Create small adjoining cavities or ‘swimthrough’ habitats (≤100 mm) on intertidal artificial structures

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

Study locations

Key messages

  • Two studies examined the effects of creating small adjoining cavities or ‘swimthrough’ habitats on intertidal artificial structures on the biodiversity of those structures. One study was on an open coastline in the UK and in an estuary in the Netherlands and one was on an open coastline in South Africa.

COMMUNITY RESPONSE (2 STUDIES)

  • Invertebrate community composition (1 study): One replicated, controlled study in South Africa found that creating small swimthrough habitats on intertidal artificial structures did not alter the mobile invertebrate community composition on structure surfaces.
  • Overall richness/diversity (1 study): One replicated study in the UK and the Netherlands found that varying the size and arrangement of small swimthrough habitats created on intertidal artificial structures did not increase the combined macroalgae and invertebrate species richness in and on the structures.
  • Invertebrate richness/diversity (1 study): One replicated, controlled study in South Africa found that creating small swimthrough habitats on intertidal artificial structures did not increase the mobile invertebrate species richness or diversity on structure surfaces.

POPULATION RESPONSE (2 STUDIES)

  • Invertebrate abundance (2 studies): One replicated, controlled study in South Africa found that creating small swimthrough habitats on intertidal artificial structures increased the mobile invertebrate abundance on structure surfaces. One replicated study in the UK and the Netherlands found that varying the size and arrangement of small swimthrough habitats altered the invertebrate abundance in and on structures.

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 study in 2011–2014 on 30 rock gabions on open coastline in the Irish Sea, UK and in the Eastern Scheldt estuary, Netherlands (Firth et al. 2014) found that gabions with small swimthrough habitats created amongst rocks of mixed sizes (small and large) supported similar macroalgae and invertebrate species richness and abundance to those amongst rocks of regular sizes (small or large), but that abundance was higher on gabions with regular small rocks than regular large ones. In the UK, after 12 months, 12 mobile and non-mobile invertebrate species were recorded in and on gabions with swimthroughs. Species richness and abundance was similar in and on gabions with swimthroughs amongst mixed-sized rocks (9 species/gabion, 252 individuals/gabion) and regularly-sized ones (8 species/gabion, 191–366 individuals/gabion). Abundance was higher in and on gabions with small regular rocks (366 individuals/gabion) than large regular ones (191/gabion). In the Netherlands, after 16 months, 14 macroalgae, mobile and non-mobile invertebrate species were recorded and overall species richness was similar on all gabion designs (data not reported). Small swimthrough habitats were created amongst rocks in gabion baskets (500 × 500 × 300 mm; 76 mm mesh size). Swimthroughs were either amongst rocks of mixed sizes (small: 60–100 mm and large: 180 mm), or amongst regularly-sized small or large rocks. Five of each design were placed at midshore on a boulder beach in the UK in April 2011 and at lower-midshore on a sandy beach in the Netherlands in September 2012. UK gabions were dismantled and invertebrates counted after 12 months. In the Netherlands, macroalgae and invertebrates on external horizontal gabion surfaces were counted after 16 months.

    Study and other actions tested
  2. A replicated, controlled study (year not reported) in two intertidal boulder fields on open coastline in the Indian Ocean, South Africa (Liversage et al. 2017) found that small swimthrough habitats created under concrete blocks supported similar mobile invertebrate species richness, diversity and community composition to blocks without swimthroughs, but higher mobile invertebrate abundance. Swimthrough habitats supported similar mobile invertebrate species richness, diversity and community composition (data reported as statistical model results) but higher mobile invertebrate abundance (3 individuals/dm2) compared with blocks without swimthroughs (1/dm2). Small swimthrough habitats (length: 290 mm; width: 70 mm; height: 20 mm) were created on the undersides of concrete blocks (250 × 150 × 40 mm) using a mould. Twelve blocks with swimthroughs and 12 without were placed on the seabed in each of two natural boulder-fields (material, shore level and month/year not reported). Mobile invertebrates on the horizontal surface (roof) of swimthrough habitats and on the equivalent undersurface of blocks without swimthroughs were counted from photographs after seven weeks. Some blocks were missing and no longer provided habitat (numbers not reported).

    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

What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 18

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.


Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape Programme Red List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Bern wood Supporting Conservation Leaders National Biodiversity Network Sustainability Dashboard Frog Life The international journey of Conservation - Oryx British trust for ornithology Cool Farm Alliance UNEP AWFA Butterfly Conservation People trust for endangered species Vincet Wildlife Trust