Long-term modifications of coastal defences enhance marine biodiversity

  • Published source details Martins G.M., Jenkins S.R., Neto A.I., Hawkins S.J. & Thompson R.C. (2016) Long-term modifications of coastal defences enhance marine biodiversity. Environmental Conservation, 43, 109-116.


This study is summarised as evidence for the following.

Action Category

Create pit habitats (1–50 mm) on intertidal artificial structures

Action Link
Biodiversity of Marine Artificial Structures
  1. Create pit habitats (1–50 mm) on intertidal artificial structures

    A replicated, randomized, controlled study in 2006–2014 on an intertidal seawall on open coastline in the Atlantic Ocean, Azores (Martins et al. 2016; same experimental set-up as Martins et al. 2010) found that creating pit habitats on the seawall had mixed effects on macroalgae and invertebrate abundances depending on the species, site and pit size and density. After seven years, abundance was higher on seawall surfaces with pits than those without for limpets Patella candei in three of four comparisons (1–20 vs 2 individuals/surface), for barnacles Chthamalus stellatus in two of four comparisons (8–27 vs 11% cover), and for periwinkles Tectarius striatus in one of four comparisons (2–11 vs 1 individuals/surface). Limpets and barnacles were more abundant on surfaces with large pits (limpets: 8–20/surface; barnacles: 25–27%) than small (limpets: 1–8/surface; barnacles: 8–12%). The opposite was true for periwinkles (large pits: 2/surface; small: 7–11/surface). Limpets were more abundant on surfaces with high-density pits (8–20/surface) than low-density (1–8/surface), whereas abundance did not significantly differ for barnacles (high-density: 12–27%; low: 8–25%) or periwinkles (high: 2–7/surface; low: 2–11/surface). Results were variable for small periwinkles Melarhaphe neritoides and macroalgae (see paper for results). Pit habitats were created by drilling into a basalt boulder seawall. Arrays of large (diameter: 24 mm) and small (12 mm) round pits (depth: 10 mm) were evenly-spaced on 250 × 250 mm seawall surfaces with high (16 pits/array) or low (8/array) densities. There were five surfaces with each size-density combination and five without pits, randomly arranged at midshore in each of two sites along the seawall. Limpets were removed from surfaces when pits were created in November 2006, then macroalgae and invertebrates were counted on surfaces with and without pits during low tide after 87 months.

    (Summarised by: Ally Evans)

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