Seasonal variability of meio- and macrobenthic standing stocks and diversity in an Arctic fjord (Adventfjorden, Spitsbergen)

Strong environmental seasonality is a basic feature of the Arctic system, still there are few published records of the seasonal variability of the Arctic marine biota. This study examined the year-round seasonal changes of soft bottom macro- and meiobenthic standing stocks and diversity on a station located in an Arctic fjord (Adventfjorden, Spitsbergen). The seasonality observed in benthic biota was related to the pelagic processes, primarily the seasonal fluxes of organic and inorganic particles. The highest abundance, biomass and richness of benthic fauna occurred in the spring after the phytoplankton bloom. During the summer, when a high load of glacial mineral material was transported to the fiord, the number of both meio- and macrobenthic individuals decreased remarkably. The strong inorganic sedimentation in summer was accompanied by a decline in macrobenthic species richness, but had no effects on evenness. Redundancy analysis (RDA) pointed to granulometric composition of sediments (depended on mineral sedimentation) and organic fluxes as factors best related to meio- and macrobenthic taxonomic composition, but no clear seasonal trend could be observed on the nMDS plots based on meiobenthic higher taxa or macrobenthic species abundances in the samples. This study addresses the possible effects of changes in the winter ice cover on the fjordic benthic systems because it was performed in a year with no ice cover on the fjord

Learning biophysically-motivated parameters for alpha helix prediction

<p>Abstract</p> <p>Background</p> <p>Our goal is to develop a state-of-the-art protein secondary structure predictor, with an intuitive and biophysically-motivated energy model. We treat structure prediction as an optimization problem, using parameterizable cost functions representing biological "pseudo-energies". Machine learning methods are applied to estimate the values of the parameters to correctly predict known protein structures.</p> <p>Results</p> <p>Focusing on the prediction of alpha helices in proteins, we show that a model with 302 parameters can achieve a Q_{<it>α </it>}value of 77.6% and an SOV_{<it>α </it>}value of 73.4%. Such performance numbers are among the best for techniques that do not rely on external databases (such as multiple sequence alignments). Further, it is easier to extract biological significance from a model with so few parameters.</p> <p>Conclusion</p> <p>The method presented shows promise for the prediction of protein secondary structure. Biophysically-motivated elementary free-energies can be learned using SVM techniques to construct an energy cost function whose predictive performance rivals state-of-the-art. This method is general and can be extended beyond the all-alpha case described here.</p

Molluscs in Kongsfjorden (Spitsbergen, Svalbard): a species list and patterns of distribution and diversity

This paper presents a survey of the mollusc fauna in Kongsfjorden, an Arctic glacial fjord in Spitsbergen, Svalbard, based on 197 samples collected with van Veen grabs, dredges, scuba-diving collections and baited traps at depths ranging from 5 to 390 m. Eighty-seven mollusc species were recorded. The species distribution accords well with the distribution of the main substrata: barren rock, kelp bed, gravel and soft bottom. For the most common substrate type, the soft bottom, the distribution and diversity of molluscs were analysed in relation to environmental factors. Glacial activity (particularly the inflow of glacial meltwater loaded with mineral solids) is responsible for the main gradients of environmental variables in the fjord. Silt concentration in sediments, the water temperature near the bottom and inorganic suspensions in the surface water best predict the species distribution of the soft bottom. Two faunal associations located in glacial bays and three faunal associations in the central basin of the fjord can be distinguished for the fauna of the soft bottom. Molluscs are much more abundant in glacial bays (200–300 individuals (ind.) 0.1 m 2 ) than in the central basin assemblages (30–40 ind./0.1 m 2 ). Yoldiid ( Yoldiella solidula , Y. lenticula and Yoldia hyperborea ) and thyasirid bivalves ( Thyasira dunbari , T. gouldi and Axinopsida orbiculata ) cope particularly well with glacial sedimentation and occur in high quantities in glacial bays. Although there is no effect of glacial disturbance on the molluscan sample species richness and species diversity, there are significant clines of evenness and taxonomic distinctness in areas near to the glacier. The patterns of molluscan diversity are not fully consistent with the patterns described for complete macrobenthic communities

Impact of early food input on the Arctic benthos activities during the polar night

In Arctic areas where benthic primary production does not occur or is not sufficient, the benthos depends on episodic events of food inputs from overlying waters, in particular spring ice algal and phytoplankton blooms. Climate change is expected to lead to earlier ice melts and subsequently to earlier spring blooms and food inputs to the benthos. The goal of the present study was to characterize benthic community structure and activities during the polar night in Rijpfjorden, a high Arctic fjord from Svalbard, and to assess experimentally how earlier climate-induced food inputs can impact these benthic activities. Two concentrations of freeze-dried phytoplankton were added to intact sediment cores, while additional control cores did not receive food addition. Sediment oxygen demand (SOD), nutrient fluxes, bioturbation coefficients (as indicator of benthic activities) and contents of organic matter and pigments in sediments were measured at the beginning of the experiment and 9 days after the addition. In the initial polar night conditions, SOD was similar to 4.2 mmol O-2 m(-2) d(-1), bioturbation coefficients were null for biodiffusion and 1.08 y(-1) for bioadvection, and benthic biomass was 1.36 g 0.1 m(-2). In the cores with food addition, the phytoplankton added was quickly consumed, and after 9 days, SOD and bioturbation were higher in the food treatments compared with the control cores, both being higher with higher food concentration. This study documented a clear and quick response in benthic activities following the food input, suggesting that in winter/early spring, Arctic benthos may depend on early food inputs for its activities. Climate-induced changes in food supply to the seafloor could have drastic consequences for the benthic ecosystem functioning

Macrobenthic biodiversity response to climate warming driven environmental change in the Arctic deep-sea (HAUSGARTEN, Greenland Sea 79°N)

Large-scale simulations of global climate predicts continuous increase in air and water temperature, leading to further reduction in ice-cover in Arctic. Monitoring of natural, temporal variability of characteristics of deep sea ecosystems in that climate change sensitive area, are crucial for capture of the moment and the nature of the biological response to changes in environmental regimes. Research was localized in HAUSGARTEN area, where the long-term interdisciplinary monitoring program of structures and functions of deep sea ecosystem in Arctic was established by Alfred Wegener Institute in Bremenhaven (AWI, Germany). HAUSGARTEN is located on the border between the Arctic Ocean and the northern North Atlantic in the region of marginal ice zone - an area very sensitive to possible effects of the global climate change. Between years 2004 and 2008, the anomalously warm surface waters (with temperatures >3°C), called Warm Water Anomaly (WWA), occurred in the central HAUSGARTEN area. It had a significant influence on the whole marine ecosystem – from pelagic zone to the deep sea bottom. We aimed to explore the response of macrobenthic communities to environmental change in HAUSGARTEN region. The study is based on samples collected before (2000) and after the WWA (2010, 2017). Macrofauna samples were collected from board of r/v “Polarstern”, at stations located along the bathymetric gradient from shelf to abyssal plain (230-5561m). Macrofauna species composition and diversity has been compared among the three sampling years to explore if and how it responded to the climate warming driven environmental change