The deep seafloor harbours one of the most biodiverse ecosystems on our planet: cold-water coral reefs. Like their tropical counterparts, cold-water corals (CWCs) form structurally complex habitats that support a diverse and productive reef community. It is still paradoxical how such a rich ecosystem can thrive in the deep sea, an environment that is typically considered to be food limited. This VIDI project targets this paradox by an integrated study on the delivery, uptake and processing of organic matter by CWC-reef communities.
The basis of this proposal is a framework for the functioning of CWC-reef communities in the deep sea, which is based on hypotheses generated from preliminary findings, and has three key elements: (1) direct field measurements indicate that organic matter respiration by CWC-reef communities is much higher than respiration in off-reef sediments, indicating an enhanced organic matter uptake, (2) a coupled hydrodynamic-biogeochemical model suggests that this enhanced uptake can be explained by episodic vertical transport of organic matter, focussed to the reef community and (3) recycling of organic matter within the reef community, with sponges as key mediator, ensures the retention and efficient utilization of available organic matter.
This framework will be verified and validated for the 600-m deep CWC reefs at Rockall Bank (Irish Margin) through an integration of empirical data, acquired with state-of-the-art measurement techniques, and mathematical models. Models will guide sampling strategies, while the data will feed back into the models for calibration and fine-tuning. The validated models will lead to an improved understanding of the functioning of this unique ecosystem in the present-day and will allow forecasting future effects of reduced organic matter export to the deep sea on the functioning CWC-reef communities. One of the measurement techniques will be further developed with industry partners for use in environmental impact studies.