Abstract. Framework-forming cold-water corals (CWCs) are ecosystem engineers that build mounds in the deep sea that can be up to several hundred metres high. The effect of the presence of cold-water coral mounds on their surroundings is typically difficult to separate from environmental factors that are not affected by the mounds. We investigated the environmental control on and the importance of ecosystem engineering for cold-water coral reefs using annotated video transect data, spatial variables (MEMs), and hydrodynamic model outputs in a redundancy analysis and with variance partitioning. Using available hydrodynamic simulations with cold-water coral mounds and simulations where the mounds were artificially removed, we investigated the effect of coral mound ecosystem engineering on the spatial configuration of reef habitat and discriminated which environmental factors are and which are not affected by the mounds. We find that downward velocities in winter, related to non-engineered environmental factors, e.g. deep winter mixing and dense-water cascading, cause substantial differences in reef cover at the broadest spatial scale (20–30 km). Such hydrodynamic processes that stimulate the food supply towards the corals in winter seem more important for the reefs than cold-water coral mound engineering or similar hydrodynamic processes in summer. While the ecosystem-engineering effect of cold-water corals is frequently discussed, our results also highlight the importance of non-engineered environmental processes. We further find that, due to the interaction between the coral mound and the water flow, different hydrodynamic zones are found on coral mounds that likely determine the typical benthic zonations of coral rubble at the mound foot, the dead coral framework on the mound flanks, and the living corals near the summit. Moreover, we suggest that a so-called Massenerhebung effect (well known for terrestrial mountains) exists, meaning that benthic zonation depends on the location of the mound rather than on the height above the seafloor or water depth. Our finding that ecosystem engineering determines the configuration of benthic habitats on cold-water coral mounds implies that cold-water corals cannot grow at deeper depths on the mounds to avoid the adverse effects of climate change.
Building your own mountain: the effects, limits, and drawbacks of cold-water coral ecosystem engineering
Anna-Selma van der Kaaden,S. Maier,Silu Chen,L. D. De Clippele,Evert de Froe,T. Gerkema,J. van de Koppel,F. Mienis,C. Mohn,M. Rietkerk,K. Soetaert,D. van Oevelen
Published 2024 in Biogeosciences
ABSTRACT
PUBLICATION RECORD
- Publication year
2024
- Venue
Biogeosciences
- Publication date
2024-02-22
- Fields of study
Not labeled
- Identifiers
- External record
- Source metadata
Semantic Scholar
CITATION MAP
EXTRACTION MAP
CLAIMS
CONCEPTS
- benthic zonation
The spatial arrangement of different benthic habitat types across a mound.
- cold-water coral mounds
Deep-sea mound-shaped reef structures built by framework-forming cold-water corals.
- ecosystem engineering
The alteration of local habitat and flow conditions by organisms through their physical structures and activity.
- hydrodynamic zones
Distinct flow-regime areas that occur on and around coral mounds.
- massenerhebung effect
A mountain-related zonation concept in which habitat distribution depends on location on the mound rather than simple elevation or depth.
- non-engineered environmental factors
Environmental conditions that are not modified by the presence of the coral mounds.
- reef cover
The amount of reef habitat present along the annotated video transects.
- winter downward velocities
Downward water-flow velocities in winter used here as a hydrodynamic variable from the simulations.
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