Create 'rock pools' on intertidal artificial structures

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

Study locations

Key messages

COMMUNITY RESPONSE (17 STUDIES)

  • Overall community composition (16 studies): Thirteen replicated, controlled studies (including one randomized, six paired sites and three site comparison studies) in Australia the UK, the USA, Spain and Malaysia, reported that rock pools created on intertidal artificial structures, along with holes in two studies, supported macroalgae, mobile invertebrate, non-mobile invertebrate and/or fish species that were absent from structure surfaces without pools or holes. One of the studies also found that pools supported different combined macroalgae and invertebrate community composition to surfaces without pools. One replicated, paired sites, controlled study in Australia found mixed effects on the community composition depending on the pool depth, shore level and site. One of the studies found that created pools supported different combined macroalgae and non-mobile invertebrate communities but similar combined mobile invertebrate and fish communities to natural rock pools, while one found that combined mobile invertebrate and fish communities differed to natural pools. Two of the studies found that the pool depth did not affect the community composition, while one found that the pool angle did. One replicated study in Ireland found that the shore level and wave-exposure affected the community composition, and that wave-sheltered pools filled with sediment within two years. One replicated, randomized study in Australia found that adding short flexible habitats into pools had mixed effects on community composition depending on the species group and site.
  • Overall richness/diversity (15 studies): Nine of 12 replicated, controlled studies (including one randomized, six paired sites and two site comparison studies) in Australia, the UK, Spain and Malaysia found that rock pools created on intertidal artificial structures, along with holes in two studies, supported higher combined macroalgae, invertebrate and/or fish species diversity and/or richness than structure surfaces without pools or holes. Three studies reported similar combined macroalgae and invertebrate or combined mobile invertebrate and fish species richness in pools and on structure surfaces. One of the studies found that combined macroalgae, invertebrate and fish species richness in created pools was similar to natural rock pools, while one reported lower combined mobile invertebrate and fish species richness in created pools. Two of the studies, along with one replicated study in Ireland, found that the shore level of pools, along with holes in one, did not affect the species richness, but in one, the functional richness (species grouped according to their role in the community) was lower in highshore pools than midshore. Three of the studies found that the pool depth had no effect on species richness, one found higher richness in tilted pools than horizontal ones, and one replicated, randomized study in Australia found that adding short flexible habitats into pools had mixed effects depending on the species group and site. One before-and-after study in Australia reported that creating pools, along with reducing the slope of a structure, increased the combined macroalgae, invertebrate and fish species richness on the structure.
  • Fish richness/diversity (1 study): One replicated, paired sites, controlled and site comparison study in Australia reported that creating rock pools on an intertidal artificial structure did not increase the fish species richness on and around the structure.

POPULATION RESPONSE (4 STUDIES)

  • Overall abundance (1 study): One replicated, randomized study in Australia found that adding short flexible habitats into rock pools created on intertidal artificial structures had mixed effects on macroalgae, invertebrate and fish abundance in pools, depending on the species group and site.
  • Algal abundance (1 study): One replicated, paired sites, controlled study in Australia found that creating rock pools on intertidal artificial structures had mixed effects on macroalgal abundances depending on the pool depth, shore level, species group and site.
  • Invertebrate abundance (2 studies): Two replicated, controlled studies (including one with paired sites) in Australia found that creating rock pools on intertidal artificial structures, along with holes in one, had mixed effects on limpet or combined invertebrate abundances, depending on the shore level, pool depth, species group and/or site.
  • Fish abundance (1 study): One replicated, paired sites, controlled and site comparison study in Australia found that creating rock pools on an intertidal artificial structure had mixed effects on the fish abundance on and around the structure, depending on the species group and site.

BEHAVIOUR (3 STUDIES)

  • Use (2 studies): Two studies (including one before-and-after study) in Australia reported that rock pools created on intertidal artificial structures, along with holes in one study, were used by sea slugs, urchins, octopuses, macroalgae, invertebrates and fishes.
  • Fish behaviour change (1 study): One replicated, randomized study in Australia found that adding short flexible habitats into rock pools created on intertidal artificial structures did not increase the number of bites fishes took of pool surfaces.

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, controlled study in 2006–2007 on an intertidal seawall in Sydney Harbour estuary, Australia (Chapman & Blockley 2009) reported that rock pools created on the seawall, along with holes, supported higher macroalgae and non-mobile invertebrate species richness than seawall surfaces without pools or holes, and found that limpet Siphonaria denticulata abundance was higher in pools than on surfaces at highshore, but lower at mid and lowshore. After 12–14 months, pools supported 15–37 macroalgae and non-mobile invertebrate species groups/site (highshore: 15–21/site; midshore: 24–36/site; lowshore: 30–37/site), while seawall surfaces without pools or holes supported 2–21/site (highshore: 2–3/site; midshore: 7–11/site; lowshore: 19–21/site) (data not statistically tested). At least 22 species (≥12 macroalgae, ≥10 non-mobile invertebrates) recorded in pools were absent from surfaces without. At highshore, limpets were more abundant in pools (3–59 limpets/pool) than on seawall surfaces (0–8/surface), but the opposite was true at midshore (1–2/pool vs 78–214/surface) and lowshore (0/pool vs 4–10/surface). It is not clear whether these effects were the direct result of creating rock pools or holes. Rock pools were created during July–September 2006 by replacing seawall blocks with water-retaining troughs during construction of a vertical sandstone seawall. Six rectangular pools (length: 600 mm; width: 300 mm; depth: 50 mm; volume: 9 l) were created at highshore, midshore and lowshore in each of three sites along the seawall. Pools were shaded. Pools were compared with six seawall surfaces (length: 600 mm; width: 300 mm) at each shore level and site. Macroalgae and invertebrates were counted in pools and on seawall surfaces during low tide in September 2007.

    Study and other actions tested
  2. A replicated, paired sites, controlled study in 2009–2010 on two intertidal seawalls in Sydney Harbour estuary, Australia (Browne & Chapman 2011, same experimental set-up as Browne & Chapman 2014) reported that rock pools created on the seawalls supported more macroalgae and invertebrate species than seawall surfaces without rock pools, but data were not statistically tested. After seven months, a total of 33 macroalgae and invertebrate species were recorded in pools compared with 20 on seawall surfaces without pools. Twenty-five species (5 macroalgae, 7 non-mobile invertebrates, 13 mobile invertebrates) recorded in pools were absent from seawall surfaces without. Rock pools were created by attaching concrete pots to vertical sandstone seawalls in December 2009. Six half-flowerpot shaped pools (top diameter: 360 mm; depth: 380 mm; volume: 10 l) were attached at midshore on each of two seawalls. Pools were compared with seawall surfaces (500 × 500 mm) adjacent to each pool. Macroalgae and invertebrates were counted in pools and on seawall surfaces during low tide after seven months. Two pools were missing and no longer provided habitat.

    Study and other actions tested
  3. A study (year not reported) on an intertidal seawall in Sydney Harbour estuary, Australia (Chapman & Underwood 2011) reported that rock pools created on the seawall, along with holes, were used by mobile invertebrates from at least three species groups. Sea slugs (Opistobranchia), urchins (Echinoidea) and octopuses (Octopoda) were recorded in pools and holes. It is not clear whether these effects were the direct result of creating rock pools or holes. Rock pools were created, along with holes, by replacing seawall blocks with sandbags during maintenance of a vertical sandstone seawall, then removing the sandbags to leave shaded water-retaining depressions in the wall. No other details were reported.

    Study and other actions tested
  4. A before-and-after study in 2012–2013 on an intertidal seawall in Sydney Harbour estuary, Australia (Heath & Moody 2013) reported that creating rock pools on the seawall, along with reducing the slope of the wall, increased the macroalgae, invertebrate and fish species richness on the wall. A total of 25 macroalgae, invertebrate and fish species were recorded in pools and on the seawall after pools were created and the slope was reduced, compared with 10 species on the seawall before (data not statistically tested). It is not clear whether these effects were the direct result of creating rock pools or reducing the slope of the seawall. However, several macroalgae, invertebrate and fish species recorded in pools were absent from the seawall before pools were created. Rectangular rock pools (area: 2 m2; depth: 300 mm; volume: 600 l) were created using large rectangular sandstone blocks during reconstruction of a sandstone boulder seawall in July 2012. Pools were lined with pond-liners with limestone gravel and blocks in the base. There were two pools at midshore and one at highshore along the seawall. The slope of the seawall was also reduced during reconstruction. Macroalgae, invertebrates and fishes were counted during low tide on the wall before reconstruction and on the wall and in pools after reconstruction in 2013 (sampling details and month not reported).

    Study and other actions tested
  5. A replicated, paired sites, controlled study in 2009–2010 on two intertidal seawalls in Sydney Harbour estuary, Australia (Browne & Chapman 2014; same experimental setup as Browne & Chapman 2011) reported that rock pools created on the seawalls supported similar macroalgae and invertebrate species richness to seawall surfaces without pools, but found that community composition and abundances varied depending on the pool depth, shore level, species group and site. After seven months, macroalgae and invertebrate species richness was similar in deep pools (highshore: 7–10 species groups/site; midshore: 16–23/site), shallow pools (highshore: 11/site; midshore: 23/site) and on seawall surfaces without pools (highshore: 10/site; midshore: 12–18/site) (data not statistically tested). Abundances and community composition varied in pools and on seawall surfaces depending on the pool depth, shore level and site (see paper for results). Rock pools were created by attaching concrete pots to vertical sandstone seawalls in December 2009. Six deep (depth: 380 mm; volume: 10 l) and six shallow (220 mm; 6 l) half-flowerpot shaped pools (top diameter: 360 mm) were attached at both highshore and midshore on each of two seawalls. Pools were compared with seawall surfaces adjacent to each pool with surface areas matching inside pool surfaces (deep: 500 × 500 mm, reported from Browne & Chapman 2011; shallow: not reported). Macroalgae and invertebrates were counted in pools and on seawall surfaces during low tide over seven months. Five deep and 10 shallow pools were missing and no longer provided habitat.

    Study and other actions tested
  6. A replicated, controlled study in 2010–2011 on an intertidal seawall in the Teign estuary, UK (Firth et al. 2014a) found that rock pools created on the seawall, along with holes, supported higher macroalgae and invertebrate species richness than seawall surfaces without pools or holes. After 19 months, macroalgae and invertebrate species richness was higher in pools (3 species/pool) than on seawall surfaces without (1/surface). Barnacles (Cirripedia) were recorded only in pools. It is not clear whether these effects were the direct result of creating rock pools or holes. Rock pools were created in May 2010 by replacing seawall blocks with water-retaining troughs during construction of a vertical sandstone seawall. Fifteen square pools (150 × 150 mm; depth/volume not reported) were created at highshore. Pools were shaded. Pools were compared with 15 mortar seawall surfaces (150 × 150 mm). Macroalgae and invertebrates were counted in pools and on seawall surfaces during low tide after 19 months. Three pools and seven surfaces had been buried by sediment and no longer provided habitat.

    Study and other actions tested
  7. A replicated, controlled study in 2012–2013 on an intertidal groyne on open coastline in the Irish Sea, UK (Firth et al. 2014b) reported that rock pools created on a concrete block placed in the groyne supported similar macroalgae and invertebrate species richness to groyne surfaces without pools. Data were not statistically tested. After 13 months, a total of five species were recorded in large deep pools, four in small deep pools, three in each of large and small shallow pools, and four on groyne surfaces without pools. Rock pools were created in the top surface of a concrete block (1.5 × 1.5 × 1 m) using a mould. Cylindrical pools were either large (diameter: 250 mm) or small (150 mm), and either deep (depth: 200 mm) or shallow (100 mm). There were three of each size-depth combination. The block was placed at midshore in a boulder groyne during construction in February 2012. Pools were compared with horizontal surfaces of adjacent groyne boulders (dimensions/material not reported). Macroalgae and invertebrates were counted in pools and on groyne surfaces during low tide over 13 months.

    Study and other actions tested
  8. A replicated, paired sites, controlled study in 2012–2013 on an intertidal breakwater on open coastline in the Irish Sea, UK (Firth et al. 2014c) found that rock pools created on the breakwater supported higher macroalgae and invertebrate species richness than breakwater surfaces without pools. After nine months, macroalgae and invertebrate species richness was higher in pools (4 species/pool) than on breakwater surfaces without (2/surface). Two species groups (1 macroalgae, 1 mobile invertebrate) recorded in pools were absent from breakwater surfaces. Rock pools were created on a boulder breakwater in June 2012 by pouring concrete into existing core holes in breakwater boulders. Nine cylindrical pools were created (depth: 100 mm; diameter/shore level not reported). Pools were compared with horizontal surfaces on breakwater boulders adjacent to each pool with surface areas matching inside pool surfaces (dimensions/material not reported). Macroalgae and invertebrates were counted in pools and on breakwater surfaces during low tide after nine months. Four pools leaked water and did not provide rock pool habitat.

    Study and other actions tested
  9. A replicated, paired sites, controlled and site comparison study in 2012–2013 on an intertidal breakwater on open coastline in the Irish Sea, UK (Evans et al. 2016) found that rock pools created on the breakwater supported higher macroalgae, invertebrate and fish species richness than breakwater surfaces without pools, and similar species richness but different community composition to natural rock pools. After 18 months, a total of 23 macroalgae, invertebrate and fish species were recorded in created pools and 14 on breakwater surfaces without pools (data not statistically tested). Community composition (data reported as statistical model results) and average species richness was similar in deep and shallow created pools (both 8 species/pool), and richness was higher in both than on surfaces without (6/surface). Twenty species (7 macroalgae, 6 mobile invertebrates, 6 non-mobile invertebrates, 1 fish) recorded in pools over 18 months were absent from breakwater surfaces. Species richness and the mobile invertebrate and fish community composition were similar in created and natural pools, but the macroalgae and non-mobile invertebrate community composition differed (data reported as statistical model results). Rock pools were created in April 2012 by drilling into horizontal surfaces of a granite boulder breakwater using a core-drill. Nine deep (depth: 120 mm; volume 2.1 l) and nine shallow (50 mm; 0.9 l) cylindrical pools (diameter: 150 mm) were drilled at midshore. Pools were compared with breakwater surfaces on horizontal and vertical boulder surfaces adjacent to each pool, with surface areas matching the inside pool surfaces (deep-vertical: 230 × 230 mm; shallow-vertical: 150 × 150 mm; both-horizontal: 130 × 130 mm; A. Evans pers. comms.), and also with natural rock pools on three nearby reefs. Both were pre-cleared of organisms. Macroalgae, invertebrates and fishes were counted in pools and on breakwater surfaces during low tide over 18 months.

    Study and other actions tested
  10. A replicated study in 2013–2015 on an intertidal causeway on open coastline in Galway Bay, Ireland (Firth et al. 2016) reported that rock pools created on the wave-exposed side of the causeway were used by macroalgae, invertebrates and fish, but that pools created on the wave-sheltered side filled with sediment and failed to provide rock pool habitat. After 24 months, a total of 72 macroalgae, invertebrate and fish species groups (highshore: 37; midshore: 63) from 11 functional groups (highshore: 10; midshore: 11) were recorded in pools on the wave-exposed side of the causeway (data not statistically tested). Average species richness was similar in highshore (14 species groups/pool) and midshore (17/pool) pools, but the community composition differed (data reported as statistical model results). The average number of functional groups was lower in highshore (7/pool) than midshore (9/pool) pools. Rock pools were created by pouring concrete around buckets in the base of Shepherd Hill Energy Dissipation units on a causeway, then removing the buckets to leave bucket-shaped pools (top diameter: 130–140 mm; bottom diameter: 110 mm; depth 100–120 mm). Twenty pools were created at both highshore and midshore on each side of the causeway (wave-exposed, wave-sheltered) in June 2013. Macroalgae, invertebrates and fishes in pools were counted during low tide over 24 months and in the laboratory after 24 months. Species were grouped into functional groups according to their role in the community (shape/structure and feeding strategy). All pools on the sheltered side had filled with sediment and no longer provided rock pool habitat.

    Study and other actions tested
  11. A replicated, controlled study in 2013–2014 on an intertidal seawall in the Hudson River estuary, USA (Perkol-Finkel & Sella 2016) reported that rock pools created on the seawall supported macroalgae, invertebrate and fish species that were absent from seawall surfaces without rock pools. After nine months, pools supported 89–100% cover of macroalgae and non-mobile invertebrates and at least seven species (1 macroalgae, 2 non-mobile invertebrates, 3 mobile invertebrates, ≥1 fish) that were absent from seawall surfaces without pools. Rock pools were created by placing concrete troughs amongst a boulder seawall during construction. Seven rectangular pools (volume: 59 l; other dimensions not reported) with stepped sides were installed at highshore in November 2013. Macroalgae, invertebrates and fishes were counted during low tide in pools and on surrounding seawall surfaces at the same shore level (details not reported) after nine months.

    Study and other actions tested
  12. A replicated, paired sites, controlled and site comparison study in 2014–2015 on three intertidal seawalls in Sydney Harbour estuary, Australia (Morris et al. 2017) found that creating rock pools on one seawall did not increase the fish species richness on and around the wall, but had mixed effects on fish abundances depending on the species group and site. Over the first 12 months, pelagic fish species richness was similar around the seawall with rock pools (1–3 species/survey) and those without (1–2/survey) and there were no clear differences in maximum abundances (0–26 vs 0–13 individuals/survey), which varied by species group and site (see paper for results). For the seawall with pools, pelagic fish species richness in and around pools (1–2 species/survey) was similar to seawall surfaces without (2–4/survey), and maximum abundances varied by species group (with pools: 0–39 individuals/survey; without: 0–30/survey). After 15–21 months, benthic fish species richness in and around pools was similar to seawall surfaces without (both 9 species in total). Total abundance was higher for pools than surfaces for one species (12 vs 1 individuals), but similar for 10 others (0–15 vs 0–22). One species recorded in and around pools was absent from surfaces without. Rock pools were created by attaching concrete pots to a vertical sandstone seawall in February 2014. Five half-flowerpot shaped pools (top diameter: 315 mm; volume: 7l; depth not reported) were attached at midshore in each of two sites along the seawall. Pools were compared with seawall surfaces without pools (dimensions not reported) adjacent to each site and on two other seawalls without pools. Fishes were counted in, on and around pools and seawall surfaces from time-lapsed photographs and videos during 7–10 high tides over 21 months.

    Study and other actions tested
  13. A replicated, randomized study in 2016 on two intertidal seawalls in Sydney Harbour estuary, Australia (Morris, Golding, Dafforn & Coleman 2018) reported that rock pools created on the seawalls supported macroalgae, invertebrates and fishes, and found that adding short flexible habitats (coir panels) to pools had mixed effects on community composition, species richness and abundances depending on the species group and site. Over eight months, during low tide, a total of 44 macroalgae, invertebrate and fish species groups were recorded in pools with coir and 57 in pools without (data not statistically tested). Average macroalgae and non-mobile invertebrate species richness was lower in pools with coir (9 species/pool) than without (12/pool) and the community composition differed (data reported as statistical model results), while abundances varied depending on the species group and site (data not reported). Mobile invertebrate and fish species richness was also lower in pools with coir (2 species/pool) than without (3/pool), but their abundance was similar (data not reported), while effects on their community composition varied by site. During high tide, a total of 13 fish species were recorded in and around pools with coir and 14 in and around pools without, while 49 mobile invertebrate species groups were recorded in each. Average fish species richness, abundance, community composition, and the number of bites they took, were all similar in pools with and without coir (data not reported). Mobile invertebrate species richness in pools with coir (8–11 species/pool) and without (9–16/pool) varied by site, but the community composition was similar. Rock pools were created in January–February 2016 by attaching concrete pots to two vertical sandstone seawalls. Five half-flowerpot shaped pools (top diameter: 315 mm; depth: 300 mm; volume: 7 l) with coir panels on one inside surface and five without were randomly arranged at midshore in each of two sites along each seawall. Macroalgae, invertebrates and fishes were counted in pools during low tide over eight months. Mobile invertebrates and fishes were also surveyed during two high tides using a suction pump and videos, respectively. Three pools were missing and no longer provided habitat.

    Study and other actions tested
  14. A replicated, controlled and site comparison study in 2013–2015 on two intertidal seawalls in Sydney Harbour estuary, Australia (Morris, Martinez, Firth & Coleman 2018) reported that rock pools created on the seawalls supported similar mobile invertebrate and fish species richness to seawall surfaces without pools, and different community composition with lower richness compared with natural rock pools. Over 18 months, a total of 10 mobile invertebrate and fish species groups were recorded in created pools, 10 on seawall surfaces without pools, and 32 in natural pools (data not statistically tested). Five species groups (4 mobile invertebrates, 1 fish) recorded in created pools were absent from seawall surfaces without pools. After 18 months, community composition differed in created and natural pools (data reported as statistical model results). Rock pools were created in December 2013 by attaching concrete pots to two vertical concrete and sandstone seawalls. Five half-flowerpot shaped pools (top diameter: 315 mm; volume: 7 l; depth not reported) were attached at midshore on each seawall. Pools were compared with seawall surfaces (details not reported) and with natural rock pools, cleared of organisms, on a nearby reef. Mobile invertebrates and fishes were counted in three created and natural pools and on seawall surfaces during low tide over 18 months.

    Study and other actions tested
  15. A replicated, paired sites, controlled study in 2014–2015 on one intertidal breakwater and two groynes on open coastline in the Alboran Sea, Spain (Ostalé-Valriberas et al. 2018) found that rock pools created on the structures supported different macroalgae and invertebrate community composition with higher species diversity and richness than structure surfaces without pools. After 12 months, macroalgae and invertebrate species diversity (data reported as Shannon index) and richness were higher in pools (9 species/pool) than on structure surfaces without (6/surface), and the community composition differed (data reported as statistical model results). Upper-midshore pools supported similar richness to lower-midshore ones (8 vs 9 species/pool). Eight species (4 macroalgae, 4 mobile invertebrates) recorded in pools were absent from structure surfaces without. Rock pools were created in February 2014 by drilling into horizontal surfaces of three limestone boulder structures (1 breakwater, 2 groynes; treated as 1 site) using a jackhammer. Five irregularly-shaped pools (average length: 176 mm; width: 137 mm; depth: ≤20 mm; volume: 0.4 l) were drilled at both upper-midshore and lower-midshore on each structure. Pools were compared with breakwater/groyne surfaces (200 × 200 mm) adjacent to each pool. Macroalgae and invertebrates were counted in pools and on structure surfaces from photographs over 12 months.

    Study and other actions tested
  16. A replicated, randomized, controlled study in 2014–2016 on an intertidal seawall in a marina in the Coral Sea, Australia (Waltham & Sheaves 2018) reported that rock pools created on the seawall supported higher macroalgae and invertebrate species richness than seawall surfaces without pools, and that tilted pools supported different community composition with higher species richness than horizontal ones. Over 24 months, a total of 16 macroalgae and invertebrate species groups were recorded in both landward- and seaward-tilting pools, 11 in horizontal pools, and 10 on seawall surfaces without pools (data not statistically tested). Community composition was similar in landward- and seaward-tilted pools, but both differed to horizontal pools (data reported as statistical model results). Ten species (2 macroalgae, 5 mobile invertebrates, 3 non-mobile invertebrates) recorded in pools were absent from seawall surfaces. Sediment accumulation was similar in all pools (34–45 mm depth). Rock pools were created by attaching concrete troughs to a boulder seawall in June 2014. Rectangular pools (length: 400 mm; width: 250 mm; depth: 350 mm; volume: 35 l) were either horizontal or tilted 45° towards the land or sea, thus shaded. There were three of each randomly arranged at midshore along the seawall. Macroalgae and invertebrates were counted in pools and on seawall surfaces (details not reported) during low tide over 24 months. One horizontal pool was missing and no longer provided habitat.

    Study and other actions tested
  17. A replicated, controlled study in 2013–2018 on an intertidal seawall in the Solent strait, UK (Hall et al. 2019) found that rock pools created on the seawall supported higher macroalgae, invertebrate and fish species richness than seawall surfaces without pools. After five years, macroalgae, invertebrate and fish species richness was higher in and on pools (10 species/pool) than on seawall surfaces without (7/surface). Fourteen species (6 macroalgae, 6 mobile invertebrates, 1 fish) recorded in pools over five years were absent from seawall surfaces without. Rock pools were created in September 2013 by attaching concrete pots (VertipoolsTM) to a vertical concrete seawall. Five triangular VertipoolsTM (length: 800 mm; width: 300 mm; depth: 10–200 mm; volume: 10 l) were attached at mid-highshore. Pools were compared with five seawall surfaces with surface areas matching the inside and outside pool surfaces (500 × 500 mm). Macroalgae, invertebrates and fishes were counted during low tide in and on pools (averaged over inside and outside surfaces) on 10 occasions and on seawall surfaces on four occasions over five years.

    Study and other actions tested
  18. A replicated, paired sites, controlled study in 2015–2018 on three intertidal seawalls in Penang Strait, Malaysia (Chee et al. 2020) found that rock pools created on the seawalls supported higher macroalgae and invertebrate species richness than seawall surfaces without pools. After 36 months, a total of 14 macroalgae and invertebrate species were recorded in pools and six on seawall surfaces without (data not statistically tested). Average species richness was higher in pools (13 species/pool) than on seawall surfaces (6/surface). Community composition (data reported as statistical model results) and species richness were similar in deep and shallow pools (both 11 species/pool). Thirteen species (1 macroalgae, 11 mobile invertebrates, 1 non-mobile invertebrate) recorded in pools over 36 months were absent from seawall surfaces. Rock pools were created in October 2015 by drilling into horizontal surfaces of three granite boulder seawalls using a core-drill. Fifteen deep (depth: 120 mm; volume: 2.1 l) and 15 shallow (50 mm; 0.9 l) cylindrical pools (diameter: 150 mm) were drilled at midshore on each seawall. Pools were compared with seawall surfaces, cleared of organisms, adjacent to each pool, with surface areas matching the inside pool surfaces (deep: 270 × 270 mm; shallow: 200 × 200 mm). Macroalgae and invertebrates were counted in pools and on seawall surfaces during low tide over 36 months.

    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.

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Biodiversity of Marine Artificial Structures

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Biodiversity of Marine Artificial Structures

Biodiversity of Marine Artificial Structures - Published 2021

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