Bentho-pelagic research focus
The framework of our activities is the research program Polar regions and Coasts in a changing Earth System (PACES) which is part of the research field Earth and Environment of the Helmholtz Association of German Research Centres (HGF). Within the current PACES II programm (2014 - 2018), we participate in the topics:
• Topic 1: Changes and regional feedbacks in Arctic and Antarctic
Workpackage 1.6 Large scale variability and change in polar benthic biota and ecosystem functions
• Topic 2: Fragile costs and shelf seas
Workpackage 2.3 Evolution and adaptation to climate change and anthropogenic stress in coastal and shelf systems
Workpackage 2.5 Interface processes and physical dynamics of the coastal ocean
The section BPP's long term goal is to quantify the structure and function of polar makrobenthic organisms, their interaction with the pelagic system and susceptibility to natural disturbances and climate change. A mechanistic understanding of the bentho-pelagic processes can serve as important baseline to model the biological responses to polar climate change.
Although retreating ice-shelves, increased iceberg calving and changing seasonal pack-ice cover are expected to have important repercussions on the Antarctic benthos, reliable data on benthic productivity and material cycling are still lacking. We aim at filling this gap to better understand the dynamics of Antarctic benthic communities and ecological functions by carrying out the first direct measurements to date on important process variables in situ, using advanced underwater technologies. While the focus is on sponges and corals, large skeletal filter-feeders providing important habitat for other organisms, we also study mobile sentinel species for climate change such as pinnipeds and fish, which play an important role in the Antarctic ecosystem as apex predators. The midterm goal is to combine results from investigations in structure and processes to better understand the biotic and environmental factors governing the distribution of biodiversity and biomass as well as their feedbacks to Antarctic climate change.
Benthic Responses to Larsen Ice Shelf Collapse in the Antarctic Peninsula Region
We monitor the colonization of the seafloor under the former ice shelves over years to decades after their disintegration due to regional warming.
The collapse of the ice shelves along the eastern margins of the Antarctic peninsula has exposed vast areas covered for thousands of years under permanent ice to a seasonal supply of cryo-pelagic primary production. The northernmost Larsen A ice shelf disintegrated in 1995, Larsen B in 2002 and a huge iceberg calved from Larsen C in 2017 in the south of the Antarctic Peninsula. The timing of events allows us to explore the response of the benthic communities to different times of exposure to cryo-pelagic production. But research in this region is a challenged by notoriously difficult sea-ice conditions making the Larsen region one of the least accessible in Antarctica. In the one repeat visit so far to Larsen A, we found that glass sponges were able to double their biomass between 2007 and 2011. The rapid growth suggests that filter-feeders take advantage of the unprecedented high fluxes of organic carbon reaching the seafloor. Future expeditions with RV Polarstern will explore the flow of carbon to better understand how Antarctic communities respond to climate change.
Research at the Filchner Outflow System
The region of the Filchner Outflow System (southern Weddell Sea) is considered a "hot spot", both in terms of biology and physical oceanography.
The factors contributing to this oceanic area of enhanced food availability and its relation to physical processes are not yet understood. By including biotic components from phytoplankton via benthic organisms and fishes to seals and abiotic parameters such as bottom topography, sediment structure, and hydrographic features, we aim to comprehensively investigate the Filchner Outflow System. Here the outflow of ice shelf water of the Filchner Ronne Ice Shelf interacts with warm deep water of the Weddell Gyre circulation. This interaction is supposed to be the primary cause that converts this area into a biological "hotspot" where all trophic level interactions are maximised. Oceanographic models predict marked changes in the hydrographic features of the Filchner Outflow System with potentially dramatic changes for the biodiversity in this area. Physical, biogeochemical and ecological studies with RV Polarstern in the Filchner Outflow System and in the south-eastern Weddell Sea shall characterize this hotspot in detail.
The Benthos Disturbance Experiment (BENDEX)
Iceberg strandings occur regularly on the Weddell Sea shelves and have been shown to play a substantial role in structuring benthic and demersal fish biodiversity.
The artificial Benthic Disturbance Experiment BENDEX was initiated in 2003 and simulates the impact of grounding icebergs on the seafloor and follows the steps and timescales of recovery of disturbed benthos and fish communities. The timescale of recolonization after disturbance is considered as an important scientific question, because it is strongly related to the vulnerability and resilience of cold water systems. After two revisits of the disturbed site in 2011 and 2014 first new colonizers and increases in biomass and organism densities became obvious but more regular resampling campaigns are necessary to document the recovery of the partly long-lived organisms.
International Integration and Consideration
Sea-bed inhabiting communities in the eastern Weddell Sea and along the Antarctic Peninsula are relatively well known due to regular surveys in the past 30 years, especially by applying imaging technology and through conceptual as well as numeric models.
Studies on biodiversity, its relationship to ecosystem functions and the response of various biota to climate change are put into a wider context through international cooperation. Important integrative initiatives in this context are the scientific research programme "Antarctic Thresholds - Ecosystem Resilience and Adaptation" (AnT-ERA), and the report "Antarctic Climate Change and the Environment" (ACCE) of the "Scientific Committee on Antarctic Research" (SCAR), and the "Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services" (IPBES) of the United Nations and the "Southern Ocean Observing System" (SOOS) endorsed by the "Scientific Committee on Oceanic Research" (SCOR) and supported by SCAR. Data on animal groups such as sponges, cnidarians, sea-squirts, bryozoans, echinoderms, and fish are uploaded to the data repositories ANTABIF and PANGAEA and disseminated by stakeholder-oriented initiatives and tools.