Study

Making seawalls multifunctional: the positive effects of seeded bivalves and habitat structure on species diversity and filtration rates

  • Published source details Vozzo M.L., Mayer-Pinto M., Bishop M.J., Cumbo V.R., Bugnot A.B., Dafforn K.A., Johnston E.L., Steinberg P.D. & Strain E.M.A. (2021) Making seawalls multifunctional: the positive effects of seeded bivalves and habitat structure on species diversity and filtration rates. Marine Environmental Research, 165, 105243.

Actions

This study is summarised as evidence for the following.

Action Category

Transplant or seed organisms onto intertidal artificial structures

Action Link
Biodiversity of Marine Artificial Structures

Create grooves and small protrusions, ridges or ledges (1–50 mm) on intertidal artificial structures

Action Link
Biodiversity of Marine Artificial Structures
  1. Transplant or seed organisms onto intertidal artificial structures

    A replicated, randomized, controlled study in 2015–2016 on two intertidal seawalls in Sydney Harbour estuary, Australia (Vozzo et al. 2021) reported that 60% of oysters Saccostrea glomerata transplanted onto settlement plates survived, and found that macroalgae and invertebrate species richness, diversity and abundances varied depending on the presence and depth/height of grooves and ridges or ledges on plates, the species group and site. After 12 months, 60% of transplanted oysters survived. The macroalgae and invertebrate species richness was higher on settlement plates with transplanted oysters (18–19 species/plate) than without (8–10/plate) when there were no or shallow/short grooves and ridges or ledges on plates. When deep/tall grooves and ridges or ledges were present, richness was similar on plates with and without transplanted oysters (17 vs 15/plate). The same was true for species diversity (data reported as Shannon index) and at one site for macroalgae and non-mobile invertebrate abundance (no or short/shallow grooves and ridges: 102–128% cover with oysters vs 30% without; deep/tall grooves and ridges: 98–108% with oysters vs 77–99% without). At the second site, no significant differences were found (with oysters: 126–150%; without: 87–121%). Oyster (Ostreidae) and mobile invertebrate abundances were higher on plates with transplanted oysters (oysters: 101–152 individuals/plate; mobiles: 83–156/plate) than without (oysters: 15–91/plate; mobiles: 12–38/plate). Eighteen species (2 macroalgae, 15 mobile invertebrates, 1 non-mobile invertebrate) recorded on plates with transplanted oysters were absent from those without. See paper for full results. Juvenile oysters were attached to concrete settlement plates (250 × 250 mm) using epoxy glue and transplanted onto vertical sandstone seawalls. Plates had 52 oysters/plate in patches of 4–5 individuals or no oysters, and textured surfaces with or without deep/tall (50 mm) or shallow/short (25 mm) grooves and small ridges or ledges. Five of each transplant-grooves/ridges combination were randomly arranged at midshore on each of two seawalls in November 2015. Macroalgae and invertebrates on plates were counted in the laboratory after 12 months.

    (Summarised by: Ally Evans)

  2. Create grooves and small protrusions, ridges or ledges (1–50 mm) on intertidal artificial structures

    A replicated, randomized, controlled study in 2015–2016 on two intertidal seawalls in Sydney Harbour estuary, Australia (Vozzo et al. 2021) found that creating groove habitats and small ridges or ledges on the seawalls had mixed effects on macroalgae and invertebrate species richness, diversity and abundances, depending on the depth/height of grooves and ridges, the species group and site. After 12 months, the macroalgae and invertebrate species richness was higher on settlement plates with deep/tall grooves and ridges or ledges (15 species/plate) than plates with shallow/short ones (10/plate) and plates without (8/plate), which were similar. At one site, the same was true for species diversity (data reported as Shannon index) and macroalgae and non-mobile invertebrate abundance (deep/tall: 77–99% cover; shallow/short: 30%; none: 31%). At the second site, no significant differences were found (deep/tall: 116–120%; shallow/short: 102%; none: 87%). Oyster (Ostreidae) abundance was higher on plates with grooves and ridges/ledges (52–91 individuals/plate) than without (15/plate), while mobile invertebrate abundance did not significantly differ (23–49 vs 11/plate). Twenty-three species (4 macroalgae, 14 mobile invertebrates, 5 non-mobile invertebrates) recorded on plates with grooves and ridges/ledges were absent from those without. The orientation of grooves and ridges or ledges had no clear effect on results. See paper for full results. Concrete settlement plates (250 × 250 mm) were moulded with and without groove habitats and small ridges or ledges. Plates with grooves and ridges or ledges had four grooves (length: 250 mm; width: 15–50 mm) between five vertical ridges or horizontal ledges (length: 250 mm; width: 17–65 mm). Grooves, ridges and ledges were either deep/tall (depth/height: 50 mm) or shallow/short (25 mm). Five of each were randomly arranged at midshore on each of two vertical sandstone seawalls in November 2015. Plates had textured surfaces. Macroalgae and invertebrates on plates were counted in the laboratory after 12 months.

    (Summarised by: Ally Evans)

Output references
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