio-optical variability in the Vaigat-Disko Bay and Godthabsfjord along the southwest coast of Greenland. The dataset consists of state-of-the-art profiler measurements of hyperspectral apparent and inherent optical properties of water complemented by traditional observations of Secchi disk and Forel Ule scale in the context of ocean color. Water samples were collected and analyzed for concentration of optically active constituents (OACs). Near-surface observations of hydrographic parameters revealed three different water masses in the Bay: meltwater plume, frontal zone, and Atlantic water mass. Underwater spectral light availability reveals three different spectral types. Low salinity, increased temperature, deep euphotic depths, and case-1 water type remote sensing reflectance spectra with tabletop peaks in the 400–500 nm wavelength range characterize the glacial meltwater plume in the Vaigat-Disko Bay. The conservative relationship between salinity and chromophoric dissolved organic matter (CDOM) commonly observed in estuarine and shelf seas is weaker in the Godthabsfjord and reverses in the Vaigat-Disko Bay. Efficiency of machine learning techniques such as cluster analysis is tested in delineating water masses in the bay w.r.t. hydrographic and bio-optical parameters. Tests of optical closure yield low root mean square error at longer wavelengths. The study provides strong evidence that despite similar geographic setting, fjord ecosystems exhibit contrasting bio-optical properties which necessitate fjord-specific investigations.

Environmental drivers of benthic community structure in a deep sub-arctic fjord system

Fjords are unique geomorphological features that are found globally along (previously) glaciated coasts. They are characteristic for the entire Norwegian coast, where growing human populations and economic development increasingly impact the associated fjord ecosystems, and accordingly basic knowledge about ecosystem structure and functioning is needed. Knowledge about benthic systems within deep basins (over 400 m) of sub-Arctic fjords is currently missing and it remains questionable whether our understanding of similarly deep temperate fjords or shallower sub-arctic fjords is directly transferable to such systems. This study aims to investigate the patterns of soft-bottom benthic communities within a northern Norwegian deep multibasin fjord system and relate them to the prevailing environmental conditions, following a sampling strategy of many-sites with one-sample each. Here we show that oxygen content of the water and organic matter gradients in the sediment, structure the benthic communities of the fjord reflecting the main basins. We found that the community of the deepest basin (>700 m) of this sub-Arctic fjord is similar to the community just outside of Tysfjord at the same depth but differ from other communities within the fjord. Furthermore, the deep basin community reflects deep communities of temperate fjords and the deep Skagerrak. The community within the innermost basin is well adapted to periodic hypoxia with low quality or degraded food supply. Our results demonstrated that fjord specific multibasin topography and the corresponding environmental factors are important drivers of ecological processes, which resulted in distinct benthic communities in each of the three basins. The management of such heterogeneous fjord ecosystems should take an adaptive approach and apply measures that take the differences of these benthic communities into account.

Spatial distribution of mercury in seawater, sediment, and seafood from the Hardangerfjord ecosystem, Norway

Hardangerfjord is one of the longest fjords in the world and has historical mercury (Hg) contamination from a zinc plant in its inner sector. In order to investigate the extent of Hg transferred to abiotic and biotic ecosystem compartments, Hg and monomethylmercury (MeHg) concentrations were measured in seawater, sediment, and seafood commonly consumed by humans. Although total mercury in seawater has been described previously, this investigation reports novel MeHg data for seawater from Norwegian fjords. Total Hg and MeHg concentrations in seawater, sediment, and biota increased towards the point source of pollution (PSP) and multiple lines of evidence show a clear PSP effect in seawater and sediment concentrations. In fish, however, similar high concentrations were found in the inner part of another branch adjacent to the PSP. We postulate that, in addition to PSP, atmospheric Hg, terrestrial run-off and hydroelectric power stations are also important sources of Hg in this fjord ecosystem. Hg contamination gradually increased towards the inner part of the fjord for most fish species and crustaceans. Since the PSP and the atmospheric Hg pools were greater towards the inner part of the fjord, it is not entirely possible to discriminate the full extent of the PSP and the atmospheric Hg contribution to the fjord food web. The European Union (EU) Hg maximum level for consumption was exceeded in demersal fish species including tusk (Brosme brosme), blue ling (Molva dypterygia) and common ling (Molva molva) from the inner fjord (1.08 to 1.89 mg kg−1 ww) and from the outer fjord (0.49 to 1.07 mg kg−1 ww). Crustaceans were less contaminated and only European lobster (Homarus gammarus) from inner fjord exceeded the EU limit (0.62 mg kg−1 ww). Selenium (Se) concentrations were also measured in seafood species and Se-Hg co-exposure dynamics are also discussed.

Drastic difference in cadmium concentration in mussels (Mytilus chilensis) observed between seasons in natural bed and aquaculture systems in Chile.

Globally, Chile is the second largest producer of mussels, with 99% of production concentrated in the inland sea of the Los Lagos Region, Southern Chile. This study reveals that seasons produce a drastic difference in the cadmium concentration (Cd) in marine mussels in bay, channel, and fjord ecosystems in this area. As the global mussel industry continues its rapid expansion, a complete understanding of cadmium pathways is critical in order to minimize the cadmium content in harvests. In this study, biweekly sampling was conducted in Chiloé (Southern Chile), during five consecutive seasons from June 2014 to November 2015. Cadmium in the soft tissues (ST) and in the content of the digestive gland (CDG) of Mytilus chilensis were investigated, in addition to resuspensions and seston to determine the effect of the seasons on metal bioassimilation capacity. In spring, the (Cd) between CDG and ST varied by approximately 2mg Cd kg-1 dry mass (DM). In summer and autumn, the (Cd) in CDG increased from 3 to 6mg Cd kg-1 while the (Cd) in ST decreased from 2.5 to 1.5mg Cd kg-1 DM. The three ecosystems showed the same cadmium bioconcentration trends in all seasons, revealing coherent global trends. These findings should caution the industry and coastal populations about the seasonal variability and intensity of cadmium metal transfer to biofilters, especially because of the adverse effects of cadmium consumption on human health. Additionally, this study found that mussels in natural beds concentrate more Cd (> 1mg Cd kg-1 DM) than in industrial facilities. Multiregression analysis showed and explained the cadmium in CDG for three ecosystems: channel (R2 0.9537), bay (R2 0.5962), and fjord (R2 0.4009). The independent variable nocturnal seston was able to explain the increase in cadmium.

Tight trophic association between benthic diatom blooms and shallow-water megabenthic communities in a rapidly deglaciated Antarctic fjord

This study reports isotopic evidence of a unique and highly efficient trophic structure based on a rarely reported benthic diatom species in a rapidly warming Antarctic fjord (Marian Cove; MC). Recent surveys of MC revealed a very conspicuous feature, an intense, persistent benthic diatom bloom (‘benthic diatom bush’) overgrowing a variety of common megabenthic fauna, primarily filter feeders (bivalves, ascidians, and demosponges), which occurred widely at shallow depths. To ascertain if the benthic diatom bloom is consumed as a primary food source, δ13C and δ15N were analyzed in the associated filter feeders and other herbivores, as well as in the diatom bush and other potential food sources (microphytobenthos, sedimentary organic matter and macroalgae). The analysis showed that the δ13C values of all filter feeders (−23.5 to −25.2‰) were very similar to those of the diatom bush (−23.1 to −23.6‰), strongly suggesting that these benthic diatoms are the principal diet of the associated filter feeders. The isotopic signatures of the other food sources were very close to those of the diatom bush, indicating that the organic matter had the same origin, namely benthic diatoms. Given its quality, quantity and availability, the diatom bush could be regarded as the primary food source. The benthic diatom bush was predominated by the chain-forming centric diatom Paralia sp., which occurs in shallow coastal waters with a wide range of salinity in various geographic localities. Thus, the Paralia sp. bloom in this rapidly warming fjord also indicates its potential utility as an indicator of climate-induced environmental changes. Additional isotopic analysis of other common fauna showed that the benthic food web in this fjord comprised up to four trophic levels of consumers, with starfish and isopods at the apex. Given that filter feeders comprise the largest trophic group in the cove and many other Antarctic coastal waters, the results of this study strongly suggest that benthic diatoms are of prime importance in supporting the benthic food web in MC, and possibly other nearshore Antarctic waters. Further studies on the mechanism underlying benthic diatom blooms and their relevance to climate-induced processes would provide better project future scenarios for rapidly warming fjord ecosystems.

Social\u2013ecological timelines to explore human adaptation to coastal change

Through the construction of a socio-ecological timeline for the Porsanger fjord ecosystem, this article illustrates the different ways in which environmental and social–ecological changes have influenced the adaptations of rural households in coastal Sami communities in Finnmark, north Norway. The main finding is that, although environmental change in the form of seal invasions and dwindling fish stocks directly impacted the fisheries, the introduction of a new vessel quota system decisively changed adaptive capacity and coastal Sami household adaptation strategies. These changes represented a tipping point for the social–ecological system in the period between 1986 and 1990. It is thus important to discuss the ways in which governance systems may facilitate actions to adapt to climate and biodiversity change and foster sustainable rural livelihood systems in coastal Norway. Based on traditional and local ecological knowledge on the state of the ecosystem prior to the tipping point, two relevant actions to increase the resilience of the system were identified: ensuring the possibility of re-entry into fisheries as part of rural livelihood combinations, and ecological restoration of kelp beds. Flexible diversification of livelihoods allows exploitation of a range of adjacent species without large investments in a fossile fuel-driven fisheries economy. Investing in regrowth of macroalgae to foster cod nursery areas and increase carbon sequestration can be a relevant alternative for communities that are interested in contributing to climate change mitigation on a larger scale.

Hydrographic and Biological Impacts of a Glacial Lake Outburst Flood (GLOF) in a Patagonian Fjord

Glacial lake outburst floods (GLOFs) in Northern Patagonian Ice Field affecting the Baker River basin have increased their frequency in recent years. To evaluate the impact of a GLOF in the hydrography and biological components of the plankton in the Baker Fjord, we assessed the relative contributions of terrigenous versus marine plankton carbon sources to the particulate organic matter (POM) in the fjord before and after a GLOF in the austral summer 2014. We also evaluated whether terrestrial carbon brought into the fjord by the river may reach higher trophic levels via a deposit-feeding organism the juvenile pelagic Munida gregaria. Over a 10-day period, hydrographic profiles, water samples for POM, and zooplankton samples were collected daily from three stations and two depths along the fjord’s inner section. Samples of suspended POM and tissue from M. gregaria were analyzed for stable-isotope composition of carbon (δ13C). The GLOF arrival produced a thermal front in the fjord, followed by an oscillation of the pycnocline; an abrupt increase in the total organic carbon content of POM, which was attributed to terrestrial input; and a concurrent peak in the abundance of M. gregaria, suggesting an aggregation response to the GLOF. Understanding GLOF effects on local hydrography, productivity, and food web structure provides valuable insight on the potential responses of fjord ecosystems in general to climate change-induced variability. Given present climatic trends in high-latitude zones, more frequent GLOFs might be expected in Patagonian fjords and channels as well as in other high-latitude basins.

Linking Seasonal Reduction of Microbial Diversity to Increase in Winter Temperature of Waters of a Chilean Patagonia Fjord

Since microorganisms play a major role in the biogeochemistry of the ocean, understanding structure and dynamics of natural microbial communities is crucial in assessing the impact of environmental changes on marine ecosystems. In order to identify key environmental drivers of microbial community structure in Chilean Patagonian fjords, we analyzed composition of the prokaryotic community over an annual cycle at a single sampling site in Puyuhuapi Fjord. Distinctive communities represented mainly by Actinomycetales, Rhodobacteraceae, Cryomorphaceae and Flavobacteriaceae were associated with Estuarine Fresh Waters, whereas Cenarchaeaceae and Oceanospirillales were representative of Modified Sub Antarctic Waters present in the fjord. Salinity and oxygen were first-order factors explaining segregation of microbial communities in these contrasting water masses. Positive correlations of members of Flavobacteriaceae, Alteromonadales and Verrucomicrobiales with diatoms in subsurface waters and of Flavobacteriales (Cryomorphaceae and Flavobacteriaceae), Rhodobacteraceae and Pelagibacteraceae with dinoflagellates in surface waters suggest that phytoplankton composition could define specific niches for microorganisms in Puyuhuapi fjord waters. A dramatic reduction of richness and individual abundances within Flavobacteriaceae, Rhodobacteraceae and Cenarchaeaceae families was principally explained by seasonal increase of surface water temperature, with major reduction associated with changes in temperature during winter conditions. Taxa that are sensitive to increased temperature are key components of organic matter and element cycling, and we therefore suggest that potential decrease in diversity associated with rising of surface water temperature could impact current biogeochemical status of Patagonian fjord ecosystems.

Aquaculture-derived trophic subsidy boosts populations of an ecosystem engineer

Environmental management of coastal aquaculture is focused on acute impacts of organic and nitrogenous wastes close to farms. However, the energy-rich trophic subsidy that aquaculture provides may create cascades with influences over broader spatial scales. In a fjord region with intensive fish farming, we tested whether an ecosystem engineer, the white urchin Gracilechinus acutus, was more abundant at aquaculture sites than control sites. Further, we tested whether diets influenced by aquaculture waste altered reproductive outputs compared with natural diets. Urchins formed barrens at aquaculture sites where they were 10 times more abundant (38 urchins m-2) than at control sites (4 urchins m-2). Urchins were on average 15 mm larger at control sites. In the laboratory, urchins fed aquafeed diets had 3 times larger gonad indices than urchins fed a natural diet. However, their reproduction was compromised. Eggs from females fed an aquafeed diet had 13% lower fertilisation success and 30% lower larval survival rates at 10 d compared with females fed a natural diet. A reproductive output model showed that enhanced numbers of 10 d old larvae produced by the dense aquaculture-associated aggregations of G. acutus will supersede any detrimental effects on reproduction, with larval outputs from aquaculture sites being on average 5 times greater than control sites. The results show that aquaculture waste can act as a trophic subsidy in fjord ecosystems, stimulating aggregations of urchins and promoting the formation of urchin barrens. Where finfish aquaculture is concentrated, combined effects on the wider environment may produce ecosystem-level consequences.

Next Generation Sequencing and mass spectrometry reveal high taxonomic diversity and complex phytoplankton-phycotoxins patterns in Southeastern Pacific fjords

In fjord systems, Harmful Algal Blooms (HABs) not only constitute a serious problem when affecting the wildlife and ecosystems, but also human health and economic activities related to the marine environment. This is mostly due to a broad spectrum of toxic compounds produced by several members of the phytoplankton. Nevertheless, a deep coverage of the taxonomic diversity and composition of phytoplankton species and phycotoxin profiles in HAB prone areas are still lacking and little is known about the relationship between these fundamental elements for fjord ecosystems. In this study, a detailed molecular and microscopic characterization of plankton communities was performed, together with an analysis of the occurrence and spatial patterns of lipophilic toxins in a HAB prone area, located in the Southeastern Pacific fjord region. Microscopy and molecular analyses based on the 18S rRNA gene fragment indicated high diversity and taxonomic homogeneity among stations. Four toxigenic genera were identified: Pseudo-nitzschia, Dinophysis, Prorocentrum, and Alexandrium. In agreement with the detected species, liquid chromatography coupled with mass spectrometry revealed the presence of domoic acid (DA), pectenotoxin-2 (PTX-2), dinophysistoxin-2 (DTX-2), and 13-desmethyl spirolide C (SPX-1). Furthermore, a patchy distribution among DA in different net haul size fractions was found. Our results displayed a complex phytoplankton-phycotoxin pattern and for the first time contribute to the characterization of high-resolution phytoplankton community composition and phycotoxin distribution in fjords of the Southeastern Pacific region.

Relationship between marine growth and sea survival of two anadromous salmonid fish species

This study found empirical evidence supporting the “growth–survival” paradigm in the marine phase of Arctic char (Salvelinus alpinus) and brown trout (Salmo trutta). The paradigm postulates that larger or faster-growing individuals are more likely to survive than smaller or slower-growing conspecifics. The study employed long-term (25 year) capture data from a trap in the River Halselva in Norway during annual migration between marine and freshwater environments. Similar results were found for both species. Growth during the sea sojourn and return rates were positively correlated, linking increased survival with growth. Specific growth rate, survival, and duration of the sea sojourn of first-time migrants were correlated, suggesting that common environmental conditions at sea influence annual fish productivity. Freshwater and sea temperatures affected migration timing, whereas annual variation in marine growth and survival did not correlate with temperatures. This suggests that other factors such as variation in energy intake were the main source of annual growth variations. Moreover, the marine growth rate of the two species may signal annual overall fjord ecosystem production, especially related to their main prey.

Movement of pulsed resource subsidies from kelp forests to deep fjords.

Resource subsidies in the form of allochthonous primary production drive secondary production in many ecosystems, often sustaining diversity and overall productivity. Despite their importance in structuring marine communities, there is little understanding of how subsidies move through juxtaposed habitats and into recipient communities. We investigated the transport of detritus from kelp forests to a deep Arctic fjord (northern Norway). We quantified the seasonal abundance and size structure of kelp detritus in shallow subtidal (0‒12m), deep subtidal (12‒85m), and deep fjord (400‒450m) habitats using a combination of camera surveys, dive observations, and detritus collections over 1year. Detritus formed dense accumulations in habitats adjacent to kelp forests, and the timing of depositions coincided with the discrete loss of whole kelp blades during spring. We tracked these blades through the deep subtidal and into the deep fjord, and showed they act as a short-term resource pulse transported over several weeks. In deep subtidal regions, detritus consisted mostly of fragments and its depth distribution was similar across seasons (50% of total observations). Tagged pieces of detritus moved slowly out of kelp forests (displaced 4‒50m (mean 11.8m ± 8.5 SD) in 11‒17days, based on minimum estimates from recovered pieces), and most (75%) variability in the rate of export was related to wave exposure and substrate. Tight resource coupling between kelp forests and deep fjords indicate that changes in kelp abundance would propagate through to deep fjord ecosystems, with likely consequences for the ecosystem functioning and services they provide.

Influence of Glacier Melting and River Discharges on the Nutrient Distribution and DIC Recycling in the Southern Chilean Patagonia

AbstractThe Chilean Patagonia constitutes one of the most important and extensive fjord systems worldwide, therefore can be used as a natural laboratory to elucidate the pathway of both organic and inorganic matter in the receiving environment. In this study we use data collected during an intensive oceanographic cruise along the Magellan Strait into the Almirantazgo Fjord in southern Patagonia to evaluate how different sources of dissolved inorganic carbon (DIC) and recycling may impact particulate organic carbon (POC) δ13C and influence the nutrients and carbonate system spatial distribution. The carbonate system presented large spatial heterogeneity. The lowest total alkalinity and DIC were associated to freshwater dilution observed near melting glaciers. The δ13CDIC analysis suggests that most DIC in the upper 50 m depth was not derived from terrestrial organic matter remineralization. 13C‐depleted riverine and ice‐melting DIC influence the DIC pool along the study area, but due to that DIC concentration from rivers and glaciers is relatively low, atmospheric carbon contribution or biological processes seem to be more relevant. Intense undersaturation of CO2 was observed in high chlorophyll waters. Respired DIC coming from the bottom waters seems to be almost insignificant for the inorganic carbon pool and therefore do not impact significantly the stable carbon isotopic composition of dissolved organic carbon and POC in the upper 50 m depth. Considering the combined effect of cold and low alkalinity waters due to ice melting, our results highlight the importance of these processes in determining corrosive waters for CaCO3 and local acidification processes associated to calving glacier in fjord ecosystems.

Hyposaline conditions affect UV susceptibility in the Arctic kelp Alaria esculenta (Phaeophyceae)

:The kelp Alaria esculenta represents a key species in high Arctic marine fjord ecosystems. However, the European Arctic is currently experiencing extensive environmental change. Glacial fjord systems, such as Kongsfjorden (Spitsbergen, Svalbard), are subjected to rising temperature, increased freshwater inflow from glaciers and melting snow and a changing ultraviolet (UV) radiation regime related to stratospheric ozone depletion. Thus, in addition to natural seasonality, sessile organisms require acclimation in order to adapt to an environment in transition. We examined the physiological and ultrastructural responses of A. esculenta to the combined exposure to hyposalinity and UV radiation. Photosynthetic quantum yield slightly decreased during a low-salinity treatment of 7 d. Exposure to UV radiation also lowered quantum yield, but specimens previously treated with hyposalinity were significantly less susceptible to UV than nontreated individuals. Concomitant with a loss of chlorophyll during the hyposaline treatment, phlorotannin and antioxidant contents were maintained, and samples treated with low salinities exhibited higher UV-screening characteristics as demonstrated by significantly higher absorption ratios at 300/680 nm. Ultrastructural analyses revealed a treatment-dependent swelling of cell walls and accumulations of phlorotannin-containing vesicles. Our findings point to a strategy by which kelps apply a fast and cost-efficient redistribution of phlorotannins rather than increased synthesis as a general stress response to different environmental drivers in contrast to stress-specific responses. The notion that acclimation to one stressor (low salinity) reflects increased tolerance towards a second stressor (UV radiation) supports the concept of ‘cross-acclimation’ as established for higher plants but not yet for seaweeds.

A winter dinoflagellate bloom drives high rates of primary production in a Patagonian fjord ecosystem

A dense winter bloom of the dinoflagellate Heterocapsa triquetra was observed at a fixed station (44°35.3′S; 72°43.6′W) in the Puyuhuapi Fjord in Chilean Patagonia during July 2015. H. triquetra dominated the phytoplankton community in the surface waters between 2 and 15 m (13–58 × 109 cell m−2), with abundances some 3 to 15 times higher than the total abundance of the diatom assemblage, which was dominated by Skeletonema spp. The high abundance of dinoflagellates was reflected in high rates of gross primary production (GPP; 0.6–1.6 g C m−2 d−1) and chlorophyll-a concentration (Chl-a; 70–199.2 mg m−2) that are comparable to levels reported in spring diatom blooms in similar Patagonian fjords. We identify the main forcing factors behind a pulse of organic matter production during the non-productive winter season, and test the hypothesis that low irradiance levels are a key factor limiting phytoplankton blooms and subsequent productivity during winter.Principal Component Analysis (PCA) indicated that GPP rates were significantly correlated (r = −0.8, p < 0.05) with a decrease in salinity/temperature and the presence of the Heterocapsa bloom. The bloom occurred under low surface irradiance levels characteristic of austral winter and was accompanied by strong northern winds, associated with the passage of a low-pressure system, and a water column dominated by double diffusive layering. To our knowledge, this is the first report of a dense dinoflagellate bloom during deep austral winter in a Patagonian fjord, and our data challenge the paradigm of light limitation as a factor controlling phytoplankton blooms in this region in winter.

Spatial distribution of macroalgae along the shores of Kongsfjorden (West Spitsbergen) using acoustic imaging

AbstractThe identification of macroalgal beds is a crucial component for the description of fjord ecosystems. Direct, biological sampling is still the most popular investigation technique but acoustic methods are becoming increasingly recognized as a very efficient tool for the assessment of benthic communities. In 2007 we carried out the first acoustic survey of the littoral areas in Kongsfjorden. A 2.68 km2area comprised within a 12.40 km2euphotic zone was mapped along the fjord’s coast using single- and multi-beam echosounders. The singlebeam echosounder (SBES) proved to be a very efficient and reliable tool for macroalgae detection in Arctic conditions. The multibeam echosounder (MBES) was very useful in extending the SBES survey range, even though it’s ability in discriminating benthic communities was limited. The final result of our investigation is a map of the macroalgae distribution around the fjord, showing 39% macroalgae coverage (1.09 km2) of investigated area between isobaths -0.70 m and -30 m. Zonation analysis showed that most of the studied macroalgae areas occur up to 15 m depth (93%). These results were confirmed by biological sampling and observation in key areas. The potential of acoustic imaging of macrophytes, and a proposed methodology for the processing of acoustic data, are presented in this paper along with preliminary studies on the acoustic reflectivity of macroalgae, also highlighting differences among species. These results can be applied to future monitoring of the evolution of kelp beds in different areas of the Arctic, and in the rest of the world.

High Abundance of the Epibenthic Trachymedusa Ptychogastria polaris Allman, 1878 (Hydrozoa, Trachylina) in Subpolar Fjords along the West Antarctic Peninsula.

Medusae can be conspicuous and abundant members of seafloor communities in deep-sea benthic boundary layers. The epibenthic trachymedusa, Ptychogastria polaris Allman, 1878 (Hydrozoa: Trachylina: Ptychogastriidae) occurs in the cold, high latitude systems of both the northern and southern hemispheres, with a circumpolar distribution in Arctic and sub-Arctic areas, and disjunct reports of a few individuals from Antarctica. In January-February 2010, during benthic megafaunal photosurveys in three subpolar fjords along the West Antarctic Peninsula (Andvord, Flandres and Barilari Bays), P. polaris was recorded in Antarctic Peninsula waters. The trachymedusa, identified from megacore-collected specimens, was a common component of the epifauna in the sediment floored basins at 436–725 m depths in Andvord and Flandres Bays, reaching densities up to 13 m-2, with mean densities in individual basins ranging from 0.06 to 4.19 m-2. These densities are 2 to 400-fold higher than previously reported for P. polaris in either the Arctic or Antarctic. This trachymedusa had an aggregated distribution, occurring frequently in Andvord Bay, but was often solitary in Flandres Bay, with a distribution not significantly different from random. Epibenthic individuals were similar in size, typically measuring 15–25 mm in bell diameter. A morphologically similar trachymedusa, presumably the same species, was also observed in the water column near the bottom in all three fjords. This benthopelagic form attained abundances of up to 7 m-2 of seafloor; however, most P. polaris (~ 80%), were observed on soft sediments. Our findings indicate that fjords provide a prime habitat for the development of dense populations of P. polaris, potentially resulting from high and varied food inputs to the fjord floors. Because P. polaris resides in the water column and at the seafloor, large P. polaris populations may contribute significantly to pelagic-benthic coupling in the WAP fjord ecosystems.

Genetic Structure in a Small Pelagic Fish Coincides with a Marine Protected Area: Seascape Genetics in Patagonian Fjords.

Marine environmental variables can play an important role in promoting population genetic differentiation in marine organisms. Although fjord ecosystems have attracted much attention due to the great oscillation of environmental variables that produce heterogeneous habitats, species inhabiting this kind of ecosystem have received less attention. In this study, we used Sprattus fuegensis, a small pelagic species that populates the inner waters of the continental shelf, channels and fjords of Chilean Patagonia and Argentina, as a model species to test whether environmental variables of fjords relate to population genetic structure. A total of 282 individuals were analyzed from Chilean Patagonia with eight microsatellite loci. Bayesian and non-Bayesian analyses were conducted to describe the genetic variability of S. fuegensis and whether it shows spatial genetic structure. Results showed two well-differentiated genetic clusters along the Chilean Patagonia distribution (i.e. inside the embayment area called TicToc, and the rest of the fjords), but no spatial isolation by distance (IBD) pattern was found with a Mantel test analysis. Temperature and nitrate were correlated to the expected heterozygosities and explained the allelic frequency variation of data in the redundancy analyses. These results suggest that the singular genetic differences found in S. fuegensis from inside TicToc Bay (East of the Corcovado Gulf) are the result of larvae retention bya combination of oceanographic mesoscale processes (i.e. the west wind drift current reaches the continental shelf exactly in this zone), and the local geographical configuration (i.e. embayment area, islands, archipelagos). We propose that these features generated an isolated area in the Patagonian fjords that promoted genetic differentiation by drift and a singular biodiversity, adding support to the existence of the largest marine protected area (MPA) of continental Chile, which is the Tic-Toc MPA.

Spring bloom dynamics in a subarctic fjord influenced by tidewater outlet glaciers (Godthåbsfjord, SW Greenland)

AbstractIn high‐latitude fjord ecosystems, the spring bloom accounts for a major part of the annual primary production and thus provides a crucial energy supply to the marine food web. However, the environmental factors that control the timing and intensity of these spring blooms remain uncertain. In 2013, we studied the spring bloom dynamics in Godthåbsfjord, a large fjord system adjacent to the Greenland Ice Sheet. Our surveys revealed that the spring bloom did not initiate in the inner stratified part of the fjord system but only started farther away from tidewater outlet glaciers. A combination of out‐fjord winds and coastal inflows drove an upwelling in the inner part of the fjord during spring (April–May), which supplied nutrient‐rich water to the surface layer. This surface water was subsequently transported out‐fjord, and due to this circulation regime, the biomass accumulation of phytoplankton was displaced away from the glaciers. In late May, the upwelling weakened and the dominant wind direction changed, thus reversing the direction of the surface water transport. Warmer water was now transported toward the inner fjord, and a bloom was observed close to the glacier terminus. Overall, our findings imply that the timing, intensity, and location of the spring blooms in Godthåbsfjord are controlled by a combination of upwelling strength and wind forcing. Together with sea ice cover, the hydrodynamic regime hence plays a crucial role in structuring food web dynamics of the fjord ecosystem.