Biocomplexity
Identification of driving forces of polar ecosystems
An assemblage in the eastern Weddell Sea (Antarctica) at approximately 230 m water depth dominated by very slow growing glass sponges. They indicate that this habitat has not been disturbed for a long period. Photo: J. Gutt, AWI, Germany
One of the biggest challenges in marine ecology is to understand the relationship between biodiversity and ecosystem functioning. Corresponding knowledge is essential to predict the future of marine life in case of ongoing environmental changes. The focus of this working group is the high latitude macrobenthos, because it is -together with the deep sea- least directly affected by man, but both systems regionally experience consequences of climatic changes. Therefore, results of such studies are most likely to have a general applicability. In contrast to pelagic organisms, benthic communities including demersal fish are more sensitive to environmental changes. Most species are relatively stationary; they cannot escape and reinvade immediately after an impact. As a consequence benthic communities need a certain resilience in order to survive or they get extinct. In addition, the sea-floor provides a broad variety of ecological niches that allows a high number of specialized species to coexist without direct competition. Consequently, such communities are worthwhile to be protected.
The major aims of this working group are to identify driving forces of polar ecosystems, such as physical disturbance and other environmental variability, food availability and limitation, sediment preferences, competition, larval dispersal, and recruitment of juveniles. Based on corresponding results the resilience of such benthic systems is to be assessed, and biodiversity changes in case of sustained environmental changes are to be studied and predicted. The tools for these approaches are conceptual as well as numerical models and interdisciplinary field studies.
The Antarctic sea floor and its epifauna have been totally devastated by an iceberg. Photo: J. Gutt, AWI, Germany
"Lollipop sponges" (Stylocordyla chupachups) represent together with bryozoans, ascidians, and cnidarians an intermediate stage of recolonisation after an iceberg impact. Photo: J. Gutt, AWI, Germany
Three measures of biodiversity in the high latitude Antarctic mega-benthos reveal contrasting results at two different spatial scales.
At the local scale, a late stage of recolonization after iceberg disturbance (UD=undisturbed) assumed to perform maximum interspecific competition shows unexpectedly highest diversity. In contrast, a transitional stage of recolonization (R2) has a significantly lower diversity. These findings contradict with the "Intermediate-Disturbance Hypothesis".
At a regional scale the representative patchwork of different stages of recolonization (REP) resulted in a higher biodiversity measure compared to an undisturbed assemblage (UD). This finding follows the "Patch-Dynamics Concept" in combination with the "Equal-Chance Hypothesis". In the latter the unpredictable succession of species in an ecosystem leads to an increase in diversity.
A spatially explicit individual-based model deciphers the relationship between biodiversity and ecosystem functioning. In addition, it allows for predictions of the succession of marine communities in case of environmental changes and disturbances.
Response of the Antarctic marine ecosystem to climate-induced collapse of ice shelves
Since the 1980ies the largest part of the Larsen A/B ice shelves East of the Antarctic Peninsula disintegrated during several abrupt collapse events. A first comprehensive ecological survey in 2007 showed generally low abundances of the sea-bed inhabiting fauna (benthos). Deep-sea taxa occurring in a relatively high diversity were assumed to be remnants of the ice-covered situation, e.g., holothurians, asteroids, crinoids, gastropods, and some sponges (red/orange). Fast growing or especially successfully recruiting species were interpreted as pioneers, e.g., ascidians, juvenile sponges, and hydrozoans (blue). Some of them were also found at the reference sites outside the Larsen area because the sea-bed was devastated by grounding icebergs providing space for a new succession in the benthic community. A typical deep-sea species, the holothurian Elpidia glacialis, despite being associated to the old ice-covered situation, obviously responded with fast population growth since it benefited from the additional food supply (blue-orange). Only one potential benthic invader was identified among sea-urchins (green). In addition, krill, pelagic fish, seals and whales had already occupied the new pelagic habitat. Further analyses of data from an expedition in 2011 and another follow-up survey in 2013 will provide further insights into the succession within the ecosystem and the response of key taxa to a regime shift from oligotrophic to normal Antarctic conditions.
Decay of ice shelf in the Larsen A/B areas (left). Abundances of deep-sea taxa, assumed pioneers and invadors (n/100qm) in the area (centre). Examples for key taxa (right). Modified from Gutt et al. 2011, DSR II 58; Graphics & Photos: J. Gutt, AWI/MARUM, Germany
Affiliations and contributions to international programmes
- SCAR-biology programme "Evolution and Biodiversity of the Antarctic" (EBA), member of the steering committee, co-chair of WP 5 "Impact of past, current and predicted future environmental change on biodiversity and ecosystem functioning"
- SCAR-expert group "Antarctic Climate Change and the Environment" (ACCE), member and co-editor of the ACCE report
- SCAR-programme planning group "Antarctic Thresholds - Ecosystem Resilience and Adaptation" (AnT-ERA), discussion leader
- Working group "Biodiversity" of the "Helmholtz Association of German Research Centres" (HGF), member
- SCAR "Cross-SSG Action Group on Prediction of Changes in the Physical and Biological Environments of the Antarctic", co-chair
- National Committee SCAR/IASC
Recent scientific results
- Brandt, A. and Gutt, J. (2011)
Biodiversity of a unique environment: the Southern Ocean benthos shaped and threatened by climate change, Biodiversity Hotspots: distribution and protection of conservation priority areas - Gutt, J., Barratt, I., Domack, E., et al. (2011)
Biodiversity change after climate-induced ice-shelf collapse in the Antarctic - Gutt, J., Hosie, G. and Stoddart, M. (2010)
Marine Life in the Antarctic
Outreach
- Gutt, J. and Stoddart, M. (2009)
Antarctic marine biodiversity shaped by ice, exploitation and climate change - Gutt, J. (2008)
Leben unter einem Antarktischen Schelfeis - ein biologisch "weißer Fleck" und seine Reaktion auf den Klimawandel
