Temperate Fjord Research Articles

Biogeographic gradients of picoplankton diversity indicate increasing dominance of prokaryotes in warmer Arctic fjords

Climate change is opening the Arctic Ocean to increasing human impact and ecosystem changes. Arctic fjords, the region’s most productive ecosystems, are sustained by a diverse microbial community at the base of the food web. Here we show that Arctic fjords become more prokaryotic in the picoplankton (0.2–3 µm) with increasing water temperatures. Across 21 fjords, we found that Arctic fjords had proportionally more trophically diverse (autotrophic, mixotrophic, and heterotrophic) picoeukaryotes, while subarctic and temperate fjords had relatively more diverse prokaryotic trophic groups. Modeled oceanographic connectivity between fjords suggested that transport alone would create a smooth gradient in beta diversity largely following the North Atlantic Current and East Greenland Current. Deviations from this suggested that picoeukaryotes had some strong regional patterns in beta diversity that reduced the effect of oceanographic connectivity, while prokaryotes were mainly stopped in their dispersal if strong temperature differences between sites were present. Fjords located in high Arctic regions also generally had very low prokaryotic alpha diversity. Ultimately, warming of Arctic fjords could induce a fundamental shift from more trophic diverse eukaryotic- to prokaryotic-dominated communities, with profound implications for Arctic ecosystem dynamics including their productivity patterns.

Foraminifera in temperate fjords strongly affected by glacial meltwater, Tierra del Fuego, South America

Chilean Patagonia is one of the few regions in the Southern Hemisphere where tidewater glaciers deliver torrential meltwater. We sampled the Beagle Channel and five tributary fjords, with and without glaciers, to explore modern foraminifera of this little studied region. Surface sediments (mud, sand, pebbles, and shell debris) were collected at 45 stations from water depths 15 to 250 m, along with four short cores. The soft bottom recovered at 35 stations was analyzed for grain size, Loss-on-ignition reflecting content of organic matter, and Rose-Bengal-stained foraminifera. The benthic fauna consisted of 86 attached and free-living species. Uvigerina bifurcata, Alveolophragmium orbiculatum, Ammobaculites americanus, Stainforthia fusiformis, Globobulimina notovata, and Nonionoides grateloupii were dominant. As shown by downcore distribution, U. bifurcata and A. orbiculatum occupied epifaunal and G. notovata and S. fusiformis infaunal microhabitats. Distribution of the dominant foraminifera showed no clear pattern, with the exception of S. fusiformis, which formed a monospecific assemblage in sediments enriched with organic matter. Certain subdominant species, including Cassidulinoides parkerianus, Pullenia subcarinata, and Cibicides fletcheri, showed environmental affinity to more sandy sediments, whereas the assemblage from more muddy sediments had no inherent taxa. Foraminiferal standing crop in size fraction >125 μm was mostly 100 to 500 specimens per 10 cm3 but dropped to <1 specimen near glacier fronts, where foraminifera varied greatly between stations and did not constitute a single, unified assemblage. This patchy pattern seems to result from environmental instability caused by rapidly settling mineral fines and from random dispersal and activation of propagules. It helps to interpret records of other meltwater-dominated events.

Paired environmental DNA and dive surveys provide distinct but complementary snapshots of marine biodiversity in a temperate fjord

AbstractMarine biodiversity is a key indicator of ecosystem health and can be assessed using a variety of methods, including environmental DNA (eDNA) sampling. However, the ecology of eDNA in physically dynamic nearshore environments remains uncertain, particularly with regards to how eDNA stratifies with depth. Here, we paired eDNA sampling with dive surveys at six sites in Knight Inlet, British Columbia, Canada. eDNA samples were collected from the surface, midwater column and bottom (8–25 m depth) at each site, while dive surveys focused on the bottom (benthic) habitat. Amplicon sequencing using the mitochondrial 12S rRNA gene (targeting fish) and the COI gene (targeting marine invertebrates and algae) resolved significant differences in community composition in surface waters compared with midwater and bottom. Differences by depth were greater than differences across sites, with surface waters dominated by salmon (Oncorhynchus spp.) and rotifer DNA, and midwater and bottom samples largely dominated by Pacific herring, copepods, and mussels. eDNA samples collected at the surface, therefore, may not accurately capture benthic communities, particularly in systems with high levels of freshwater input such as coastal temperate fjords. Over small spatial scales, particularly in systems with strong stratification, adding samples from different depths may be more effective at maximizing inferred diversity rather than sampling more sites. In general, there was low overlap in species detection between dive and eDNA surveys (less than 10% for each taxonomic group – fish, invertebrates, and algae). However, we observed clear strengths for each method – dive surveys provided better taxonomic resolution, while eDNA resolved greater total diversity. These results suggest that the two survey methods can be used in tandem to provide distinct and complementary snapshots of marine biodiversity in the nearshore environment.

Taphonomy and paleoecology of the Lontras Shale Lagerstätte: Detailing the warming peak of a Late Paleozoic Ice Age temperate fjord

Fjords are considered biodiversity hotspots and aquatic critical zones, being extremely sensitive to climate change due to close oceanic, terrestrial, and glacial interactions. These ecosystems have received a great deal of attention in research on current and future anthropic impacts. Despite this, there is no analog in the geological record that presents icehouse-greenhouse biological and climatic changes. Here we present an analog, through a detailed taphonomic survey of the Lontras Shale Lagerstätte (Itararé Group, Paraná Basin, Brazil), related to a climatic optimum of the end of the Late Paleozoic Ice Age (Late Pennsylvanian), in which a temperate outer paleofjord with a rich well-preserved biota was installed. In the monotone layers of black shale, we find subtle variations of the dominant skeletal type, rates of fragmentation and disarticulation, and other taphonomic aspects that define distinct taphofacies. Each of them is the result of distinct time-averaging related to mass mortality events, turbidity, and depositional hiatus periods at different scales and intensities, mixing the ecologic census with short-term and long-term within-habitat assemblages. In addition, the rich paleobiota was reconstructed with autochthonous and allochthonous benthic fauna, many marine nektonic organisms, and intense continental contribution of terrestrial bioclasts, that proliferated and were exceptionally preserved by the establishment of an anoxic temperate outer fjord. The taphofacies show an evolution in a high-frequency sequence within a highstand systems tract, linked to climatic improvement. Furthermore, taphonomic detailing can be used as a comparison of deep marine and deep lacustrine taphofacies, in addition to serving as an analog for the short-time scale biological, biogeochemical, climatic, and stratigraphic changes associated with the icehouse–greenhouse transition in the past, present, and future.

Zooplankton composition links to climate and salmon survival in a northern temperate fjord

AbstractA zooplankton time series from the eastern Strait of Juan de Fuca in the Salish Sea was explored for its relationships to climate variability and survival of Puget Sound salmon populations. Vertical net tows were conducted ~ monthly over the upper 40 m from 2003 to 2018. Species with warm‐water associations that occur year‐round in Puget Sound, and species with cold‐water associations that dominate on the continental shelf during summer upwelling, were important members of the community at different times of year. Shifts in advection from Puget Sound and the coastal ocean were indicated by the abundance of Puget Sound‐dominant copepods Ditrichocorycaeus anglicus and Paracalanus spp. in summer through mid‐fall. In contrast, the coastal upwelling species Pseudocalanus mimus, Calanus marshallae, and Acartia longiremis were most abundant in fall through early spring, despite being the seasons they are least abundant on the continental shelf. Axis 1 of a Nonmetric Multidimensional Scaling ordination of the copepod community revealed clear seasonal cycles in community structure and longer‐term variance that correlated with the Pacific Decadal Oscillation and local temperatures. Axis 2 correlated to smolt‐to‐adult survival of Puget Sound coho salmon, but not with measured environmental factors. Copepod size composition and biogeographic affinities shifted along that axis. The mechanisms driving the shifts are not clear, but may indicate changes in trophic dynamics, or cryptic responses to environmental changes. These patterns suggest the importance of large‐scale climate influences and local environmental processes that affect estuarine circulation, population growth, and links to economically important fisheries.

An 8-year record of phytoplankton productivity and nutrient distributions from surface waters of Saanich Inlet

Phytoplankton are the base of nearly all marine food webs and mediate the interactions of biotic and abiotic components in marine systems. Understanding the spatial and temporal changes in phytoplankton growth requires comprehensive biological, physical, and chemical information. Long-term datasets are an invaluable tool to study these changes, but they are rare and often include only a small set of measurements. Here, we present biological, physical and chemical oceanographic data measured periodically between March 2010 and November 2017 from the euphotic zone of Saanich Inlet, a temperate fjord on the west coast of British Columbia, Canada. The dataset includes measurements of dissolved macronutrients, total and size-fractionated chlorophyll-a, particulate carbon, nitrogen and biogenic silica, and carbon and nitrate uptake rates. This collection describes phytoplankton dynamics and the distribution of biologically-available macronutrients over time in the upper water column of Saanich Inlet. We establish a baseline for future investigations in Saanich Inlet and provide a data collection protocol that can be applied to similar productive coastal regions.

Taphonomy and Paleoecology of Lontras Shale Lagerstätte: Detailing the Interglacial Apex of a Late Paleozoic Ice Age Temperate Fjord

Taphonomy and Paleoecology of Lontras Shale Lagerstätte: Detailing the Interglacial Apex of a Late Paleozoic Ice Age Temperate Fjord

Depth-Dependent Diversity Patterns of Rocky Subtidal Macrobenthic Communities Along a Temperate Fjord in Northern Chilean Patagonia

Understanding the distribution of biodiversity along environmental gradients allows us to predict how communities respond to natural and anthropogenic impacts. In fjord ecosystems, the overlap of strong salinity and temperature gradients provides us with the opportunity to assess the spatial variation of biodiversity along abiotic environmental gradients. However, in Northern Chilean Patagonia (NCP), a unique and at the same time threatened fjord system, the variation of macrobenthic communities along abiotic environmental gradients is still poorly known. Here, we tested whether macrobenthic species diversity and community structure followed systematic patterns of variation according to the spatial variation in salinity and temperature in Comau Fjord, NCP. A spatially extensive nested sampling design was used to quantify the abundance of subtidal macrobenthic species along the fjord axis (fjord sections: head, middle, and mouth) and a depth gradient (0–21 m). The vertical structure of the water column was strongly stratified at the head of the fjord, characterized by a superficial (depth to ca. 5 m) low-salinity and relatively colder layer that shallowed and decayed toward the mouth of the fjord. The biotic variation followed, in part, this abiotic spatial pattern. Species richness peaked at high salinities (&amp;gt;27 psu) between 5 and 10 m in the head section and between 15 and 21 m in the middle and mouth sections. Diversity and evenness were also highest at these salinities and depth ranges in the head and middle sections, but at shallower depth ranges in the mouth. Information theory-based model selection provided a strong empirical support to the depth- and section-dependent salinity, but not temperature, effects on the three biodiversity metrics. Erect algae and the edible mussel Aulacomya atra numerically dominated in shallow water (0–3 m) at the head and the middle of the fjord, coinciding with the horizontal extension of the low-density water layer—these taxa were further replaced by the crustose algae Lithothamnion sp. and deep-dwelling suspension filters (e.g., corals, polychaetes, and sponges) along depth gradient. Macrobenthic biodiversity correlated, therefore, with the influence of freshwater inputs and the density-driven stratification of the water column in this ecosystem. The spatially variable (across both, horizontal and vertical fjord axes) thresholds observed in our study question the widely accepted pattern of increasing biodiversity with increasing distance from the head of estuarine ecosystems. Finally, non-linear environmental stress models provide us a strong predictive power to understand the responses of these unique ecosystems to natural and anthropogenic environmental changes.

Radium isotope ratios as a tool to characterise nutrient dynamics in a variably stratified temperate fjord

The effect of freshwater discharge on solute vertical mixing and horizontal transfer rates is evaluated in a variably stratified temperate fjord (Killary Harbour, Ireland) using the activity ratios of 224Ra and 223Ra in the water column. With high river discharge (>1.7 × 106 m3 d−1), surface 224Ra/223Ra activity ratios (ARs) decreased from 18.0 ± 7.1 to 8.6 ± 0.9 from the inner to the outer fjord and the system becomes stratified, resulting in clear differences of 224Ra/223Ra ARs between surface and bottom layers. When river discharge was low (<0.6 × 106 m3 d−1), 224Ra/223Ra ARs dipped from 19.6 ± 5.1 to 8.0 ± 1.8 in the inner system before increasing again towards the outlet to the sea up to 11.3 ± 3.6, and the water column was well mixed: the difference in 224Ra/223Ra ARs and salinity between surface and bottom layers was minimal. Longitudinal seaward decreases of surface water 224Ra/223Ra ARs within the inner fjord independently of river discharge suggested that the contribution of benthic-pelagic coupling to surface solute inventories is small in the inner section of the system. Conversely, the increase of 224Ra/223Ra ARs during low discharge conditions indicated that the slower flushing of the system, coupled with a well-mixed water column, facilitated solute transfers from deeper waters to the surface in the outer fjord. The effect of discharge on the residence time of water in the inner fjord was also determined using radium ages: longitudinal water flushing timescales are quickly reduced in the inner part of the bay with increasing discharge. We show that the degree of vertical mixing is an important driver of nutrient ratios in the system. Retention of soluble reactive phosphorus (SRP) and Ra in deep water and a higher molar N:P ratio in surface water were more likely under stratified conditions. Stratification may therefore amplify the effect of variable watershed inputs on the estuarine N:P ratio in Killary Harbour.

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.

Diazotrophs and N2-Fixation Associated With Particles in Coastal Estuarine Waters.

Putative heterotrophic bacteria carrying out N2-fixation, so-called non-cyanobacterial diazotrophs (NCDs), are widely distributed in marine waters, but details of how the O2-inhibited N2-fixation process is promoted in the oxic water column remains ambiguous. Here we carried out two experiments with water from a eutrophic temperate fjord to examine whether low-oxygen microenvironments within particulate organic matter could be loci suitable for N2-fixation. First, water enriched with natural particles or sediment showed higher N2-fixation rates than bulk water, and nitrogenase genes (nifH) revealed that specific diazotrophs were affiliated with the particulate matter. Second, pristine artificial surfaces were rapidly colonized by diverse bacteria, while putative diazotrophs emerged relatively late (after 80 h) during the colonization, and phylotypes related to Pseudomonas and to anaerobic bacteria became dominant with time. Our study pinpoints natural particles as sites of N2-fixation, and indicates that resuspension of sediment material can elevate pelagic N2-fixation. Moreover, we show that diverse natural diazotrophs can colonize artificial surfaces, but colonization by “pioneer” bacterioplankton that more rapidly associate with surfaces appears to be a prerequisite. Whereas our experimental study supports the idea of pelagic particles as sites of N2-fixation by heterotrophic bacteria, future in situ studies are needed in order to establish identity, activity and ecology of particle associated NCDs as a function of individual particle characteristics.

Microbial communities in seawater from an Arctic and a temperate Norwegian fjord and their potentials for biodegradation of chemically dispersed oil at low seawater temperatures

Biodegradation of chemically dispersed oil at low temperature (0–2 °C) was compared in natural seawater from Arctic (Svalbard) and a temperate (Norway) fjords. The oil was premixed with a dispersant (Corexit 9500) and small-droplet oil dispersions prepared. Faster biotransformation of n-alkanes in the Arctic than in the temperate seawater were associated with the initially higher abundance of the alkane-degrading genus Oleispira in the Arctic than the temperate seawater. Comparable transformation of aromatic hydrocarbons was further associated with the late emergences Cycloclasticus in both seawater sources. The results showed that chemically dispersed oil may be rapidly biodegraded by microbial communities in Arctic seawater. Compared to oil biodegradation studies at higher seawater temperatures, longer lag-periods were experienced here, and may be attributed to both microbial and oil properties at these low seawater temperatures.

Reassessment of the life cycle of the pteropod Limacina helicina from a high resolution interannual time series in the temperate North Pacific

AbstractLimacina helicina is the dominant pelagic gastropod mollusc species in temperate and polar ecosystems, where it contributes significantly to food webs and vertical flux. Currently, considerable uncertainty exists in the interpretation of L. helicina’s life cycle, hindering our understanding of its potential responses to environmental change. Here, we present size-frequency data on L. helicina collected from three consecutive years (2008–2010) in a North Pacific temperate fjord. Two methods of length-frequency analysis were used to infer the growth of L. helicina, i.e. linking successive means extracted from finite-mixture distributions, and using the ELEFAN software to fit seasonally oscillating versions of the von Bertalanffy growth equation to the available length-frequency data. Against a background of continuous low level spawning between spring and autumn, both approaches identified two sets of major cohorts, i.e. (i) spring cohorts (G1) spawned in March/April by (ii) overwintering cohorts (G). G overwintered with minimal to low growth, before undergoing rapid growth the following spring and completing the cycle by spawning the G1 generation and disappearing from the population by May/June. Our findings are discussed in the context of L. helicina response to climate change.

Interannual variability in the relationship between in situ primary productivity and somatic crustacean productivity in a temperate fjord

Interannual variability in the relationship between in situ primary productivity and somatic crustacean productivity in a temperate fjord

Continuous long-term observations of the carbonate system dynamics in the water column of a temperate fjord

A cabled underwater observatory with more than 30 sensors delivering data in real-time was used to study the dynamics of the upper pelagic carbonate system of the Koljo Fjord, western Sweden, from September to April during two consecutive years (2011–2012 and 2012–2013). In the dynamic upper ca 15m of the water column, salinity and temperature varied by up to 10 and 20°C throughout the recorded periods, respectively. Partial pressure of CO2 (pCO2), measured with newly developed optical sensors (optodes) at three water depths (5, 9.6 and 12.6m), varied between 210–940μatm, while O2 varied between 80–470μmol/L. Redfield scaled graphs (ΔO2:ΔDIC=−1.30), in which DIC was derived from pH or pCO2 and salinity-derived alkalinity (ATsal), and oxygen was measured by the sensors, were used as a tool to assess timing and occurrence of different processes influencing the dynamics of these parameters. Distinctive short-term variations of pCO2 and O2 were induced by either tidal oscillations, wind-driven water mass transport in the mixed layer or occasional transport of deep-basin water from below the thermo/halocline to the surface layer. Intensified air–sea gas exchange during short storm events was usually followed by stabilization of gas-related parameters in the water column, such as O2 concentration and pCO2, on longer time-scales characteristic for each parameter. Biological processes including organic matter degradation in late summer/autumn and primary production in early spring were responsible for slower and gradual seasonal changes of pCO2 and O2. Net primary production (NPP) rates in the Koljo Fjord were quantified to be 1.79 and 2.10gCm−2 during the spring bloom periods in 2012 and 2013, respectively, and ratios of O2 production:DIC consumption during the same periods were estimated to be −1.21±0.02 (at 5m depth in 2013), −1.51±0.02 (at 12.6m in 2012) and −1.95±0.05 (at 9.6m in 2013). These ratios are discussed and compared to previously reported O2:C ratios during primary production.

Gradients in Traits Composition and Their Relation to Environmental Complex-Gradients and Structuring Processes: a Study of Marine Sediment Species Communities

The biological reason for a species' presence under given environmental conditions is that the species possesses traits that make establishment and survival, usually also reproduction, possible under these conditions. Biological traits analysis (BTA), when coupled with environmental variables, can provide information regarding which traits are to be expected for a given environmental state. As such, BTA provides complementary information to multivariate analysis of community data based on species composition. In this study, BTA was conducted on a data set of sediment macrofauna collected from a temperate fjord system and related to a wide range of environmental variables. The biological traits were analysed in a multiple parallel ordination framework, which can enhance the reliability of the extracted gradient structure and evaluate the importance of weight given to abundance. Two traitclines, gradients in functional attributes of the species, were found in the study area. The first traitcline was related to bottom currents and sediment constituents while the second traitcline was related to current strength and particle deposition on the bottom. Together with a companion study of gradients in species composition (coenoclines), this study of functional features (traitclines) illustrates that the species composition may consist of taxonomically different, but functionally similar species, giving rise to strong gradients in species composition but weak gradients in trait category composition when subjected to ordination analyses.

Mechanisms and ecological role of carbon transfer within coastal seascapes

Worldwide, coastal systems provide some of the most productive habitats, which potentially influence a range of marine and terrestrial ecosystems through the transfer of nutrients and energy. Several reviews have examined aspects of connectivity within coastal seascapes, but the scope of those reviews has been limited to single systems or single vectors. We use the transfer of carbon to examine the processes of connectivity through multiple vectors in multiple ecosystems using four coastal seascapes as case studies. We discuss and compare the main vectors of carbon connecting different ecosystems, and then the natural and human-induced factors that influence the magnitude of effect for those vectors on recipient systems. Vectors of carbon transfer can be grouped into two main categories: detrital particulate organic carbon (POC) and its associated dissolved organic and inorganic carbon (DOC/DIC) that are transported passively; and mobile consumers that transport carbon actively. High proportions of net primary production can be exported over meters to hundreds of kilometers from seagrass beds, algal reefs and mangroves as POC, with its export dependent on wind-generated currents in the first two of these systems and tidal currents for the last. By contrast, saltmarshes export large quantities of DOC through tidal movement, while land run-off plays a critical role in the transport of terrestrial POC and DOC into temperate fjords. Nekton actively transfers carbon across ecosystem boundaries through foraging movements, ontogenetic migrations, or 'trophic relays', into and out of seagrass beds, mangroves or saltmarshes. The magnitude of these vectors is influenced by: the hydrodynamics and geomorphology of the region; the characteristics of the carbon vector, such as their particle size and buoyancy; and for nekton, the extent and frequency of migrations between ecosystems. Through a risk-assessment process, we have identified the most significant human disturbances that affect the integrity of connectivity among ecosystems. Loss of habitat, net primary production (NPP) and overfishing pose the greatest risks to carbon transfer in temperate saltmarsh and tropical estuaries, particularly through their effects on nekton abundance and movement. In comparison, habitat/NPP loss and climate change are likely to be the major risks to carbon transfer in temperate fjords and temperate open coasts through alteration in the amount of POC and/or DOC/DIC being transported. While we have highlighted the importance of these vectors in coastal seascapes, there is limited quantitative data on the effects of these vectors on recipient systems. It is only through quantifying those subsidies that we can effectively incorporate complex interactions into the management of the marine environment and its resources.

Integrating satellite observations and modern climate measurements with the recent sedimentary record: An example from Southeast Alaska

[1] Assessments of climate change over time scales that exceed the last 100 years require robust integration of high-quality instrument records with high-resolution paleoclimate proxy data. In this study, we show that the recent biogenic sediments accumulating in two temperate ice-free fjords in Southeast Alaska preserve evidence of North Pacific Ocean climate variability as recorded by both instrument networks and satellite observations. Multicore samples EW0408-32MC and EW0408-43MC were investigated with 137Cs and excess 210Pb geochronometry, three-dimensional computed tomography, high-resolution scanning XRF geochemistry, and organic stable isotope analyses. EW0408-32MC (57.162°N, 135.357°W, 146 m depth) is a moderately bioturbated continuous record that spans AD ∼1930–2004. EW0408-43MC (56.965°N, 135.268°W, 91 m depth) is composed of laminated diatom oozes, a turbidite, and a hypopycnal plume (river flood) deposit. A discontinuous event-based varve chronology indicates 43MC spans AD ∼1940–1981. Decadal-scale fluctuations in sedimentary Br/Cl ratios accurately reflect changes in marine organic matter accumulation that display the same temporal pattern as that of the Pacific Decadal Oscillation. An estimated Sitka summer productivity parameter calibrated using SeaWiFS satellite observations support these relationships. The correlation of North Pacific climate regime states, primary productivity, and sediment geochemistry indicate the accumulation of biogenic sediment in Southeast Alaska temperate fjords can be used as a sensitive recorder of past productivity variability, and by inference, past climate conditions in the high-latitude Gulf of Alaska.

Biodiversity and abundance patterns of rock encrusting fauna in a temperate fjord

Fjords are semi-enclosed systems often with usually strong physical and chemical gradients. These gradients provide the opportunity to test the influence of various physical and chemical factors on biodiversity. However study area of this investigation, Trondheimsfjord, is a large water body where especially salinity gradient along the fjord is not well pronounced. The goal of this study was to establish within a temperate fjord a baseline identifying encrusting fauna on rocks and determine the factors driving changes along the length of the fjord and changing depths. There was no trend in species composition change and increase or decrease in number of species, diversity and number of individuals along the fjord. This was likely due to the relative homogeneity of both substrate (rocks) and environmental parameters. Nevertheless, the influence of fresh water inflow in the vicinity of the river mouth was apparent by the presence of characteristic brackish-water species at these locations. Multidimensional scaling analysis revealed three separate assemblages: intertidal, shallow and deep subtidal (below 50 m). Intertidal assemblages were species poor (one to 11 species) but relatively abundant (six to 2374 indiv./m2 of rocks). Number of individuals and biomass was highest in the shallow subtidal (2059–13,587 indiv./m2 of rocks). Overall the highest species number (45) was recorded at 50 m depth which is probably result of low competition pressure yet still relatively high nutrient concentration in comparison to shallower locations. Environmental parameters (i.e., tidal currents, wave action, salinity) change more drastically with depth than along the fjord and these changes are the major driving forces in shaping encrusting assemblages in Trondheimsfjord.

The joint effects of riverine, thermal, and wind forcing on a temperate fjord lake: Quesnel Lake, Canada

Field data obtained in 2003–2004 are used to describe the influence of atmospheric and riverine forcing on the thermal history of fjord-type lakes using Quesnel Lake, British Columbia, Canada as an example. Typical of fjord-type lakes, Quesnel Lake is narrow, long (>100km total thalweg), multi-armed (three arms of comparable size), deep (maximum depth>500m), and has multiple basins separated by sills. The lake's annual thermal history responds to the joint forcing of surface heat exchange, river inputs, and wind stress. The lake's annual heat budget is dominated by surface radiative fluxes, and riverine input of heat is insignificant in this medium residence time lake (10years). Despite being insignificant to the annual heat budget, the three major rivers that feed the three arms of the lake contribute to the overall lake circulation pattern. Since these rivers have differing salinities, it is possible to identify, using temperature/salinity correlation diagrams, patterns of riverine circulation interflowing in the lake. Data from a 1-year thermistor-chain record suggests exchange between surface and intermediate waters occurs twice annually, but deep-waters below 150–250m are mainly renewed during autumn, by strong and episodic atmospheric forcing. This is because wind-forced turbulent diffusion and gravitational convection triggered by wind forced displacement of isotherms (initiating thermobaric instability) are required for full overturn and deep-water renewal.