Bentho-pelagic research focus

The framework of our activities is the research program Changing Earth - Sustaining our Future which is part of the research field Earth and Environment of the Helmholtz Association of German Research Centres (HGF). Within the current programm (2021 - 2027), we participate in the topics:

• Topic 4: Coastal Transition Zones under Natural and Human Pressure
   Subtopic 4.1 Fluxes and transformation of energy and matter in and across compartments
   Subtopic 4.2 Coastal ecosystem sustainability against the backdrop of natural and anthropogenic drivers

• Topic 6: Marine and Polar Life: Sustaining Biodiversity, Biotic Interactions, and Biogeochemical Functions
   Subtopic 6.1 Future ecosystem functionality
   Subtopic 6.3 The future biological carbon pump

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.

Focus Antarctica

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.

Focus Patagonia

Deciphering Antarctic Cold-water CORals (DACCOR)

Within the AWI Strategy Fund project DACCOR we aim to develop a proxy archive for the Southern hemisphere and especially for the Antarctic region using cold-water corals (CWC) to reconstruct temperature and pH in seawater.

Coral skeletons are of great scientific importance as climate archives, since during its formation the prevailing environmental conditions are incorporated into the skeleton and the changes in the oceans can be followed in these skeletal structures over decades and centuries. The project DACCOR aims to develop a continuous archive of warming and acidification to better constrain the complex relations underlying the historic instability of the shelf ice in the Antarctic peninsula region – an area subject to large climate variability. A multidisciplinary approach is used to investigate the ecological, physiological and molecular regulations of the skeletal formation (biomineralization) to read geochemical signatures in CWC grown under laboratory (AWI) and field conditions (Patagonia, Chile and in the Antarctic peninsula). If we succeed in deciphering CWC proxy archives DACCOR offers a temporally high-resolution documentation of the past including palaeo-records and the start of a coherent monitoring of recent climatic change beyond pure instrumental records. The project builds on the strong expertise at AWI (coral ecology and ecophysiology, biogeochemistry, geochemistry, molecular biology) and close ties to national (GEOMAR, MPI) and international partners (V. Häussermann, Huinay).