Create groove habitats (1–50 mm) on subtidal artificial structures

Overall effectiveness category Awaiting assessment
Number of studies: 2
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Effectiveness

not assessed
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not assessed
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not assessed

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Background information and definitions

Definition: ‘Groove habitats’ are depressions with a length to width ratio >3:1 and depth 1–50 mm (modified from “Crevices” in Strain et al. 2018).

Groove habitats provide organisms refuge from predation in subtidal rocky habitats (Nelson & Vance 1979). Some species preferentially settle into them (Bourget et al. 1994). The size and density of grooves is likely to affect the size, abundance and variety of organisms that can use them. Small grooves can provide refuge for small-bodied organisms but may exclude larger organisms, limit their growth and get rapidly filled-up (Firth et al. 2020). Large grooves can be used by larger-bodied organisms but may not provide sufficient refuge from predators for smaller organisms.

Grooves are sometimes present on artificial structures such as cable mattresses (Lacey & Hayes 2020) or quarried boulders (MacArthur et al. 2020). They can also form on structures through erosion, but will often be filled or repaired during maintenance works (Moreira et al. 2007), and are absent from many structures. Groove habitats can be created on subtidal artificial structures by adding or removing material, either during construction or retrospectively.

There is a body of literature investigating the effects of creating groove habitats on artificial reefs and on substrates for coral rearing or gardening (e.g. Douke et al. 1998; Rani et al. 2015). These studies are not included in this synopsis, which focusses on in situ conservation actions to enhance the biodiversity of structures that are engineered to fulfil a primary function other than providing artificial habitats.

^{Bourget E., DeGuise J. & Daigle G. (1994) Scales of substratum heterogeneity, structural complexity, and the early establishment of a marine epibenthic community. Journal of Experimental Marine Biology and Ecology, 181, 31–51.}

^{Douke A., Munekiyo M., Tsuji S. & Itani M. (1998) Effect of artificial reef for catch topshell, Batillus cornutus. Fisheries Engineering (Japan), accessed from The Agriculture, Forestry and Fisheries Research Information Technology Center, 35, 145–152.}

^{Firth L.B., Airoldi L., Bulleri F., Challinor S., Chee S.-Y., Evans A.J., Hanley M.E., Knights A.M., O’Shaughnessy K., Thompson R.C. & Hawkins S.J. (2020) Greening of grey infrastructure should not be used as a Trojan horse to facilitate coastal development. Journal of Applied Ecology, 57, 1762–1768.}

^{Lacey N.C. & Hayes P. (2020) Epifauna associated with subsea pipelines in the North Sea. ICES Journal of Marine Science, 77, 1137–1147.}

^{MacArthur M., Naylor L.A., Hansom J.D. & Burrows M.T. (2020) Ecological enhancement of coastal engineering structures: passive enhancement techniques. Science of the Total Environment, 740, 139981.}

^{Moreira J., Chapman M.G. & Underwood A.J. (2007) Maintenance of chitons on seawalls using crevices on sandstone blocks as habitat in Sydney Harbour, Australia. Journal of Experimental Marine Biology and Ecology, 347, 134–143.}

^{Nelson B.V. & Vance R.R. (1979) Diel foraging patterns of the sea urchin Centrostephanus coronatus as a predator avoidance strategy. Marine Biology, 51, 251–258.}

^{Rani M.H., Saad S., Khodzari M.F.A., Ramli R. & Yusof M.H. (2015) Scleractinian coral recruitment density in coastal water of Balok, Pahang, Malaysia. Jurnal Teknologi (Sciences & Engineering), 77, 13–18.}

^{Strain E.M.A., Olabarria C., Mayer-Pinto M., Cumbo V., Morris R.L., Bugnot A.B., Dafforn K.A., Heery E., Firth L.B., Brooks P.R. & Bishop M.J. (2018) Eco-engineering urban infrastructure for marine and coastal biodiversity: which interventions have the greatest ecological benefit? Journal of Applied Ecology, 55, 426–441.}

Study locations

Key messages

Two studies examined the effects of creating groove habitats on subtidal artificial structures on the biodiversity of those structures. Both studies were on open coastlines in Japan and northern Israel.

COMMUNITY RESPONSE (1 STUDY)

Overall community composition (1 study): One replicated, controlled study in Israel found that groove habitats created on a subtidal artificial structure, along with holes, pits and environmentally-sensitive material, altered the combined macroalgae and invertebrate community composition on structure surfaces. They also supported macroalgae, non-mobile invertebrate and fish species that were absent from a similar structure without added habitat features.
Overall richness/diversity (1 study): One replicated, controlled study in Israel found that creating groove habitats on a subtidal artificial structure, along with holes, pits and environmentally-sensitive material, increased the combined macroalgae and invertebrate species diversity on structure surfaces.

POPULATION RESPONSE (2 STUDIES)

Algal abundance (2 studies): Two controlled studies (including one replicated study) in Japan and Israel reported that creating groove habitats on subtidal artificial structures, along with holes, pits and environmentally-sensitive material in one, had mixed effects on macroalgal abundances on structure surfaces, depending on the species group.
Invertebrate abundance (1 study): One replicated, controlled study in Israel reported that creating groove habitats on a subtidal artificial structure, along with holes, pits and environmentally-sensitive material, had mixed effects on invertebrate abundances on structure surfaces, depending on the species group.
Fish abundance (1 study): One replicated, controlled study in Israel reported that creating groove habitats on a subtidal artificial structure, along with holes, pits and environmentally-sensitive material, had mixed effects on fish abundances on and around structure surfaces, depending on the species group.

BEHAVIOUR (0 STUDIES)

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

A controlled study in 1985–1989 on a subtidal breakwater block on open coastline in Toyama Bay, Japan (Watanuki & Yamomoto 1990) reported that groove habitats created on the block supported more kelp Ecklonia stolonifera but similar abundances of canopy algae Sargassum spp. compared with a block surface without grooves. Data were not statistically tested. After 42 months, there were 55 kelp individuals on the surface with large grooves (wet weight: 0.93 kg), 32 on the surface with small grooves (0.48 kg) and 20 on the surface without grooves (0.31 kg). Three canopy algae species had similar abundances and weights on the surface with large grooves (5–10 individuals, all 0.01 kg), small grooves (2–19 individuals, 0.01–0.04 kg) and without grooves (3–18 individuals, 0.05–0.17 kg). Groove habitats were created on a concrete breakwater block (2.3 × 2.3 × 0.8 m). There was one array of five large grooves (length: 644 mm; width: 46 mm; depth: 23 mm) and one of nine small grooves (length: 644 mm; width: 3 mm; depth not reported), evenly-spaced on 644 × 529 mm horizontal surfaces. One adjacent surface had no grooves. Small grooves were created by scraping using a nail (method for large grooves not reported). The block was placed on sandy seabed at 9 m depth in November 1985. Macroalgae on surfaces with and without grooves were counted and weighed (wet weight) after 42 months.
Study and other actions tested
Referenced paper
Watanuki A. & Yamamoto H. (1990) Settlement of seaweeds on coastal structures. Hydrobiologia, 204, 275-280.
A replicated, controlled study in 2012–2014 on two subtidal breakwaters on open coastline in the Mediterranean Sea, Israel (Sella & Perkol-Finkel 2015) found that groove habitats created on breakwater blocks, along with holes, pits and environmentally-sensitive material, supported different macroalgae and invertebrate community composition with higher species diversity than standard-concrete blocks without added habitats, while macroalgae, invertebrate and fish abundances varied depending on the species group. After 24 months, the macroalgae and invertebrate species diversity was higher on blocks with added habitats than without (data reported as Shannon index) and the community composition differed (data reported as statistical model results). Thirty species (7 mobile invertebrates, 14 non-mobile invertebrates, 9 fishes) recorded on and around blocks with added habitats were absent from blocks without. Species abundances varied on blocks with and without added habitats depending on the species group (see paper for results). It is not clear whether these effects were the direct result of creating grooves, holes, pits, or using environmentally-sensitive material. Groove habitats were created on breakwater blocks (1 × 1 × 1 m) using a formliner. Each block had multiple irregular grooves (length: 100–600 mm; width: 5–15 mm; depth: 10 mm; T. Hadary pers. comms.) amongst multiple holes and pits (number/spacing not reported). Five blocks of each of three patented ECOncrete^TM materials (lower pH and different cement/additives to standard-concrete) were placed at 5–7 m depth on a concrete-block breakwater during construction in July 2012. Five standard-concrete blocks (1.7 × 1.7 × 1.7 m) without added habitats were placed on a similar breakwater 80 m away. Macroalgae and invertebrates on blocks, and fishes on and around blocks, were counted over 24 months.
Study and other actions tested
Referenced paper
Sella I. & Perkol-Finkel S. (2015) Blue is the new green – ecological enhancement of concrete based coastal and marine infrastructure. Ecological Engineering, 84, 260-272.

Please cite as:

Evans, A.J., Moore, P.J., Firth, L.B., Smith, R.K., and Sutherland, W.J. (2021) Enhancing the Biodiversity of Marine Artificial Structures: Global Evidence for the Effects of Interventions. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

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This Action forms part of the Action Synopsis:

Biodiversity of Marine Artificial Structures

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Create large protrusions (>50 mm) on subtidal artificial structures Action Link	No evidence found (no assessment)	0	Synopsis Link
*Create grooves and* small protrusions, ridges or ledges (1–50 mm) on subtidal artificial structures** Action Link	Awaiting assessment	3	Synopsis Link
Manage or restrict harvesting of species on subtidal artificial structures Action Link	Awaiting assessment	3	Synopsis Link