ALBERT

Beschreibung: Arctic fjords host a diverse seaweed community forming the base of the benthic foodweb and providing habitat and shelter for a vast diversity of associated fauna. Seaweed model species as well as seaweed communities are intensively studied with reference to their general adaptive and functional traits, as well as their responses to global environmental change. Our long-term project ats Svalbard aims at a holistic understanding of seaweed ecosystem function spanning from the environmental control of gene expression to energy flow through trophic levels. Research is currently focusing on the sugar kelp Saccharina latissima and the wing kelp Alaria esculenta as abundant model species under a set of combined stressors such asthe combined stressors elevated UV-B radiation and temperature or increased sedimentation and grazing. In addition the responses of seaweeds to increased CO2 are addressed. In the frame of this global change scenario species-specific acclimation patterns are studied aton the physiological levelbase and species competition at the community level. Both approaches intendin order to predict shifts in the competitive strength of habitat engineeringa respective species, potentially resulting in a changing seaweed community. Comparative community analyses conducted in 1996-98 and 2012-2014 indicate a considerable change in seaweed biomass, a change in kelp depth limits and a change in species richness at low depth at the study site off Hansneset/Kongsfjord, Spitsbergen, but no obvious biodiversity change all possibly correlated to the recent warming of winters. The seaweed biomass maximum was shifted from 5 to 2.5m depth and overall biomass increased. Future surveys are needed to separate climate related signals against a background of high interannual variability.

Beschreibung: According to diverse model predictions Arctic seaweed systems are proposed to alter structure and composition due to global change in future. Two major factors that will influence these systems are (1) ocean warming and (2) increased glacier melting leading to a reduction in ice cover and ice-scouring and changing light quantity and quality as well as substrate characteristics. In 2012 / 13 we investigated a polar kelp system along a depth transect off Hansneset, Kongfjorden (Svalbard) and compared these data with a baseline study performed at the same site in 1996/98. Probably as a consequence of continuously ice-free winters since 2006, biomass and biodiversity changes were observed. Concurrent laboratory studies revealed the susceptibility of kelp recruitment towards a combination of increased sedimentation, warming and grazing. Furthermore we will report on ecotypic differentiation and first calculations of carbon budgets for the kelp system

Beschreibung: Our interdisciplinary, long-term project on Arctic benthic macroalgae revealed considerable change of shallow water benthic ecosystems as a consequence of environmental changes. At our Arctic study site at Hansneset, Kongsfjorden, Svalbard, we repeated a quantitative diving study of 1996/98 in 2012-2014 in the shallow rocky sublittoral from 0-15 m depth. The overall seaweed biomass had increased 1.7× and 4.7× at shallow depths (2.5 m), which supported predictions of increased productivity in the Arctic because of climate warming. The standing stock at the biomass maximum at 2.5 m comprised 14.4 kg fresh biomass m-2, a leaf area index (leaf area/sampling area) of approx. 10 and a very high kelp density. Here, the kelp composition included four species, with pronounced dominance of digitate kelp species (Laminaria digitata and/or Saccharina nigripes). Our study showed 1) uplift of kelp biomass maximum from 5 m to 2.5 m depth, 2) decrease in the lower depth limit of dominant brown algae by several m, 3) decrease in biomass of annual species, 4) considerable increase in richness from 20 to 45 species in the intertidal to shallow sublittoral (1 m depth). With respect to the associated fauna, both biomass and production increased, particularly in the shallow sublittoral (2.5-5 m), and a functional change towards the dominance of suspension feeders became apparent. These observed changes are likely a consequence of recent Arctic warming. Lack of landfast sea ice and ice-scouring during winter would reduce physical abrasion and improve irradiance conditions. However, in summer increased sedimentation with reduced phases of clear water conditions has the opposite effect by reducing the radiance and causing less light to reach the deepest part of the kelp beds. Sedimentation had revealed a negative impact on germination and formation of juvenile kelp sporophytes. Moderate grazing could partly counteract the negative effect of sedimentation but not under complete sediment coverage of the recruits (~1 mm thickness). Arctic warming, with increased temperature, less sea ice, but increased sedimentation may cause species-specific differences in sporophyte recruitment, which may lead to “winner” and “looser” species in the kelp forest in Svalbard.

Beschreibung: The analysis of the food web of an algal belt in Kongsfjorden is based on the investigation of 3 transects at Hansneset. The transsects are located in the same place as during a study in 1996-1998 allowing the demonstration of possible alterations in community structure due to global climate changes. Species composition of plants and animals, abundance and biomass have been studied. Samples were taken quantitatively by divers and were further processed in the Marine Lab. Data on basic ecological processes and parameters of the dominant components of the system as biomass, production, respiration and excretion have been measured. Diet analysis of heterotrophs has been done via analysis of stable isotope ratios C and N, and analysis of fatty acids. In a synthesis of the existent data on Kongsfjorden and the additionally gathered new data on the bentho-pelagic system of the habitats on hard bottom, a first model of the food web has been constructed with the “Ecological Network Analysis (ENA)”. ENA gives an analysis of the food web interactions and a characterization of the system in respect of stability, sensitivity to disturbance, with respect to energy flow and material cycling. Since climate warming is changing coastal arctic systems, the changing functioning of these ecosystems are discussed.

Beschreibung: The analysis of the food web of an algal belt in Kongsfjorden is based on the investigation of 3 transects at Hansneset. The transsects are located in the same place as during a study in 1996-1998 allowing the demonstration of possible alterations in community structure due to global climate changes. Species composition of plants and animals and their biomass had been studied. Samples were taken quantitatively by divers and were further processed in the Marine Lab. Data on basic ecological processes and parameters of the dominant components of the system as biomass, production, respiration and excretion have been measured. Diet analysis of heterotrophs has been done via analysis of stable isotope ratios C and N, and analysis of fatty acids. In a synthesis of the existent data on Kongsfjorden and the additionally gathered new data on the bentho-pelagic system of the habitats on hard bottom, a first model of the food web has been constructed with the “Ecological Network Analysis (ENA)”. ENA gives an analysis of the food web interactions and a characterization of the system in respect of stability, sensitivity to disturbance, with respect to energy flow and material cycling. Since climate warming is changing coastal arctic systems, the changing functioning of these ecosystems is discussed.

Beschreibung: Climate change forces retreat of Arctic glaciers and release of increased quantities of melt water and terrigenous material into coastal habitats of the Arctic such as the Kongsfjorden Ecosystem. The effect of this glacier induced physical parameters on growth and abundance of the Greenland smoothcockle (Serripes groenlandicus, Bruguière 1798) were determined. Along Kongsfjorden, at five stations with increasing distance to the Kongsbreen glacier, specimen of the cockle were collected and physical parameters were measured. Effects on growth of S. groenlandicus were analyzed by measuring variability of annual increments obtained from cockles’ thin section. Towards the glacier front temperature and Chlorophyll a content of the water column decreased, whereas total suspended matter and sedimentation rates increased. Regression analysis revealed lowest growth rate at the station close to Kongsbreen. Average standard growth index (SGI) of S. groenlandicus was lowest at this station (-0.4884±0.1763 95%CI), highest at Ny Alesund (0.1523±0.1158 95%CI), and decreased towards the mouth of Kongsfjorden (-0.0217±0.0718 95%CI and -0.1310±0.0759 95%CI, respectively at the two outer stations). Multi regression analysis revealed a strong relationship between average SGI and temperature (P〈0.001, R²=0.75) as well as total sedimented material (P=0.018, R²=0.80).

Beschreibung: In Arctic macroalgal belt ecosystems, macrozoobenthic production is thought to be an important link between primary production and higher trophic levels. Macrozoobenthic biomass and secondary production were studied along transects (2.5-15 m depth) in the macroalgal belt at Hansneset in Kongsfjorden, Svalbard, from 2012 to 2013. At 2.5m, the standing stock reached its maxima of 174.8 ± 54.4 g ash free dry weight per 1 m2, while density (4341 ind. m-2± 1127 95% CI) and production (7.0 g C m-2 y-1 ± 2.8 95% CI) were highest at 5 m water depth in 2012/13. Compared to a study from 1996/98, this re-sampling indicated a drastic change in the depth-distribution of macrozoobenthic biomass and secondary production at Hansneset. While both biomass and secondary production increased with water depth in 1996/98, this pattern was inversed in 2012/13 owing to a tenfold increase of biomass and secondary production in the upper most sublittoral (2.5-5 m). Variability of macrozoobenthic biomass and secondary production corresponded to differences in the physical environment and macroalgal vegetation along the depth gradient. In the last decade, the number of ice free days per year increased probably due to Arctic warming. As a result, shallow rocky habitats (2.5-5 m) are less affected by ice scouring, thereby opening new space for colonization by benthic fauna. However, faunal secondary production was low compared to macroalgal primary production, indicating a considerable export of most of the algal production from the shallow habitats to the adjacent areas.