Do (sandmason) aggregations classify as reefs? Quantifying habitat modifying effects

Marijn Rabaut (1) , Magda Vincx (1) , Steven Degraer (2)

1 Marine Biology Section, Biology Department
2 Management Unit of the Mathematical Model of the North Sea

The positive effects of the tube dwelling polychaete for the associated benthic community emphasizes this bio-engineer's habitat structuring capacity (Rabaut et al. in Estuar Coastal Shelf Sci, 2007). Therefore, aggregations are often referred to as reefs. The reef building capacity of ecosystem engineers is important for marine management as the recognition as reef builder will increase the protected status the concerned species. To classify as reefs however, bio-engineering activities need to significantly alter several habitat characteristics: elevation, sediment consolidation, spatial extent, patchiness, reef builder density, biodiversity, community structure, longevity and stability [guidelines to apply the EU reef-definition by Hendrick and Foster-Smith (J Mar Biol Assoc UK 86:665–677, 2006)]. This study investigates the physical and temporal characteristics of high density aggregations of . Results show that the elevation and sediment consolidation of the biogenic mounds was significantly higher compared to the surrounding unstructured sediment. Areas with aggregations tend to be extensive and patchiness is high (coverage 5–18%). The discussion of present study evaluates whether aggregations can be considered as reefs (discussing physical, biological and temporal characteristics). Individual aggregations were found to persist for several years if yearly renewal of existing aggregations through juvenile settlement occurred. This renewal is enhanced by local hydrodynamic changes and availability of attaching structures (adult tubes). We conclude that the application of the EU definition for reefs provides evidence that all physical and biological characteristics are present to classify as a reef builder. For temporal characteristics, this study shows several mechanisms exist for reefs to persist for a longer period of time. However, a direct evidence of long-lived individual reefs does not exist. As a range of aggregation development exists, ‘reefiness' is not equal for all aggregations and a scoring table to quantify reefiness is presented.

Mots clés: Reef characteristics; Reefiness; Tube dwelling polychaete

Marijn Rabaut, Magda Vincx, Steven Degraer. Do (sandmason) aggregations classify as reefs? Quantifying habitat modifying effects. Helgoland Marine Research, 2008, 63 (1), pp.37-46. ⟨10.1007/s10152-008-0137-4⟩. ⟨hal-00478113⟩