Reduce the slope of 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 reducing the slope of intertidal artificial structures on the biodiversity of those structures. The studies were in an estuary in southeast Australia.

COMMUNITY RESPONSE (1 STUDY)

  • Overall richness/diversity (1 study): One before-and-after study in Australia reported that reducing the slope of an intertidal artificial structure, along with creating rock pools, increased the combined macroalgae, invertebrate and fish species richness on the structure.

POPULATION RESPONSE (1 STUDY)

  • Algal abundance (1 study): One replicated, controlled study in Australia found that reducing the slope of an intertidal artificial structure did not increase the macroalgal abundance on structure surfaces.
  • Invertebrate abundance (1 study): One replicated, controlled study in Australia found that reducing the slope of an intertidal artificial structure did not increase the oyster or mobile invertebrate abundance on structure surfaces.

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, controlled study (year not reported) on an intertidal seawall in Sydney Harbour estuary, Australia (Chapman & Underwood 2011) found that reducing the slope of the seawall did not increase the abundance of macroalgae, oysters Saccostrea glomerata or mobile invertebrates on seawall surfaces. Over 24 months, the abundances of macroalgae, oysters and mobile invertebrates were similar on surfaces of a new sloping seawall and on remnants of the original vertical wall that it replaced (data not reported). The slope of a seawall was reduced by replacing a vertical concrete wall with a sloping wall of boulders. This increased the extent of the intertidal area from high to low shore by 2–3 m (timing and other details of the intervention not reported). Macroalgae and invertebrates were counted on 10 surfaces (dimensions not reported) in each of four sites on the new sloping wall, and 10 on a remnant of the original vertical wall, during low tide over 24 months.

    Study and other actions tested
  2. A before-and-after study in 2012–2013 on an intertidal seawall in Sydney Harbour estuary, Australia (Heath & Moody 2013) reported that reducing the slope of the seawall, along with creating rock pools on the wall, increased the macroalgae, invertebrate and fish species richness on the wall. A total of 25 macroalgae, invertebrate and fish species were recorded on the seawall and in pools after the slope was reduced and pools were created, compared with 10 species on the seawall before (data not statistically tested). It is not clear whether these effects were the direct result of reducing the slope of the seawall or creating rock pools. The slope of a sandstone boulder seawall was reduced during reconstruction in July 2012 (details not reported). Three large rock pools (area: 2 m2; depth: 300 mm; volume: 600 l) were also created on the wall. 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
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

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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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