Create natural rocky reef topography on subtidal artificial structures
Overall effectiveness category Awaiting assessment
Number of studies: 1
Background information and definitions
Definition: ‘Natural rocky reef topography’ refers to the full fingerprint of substrate topography found in natural rocky habitats.
Topography influences the settlement and survival of marine organisms on subtidal rocky substrates. Variation in topography generates variation in the physical environment and plays an important role in sustaining biodiversity and ecological functioning (Levin 1974). On rocky reefs, many habitat features that offer refuge from physical stressors and predation, such as bumps, crevices and holes, are generated as a function of substrate topography and geomorphology. The full fingerprint of natural rocky reef topography encompasses a variety of habitat features of different scales interacting within a mosaic.
Marine artificial structures often have much lower topographic variability than natural rocky reefs, which is thought to be a key reason for their reduced biodiversity (Wilhelmsson & Malm 2008). Natural rocky reef topography can be created on subtidal artificial structures by moulding or casting material during construction or retrospectively (see Evans et al. 2021).
See also: Create textured surfaces (≤1 mm) on subtidal artificial structures; Create pit habitats (1–50 mm) on subtidal artificial structures; Create hole habitats (>50 mm) on subtidal artificial structures; Create groove habitats (1–50 mm) on subtidal artificial structures; Create crevice habitats (>50 mm) on subtidal artificial structures; Create small protrusions (1–50 mm) on subtidal artificial structures; Create large protrusions (>50 mm) on subtidal artificial structures; Create small ridges or ledges (1–50 mm) on subtidal artificial structures; Create large ridges or ledges (>50 mm) on subtidal artificial structures; Create groove habitats and small protrusions, ridges or ledges (1–50 mm) on subtidal artificial structures.
Evans A.J., Lawrence P.J., Natanzi A.S., Moore P.J., Davies A.J., Crowe T.P., McNally C., Thompson B., Dozier A.E. & Brooks P.R. (2021) Replicating natural topography on marine artificial structures – a novel approach to eco-engineering. Ecological Engineering, 160, 106144.
Levin S.A. (1974) Dispersion and population interactions. American Society of Naturalists, 108, 207–228.
Wilhelmsson D. & Malm T. (2008) Fouling assemblages on offshore wind power plants and adjacent substrata. Estuarine, Coastal and Shelf Science, 79, 459–466.
Supporting evidence from individual studies
A replicated, randomized, controlled study in 2009 on a subtidal rocky reef on open coastline in the Adriatic Sea, Italy (Perkol-Finkel et al. 2012) found that creating natural rocky reef topography on settlement plates did not increase the abundance of juvenile canopy algae Cystoseira barbata that settled onto plates. After five months, there was no significant difference in the average abundance of juveniles on settlement plates with natural rocky reef topography (deep topography: 23/plate; shallow: 28/plate) and plates without (19/plate). Clay settlement plates (100 × 100 mm) were made with and without natural rocky reef topography imprinted on their surfaces using pieces of natural rock as the clay set. Six plates with each of deep (imprinted 5 mm deep) and shallow (1–2 mm) topography and six plates without were randomly arranged horizontally at 3 m depth on a rocky reef with existing adult canopy algae in March 2009. Juvenile canopy algae on plates were counted after five months.Study and other actions tested