Create small protrusions (1–50 mm) on subtidal artificial structures

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

Study locations

Key messages

  • One study examined the effects of creating small protrusions on subtidal artificial structures on the biodiversity of those structures. The study was on an open coastline in Japan.




  • Algal abundance (1 study): One controlled study in Japan reported that creating small protrusions on a subtidal artificial structure had mixed effects on the macroalgal abundance on structure surfaces, depending on the species.


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 controlled study in 1985–1989 on a subtidal breakwater block on open coastline in Toyama Bay, Japan (Watanuki & Yamamoto 1990) reported that small protrusions created on the block supported more kelp Ecklonia stolonifera but less canopy algae Sargassum spp. than a block surface without protrusions. Data were not statistically tested. After 42 months, there were 58 kelp individuals on the surface with small protrusions (wet weight: 1.09 kg) and 20 on the surface without (0.31 kg). There were 2–3 individuals of each of three other canopy algae species on the surface with protrusions (0.01–0.09 kg) and 3–18 of each on the surface without (0.05–0.17 kg). Small protrusions were created on a concrete breakwater block (2.3 × 2.3 × 0.8 m) by attaching 45 pebbles (diameter/height: 35–45 mm), evenly-spaced on a 644 × 529 mm horizontal surface. One adjacent surface had no protrusions. The block was placed on sandy seabed at 9 m depth in November 1985. Macroalgae on surfaces with and without small protrusions were counted and weighed (wet weight) after 42 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.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

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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