Cease or alter maintenance activities on subtidal 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 ceasing or altering maintenance activities on subtidal artificial structures on the biodiversity of those structures. One study was in an estuary in southeast Australia and one was in an inland bay in eastern USA.

COMMUNITY RESPONSE (1 STUDY)

  • Overall community composition (1 study): One replicated, paired sites, controlled study in the USA found that reducing the frequency of cleaning on subtidal artificial structures did not alter the combined invertebrate and fish community composition on and around structure surfaces.
  • Overall richness/diversity (1 study): One replicated, paired sites, controlled study in the USA found that reducing the frequency of cleaning on subtidal artificial structures did not increase the combined invertebrate and fish species richness or diversity on and around structure surfaces.

POPULATION RESPONSE (2 STUDIES)

  • Overall abundance (1 study): One replicated, paired sites, controlled study in the USA found that reducing the frequency of cleaning on subtidal artificial structures did not increase the combined invertebrate and fish abundance on and around structure surfaces.
  • Algal abundance (1 study): One replicated, paired sites, controlled study in the USA found that reducing the frequency of cleaning on subtidal artificial structures increased the macroalgal abundance on structure surfaces.
  • Fish abundance (1 study): One replicated, randomized, controlled study in Australia found that reducing the area cleaned on a subtidal artificial structure increased the seahorse abundance on structure surfaces.
  • Survival (1 study): One replicated, paired sites, controlled study in the USA found that reducing the frequency of cleaning on subtidal artificial structures did not increase the survival of transplanted oysters.
  • Condition (1 study): One replicated, paired sites, controlled study in the USA found that reducing the frequency of cleaning on subtidal artificial structures did not increase the growth of transplanted oysters.

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, randomized, controlled study in 2007–2008 on a subtidal swimming-enclosure net in Sydney Harbour estuary, Australia (Harasti et al. 2010) found that enclosure-net panels cleaned only along the top section supported a higher abundance of seahorses Hippocampus abdominalis and Hippocampus whitei than panels cleaned only along the bottom or from top-to-bottom. Over four months, enclosure-net panels cleaned only along the top supported more seahorses (20% of original abundance) than panels cleaned along the bottom (5%) or from top-to-bottom (3%). Maintenance activities were altered on a polypropylene swimming-enclosure net (length: 150 m; height: 3–4 m from sea surface to seabed; mesh size: 100 mm) in November 2007. Net panels (4-m sections) were either cleaned along the top only (surface to 1 m depth), the bottom only (seabed to 1 m above), or from top-to-bottom (surface to seabed). There were four panels of each treatment, randomly arranged along the net. Seahorses were removed during cleaning then replaced in the same position, while all other organisms were scraped from the net. Some panels were left uncleaned but this treatment was not considered a feasible conservation action since the weight of the net could cause it to break or sink. Eleven seahorses on each panel were tagged and monitored over four months.

    Study and other actions tested
  2. A replicated, paired sites, controlled study in 2008 on eight subtidal pontoons in the Delaware Inland Bays, USA (Marenghi et al. 2010) found that reducing the frequency of cleaning activity did not increase the survival or growth of transplanted oysters Crassostrea virginica on floats attached to the pontoons, nor did it alter the non-mobile invertebrate, mobile invertebrate and fish community composition or increase their species diversity, richness or abundance on and around floats, but it did increase the macroalgal abundance. Data for all comparisons were reported as statistical model results. Over four months, transplanted oyster survival and growth was similar on floats cleaned every four or two weeks. The same was true for the overall community composition, and the species diversity, richness and abundance of non-mobile invertebrates and of mobile invertebrates and fishes on and around oyster floats. The abundance of macroalgae was higher on floats cleaned every four than every two weeks. Maintenance activities were altered on floats holding transplanted oysters attached to pontoons during June–September 2008. Hatchery-reared oysters (61 mm average length) were transplanted into wire baskets (25 mm mesh size) submerged 0.2 m beneath plastic floats (1.0 × 0.7 × 0.3 m) and attached to pontoons. One float with oysters (6 l) and one without were attached to each of eight pontoons in June 2008. Floats were cleaned with a freshwater hose every four weeks on four pontoons and every two weeks on four. Oyster survival and growth was monitored, non-mobile invertebrates on oyster shells were counted, and mobile invertebrates and fishes on and around floats were netted (3 mm mesh size) and counted over four 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

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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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