Settlement of seaweeds on coastal structures

Published source details Watanuki A. & Yamamoto H. (1990) Settlement of seaweeds on coastal structures. Hydrobiologia, 204, 275-280.
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This study is summarised as evidence for the following.

	Action	Category
	Create groove habitats (1–50 mm) on subtidal artificial structures Action Link
	Create small protrusions (1–50 mm) on subtidal artificial structures Action Link

Create groove habitats (1–50 mm) on subtidal artificial structures

A controlled study in 1985–1989 on a subtidal breakwater block on open coastline in Toyama Bay, Japan (Watanuki & Yamomoto 1990) reported that groove habitats created on the block supported more kelp Ecklonia stolonifera but similar abundances of canopy algae Sargassum spp. compared with a block surface without grooves. Data were not statistically tested. After 42 months, there were 55 kelp individuals on the surface with large grooves (wet weight: 0.93 kg), 32 on the surface with small grooves (0.48 kg) and 20 on the surface without grooves (0.31 kg). Three canopy algae species had similar abundances and weights on the surface with large grooves (5–10 individuals, all 0.01 kg), small grooves (2–19 individuals, 0.01–0.04 kg) and without grooves (3–18 individuals, 0.05–0.17 kg). Groove habitats were created on a concrete breakwater block (2.3 × 2.3 × 0.8 m). There was one array of five large grooves (length: 644 mm; width: 46 mm; depth: 23 mm) and one of nine small grooves (length: 644 mm; width: 3 mm; depth not reported), evenly-spaced on 644 × 529 mm horizontal surfaces. One adjacent surface had no grooves. Small grooves were created by scraping using a nail (method for large grooves not reported). The block was placed on sandy seabed at 9 m depth in November 1985. Macroalgae on surfaces with and without grooves were counted and weighed (wet weight) after 42 months.

(Summarised by: Ally Evans)
Create small protrusions (1–50 mm) on subtidal artificial structures

A controlled study in 1985–1989 on a subtidal breakwater block on open coastline in Toyama Bay, Japan (Watanuki & Yamamoto 1990) reported that small protrusions created on the block supported more kelp Ecklonia stolonifera but less canopy algae Sargassum spp. than a block surface without protrusions. Data were not statistically tested. After 42 months, there were 58 kelp individuals on the surface with small protrusions (wet weight: 1.09 kg) and 20 on the surface without (0.31 kg). There were 2–3 individuals of each of three other canopy algae species on the surface with protrusions (0.01–0.09 kg) and 3–18 of each on the surface without (0.05–0.17 kg). Small protrusions were created on a concrete breakwater block (2.3 × 2.3 × 0.8 m) by attaching 45 pebbles (diameter/height: 35–45 mm), evenly-spaced on a 644 × 529 mm horizontal surface. One adjacent surface had no protrusions. The block was placed on sandy seabed at 9 m depth in November 1985. Macroalgae on surfaces with and without small protrusions were counted and weighed (wet weight) after 42 months.

(Summarised by: Ally Evans)