Study

Maximising the ecological value of hard coastal structures using textured formliners

  • Published source details MacArthur M., Naylor L., Hansom J.D., Burrows M.T., Loke L.H.L. & Boyd I. (2019) Maximising the ecological value of hard coastal structures using textured formliners. Ecological Engineering X, 1, 100002.

Actions

This study is summarised as evidence for the following.

Action Category

Create natural rocky reef topography on intertidal artificial structures

Action Link
Biodiversity of Marine Artificial Structures

Create textured surfaces (≤1 mm) on intertidal artificial structures

Action Link
Biodiversity of Marine Artificial Structures

Use environmentally-sensitive material on intertidal artificial structures

Action Link
Biodiversity of Marine Artificial Structures

Create grooves and small protrusions, ridges or ledges (1–50 mm) on intertidal artificial structures

Action Link
Biodiversity of Marine Artificial Structures

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

Action Link
Biodiversity of Marine Artificial Structures

Create pit habitats (1–50 mm) on intertidal artificial structures

Action Link
Biodiversity of Marine Artificial Structures

Create pit habitats (1–50 mm) on intertidal artificial structures

Action Link
Biodiversity of Marine Artificial Structures
  1. Create natural rocky reef topography on intertidal artificial structures

    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 creating natural rocky reef topography on the seawalls did not increase the macroalgae and invertebrate species richness on seawall surfaces, but increased invertebrate abundances at one of three sites. After 18 months, macroalgae and mobile invertebrate species richness was similar on settlement plates with and without natural rocky reef topography (both 1 species/plate). Barnacle (Cirripedia) and mobile invertebrate abundances were higher on plates with topography than without at one site (barnacles: 72 vs 34% cover; mobiles: 3 vs 1 individuals/plate), but were statistically similar at two sites (barnacles: 48–93 vs 22–83%; mobiles: 1 vs 2–3/plate). Concrete settlement plates (150 × 150 mm) were made with and without natural rocky reef topography moulded from digital scans of a natural boulder surface. Eight plates with topography and eight without were randomly arranged at upper-midshore on each of three vertical concrete seawalls in April–May 2016. Macroalgae and invertebrates on plates were counted from photographs over 18 months.

    (Summarised by: Ally Evans)

  2. Create textured surfaces (≤1 mm) on intertidal artificial structures

    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 creating textured surfaces on seawall surfaces, along with using environmentally-sensitive material, had mixed effects on macroalgae and invertebrate species richness and invertebrate abundances, depending on the type of texture created and the site. After 18 months, plates with and without texture supported similar macroalgae and mobile invertebrate species richness in seven of eight comparisons (textured: 1–2 species/plate; untextured: 1/plate). At one site (1 comparison), cast-textured plates supported more species (2/plate) than untextured plates (1/plate). Textured and untextured plates also supported similar mobile invertebrate abundance in five of eight comparisons (textured: 1–2 individuals/plate; untextured: 1–3/plate). At one site (3 comparisons), textured plates supported more mobile invertebrates (3–5 individuals/plate) than untextured plates (1/plate). Barnacle (Cirripedia) cover was higher on plates with texture (67–95%) than without (22–83%) in six of eight comparisons, but did not significantly differ at one site (2 comparisons; textured: 46–51%; untextured: 22%). It is not clear whether these effects were the direct result of creating texture or using environmentally-sensitive material on some plates. Settlement plates (150 × 150 mm) were made with and without textured surfaces, created by scraping with a wire brush, moulding with barnacle-shaped impressions, or casting with crushed foil. ‘Scrape-textured’, ‘mould-textured’ and untextured plates were concrete, while ‘cast-textured’ plates were limestone-cement (environmentally-sensitive material). Eight plates with each of scrape-textured, mould-textured and untextured surfaces were randomly arranged at upper-midshore on each of three vertical concrete seawalls in April–May 2016. Eight cast-textured plates were attached on each of two walls. Macroalgae and invertebrates on plates were counted from photographs over 18 months.

    (Summarised by: Ally Evans)

  3. Use environmentally-sensitive material on intertidal artificial structures

    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.

    (Summarised by: Ally Evans)

  4. Create grooves and small protrusions, ridges or ledges (1–50 mm) on intertidal artificial structures

    A replicated, randomized, controlled study in 2016–2017 on two intertidal seawalls on open coastline in the English Channel and in the Forth estuary, UK (MacArthur et al. 2019) found that creating groove habitats and small ridges on settlement plates, along with using environmentally-sensitive material, increased the macroalgae and invertebrate species richness and invertebrate abundance on plates at one of two sites. After 18 months, at one of two sites, macroalgae and mobile invertebrate species richness was higher on plates with grooves and ridges (2 species/plate) than without (1/plate). The same was true for mobile invertebrate abundance (9 vs 1 individuals/plate) and barnacle (Cirripedia) cover (48 vs 34%). At the second site, plates with and without grooves and ridges supported similar richness (both 1 species/plate), mobile invertebrate abundance (1 vs 3 individuals/plate) and barnacle cover (84 vs 83%). It is not clear whether these effects were the direct result of creating grooves and ridges or using environmentally-sensitive material. Settlement plates (150 × 150 mm) were moulded with and without groove habitats and small ridges. Plates with grooves and ridges had six chevron-shaped grooves between seven ridges with variable dimensions (maximum depth/height: 30 mm). Eight limestone-cement (environmentally-sensitive material) plates with grooves and ridges and eight concrete plates without were randomly arranged at upper-midshore on each of two vertical concrete seawalls in April–May 2016. Macroalgae and invertebrates on plates were counted from photographs over 18 months.

    (Summarised by: Ally Evans)

  5. Create groove habitats (1–50 mm) on intertidal artificial structures

    A replicated, randomized, controlled study in 2016–2017 on two intertidal seawalls in the Clyde and Forth estuaries, UK (MacArthur et al. 2019) found that creating groove habitats on the seawalls, along with pits, had mixed effects on the macroalgae and invertebrate species richness and invertebrate abundances, depending on the site. After 18 months, at one of two sites, macroalgae and mobile invertebrate species richness and mobile invertebrate abundances were higher on settlement plates with grooves and pits (4 species/plate, 11 individuals/plate) than without (1 species/plate, 1 individual/plate), but barnacle (Cirripedia) cover was similar on plates with and without grooves and pits (15 vs 22%). At the second site, richness and mobile invertebrate abundances were similar on plates with and without grooves and pits (2 vs 1 species/plate, both 3 individuals/plate), while barnacle cover was lower on plates with grooves and pits (73 v 83%). It is not clear whether these effects were the direct result of creating grooves or pits. Concrete settlement plates (150 × 150 mm) were moulded with and without groove habitats and pits. Plates with grooves and pits had seven grooves amongst 37 pits, both with variable dimensions (maximum depth: 30 mm). Eight plates with grooves and pits and eight without were randomly arranged at upper-midshore on each of two vertical concrete seawalls in April–May 2016. Macroalgae and invertebrates on plates were counted from photographs over 18 months.

    (Summarised by: Ally Evans)

  6. Create pit habitats (1–50 mm) on intertidal artificial structures

    A replicated, randomized, controlled study in 2016–2017 on two intertidal seawalls in the Clyde estuary and on open coastline in the English Channel, UK (MacArthur et al. 2019a) found that creating pit habitats on seawall surfaces, along with using environmentally-sensitive material, increased the macroalgae and invertebrate species richness on surfaces at one of two sites, and increased invertebrate abundances at both sites. After 18 months, at one of two sites, macroalgae and mobile invertebrate species richness was higher on settlement plates with pits (2 species/plate) than without (1/plate), but was statistically similar on plates with and without pits at the second site (2 vs 1/plate). At both sites, plates with pits had higher mobile invertebrate abundance (4–11 individuals/plate) and barnacle (Cirripedia) cover (49–74%) than plates without (mobiles: 1/plate; barnacles: 22–34%). It is not clear whether these effects were the direct result of creating pits or using environmentally-sensitive material. Settlement plates (150 × 150 mm) were moulded with and without pit habitats. Plates with pits had multiple irregular pits (maximum depth: 30 mm). Eight limestone-cement (environmentally-sensitive material) plates with pits and eight concrete plates without were randomly arranged at upper-midshore on each of two vertical concrete seawalls in April–May 2016. Macroalgae and invertebrates on plates were counted from photographs over 18 months.

    (Summarised by: Ally Evans)

  7. Create pit habitats (1–50 mm) on intertidal artificial structures

    A replicated, randomized, controlled study in 2016–2017 on two intertidal seawalls in the Clyde and Forth estuaries, UK (MacArthur et al. 2019b) found that creating pit habitats on the seawalls, along with grooves, had mixed effects on the macroalgae and invertebrate species richness and invertebrate abundances, depending on the site. After 18 months, at one of two sites, macroalgae and mobile invertebrate species richness and mobile invertebrate abundances were higher on settlement plates with pits and grooves (4 species/plate, 11 individuals/plate) than without (1 species/plate, 1 individual/plate), but barnacle (Cirripedia) cover was similar on plates with and without pits and grooves (15 vs 22%). At the second site, richness and mobile invertebrate abundances were similar on plates with and without pits and grooves (2 vs 1 species/plate, both 3 individuals/plate), while barnacle cover was lower on plates with pits and grooves (73 v 83%). It is not clear whether these effects were the direct result of creating pits or grooves. Concrete settlement plates (150 × 150 mm) were moulded with and without pit habitats and grooves. Plates with pits and grooves had 37 round pits amongst seven grooves, both with variable dimensions (maximum depth: 30 mm). Eight plates with pits and grooves and eight without were randomly arranged at upper-midshore on each of two vertical concrete seawalls in April–May 2016. Macroalgae and invertebrates on plates were counted from photographs over 18 months.

    (Summarised by: Ally Evans)

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