Use environmentally-sensitive material on intertidal artificial structures

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Study locations

Key messages

  • Eight studies examined the effects of using environmentally-sensitive material on intertidal artificial structures on the biodiversity of those structures. Three studies were on open coastlines in the UK and Ireland, and one was in each of an estuary in southeast Australia, a marina in northern Israel, and a port in southeast Spain. One was on an open coastline and in estuaries in the UK, and one was on island coastlines in the Singapore Strait and in estuaries in the UK.

COMMUNITY RESPONSE (6 STUDIES)

  • Overall community composition (4 studies): Two of four replicated, controlled studies (including three randomized and one paired sites, before-and-after study) in Australia, the UK, Israel, and Singapore and the UK, found that using hemp-concrete in place of standard-concrete on intertidal artificial structures, or using ECOncreteTM, along with creating grooves, small ledges and holes, altered the combined macroalgae and invertebrate community composition on structure surfaces. One of the studies, along with one other, found that using shell-concrete or reduced-pH-concrete did not. One study found that using sandstone in place of basalt had mixed effects, depending on the site. Two of the studies reported that ECOncreteTM surfaces with added habitats or reduced-pH-concrete surfaces supported macroalgae, mobile invertebrate and/or non-mobile invertebrate species that were absent from standard-concrete structure surfaces.
  • Algal community composition (1 study): One replicated, randomized, paired sites, controlled study in Spain found that using different materials (sandstone, limestone, slate, gabbro, concrete) on an intertidal artificial structure altered the diatom community composition on structure surfaces.
  • Overall richness/diversity (4 studies): Two of four replicated, controlled studies (including three randomized and one paired sites, before-and-after study) in the UK, Israel, and Singapore and the UK found that using hemp-concrete, shell-concrete or reduced-pH-concrete in place of standard-concrete on intertidal artificial structures did not increase the combined macroalgae and invertebrate species richness on structure surfaces. One study found that using ECOncreteTM, along with creating grooves, small ledges and holes, did increase the species richness and diversity. One found that using limestone-cement, along with creating pits, grooves, small ridges and texture, had mixed effects depending on the site.
  • Algal richness/diversity (1 study): One replicated, randomized, paired sites, controlled study in Spain found that using quarried rock in place of concrete on an intertidal artificial structure did not increase the diatom species richness or diversity on structure surfaces.
  • Invertebrate richness/diversity (1 study): One replicated, randomized, controlled study in the UK found that using hemp-concrete in place of standard-concrete on intertidal artificial structures increased the mobile invertebrate species richness on structure surfaces, but using shell-concrete did not.

POPULATION RESPONSE (7 STUDIES)

  • Overall abundance (1 study): One replicated, randomized, controlled study in the UK found that using hemp-concrete or shell-concrete in place of standard-concrete on intertidal artificial structures increased the combined macroalgae and non-mobile invertebrate abundance on structure surfaces.
  • Algal abundance (5 studies): Four of five replicated, controlled studies (including four randomized and one paired sites study) in Australia, Spain, Singapore, the UK and Ireland found that using sandstone in place of basalt, quarried rock in place of concrete, or altering the composition of concrete on intertidal artificial structures had mixed effects on the macroalgal or microalgal abundance on structure surfaces, depending on the species group, site, wave-exposure and/or the type of material tested. One study found no effect of reducing the pH of concrete on macroalgal abundance.
  • Invertebrate abundance (4 studies): Two of four replicated, controlled studies (including three randomized studies) in Australia, the UK, Singapore and the UK and Ireland found that using sandstone in place of basalt or reducing the pH of concrete on intertidal artificial structures did not increase the abundance of tubeworms, oysters, limpets, barnacles and/or combined invertebrates on structure surfaces. Two studies found that using limestone-cement, along with creating pits, grooves, small ridges and texture, or altering the composition of concrete had mixed effects on the mobile invertebrate and/or barnacle abundance, depending on the site, wave-exposure and/or the type of material tested.

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

  1. A replicated, randomized, controlled study in 2008–2009 on two intertidal rocky reefs on open coastlines in the Celtic Sea and the English Channel, UK (Coombes et al. 2011) found that limestone settlement plates supported lower microalgal abundance than concrete plates, while abundance on granite plates was higher than or similar to concrete depending on the type of microalgae. After eight months, round microalgal abundance was lower on limestone plates (5% cover) than concrete (61%), and higher than both on granite plates (82%). Filamentous microalgae was less abundant on limestone (13%) than granite (33%) and concrete (30%), which were similar. Settlement plates (100 × 100 mm) were made from limestone, granite and concrete. Two of each were randomly arranged horizontally in each of two patches at midshore on each of two rocky reefs in May 2008. Microalgal cover on plates was measured using a scanning electron microscope after eight months.

    Study and other actions tested
  2. A replicated, randomized, controlled study in 2007–2008 in four intertidal boulder-fields in Sydney Harbour estuary, Australia (Green et al. 2012) found that using sandstone boulders in place of basalt boulders altered the macroalgae and non-mobile invertebrate community composition in two of four sites, and that abundances varied depending on the species group and site. After 10 months, macroalgae and non-mobile invertebrate community composition differed on sandstone and basalt boulders in two of four sites, but was similar in the other two sites (data reported as statistical model results). Sandstone boulders supported higher non-turf macroalgal abundance (0–17% cover) than basalt boulders (0–10%), and higher turf macroalgal abundance at one site (sandstone: 48%; basalt: 1%), but similar turf abundance at the other three sites (14–31 vs 9–25%). Sandstone boulders supported similar abundances of tubeworms (Serpulidae) and oysters (Ostreidae) to basalt boulders (tubeworms: 7–24 vs 8–27%; oysters: 0–9 vs 1–9%), but fewer barnacles (Cirripedia) (0 vs 1–2%). Five sandstone and five basalt oval quarried boulders (diameter: 350 mm) were randomly arranged at lowshore in each of two basalt (artificial) and two sandstone (unspecified) boulder-fields in June 2007. Macroalgae and non-mobile invertebrates were counted on boulders over 10 months.

    Study and other actions tested
  3. A replicated, randomized, controlled study in 2014–2015 on an intertidal rocky reef on open coastline in the Irish Sea, UK (Dennis et al. 2018) found that hemp-concrete and shell-concrete settlement plates supported higher macroalgae and invertebrate cover than standard-concrete plates, and that hemp-concrete supported higher species richness than shell- and standard-concrete plates, with different community composition to standard-concrete plates. After 12 months, macroalgae and non-mobile invertebrate cover was similar on hemp-concrete (92% cover) and shell-concrete (74%) plates, and higher on both than standard-concrete plates (25%). Mobile invertebrate species richness was higher on hemp-concrete (8 species groups/plate) than shell-concrete (4/plate) and standard-concrete (3/plate), which were similar. Macroalgae and non-mobile invertebrate species richness was similar on all materials (hemp: 7/plate; shell: 6/plate; standard: 5/plate). Macroalgae and invertebrate community composition differed on hemp-concrete and standard-concrete, but shell-concrete was similar to both (data reported as statistical model results). Settlement plates (150 × 150 mm) were moulded from hemp-concrete, shell-concrete and standard-concrete. Five of each were randomly arranged horizontally at mid-lowshore on a rocky reef in October 2014. Macroalgae and invertebrates on plates were counted in the laboratory after 12 months.

    Study and other actions tested
  4. A replicated, randomized, paired sites, controlled, before-and-after study in 2014–2016 on an intertidal seawall in a marina in the Mediterranean Sea, Israel (Perkol-Finkel et al. 2018) found that seawall panels made from ECOncreteTM, along with grooves, small ledges and holes created on them, supported higher macroalgae and invertebrate species diversity and richness and different community composition compared with standard-concrete seawall surfaces without added habitats. After 22 months, macroalgae and invertebrate species diversity (data reported as Shannon index) and richness was higher on ECOncreteTM panels with added habitats (8 species/quadrat) than on standard-concrete seawall surfaces without (3/quadrat), and compared with seawall surfaces before panels were attached (2/quadrat). Community composition differed between ECOncreteTM panels and standard-concrete surfaces (data reported as statistical model results). Five species groups (1 macroalgae, 4 non-mobile invertebrates) recorded on panels were absent from standard-concrete surfaces. It is not clear whether these effects were the direct result of using environmentally-sensitive material or creating grooves, ledges and/or holes. Seawall panels (height: 1.5 m; width: 0.9 m; thickness: 130 mm) were made from patented ECOncreteTM material using a formliner. Panels had multiple grooves, small ledges and holes. Four panels were attached to a vertical concrete seawall in November 2014. The top 0.3 m were intertidal. Panels were compared with standard-concrete seawall surfaces cleared of organisms (height: 0.3 m; width: 0.9 m) adjacent to each panel. Macroalgae and invertebrates were counted in one 300 × 300 mm randomly-placed quadrat on each panel and seawall surface during high tide over 22 months.

    Study and other actions tested
  5. A replicated, randomized, paired sites, controlled study (year not reported) on an intertidal seawall in Ceuta Port in the Alboran Sea, Spain (Sempere-Valverde et al. 2018) found that sandstone settlement plates had higher chlorophyll-a and diatom abundance than limestone, slate, gabbro and concrete plates, and that material altered the diatom community composition but not their species richness or diversity. After two months, chlorophyll-a density was higher on sandstone settlement plates (18 μg/cm2) than limestone (3 μg/cm2), slate (3 μg/cm2) and concrete (6 μg/cm2) plates, which were all similar, while gabbro plates were similar to all materials (13 μg/cm2). Diatom species diversity and richness (data not reported) was similar on all materials, while their community composition differed (data reported as statistical model results), but it was not clear which materials differed. Total diatom abundance was higher on sandstone plates (841 individuals) than limestone (329), slate (104), gabbro (275) and concrete (173). Settlement plates (170 × 170 mm) were made from sandstone, limestone, slate, gabbro and concrete. One of each was randomly arranged horizontally on each of five midshore boulders along a limestone boulder seawall (month/year not reported). Plate surfaces had grooves and small protrusions created on them. Microalgae and chlorophyll-a on plates were measured using a scanning electron microscope and spectrophotometer, respectively, after two months.

    Study and other actions tested
  6. A replicated, randomized, controlled study in 2016–2017 on three intertidal seawalls in the Clyde and Forth estuaries and on open coastline in the English Channel, UK (MacArthur et al. 2019) found that using limestone-cement in place of concrete in settlement plates, along with creating pits, grooves, small ridges and textured surfaces, had mixed effects on macroalgae and invertebrate species richness and invertebrate abundances on plates, depending on the site. After 18 months, in three of six comparisons, macroalgae and mobile invertebrate species richness was higher on limestone-cement settlement plates with added habitats (2 species/plate) than concrete plates without (1/plate). In four of six comparisons, the same was true for mobile invertebrate abundance (limestone-cement: 4–11; concrete: 1–2 individuals/plate) and barnacle (Cirripedia) cover (48–74 vs 22–34%). In the other comparisons, no significant effects were found for richness (3 comparisons: 1–2 vs 1/plate), mobile abundances (2 comparisons: 1–2 vs 2–3/plate) or barnacle cover (2 comparisons: 46–84 vs 22–83%). It is not clear whether these effects were the direct result of using environmentally-sensitive material or creating pits, grooves, ridges and/or texture. Settlement plates (150 × 150 mm) were moulded from limestone-cement or concrete. Limestone-cement plates had pits, grooves and ridges, or textured surfaces, while concrete plates did not. Eight plates of each limestone-cement design were randomly arranged at upper-midshore on each of two vertical concrete seawalls in April–May 2016. Eight concrete plates were attached on both walls plus one other. Macroalgae and invertebrates on plates were counted from photographs over 18 months.

    Study and other actions tested
  7. A replicated, controlled study in 2018–2019 on four intertidal seawalls on island coastlines in the Singapore Strait, Singapore, and in the Plym and Tamar estuaries, UK (Hsiung et al. 2020) found that reducing the pH of concrete settlement plates did not alter the macroalgae and invertebrate community composition or increase their species richness or abundance on plates. Over 12 months, reduced-pH-concrete settlement plates supported 59 invertebrate species in total (Singapore: 46; UK: 13), while standard-concrete plates supported 57 (Singapore: 48; UK: 9) (data not statistically tested). Ten invertebrate species (8 mobile, 2 non-mobile) recorded on reduced-pH plates were absent from standard-concrete plates. After 12 months, macroalgae and invertebrate community composition (data reported as statistical model results) and species richness was similar on reduced-pH plates (3–21 species/plate) and standard-concrete plates (3–20/plate). The same was true for invertebrate abundance (6–187 vs 11–216 individuals/plate) and cover of limpets (Patellidae, Fissurellidae, Siphonariidae, Lottioidea) (both 1–5% cover), barnacles (Cirripedia) (18–24 vs 18–25%), ephemeral green macroalgae (4–5 vs 5–8%) and encrusting macroalgae (35 vs 29%). Concrete settlement plates (200 × 200 mm) were moulded with reduced pH (pH 7–10) and standard pH (pH 12–13). Twenty-four of each were attached at a 60° angle at midshore on each of two seawalls in both Singapore and the UK during February–March 2018. Plates had water-retaining pits created on them. Macroalgae on plates were counted from photographs and invertebrates in the laboratory over 12 months. Eight plates were missing and no longer provided habitat.

    Study and other actions tested
  8. A replicated, randomized, controlled study in 2018 on an intertidal breakwater on open coastline in the Irish Sea, Ireland (Natanzi et al. 2021) found that replacing standard Portland-cement with Ground Granulated Blast-Furnace Slag (GGBS), limestone-aggregate with granite-aggregate, and omitting plasticiser in concrete settlement plates had mixed effects on microalgal and barnacle (Cirripedia) abundances, depending on the material combination, wave-exposure and species group. After one month, on the wave-sheltered side of the breakwater, microalgal biomass was higher on plates with GGBS-cement (0.14–2.48 μg/cm2) than standard-cement (0.03–0.74 μg/cm2). Barnacle abundance varied depending on the aggregate and presence of plasticiser (GGBS-cement: 316–2,961 individuals/plate; standard-cement: 603–1,869/plate). There was no significant difference in microalgal or barnacle abundance between plates with granite-aggregate (microalgae: 0.03–1.66 μg/cm2; barnacles: 316–2,961/plate) and limestone-aggregate (microalgae: 0.06–2.48 μg/cm2; barnacles: 973–2,263/plate), or between plates without and with plasticiser (microalgae: 0.06–2.48 vs 0.03–1.66 μg/cm2; barnacles: 316–2,263 vs 603–2,961/plate). On the exposed side of the breakwater, results varied depending on the cement-aggregate-plasticiser combination and species group. Concrete settlement plates (200 × 200 mm) were moulded with different cement (GGBS, standard Portland-cement), aggregates (granite, limestone) and additives (no plasticiser, plasticiser). Six plates of each binder-aggregate-additive combination were randomly arranged vertically at mid-lowshore on the wave-sheltered side of a boulder breakwater in April 2018. Two plates of each were attached on the wave-exposed side. Microalgal biomass on plates was measured using a fluorometer and barnacles were counted from photographs after 1 month.

    Study and other actions tested
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?

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Biodiversity of Marine Artificial Structures

This Action forms part of the Action Synopsis:

Biodiversity of Marine Artificial Structures
Biodiversity of Marine Artificial Structures

Biodiversity of Marine Artificial Structures - Published 2021

Enhancing biodiversity of marine artificial structures synopsis

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