Area-independent effects of water-retaining features on intertidal biodiversity on eco-engineered seawalls in the tropics

Published source details Loke L.H.L., Heery E.C., Lai S., Bouma T.J. & Todd P.A. (2019) Area-independent effects of water-retaining features on intertidal biodiversity on eco-engineered seawalls in the tropics. Frontiers in Marine Science, 6, 16.
Share Tweet Email

Actions

This study is summarised as evidence for the following.

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

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

A replicated, randomized, controlled study in 2010–2011 on two intertidal seawalls on island coastlines in the Singapore Strait, Singapore (Loke et al. 2019) found that concrete settlement plates with groove habitats and small ridges supported higher macroalgae and invertebrate species richness and abundance than granite plates without grooves or ridges, but that community composition and limpet Siphonaria guamensis abundance varied depending on the site and whether grooves and ridges were partially-covered. After eight months, macroalgae and invertebrate species richness and abundance were higher on settlement plates with partially-covered grooves and ridges (20 species/plate, 89 individuals/plate) than uncovered grooves and ridges (14 species/plate, 43 individuals/plate) and plates without grooves and ridges (10 species/plate, 40 individuals/plate). Community composition differed on plates with and without grooves and ridges in three of four comparisons (data reported as statistical model results). At one of two sites, there were 250 limpets/plate with partially-covered grooves and ridges, 420/plate with uncovered grooves and ridges and 225/plate without grooves and ridges (data not statistically tested). At the second site, limpet abundance was 0/plate for each. Settlement plates (200 × 200 mm) were moulded with and without groove habitats and small ridges. Plates with grooves and ridges were concrete with five concentric circular grooves and ridges/plate (8–56 mm width, depth/height and spacing). Some were partially-covered with water-retaining and light-shading plates. Plates without grooves or ridges were granite fragments set in cement. Granite may be considered an environmentally-sensitive material compared with concrete (see “Use environmentally-sensitive material on intertidal artificial structures”). Ten of each design were randomly arranged at lowshore on each of two granite boulder seawalls in August 2010. Macroalgae and invertebrates on plates were counted in the laboratory after eight months. Seven plates with grooves and ridges and four without were missing and no longer provided habitat.

(Summarised by: Ally Evans)