Beschreibung: 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.

Beschreibung: We present bathymetric patterns in benthic community structure and functioning at the LTER (Long-term Ecological Research) observatory HAUSGARTEN in the Fram Strait. Meiofauna, macrofauna and sediments were sampled at 15 stations along a bathymetric gradient from Spitsbergen coastal waters (100-300m) across the Vestnesa Ridge (1000m) to a Molloy Hole (5561m). Benthic organisms were identified, enumerated and photographed to obtain individual dimensions, biovolume and biomass. Secondary production, respiration and carbon demand were estimated based on individual biomass data. Benthic size spectra were constructed by plotting the biomass against the log2-transformed size classes. Benthic standing stocks, production and carbon demand declined with depth alongside with the decline in food quantity and quality (as indicated by POC and chlorophyll a content in sediments). Compared to those for the meiofauna, bathymetric clines were stronger for macrofauna and a transition towards a system dominated by smaller organisms in deeper ocean zones could be documented. Meiofauna:macrofauna biomass and production ratios increased from 0.1 and 0.6, respectively, in coastal waters to 0.3 and 1.9 on the rise (4042-5102m). The benthic biomass size spectra was bimodal in shape, the width of size spectra declined with increasing depth (from 32 to 23 classes). A reduction of the number of size classes was stronger in macrofaunal part of the spectra. The largest and the smallest size classes as well as the peak in biomass for macrofauna were shifted towards smaller sizes in deeper zones. Fragmented size spectra observed at the two stations (including the Molloy Hole) could be interpreted as effects of physical sediment disturbance (by currents or bioturbation) and resulted in dramatic increase in meiofauna:macrofauna ratio in biomass (0.8) and production (6.5) in the Molloy Hole. The presented patterns are likely to be modified by on-going regional changes in ice coverage and productivity, and the food supply to the deep sea in the course of the climate warming.

Beschreibung: Polar marine regions are facing rapid changes induced by climate change, with consequences for local faunal populations, but also for overall ecosystem functioning, goods and services. Yet given the complexity of polar marine ecosystems, predicting the mode, direction and extent of these consequences remains challenging. Trait-based approaches are increasingly adopted as a tool by which to explore changes in functioning, but trait information is largely absent for the high latitudes. Some understanding of trait–function relationships can be gathered from studies at lower latitudes, but given the uniqueness of polar ecosystems it is questionable whether these relationships can be directly transferred. Here we discuss the challenges of using trait-based approaches in polar regions and present a roadmap of how to overcome them by following six interlinked steps: (1) forming an active, international research network, (2) standardizing terminology and methodology, (3) building and crosslinking trait databases, (4) conducting coordinated trait-function experiments, (5) implementing traits into models, and finally, (6) providing advice to management and stakeholders. The application of trait-based approaches in addition to traditional species-based methods will enable us to assess the effects of rapid ongoing changes on the functioning of marine polar ecosystems. Implementing our roadmap will make these approaches more easily accessible to a broad community of users and consequently aid understanding of the future polar oceans.

Beschreibung: Macroecology provides a novel conceptual framework for analysis of the distribution and abundance of organisms at very large scales. Its rapid development in recent years has been driven primarily by studies of terrestrial taxa; the vast potential of marine systems to contribute to the macroecological research effort remains largely untapped. International collaborative efforts such as MarBEF have provided fresh impetus to the collation of regional databases of species occurrences, such as the newly available MacroBen database of the European soft sediment benthic fauna. Here, we provide a first macroecological summary of this unique database. We show that in common with almost all previously analysed assemblages, the frequency distribution of regional site occupancies across species in the MacroBen database is strongly right-skewed. More unusually, this right skew remains under logarithmic transformation. There is little evidence for any major differences between higher taxa in this frequency distribution (based on the 8 animal classes for which we have sufficient data). Indeed, considerable variation in occupancy persisted across the taxonomic hierarchy, such that most variation occurred between species within genera. There was a weak positive relationship between local population density and regional occupancy across species, but this abundanceoccupancy relationship varied considerably between higher taxa and between geographical areas. Our results highlight the potential of databases such as MacroBen to consolidate macroecological generalities and to test emerging theory.

Beschreibung: Time-series studies of arctic marine ecosystems are rare. This is not surprising since polar regions arelargely only accessible by means of expensive modern infrastructure and instrumentation. In 1999, theAlfred Wegener Institute, Helmholtz-Centre for Polar and Marine Research (AWI) established the LTER(Long-Term Ecological Research) observatory HAUSGARTEN crossing the Fram Strait at about 79◦N.Multidisciplinary investigations covering all parts of the open-ocean ecosystem are carried out at a totalof 21 permanent sampling sites in water depths ranging between 250 and 5500 m. From the outset,repeated sampling in the water column and at the deep seafloor during regular expeditions in summermonths was complemented by continuous year-round sampling and sensing using autonomous instru-ments in anchored devices (i.e., moorings and free-falling systems). The central HAUSGARTEN stationat 2500 m water depth in the eastern Fram Strait serves as an experimental area for unique biologicalin situ experiments at the seafloor, simulating various scenarios in changing environmental settings.Long-term ecological research at the HAUSGARTEN observatory revealed a number of interesting tem-poral trends in numerous biological variables from the pelagic system to the deep seafloor. Contrary tocommon intuition, the entire ecosystem responded exceptionally fast to environmental changes in theupper water column. Major variations were associated with a Warm-Water-Anomaly evident in sur-face waters in eastern parts of the Fram Strait between 2005 and 2008. However, even after 15 years ofintense time-series work at HAUSGARTEN, we cannot yet predict with complete certainty whether thesetrends indicate lasting alterations due to anthropologically-induced global environmental changes of thesystem, or whether they reflect natural variability on multiyear time-scales, for example, in relation todecadal oscillatory atmospheric processes.

Beschreibung: Deep-sea benthic communities and their structural and functional characteristics are regulated by surface water processes. Our study focused on the impact of changes in water depth and food supplies on small-sized metazoan bottom-fauna (meiobenthos) along a bathymetric transect (1200–5500 m) in the western Fram Strait. The samples were collected every summer season from 2005 to 2009 within the scope of the HAUSGARTEN monitoring program. In comparison to other polar regions, the large inflow of organic matter to the sea floor translates into relatively high meiofaunal densities in this region. Densities along the bathymetric gradient range from approximately 2400 ind. 10 cm-2 at 1200 m to approximately 300 ind. 10 cm-2 at 4000 m. Differences in meiofaunal distribution among sediment layers (i.e., vertical profile) were stronger than among stations (i.e., bathymetric gradient). At all the stations meiofaunal densities and number of taxa were the highest in the surface sediment layer (0–1 cm), and these decreased with increasing sediment depth (down to 4–5 cm). However, the shape of the decreasing pattern differed significantly among stations. Meiofaunal densities and taxonomic richness decreased gradually with increasing sediment depth at the shallower stations with higher food availability. At deeper stations, where the availability of organic matter is generally lower, meiofaunal densities decreased sharply to minor proportions at sediment depths already at 2–3 cm. Nematodes were the most abundant organisms (60–98%) in all the sediment layers. The environmental factors best correlated to the vertical patterns of the meiofaunal community were sediment-bound chloroplastic pigments that indicate phytodetrital matter.

Beschreibung: The current understanding of Arctic ecosystems is deeply rooted in the classical view of a bottom-up controlled system with strong physical forcing and seasonality in primary-production regimes. Consequently, the Arctic polar night is commonly disregarded as a time of year when biological activities are reduced to a minimum due to a reduced food supply. Here, based upon a multidisciplinary ecosystem-scale study from the polar night at 79°N, we present an entirely different view. Instead of an ecosystem that has entered a resting state, we document a system with high activity levels and biological interactions across most trophic levels. In some habitats, biological diversity and presence of juvenile stages were elevated in winter months compared to the more productive and sunlit periods. Ultimately, our results suggest a different perspective regarding ecosystem function that will be of importance for future environmental management and decision making, especially at a time when Arctic regions are experiencing accelerated environmental change.