Happy Birthday, HAUSGARTEN Observatory! | Polarjournal
OFOS (Ocea Floor Observing System) is a towed photo/video system that provides information on the large-scale distribution of larger animals on the bottom of the HAUSGARTEN area. The comparison with images from the past ten years provides the scientists with information about temporal changes in the density and composition of this so-called epibenthos. (Photo: OFOS/James Taylor)

20 years ago, scientists at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) laid the “corner stone” for a unique long-term observatory in the partially ice-covered Fram Strait between Greenland and Spitsbergen, which they call their HAUSGARTEN (Backyard). The deep-sea observatory is the first and still the only one of its kind for year-round physical, chemical and biological observations in a polar region. Researchers here are investigating how a polar marine ecosystem is changing in times of global change.

As a result of climate change, the Arctic is changing at a rapid pace. However, observational programs that provide information on changes in the Arctic marine ecosystem are scarce. For the most part, the polar regions are only accessible with modern and expensive infrastructure and instrumentation. The HAUSGARTEN study stations cover approximately 30,000 km2 between 78° and 80° North and between 6° West and 11° East. In this area, deep-sea researchers and oceanographers conduct regular investigations in a network of a total of 21 stations with water depths between 250 and 5500 meters. They are exploring all areas of the marine ecosystem from the water surface to the deep sea to determine the consequences of climatic changes on marine Arctic biodiversity in a multidisciplinary approach. Sampling and measurements in the water column and on the deep-sea floor take place annually during regular expeditions in the summer months. In addition, instruments anchored to the seafloor continuously sample and measure the seafloor; recently, mobile, autonomous instruments have also been deployed throughout the year.

The map shows the location of HAUSGARTEN between Greenland and Svalbard. A total of 21 measuring stations at various depths provide information on changes in the Arctic Ocean. (Graphic: AWI)

“In the summer of 1999, we mapped the seafloor in HAUSGARTEN on a large scale for the first time using the French underwater robot Victor 6000,” recalls the founder, Dr. Thomas Soltwedel, a biologist at the Alfred Wegener Institute. “Actually, we had a different overarching question at that time: What causes/enables the high species diversity in the deep sea? We then decided to conduct our investigations on this question always at the same position in order to get an idea of natural fluctuations in the environmental conditions in the study area over time – this is how the time series came into being”. Meanwhile, in times of global climatic change, the focus is on how a polar marine ecosystem is changing as a result of global change.

The Victor 6000 deep-sea vehicle weighs around 4 tons and is controlled via 8,500 m long cables. It can operate down to depths of 6,000 m and can perform a very wide range of tasks such as sampling, measurement and imaging. (Photo: Michael Klages)

In the eastern Fram Strait, the HAUSGARTEN observatory has served since its inception as an experimental field for unique long-term biological experiments at the bottom of the Arctic deep sea. Various experiments in different disciplines show that organisms living in deep-sea regions of the Arctic Ocean are not as sluggish in their response to change as commonly believed. But the colonization of new places happens very slowly. Thus, if resource extraction plans are implemented in the deep sea, it could cause long-term damage that is almost impossible to repair. Continuous ecological surveys at HAUSGARTEN have already revealed a number of interesting temporal trends. The widespread notion that deep-sea ecosystems respond very sluggishly, if at all, to environmental changes in surface water had to be revised. Between the years 2005 and 2008, there was a pulse-like, significant increase in water temperatures of about 2 °C in the Fram Strait. This led to profound changes in the composition of the plant plankton in the light-flooded surface water, which then caused a rapid response specifically from the smaller organisms living on and in the deep seafloor, as these organisms meet their nutritional needs exclusively from dead plankton that have sunk to the seafloor. Larger ground dwellers were slower to respond in numbers and species composition with about a one-year lag.

The deep-sea regions of the Arctic Ocean are very much a living world, home to larger species like this octopus. Rapid changes in their environment could lead to the loss of such species. (Photo: OFOS/James Taylor)

“Even after 20 years of intensive observations in the HAUSGARTEN observatory area, we still cannot say with complete certainty whether the observed changes reflect the natural variability of a marine polar ecosystem, or whether the observed trends are caused by anthropogenic climate change and thus possibly permanent,” says Thomas Soltwedel. A recent scientific study could show in a modeling approach that time series of about 30 years are needed to distinguish climate change-driven changes in the marine ecosystem from natural variability and to develop robust predictive models. About two-thirds of this assumed time span has now been covered at HAUSGARTEN. Currently, the long-term investigations are being continued during the ongoing Polarstern expedition PS121.

Currently, the German research icebreaker Polarstern is in the area of the HAUSGARTEN observatory as part of this year’s investigations. (Photo: AWI / Martin Schiller)

Source: Alfred Wegener Institute

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